Electric start for suitcase inverter generator by using its alternator as a BLDC motor?

I'm posting here in the hope that I can get some guidance on how to add an electric start feature to a cheap inverter generator cursed by the traditional recoil pull starter (the Devil's invention, imho). Apologies beforehand for what is a rather long initial post but I thought it best to appraise you of my thoughts and what I know of the problems involved in my proposed electronic add-on starter solution.

Not too long after purchasing a Parkside PGI 1200 B2 inverter genset from Lidl (UK) for the miserly sum of 99 quid about two months ago (third time lucky[1]), I was wishing for an electric start feature to relegate its accursed recoil starter to that of 'emergency only' status.

Now an obvious way to 'electric start' such ICE powered kit cursed by the infamous 'recoil starter', is to use a cordless electric drill with a socket wrench on a longish extension mounted in the chuck to crank the engine into life via the retaining bolt head on the exposed end of the engine shaft. In the case of that PGI 1200 B2, this isn't an option since the inverter module blocks such access.

Having already viewed the innards of this model of suitcase generator, I knew that buying an add-on electric starter motor option was, well, not an option. I did briefly entertain the notion of a Heath Robinson electric drive attachment to the starting rope handle or even something that would turn it into a less obnoxious 'kick start' mechanism before it occurred to me that the damn thing was already possessed of the necessary starter motor essentials - it just lacked the required BLDC motor drive module circuitry was all.

What had inspired me were several youtube videos I'd come across several months earlier, demonstrating the use of car and truck alternators as BLDC motors using R/C brushless ESC modules (a radio controlled (BLDC motor) Electronic Speed Controller). In particular, this video at:-

where a purpose made electric scooter BLDC module had been used rather than a cheaper R/C brushless ESC .

In this case he'd used a 1500W rated module. I'm obviously not going to want to push more than double the alternator's 5 or 6 amps maximum rating through its windings so I reckon something like a 40 dollar SPD-3648350BLDC module would more than suffice with its 18A maximum current limiting feature. However, if I'm going to use such low voltage modules, I'll obviously have to add a high voltage isolating relay (probably a solid state one for speed and reliability) to protect it against the 350/400 voltage once the engine has fired up.

It turns out that I'm not the first to ponder the possibility of doubling up the utility of the three phase multi-pole PM 170/340v alternator that's used to supply the inverter module with the required

175 to 200/350 to 400vdc (120v 60Hz/240v 50Hz gensets), by adding a suitable BLDC motor drive module along with a 12v battery and a converter to produce the required 48 vdc to crank the engine at 400 to 500 rpm (just 10 to 12 percent of its normal running speed, circa 3900 to 4600 rpm). A google search took me to the "allaboutcircuits" forum where a member had posed the exact same question way back in February 2011

He had pretty much the right idea although his thoughts about using a

170v converter to power a modified R/C brushless ESC and a cranking speed of only 100rpm were rather at odds with each other (never mind that such controllers typically max out at 6 cell's worth of LiPo battery pack voltage (22.2 to 25.2 volts) and 100rpm would most likely be far too slow to generate sufficient voltage to initialise the inverter and ignition module(s). Unfortunately, he didn't receive any helpful replies.

In the case of the 120v 60Hz inverter gensets, a repurposed cheap commodity R/C brushless ESC probably would suffice - sadly for me, not so in the case of the 230/240v 50Hz inverter gensets. :-(

I figured that a minimum cranking speed of 400rpm would be needed[2], necessitating at least ten percent of the 350 to 400 peak voltage generated at 4000 rpm to power the BLDC motor module which equates to a

40 to 50 volt requirement for a cranking speed of 4 to 5 hundred rpm.

I might be able to get away with half that voltage (and cranking speed) if I can use the starter battery to power the ignition module. Unfortunately, I don't have a workshop manual with schematic diagram(s) for my specific generator to check out the viability of such a modification.

Considering just how old that forum posting is (over 7 years old!), I'm surprised at the absence of such an electric starting option in the inverter modules used in current designs of commodity inverter suitcase generators available today. After all, the extra components could quite easily be integrated into the inverter module since they're essentially just an extra bit of Silicon 'real estate'.

Anyhow, those are my thoughts on the modern day version of the Dynastart (tm) system as used with a small two cylinder four stroke marine gasoline engine (auxiliary propulsion and battery charging in a 30 foot sailing sloop) where a specially designed dynamo was also used to provide starting torque via a pair of V belts wrapped around a 50cm or so diameter engine flywheel grooved to accept said drive belts.

My main problem is more to do with sourcing suitable hardware as well as trying not to re-invent the wheel if I can avoid it. For all I know, purpose made for inverter generator 'electric starter kits' may already be available (it is 2018 after all!).

==================================================================== NOTES:

[1] The 1st one ran just long enough to prove it was immune from the dreaded capacitive loading induced overvolting effect that ordinary petrol (gasoline) generators are afflicted with (the real reason why they're unsuited as backup power for UPS protected computer kit), before it dislodged the alternator connection to the inverter module and kicked out with an overload signal.

The 2nd unit failed to start until I disconnected the low oil level sensor wire. The engine vibrations unstuck the jammed oil level sensor float but since I'd initially assumed it was a low oil *pressure* switch, I was reluctant to keep hold of it so it too went back to Lidl for a refund.

By the time I'd discovered the true nature of these show stopping faults (and the ease by which they could be fixed), the original store had run out of stock. However, to my surprise, another local Lidl store turned out to still have three left so I bought two to reduce the risk of them being out of stock should my next one also need to be swapped out. Both proved to work ok so I chose what I thought was the better example and returned the 'spare' for a refund.

