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 2011He 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.