The problem with these Parkside inverter generators was less to do with Parkside's quality control and more to do with Lidl's oddball stock control whereby unsold stock *has* to make way for "The Next Week's Offers" since the shop floor is also the store's only warehousing space, resulting in these generators accumulating hundreds, if not thousands, of road miles over the UK's motorway network, being shunted from store to store or main depot. It's no wonder that oil sensor floats get jammed or connectors dislodged (BTW, both trivial to fix issues once you're aware of them).

As inverter generators go, they seem nothing short of perfection compared to other commodity inverter gensets in this market segment. It's true they're not as quiet as the Honda inverter generators but, until very recently, Honda were in a class of their own in this regard.

[2] This was after guestimating the power strokes per second rate I could achieve with the recoil starter (ignition off whilst re-priming the fuel line and float chamber) from which I could calculate a cranking rpm figure. It sounded about 5 such cycles per second, making it 10 revs per second or 600rpm.

My gut feeling is that 4 to 5 hundred rpm should suffice. However, I could well be over-estimating the cranking speed requirement so it might pay me to simply buy (or better yet, borrow) a cheapish 6 cell rated R/C brushless ESC module to do some initial tests with a pair of 12v SLAs, with the spark plug removed and then fitted but ignition disabled before worrying about protecting the module from the 350/400 volts when the engine fires up. There's little point in worrying about adding a disconnect relay if this 'Proof of concept' testing fails to deliver any encouragement to proceed further.

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Johnny B Good
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Johnny B Good
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Electric drill starter. Lots of YouTube videos showing various ways to do it: The basic trick is to use some kind of directional clutch so that when the generator starts, it doesn't spin the drill out of your hands. If the generator already has a good clutch on the recoil starter, then you don't need to add one. However, if you're going to spin the drive shaft directly, you'll need one. Or, you could just use a socket drive, butcher the shroud, and take your chances as in this video:

These are all the same but from multiple vendors:

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Jeff Liebermann

More:

Here's the product page for Jumpstart by Troy-Bilt: and eBay:

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Jeff Liebermann     jeffl@cruzio.com 
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Jeff Liebermann

Umm, didnt the OP mention the access to the crankshaft was blocked ?

Reply to
Rheilly Phoull

I did indeed! I guess that's one good reason not to try and explain

*everything* in one huge post (all too easy for such detail to get lost in the 'noise'). :-(

I did check out the links on the off chance there were some that did

*not* involve access to the nut on the end of the crankshaft. Believe me, if I'd had access to the crankshaft end, I'd have gone for that option in a heartbeat. I'm all for a pragmatic solution, talking of which, I'm considering the use of a cheap(ish) R/C brushless ESC module (6 cell LiPo version) with a couple of 12v SLAs just to test the viability of the whole "Turn the alternator into a starter motor" concept.

Despite my misgivings about the limited cranking speed (200 rpm or so in this case), it might still prove sufficient - I've had the damn thing 'kick back' when I've hit the compression point too soon to have built up enough speed due to not feeling my way just past compression (ignition off) to give myself a run up via the subsequent exhaust/induction/ compression strokes.

As I've said before, it's all too easy to over-think the problem and end up over-engineering a solution. The need to save a 24v rated ESC module from getting fried by the resulting 350 to 400 volts when the engine fires up shouts "Over-engineered!" loudly enough as things stand already.

My gut feeling is that the alternator can provide enough starting torque when run off a suitable BLDC motor controller module but I do wonder whether, in over 7 years, it's already been considered (after all, it

*does* seem to be such a "No-Brainer" electric starting option) and discounted for the lack of the necessary 'grunt'.

TBH, if you're going to give this option *any* thought at all, you'd consider using the microprocessor controller in the BLDC motor drive module to do something a little more sophisticated than merely emulate a dumb electric starter motor designed to brute force its way past the compression point.

The key obstacle here is the torque required to overcome compression without any run up to recruit the flywheel inertia. I'm pretty sure there'll be more than ample cranking torque once the initial resistance to compression has been overcome and the engine starts turning.

A blindingly obvious way to overcome this problem is to have the BLDC module crank the engine backwards until it hits and detects the compression loading before reversing the direction using the compression to bounce the shaft into rotating in the right direction with a whole 630 degrees or so's worth of 'run up' to build up the necessary speed to carry through the next compression stroke without risk of 'kick back'. It's not as if the BLDC modules are lacking the 'Smarts' required to run such an algorithm - "Work smarter, not harder!" would the obvious solution in this case. :-)

Assuming such an electric start system using the inverter genset's own built in three phase PM alternator for the 'grunt work' is viable (and I rather think it is), then there would seem to be a small window of opportunity for a cheeky startup to go into mass production of add-on electric start modules for the many thousands of commodity priced pull start inverter gensets already sold.

I say "small window of opportunity" since such extra circuitry can so readily be incorporated into the inverter modules (where it's best implemented in the first place) of later production inverter gensets once the manufacturers realise they've 'missed a trick' by allowing a cheeky upstart company the opportunity to take advantage of their oversight.

The manufacturers can charge a premium for the luxury electric start 'feature' at little more than the cost of a lightweight 6 cell Li-ion battery pack and a few extra inches of wiring and an ignition/starter keyswitch. They can still charge a premium for generators that are merely "Electric start capable", requiring a battery and ignition switch upgrade kit bought from the manufacturer who will make a nice profit at the expense of any such cheeky upstart company.

It's not as if any of this tech is costly to produce, so where the hell are all the "Inverter genset electric start upgrade packs"? :-)

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Johnny B Good
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Johnny B Good

You do realise that cheap gennies have very short operational lives, making extensive work on them pointless. If you want something worth tinkering wi th get a Listeroid from some 3rd world country. Tinkering is not optional & they will run for a lifetime, day in day out, once fully built. Listeroids also use a fraction as much fuel as modern junkboxes.

NT

Reply to
tabbypurr

Probably, but I missed it in the flurry of words. I couldn't find a decent photo of the insides of the Parkside PGI 1200 B2 inverter generator and therefore could not determine what might be blocking access.

Looking again, I find: The operator was able to start it in one easy pull. However, this appears to be a different version of the generator, where the pull starter is on a plastic panel that presumably could be removed. That would have been too easy. Here's the manual for the INVERTER GENERATOR PGI 1200 A1: The OP states that he has a B2, not A1 model. Oh well.

This is the B2 model with the recoil starter between the engine and the front panel: (19:50) Starting at 13:40, getting the B2 going took 13 pulls. Yep, doesn't start very easily. Removing the recoil starter assembly and drilling an access hole in the front panel might aesthetically disgusting, but would do the job. So much for new and improved.

The B2 manual is at: Since the manual does not show an exploded view, I can't tell if drilling a hole might work or if some kind of pancake form factor motor might fit.

My next step would be to tear off the various plastic panels and let's see what's inside.

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From new, pretty well all of these engine vacuum driven fuel pumped carburettors needed several pulls on the starter cord to finally prime the float bowl so, since this was effectively an unboxing video (but with very little actual unboxing shots), 13 pulls doesn't seem excessive in the circumstances.

The priming procedure when the generator has been allowed to run the fuel line dry (float bowl and fuel pump and the line in between and the one to the fuel shut off valve) prior to being put into storage isn't quite so protracted (about five leisurely pulls with the ignition off to eliminate the recoil starter's nasty surprise of 'Kickback'). Thus primed, it usually starts on the next pull or two.

I know some pull start inverter generators incorporate a 'Priming Bulb' to provide pulses of suck 'n' blow to operate the fuel pump independently of the engine but, like the piece of shit Workzone 1800/2000W inverter genset sold by Aldi a week ago that I sampled three of before concluding they were utter s**te, this one isn't so blessed.

A fuel priming lever would have removed a lot of the effort required to start it after its been retrieved from 'dry' storage. I could probably add a priming squeeze bulb without compromising the warranty but I'll wait and see how my electric starter project goes before I look to adding that enhancement (it won't matter so much with electric start but it's one hell of a bonus when your only option is that accursed recoil starter mechanism).

For that, you'll need to track down a workshop manual and they're rather thin on the ground for the cheaper commodity generators.

I'd already done that when I was delving into the 2nd unit which had suffered a stuck oil level float switch. The job would have been a lot easier if I hadn't been concerned about voiding the warranty by having to work around a bolt protected by a sticker obviously intended as an anti- tamper label by bending the plastic side panel aside to gain minimal access to other fixing bolts and screws.

The air intake vent at the front, opposite the rear end where the silencer and ventilation exhausts live, is straddled by the inverter module which blocks access to the recoil starter mechanism (the usual access to the flywheel retention bolt).

I could probably replace the recoil starter mechanism with such a pancake motor, replete with a planetary reduction gearbox and free-wheel coupling, but I'd lose the emergency recoil starter option unless I can extend the case to refit it ahead of the pancake starter motor assembly.

Considering what my options are with regard to relegating the pull cord to 'emergency use only', you can perhaps understand why I'm considering using the alternator as a BLDC starter motor.

If it's at all viable, this completely eliminates any sort of complicated mechanical modification, reducing the job to a much easier to implement installation of a suitable BLDC motor drive module and a high voltage solid state isolation relay (unless I can get hold of a BLDC motor drive module designed to tolerate the expected 350 to 400v output when the BLDC motor starts operating as a high voltage alternator).

Thinking about it, I don't really need turn on resistances as low as 7m? in a low voltage BLDC controller module since the alternator stator coil resistance is likely to be around an ohm per winding[1] so a higher motor voltage BLDC controller with turn on values measured in tens of m? rather than m? should nicely suffice in this case so I'm still floundering around looking for the best way to implement a practical and cost effective electric starter solution.

If I can get enough cranking speed using just 24v, I can simply use a pair of 12v SLAs (or possibly a 6 cell Li-ion battery pack). If I need to use 40 to 50 volts, it would make more sense to stick with a 12v SLA and use a DC-DC boost converter module to generate the higher voltage. I'll probably need an 8A rated 48v converter module for this task (assuming a brute force approach to the task of overcoming compression resistance).

In the meantime, I'll keep searching for suitable BLDC motor controllers and keep an eye on this thread for any further advice that might appear from those with more knowledge and experience in this field than my own.

[1] I haven't actually measured the stator windings resistance yet so this is just an educated guess. Furthermore for obvious reasons, the windings will most likely be connected in star (wye) rather than delta form with no access to the neutral point so regardless of the actual arrangement, I'll only be able to measure phase to phase anyway. However, that will at least inform me of the maximum possible stall current for any given BLDC motor controller supply voltage.
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Johnny B Good
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Johnny B Good

Some motors have a primer bulb to manually pump gas into the carb. Done correctly, I can start a small engine with one or two pulls of the recoil starter. Of the saws I own or have serviced, the worst is my Stihl MS180 (upper right) which takes exactly 6 pulls when cold starting. However, once it runs for a while, and the carb fills with gas, it will warm restart in one pull.

I would consider 13 pulls to be rather excessive.

Ok, that's normal. Five pulls is about right. I run my saws dry and empty the tank in the fall, when I'm done using them (except for one for emergencies where I put some Sta-Bil in the tank). I haven't had to disassemble, clean, or rebuild any carburetors for a long time.

Yes, kickback sucks. It happens to me fairly often. I pull on the starter rope normally a few times. Then, it acts like the starter rope is stuck. I pull on the rope, which lifts the saw in the air, while simultaneously aims my face into the saw. After a few close calls, I'm VERY careful when starting a cold motor.

Ummm... I take it that you don't like this inverter generator, and by implication also don't like the primer bulb concept? I don't want to go into the pros and cons of primer bulbs. Let's just say they're a necessary evil without which you would be draining the tank and carb after every use and possibly removing crud from the carb.

I think a fuel shutoff petcock and carb drain would be more useful. You would have the option of leaving gas in the tank as long as necessary. If it's been sitting for months, drain the carb, or flush it with carb cleaner. Most larger gas generators, motorcycles, and paint sprayers have this feature.

You're not going to preserve the warranty after installing a starter motor unless you're VERY careful. Your decision. Electric start or warranty. Pick one.

How many pulls does it take to cold start your generator? If 13, then maybe you have a point. If 5, don't bother, and just get some more exercise.

I think the term is "service manual". I have one for almost everything I own (usually in PDF format). Unfortunately, many are in foreign languages where Google Translate is nearly useless. I couldn't find a Parkside PGI 1200 B2 Service Manual.

You should have taken photos. These days, I don't work on anything without taking photos of my work. It's mostly to help remember how things go together, but also to show others what is involved.

Use some solvent to loosen the glue on the label. The solvent will evaporate, but the glue will remain attached to the label. When you're ready to re-attach the label, a little more solvent will soften the glue again. This works on many labels, but not all of them. Some labels use ink that is soluble in chlorinated hydrocarbon solvents resulting in a destroyed label. On a plastic or painted case, your choice of solvents may attack the plastic or paint. Start at the low end of the scale with 70% isopropyl alcohol and work your way up to stronger (and more toxic) solvents.

Ok. Drilling a hole in the inverter module is not going to work.

Can you remove the recoil starter, and attach a clutch and sprocket gear to the drive shaft? If so, you can attach a bicycle chain to the sprocket gear and hang the starter motor out to the side.

Since the recoil starter and electric starter want to both occupy the same space, you'll have to decide which one you want.

(I'm out of time...)

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Jeff Liebermann     jeffl@cruzio.com 
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Not quite as small a fraction as you might think. However, they can be run on duty free diesel for about half the cost of a petrol/gasoline generator. Indeed they're not fussy about what fuel oil you choose to run them on so you have a lot more fuelling options.

Thank you for that sage advice. I do appreciate what you're saying but unfortunately, I'm not trying to live off grid and nor do I have the space to install such venerable machinery. On top of which, the standard generator heads typically fitted to these listeroids[1] no longer suit the needs of modern day lighting and computer loadings, particularly true in the case of my venerable Smartups2000 with its 9.4?F's worth of capacitive loading across its mains input which sends conventional single phase AVR controlled 230vac 50Hz alternators into a massive over-volting state as a result.

Lagging current loadings are merely the usual low power factor issue without the overvolting effect on the standard AVR controlled single phase alternators used in conventional generators but the slightest sniff of excess leading current from just a single 3.3?F fluorescent lamp PFC capacitor across the output of a 2.8KVA generator was enough to send its nominal 230v north of the 275v mark. I'm sure you can appreciate the problem caused by the Smartups2000 with its 9.4?F's worth across that genset's output.

There is a very good reason why I blew a whole 99quid on that Parkside PGI 1200 B2 inverter genset. Basically, it was because I knew the inverter type lacked this overvolting defect in the face of capacitive loads and so was the only viable backup option for my Smartups2000 battery backed 'protected supply'. I could have spent over a thousand quid on SLAs to extend the autonomy of the UPS into the 8 to 12 hour region but even if they were never to be called upon to provide emergency backup power, I'd be lucky to see more than a decade's worth of service life from them before having to blow yet another grand's worth on a replacement battery pack.

I don't expect to be running the generator for more than half a dozen hours a year (monthly half hour test runs being the most likely consumption of generator hours) but I like to be prepared against power outages to maintain all the lighting, the CH/DHW (pump, controller and zone valve), my IT kit (NAS box, desktop PC, a Gbit switch and a couple of routers) along with the 4K smart TV in the living room to allow the missus to watch her favourite soap operas without interruption.

At just 1000W continuous (actually 980W) with a 1200W 30 seconds surge rating, it's a bit on the marginal side but surprisingly do-able (upgrading the lighting to LED was what proved to be the key to this unexpected result). I was tempted by Aldi's recent Workzone 1800/2000W inverter gensets (three times no less before I gave up the whole idea of a generator upgrade) but they proved to be quite frankly, pure unadulterated s**te.

Unless we're due another unusually mild winter, the risk of power outages due to the government's mishandling of the Nuclear power plant construction programme that is now woefully years behind schedule, looms ever larger so it seemed only timely to purchase a backup generator that was compatible with modern day lighting loads and computer kit.

When Lidl put the latest B2 model on offer for just 99 quid two months ago, it was such a 'bargain of the decade' I just had to buy one, even though it was initially just to verify its compatibility with my Smartups2000. It was some 30 quid cheaper than the A1 version which I notice are still available in my local Lidl store (and rather surprisingly, still at their original elevated price of 129 quid).

Needless to say, I wasn't in the least tempted. It wasn't just on account of their higher price but also because of their retro 80's 'Cheap two stroke petrol generator' looks complete with a gravity fed fuel system from the classic top mounted steel fuel tank.

Don't be fooled by the side panels, they're just cosmetic coverings on an otherwise open frame chassis. It's true enough that the plastic carapace of the B2 model hardly improves its noise footprint over that of its predecessor but at least it has a slightly larger capacity tank and a more economic fuel consumption rating (0.68L/hour at 67% loading versus the 0.88L/hour of the A1 model, also at 67% load).

TBH, those little PGI 1200 B2s are such a bargain at 99 quid that if they ever become available again at that price, I'd snap up another two just to keep one as a spare (never mind that if either or both prove to have their first overload thresholds set above the nominal 1000W limit rather than 2% below it as is the case with my current unit, I'll be swapping inverter modules to correct the shortfall (unlike most inverter modules, the one used here is completely devoid of trimpots), hopefully leaving me with a pair of gensets both set above the 1000W limit for their first stage overload state (where you have 30 seconds to remedy the overload before the inverter module shuts down). The 1200W surge rating is the upper limit which, if exceeded, will trigger an immediate shut down.

If only one or neither meets or exceeds the specified overload limit, it just means I'll have to carry on the exchange/refund dance until I either land up with two good units or else run out of exchange options. Hopefully, my current inverter genset is the exception rather than the rule over this business of being set 2% below rather than 2 to 5 percent above the specified limit.

This time round, I'll know exactly how to deal with the two most common stock faults that arise from their being mishandled in transit, stuck oil level sensor floats and dislodged connectors in the wiring going to the inverter module - both show stoppers yet trivial to fix. :-)

[1] Obviously, a permanent magnet three phase alternator wired to a high voltage rectifier pack and geared to produce 420vdc on no load could be used to power an inverter module (in essence a bridged pair of class D amps driven from a 50Hz sinewave reference signal) to get round this voltage instability impediment as well as improve on the best efficiency of the standard single phase alternator typically used to directly generate the required 50Hz 240vac voltage supply.

As long as the DC voltage feeding the inverter module doesn't dip below

340v, it will be able to sustain the 240vac right up to its maximum rated current limit, assuming of course that this doesn't exceed the three phase PM alternator's maximum ratings.
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Johnny B Good
Reply to
Johnny B Good

d
s

marketing speak

not hard to add an inductive load to protect against capacitive loads

PFC

t

sounds more pointless than I expected Gas lighting is cheap & reliable, far more of both than any genny.

that's a hard way to do a simple task.

NT

Reply to
tabbypurr

if it's anything like the Briggs & Stratton engines with the a similar configuration there's a ratchet on the flywheel that disengages from the rope pulley centrifugally. (B&S' designuses steel balls that engage by gravity)

So you you could remove the rope pulley and modify it to take a chain or a toothed belt instead (maybe cut it up and rivet a bicycle sprocket on there) and then you can use whatever motor you want.

Some B&S engines also have a ring gear on the flywheel which can be used for electric start not that this likey to be an exact clone.

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     ?
Reply to
Jasen Betts

???

Yeah, I used to think that too. :-(

Believe me, that's exactly what I tried but it failed to remedy the problem. In retrospect, I'd have been better off fitting a 4.7?F PFC capacitor to the generator to force the rotor into saturation and use an auto-transformer to step the resulting 280vac back down to 240vac. Once afflicted by a modest capacitive loading, any additional capacitance would have had little if any further effect (other than for the issue of the extra leading current being drawn). However, I'd have been placing additional stress on the stator windings so probably not the best of pragmatic solutions.

You're entitled to your opinion but I think you've rather missed the point of the exercise.

Not in these modern times with cheap commodity priced 'electronic solutions'. :-)

BTW, why are you subscribed to SED if you deem such a solution to be "a hard way to do a simple task."? That view would have been valid three decades back when such 'complex solutions' would have required a complex circuit board populated with hundreds of discrete components including a microprocessor with a few dozen series 74 TTL chips thrown in for good measure.

Now that all of that required silicon wizardry (and more) can be packaged into a one square inch PCB weighing a mere 6.6g (30A cont 25.2v brushless ESC module designed to drive a quadcopter motor - product code: FPV 30A-6S) for less than 20 quid (), such a view seems somewhat antiquated today. Presumably (BICBW) you're subscribed here to get up to speed on modern electronic technologies and practices.

The inverter modules are much bigger since they're dealing with power conversion from an unregulated 350vdc supply to a constant 50Hz 230vac at the kilowatt level where, even with a conversion efficiency of 97 to 98 percent, you still have to deal with some 25 to 40 watts of dissipation whilst keeping device temperatures below the 398K mark in ambient temperature conditions up to 313K or higher.

The modules, as a consequence of this requirement, are mostly heatsink, shaped to allow the whole attached PCB to be fully embedded into a tough epoxy potting compound to protect against the harsh environmental conditions imposed by a small ICE running in the exposed conditions of an exterior environment.

Combining a mechanically simpler PM three phase alternator with a dedicated inverter module is both cheaper to manufacture and more efficient than the more traditional single phase 50Hz 230vac alternator which uses a voltage regulator system that draws power from its output to drive magnetisation current through the field winding via a set of slip rings and brushes. The energy loss in an inverter module is only a fraction of that consumed in the field winding of a conventional AVRd single phase 50Hz 230v alternator of equivalent power output.

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Johnny B Good
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Johnny B Good

I remember the electric starter motor steel ball bearing clutch system used on my younger brother's Honda CB160, over forty years ago now, which relied on springs to hold the three radially disposed balls within the starter pinion against the crankshaft where the servo effect was used to wedge them against the crankshaft to lock the starter gear pinion when driven by the starter motor and then release their grip when the engine fired up and the shaft overtook the starter pinion. It was a deceptively simple system that didn't look durable enough for the task.

The use of ball bearings in a 'free-wheel' styled starter pinion drive has a pedigree that goes back at least as far as Honda's CB160 motorcycle production days (if not further) but the use of gravity rather than spring pressure seems a bit of a hit 'n' miss system to me. Are you sure the system relied on gravity rather than something more positive like spring force?

That would involve an actual mechanical modification which looks like it will cost me the use of the rope starting option, neither of which I see as particularly appealing.

If this is a clone of anything, the most likely candidate will be the classic Honda EU1000i (which seems to be the basic pattern for pretty well all the other commodity brands of inverter gensets trying to get a slice of this market).

You're more likely to see a flywheel ring gear starter option on open frame gensets rather than on the smaller 1 to 2 KW Honda EU series clones. The little Parkside PGi1000/1200 B2 has no such provision but, as I see it, there's little point when all that's missing is a BLDC motor starter module to use the existing three phase PM alternator for this task.

I've already considered those options (and then some!), including even briefly considering the quick 'n' dirty battery powered cordless drill option. It was whilst I was pondering the utter futility of mechanically modifying the engine to add a seperate traditional starter motor, that I had a sudden epiphany, triggered by the memory of a series of youtube videos concerning alternator to BLDC motor conversion projects some months earlier.

What went through my mind at the time of this epiphany was something very like:-

"Well, f*ck me! Why am I wasting my time trying to shoehorn a starter motor into this thing when it already has the electromechanical essence of a BLDC motor already fitted and installed? This just needs the one essential ingredient to be added to the mix, namely a suitable BLDC controller module (and a starter battery and switch) and "It's Job done!""

I was, of course, referring to the high voltage (circa 350 to 400 volt) three phase multi-pole permanent magnet alternator that's directly driven by the engine (indeed the outer rotor carrying the neodymium magnets is also the engine's flywheel) which supplies the inverter module with the required 350 to 400 volts DC power which it converts to 50Hz 230vac power.

Whether you choose to call it a three phase PM alternator or a BLDC motor, the electro-mechanicals remain the same. The gauge of wire, the number of turns and choice of topology (delta or star) may be optimised differently between the two functions depending on whether you want it to generate 230v 50Hz ac current or you want it to operate as a 230v 50Hz ac synchronous motor plus any other number of variations to account for different frequencies and/or voltages in either mode.

Now that I have a rather neat solution to the problem of endowing this and, for that matter all such inverter gensets, with an electric starter option in mind, my question has been narrowed down from a general "How do I add an electric starter to this genset?" to the more specific "What is the best way to drive the 350v three phase PM alternator in my inverter genset as a BLDC starter motor?".

It's a pity I hadn't framed my question that succinctly in the first place but it's only after receiving so much advice on every alternative but the one I'm after (all of which I'd already considered and discounted) that the need to restate my question becomes apparent. Not to put too fine a point on it, the question I'm really asking is this:-

"What is the best way to drive the 350v three phase PM alternator in my inverter genset as a BLDC starter motor?"

I can understand why such alternatives were being offered. A lot of similar pleas for help often involve needlessly complex electronic solutions to problems that can often be better addressed more pragmatically using a low tech option. Believe me, the complexity of a BLDC motor controller *is* the most pragmatic solution in this case. :-)

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Johnny B Good
Reply to
Johnny B Good

some kind of BLDC controller, sensored using three HALL elements rather than sensorless is probably preferable with the low speed and uneven load from the engine

3x half-bridge drivers that can handle the starting current and the voltage of the generator running, something like this might work
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when the motor starts, the diodes in the half-bridges will basically form a 3-phase rectifier so a diode to isolate the battery

and some way to stop commutation when the voltage rises

Reply to
Lasse Langwadt Christensen

g

it's meaningless. And if you were to ascribe it a meaning, still valueless. Classic marketing talk.

f
t

sends

a

Not enough inductive current I presume.

ent

s
r
e

I have if there is one.

f
d

with respect there are easier ways. I'm sorry if pointing that out upset yo u.

NT

Reply to
tabbypurr

this is a friction clutch? sounds kind of dodgy

Just gravity, it'a ratchet clutch with centrifugal release not a friction clutch.

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there's 6 ball slots and 5 teeth so the rope spool only needs to rotate a little before one of them catches.

The back of the tray that holds the balls is dished slightly so that the same clutch can be used on the top of vertical-crank engines.

put a pulley on the starter motor shaft fer emergencies.

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     ?
Reply to
Jasen Betts

====snip====

I'm only too aware of the problem that can result when a sensorless BLDC controller has to fight compression resistance without any run up to recruit the flywheel inertia to assist pulling through this part of the engine cycle.

However, I'd like to avoid modifying the alternator with add on sensors if possible. One technique that comes to mind is to detect the lack of acceleration to determine that the engine is at the start of the compression stroke and to use this to reverse the direction of the motor until it detects the 'previous' compression stroke whereupon it switches back to forward, using the compression to help bounce it into forward acceleration so that there is sufficient inertial energy built up in the flywheel to push through the next and subsequent compression strokes until the engine either fires up or the start sequence times out.

ND/4454409

I've been studying the product info on that family of driver chips, in particular the SCM1246MF which looks the most promising with its 400v Vbb rating and the IGBT max voltage ratings of 600v and a 30A drive rating. I'm planning on using a 24v starter battery for my initial tests so the Vsat figure of 1.7v at 30A isn't a major problem especially as the phase winding resistance is likely to be around an ohm (yet to be tested) so max starting current (hence torque) from standstill will likely be limited to around the 20A mark (about four times the normal maximum 30 seconds output current limit as an alternator).

I've no idea whether this will provide sufficient torque to ease past the compression resistance without any run up with sufficient alacrity to avoid burning out the alternator windings (effectively trying to emulate the brute force and ignorance algorithm of an actual dumb starter motor system), hence my thoughts on detecting a losing battle so as to sneak up on the compression cycle from behind by reversing the drive until it detects hitting the back end of the 'previous' compression before switching back to forward drive to take advantage of the bounce back from the reversed compression cycle and an extended run up through some 630 degrees worth of rotation to take, so to speak, the enemy by surprise. :-)

That was the other problem that's been on my mind ever since I'd initially considered the use of a 30A rated R/C brushless ESC module rated for 6 cell's worth of LiPo battery (25.2v). In this case, I was figuring on using a solid state high voltage relay for its speed and reliability to disconnect the low voltage controller in a timely enough fashion to protect it against the alternator voltage once the engine had fired up.

Using a high voltage half bridge driver module removes the need to isolate the module from the alternator's output voltage terminals and transfers the problem elsewhere, in this case, the need to fit a blocking diode in series with the Vbb connection to stop the driver module's fast recovery diodes backfeeding the 350/400 volts into a poor defenceless battery (or a 48v DC-DC converter module if 24v operation doesn't provide sufficient cranking speed). I think detecting when to disable the commutation should be a fairly trivial task.

This does have the merit of simplifying the high voltage isolation requirement to a somewhat more foolproof single high voltage high current diode as opposed to the more complex issue of isolating the three separate phase connections via a three pole solid state relay (assembly) with similar voltage and current rating requirements and a circuit to detect when the engine fires up and to switch the SS relay off in a timely fashion before the ESC module can be killed by the excess voltage. All in all, the use of a 3 pole SS relay seems a rather more fraught option to go for.

If I could beg borrow or steal a 6S rated 20 or 30 amp ESC module, it would only be to use it for initial basic testing with the ignition disabled. I'd certainly not bother with a 3 pole isolating relay module to press it into actual service even if the initial test results did prove favourable. At that stage, I'd be looking to use a high voltage BLDC motor controller module to demote the isolation issue to starter voltage supply protection.

I've studied the product data sheets on those half bridge driver modules and it appears that I'll still have to connect and setup a processor module to make a complete BLDC motor controller unit. This was something I was hoping to avoid by using a more intelligent sensorless BLDCM controller unit with a self learning feature built in.

The problem here is that the high voltage BLDCM controllers might not have such a feature built in. I've seen the lower voltage 24 to 84 volt rated controllers designed for model aircraft and electric bicycle and go- kart BLDCMs with such a learning feature built in but there's no guarantee that'll be true for the higher voltage kit designed for washing machine/tumble drier motors and fridge/freezer compressor motors where they're more likely to be supplied as pre-programmed spares.

However, I'm still new to this technology so getting hold of a suitable high voltage BLDCM controller with a self learning feature may not be quite as hard as I fear. I'm hoping that maybe I've been over-thinking the potential issue of compression resistance and that there'll be no need to incorporate a special "take the compression by surprise" starter algorithm so I can utilise a self learning module otherwise I'll have no choice but to get my hands dirty customising the controller program.

I'm still open to any advice on this matter. Oh, one final question that's just occurred to me, if I have (or can gain) access to the neutral connection on the alternator, will this be of any use to gain a 70(?)% cranking speed boost from any given starter voltage?

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Johnny B Good
Reply to
Johnny B Good

That still doesn't really make a lot of sense. I looked at the fuel consumption graph for bio-diesel and for the 1KW point on the graph it equated to 0.64 litres per hour which is only slightly less than the 0.68 litre per hour figure for the 670W output level of the PGI 1200 B2. To be fair, that's an apples and oranges comparison but I don't have a graph for the Parkside units.

Alternatively, at the 700W level, the Listeroid graph shows a 0.15 US gal per hour rate which equates to 0.57 litre per hour despite the reduced efficiency of the consumption per KWH figure which flattens out in the range 1250 to 2500 watts at a per KWH peak of 0.5 litre per KWH of energy generated. When you look at the 500W figure that per KWH consumption hits the 0.98 litre mark which is likely much higher than the Parkside's consumption rate at this production level (500W load).

If the generator spends most of its run time operating at the 300W level, the litre per KWH rate gets even worse leaving the Parkside the winner in this case but, of course, that neglects the much lower cost per litre of duty free diesel over that of petroleum (gasoline).

Also, the Listeroid graph is handicapped by the use of a conventional single phase 230v alternator generator head and the extra losses of a drive belt totally absent in the case of the direct drive PM three phase alternator powered inverter suitcase generator.

For anyone living off-grid, the choice of a large low revving diesel prime mover to drive a generator head (whether it's a conventional single phase 230v alternator or a geared up three phase PM alternator with inverter module), is a no-brainer one. However, for someone looking for an emergency backup generator to mitigate winter outages or looking for a more luxurious wilderness trekking experience, the lightweight suitcase inverter genset becomes the no-brainer option (that 1KW Parkside unit only weighs in at a mere 13Kg!).

Judging by the effect it had on my first Parkside genset, I'd say it had provided ample inductive current. I'd forgotten that I still had it in circuit when I hooked up the first generator to the cable leading into the basement to my Smartups2000 (not yet plugged into the business end of that cable), so was surprised when the generator started labouring when I plugged it in.

The extra vibration must have been the final straw on the already loosened connector because after correcting my mistake by removing the no longer required inductor, I only got about 30 seconds run time before the generator stopped with an overload signal as a consequence of one of the phases disconnecting. Luckily, this had been just long enough to verify that I no longer had a capacitive over-volting issue with the Smartups2000 so was happy to seek a replacement rather than a refund from Lidl.

It was just unfortunate that this 2nd one wouldn't start because of a stuck oil level sensor float until I disconnected a suspiciously loose single wire connector which proved to be said engine sensor terminal connection which, like the oil pressure warning switch used in automotive engines which signal the lack of pressure by completing the connection to engine chassis earth to light up a warning light on the dash - in this case disable the ignition to prevent the engine destroying itself for a lack of oil rather for a lack of oil pressure.

Unfortunately at that time, I hadn't come across the comments which had mentioned that it was a float level sensor that could end up jammed by transit handling abuse rather than, as I'd initially presumed, a pressure sensing switch which, despite the engine vibrations unjamming the float, left me a little uneasy about the possibility of an intermittent fault in an oil pressure sensing switch.

If I'd been aware of the true nature of this low oil sensor, I wouldn't have felt the need (out of the principle that "discretion is the best part of valour") to return it to Lidl for yet another replacement it turned out they didn't have which left me without a generator until I discovered another cache of three a week later in another local Lidl that I'd wrongly assumed wouldn't have been chosen to stock this "bargain of the decade".

Remembering my several trips back and forth with the first two, I bought two with the intention of returning the surplus unit for a refund once I'd decided which of the two was going to be 'surplus to requirements' after checking for the stock faults I had now become aware of by this stage.

If both had proved defective, I could have returned both in one trip rather than two seperate trips. As it happened both checked out ok leaving me to select which to keep hold of on the basis of minor niggles. Unfortunately, it never occurred to me to verify the claimed overload wattage calibration setting so I landed up with the one that signalled this state at the 980W mark rather than the expected 1030 to 1050 watt mark.

I suppose it's just possible that the other could have been set exactly the same, possibly all of them, in which case I'd be left to consider a calibration error on my test equipment being on the wrong side of the

+/-3% accuracy tolerance range (both my analogue and two digital wattmeters being within 1% of each others' readings in the 1 to 1000W range makes this unlikely though not impossible).

If Lidl ever put these B2 models back on offer at the same 99 quid price, I'll be snapping a couple of them up for testing. At that price, it's well worth holding a spare in reserve anyway.

Normally, with such miscalibration issues as this, I'd be adjusting the relevant trimmer. Unfortunately, the inverter module used is completely devoid of any such trimmers - presumably they're preset in the factory (possibly via a JTAG connector - there are a couple of unused header blocks that could be candidates for this function).

If I ever track down the relevant JTAG programming instructions, I'll trouble myself to bodge up a connector and configure an interface for the PC or laptop, otherwise my best bet is to acquire more examples and select the best (inverter module).

====snipped quotage, including a non sequitur one liner reply====

Not annoyed, irritated? yes! but annoyed? no.

Ok, suggest an 'easier way' then.

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Johnny B Good
Reply to
Johnny B Good

So o o o h..., not just me then? :-)

That's piling one bodge on top of another. No thanks! I prefer my "Heath Robinson" bodges to be kept nicely out of sight, safely tucked away in the silicon innards of a well hidden BLDCM controller module, thank you very much. :-)

Such gross mechanical modifications to graft an electric starter motor onto a small 54cc 4 stroke petrol engine that already has the makings of a BLDC starter motor in the guise of an alternator flywheel seems such an unnecessary exercise when all that seems to be lacking is a suitable BLDCM controller and starter battery pack.

I'm not sure whether a simple self learning BLDCM controller can be used to brute force the issue of overcoming engine compression resistance or whether I'll need to program the controller to 'sneak its way past' this obstacle to attaining cranking speed before the current required to generate the required starting torque burns out the motor/alternator coil windings.

Right now, I have no empirical data by which to judge the viability of my 'Clever Idea'(tm), only a gut feeling that it aught to be possible (even if it needs a "Brains not Brawn" approach to the problem by way of a custom starter motor controller algorithm in the BLDCM controller module's micro-controller).

At the moment, I've had a recent thought about the possible benefit of gaining access to the neutral connection on the star wired alternator to improve the 'K' factor (an rpms per volt BLDC motor figure of merit used by the aero modelling community). My first gut feeling on this is that there may be a 70% or so cranking speed boost at stake but I haven't had a chance to consider it any further.

It might turn out to be a "Red Herring" chase on my part. Continuing with the fishy pun theme, I'm obviously still 'floundering' around with this project so any assistance in the matter of BLDC motor controllers to convert a 350v three phase PM alternator into a starter motor would be greatly appreciated now.

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Johnny B Good
Reply to
Johnny B Good

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