iductive heater cooking on ebay lipo battery

I got one of these:

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used it in series with the'unknown' one from my RC plane, so two different 11.1 V lipos:

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Charged both batteries with the 'official' RC plane balancing charger:

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Note the large terminal connections I put on the batteries.

And looked at the clock, powered the induction heater from it, with a pan with some water in it.

Water cooking after about 2 minutes. Monitored the total voltage, staring at 22.5 V and switched off at 20.1 V, that makes 3.35 V per cell. Got about 5 minutes,

For a 2200 mAh battery, discharging at about 18 A, = (2.2 / 18) * 60 = 7.3 minutes, so a bit short of that, but there may be a number of reasons.

1) everything gets hot[1], even those large terminal blocks get hot, and I measured the voltage behind those 4 blocks, easily drop a few hundred mV.

2) but the real reason I switched off was that the green lipo (now 2 years old and used) got hot, say maybe 50 C, and hotter than the new Chinese one. And that green lipo is not specified at 20 C discharge or any discharge level, both are 2200 mAh however.

So, anyways, it is possible to use this to make scrambled eggs, or bacon and eggs, for breakfast. or even cook water for a cuppa. Bake fish, etc.

But not more than that, And then let solar cell or plutanium or just somebody on a bike :-) charge it again. Slaves come to mind, donkeys, or wind, not much sun today.

The safe thing is to get an other lipo from ebay to have 2 the same, maybe add one in series too to get 33.3 V

I did receive the parts for the charge balancing 2N2955 and TL431, TL431 seems right on voltage.

But the gist is: It is essential to measure lipo temperature, couple of diodes or LM335 should do, ..PIC more analog inputs needed...

[1] Only soldered connection do not get hot. Anything else will get lose anyways over time.
Reply to
Jan Panteltje
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On a sunny day (Sun, 24 Jan 2016 11:16:47 GMT) it happened Jan Panteltje wrote in :

PS as to political correct regarding the 6 letter word at the start of the previous sentence, for those that say racism is used in awarding the grammies or whatever for acting, lemme put it this way: If you play a crack addicted black, and in reality you _are_ a crack addicted black, then that is not acting! Comprandre?

Learn to act. I removed the next sentence, but it started with 'F*ck' and ended with 'you' ,and included '0bama'. For 10,000 Europe you can have a copy.

I am out of smileys.

Reply to
Jan Panteltje

Yes, I noticed. Big mistake. Those terminals are rated at 20-63A: and should work. However, I have my doubts. They also have only one problematic connection per wire, instead two screws (almost a point connection). The original XT60 terminals are good up to about 60A and have a lower contact resistance. I suggest you buy a bag of XT60 terminals, some shrink tube, and solder them to the wires: I just received 100 of these and am randomly replacing crap 0.093 Molex and Anderson Power Pole connectors on all my radios.

Ummm... that's for draining the LIPO battery completely, which is the standard method for destroying the battery. The depth of discharge and the number of surviving charge cycles are inversely related. Something like this: My guess(tm) is you can safely get about half your expected runtime, or about 3.6 minutes cooking time.

Incidentally, I use the same size 11.1v 2200 ma-hr battery in my quadcopter. The ones I've purchased from HobbyKing work well and seem to have the rated capacity. The crap I've bought on eBay and Amazon are at best half of what the vendor specifies. Try running a discharge test on the battery before trusting the vendors numbers. Hmmm... price went up slightly: Note that the max discharge spec is 25C or 55A. You could probably arc weld with the battery, if your connectors could handle it.

Too much drop. Is that a "few" hundred mV each or for the entire assembly (i.e. wire to wire)? I'll guess(tm) 0.4V times 20A = 8 watts which will probably scorch the nylon connection insulators. Do you have fire insurance on your house?

Different chemistry and different internal resistances will cause different amounts of internal heating. The 2200 ma-hr is probably a lie. If my tinkering with 18650 cells is any indication of quality, you can expect wide variations in performance, quality, survivability, and creative specmanship.

Yep. My guess(tm) is that if you continue to discharge the batteries to zero, you'll get about 10 charge cycles before the battery destroys itself. At $16 for the battery, that's $1.60 per breakfast. Not too bad for "fuel" but rather ecologically disgusting.

Fat pin and barrel connections (XT60) do quite well by increasing the connection area. Your screw terminals are almost point contacts where the screw compresses the stranded wires. Some have a strip of copper under the screw head to increase by contact area, and also prevent the screw from shredding the stranded wire. However, it doesn't add much to the total contact area.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

On a sunny day (Sun, 24 Jan 2016 10:51:28 -0800) it happened Jeff Liebermann wrote in :

Yea, that is the connectors I did cut off :-) The green one had flat contacts, any idea what those are called? I did leave some wire on the cut off parts so I can use those in my laser arrow RC plane, simply solder on again.

There is also a graph of temperature versus cycles and lifetime, above 50 degrees C lifetime goes down really fast.

Yes, its charging now, takes several hours on the small lipo charger.

Well, I dunno, this ebay battery (see link above) so far seems OK. Time will tell though. Also note the feedback in the ebay links. And thse are half teh price I pay here (or even a third) in the local RC shop!

It says: Hello shopper! We noticed you've been looking at this product for a while and we would like to offer you a discount. If you click on the add to cart button below we can offer you this product for EU10.08. This offer will only show once. If you leave this page or close this window you will not see this offer again.

LOL get people to buy, what do *you* pay for those?

It is cheap, it says 10 Euro 86 cents, But maybe also made in China.. Mine are specified at 40 C.

Yes, and the garden door is 2 steps way, and I also have some pavement terras there, and a big set of pliers at hand to carry the stuff there. Never needed so far, If I do I hope I will be able to grab a camera ;-)

I switch off at 3.5 V per cell or so.

Because I tinned the wires they press all the way against the metal of the connection blocks. but tinned wires get compressed in screw terminals, and get lose. You need to use those copper tubes (dunno the English word) to keep the strands together, not tin anything.

Anyways this is just testing. I may or may not buy a large 15Ah Lifepo4 24 V.

Next test is for the charge balancing and charging. Will be using Tim Williams system with a parallel regulator on each cell, limit to 4.2 V. Got some nice small TO220 heatsinks for the 2N2955 TL431 circuits too.

Reply to
Jan Panteltje

ann

MG_5473.JPG

arrow RC plane,

= 7.3 minutes,

shop!

like to offer you a discount.

ct for EU10.08.

again.

hundred mV.

rras there,

ars old and used) got hot,

rge level, both are 2200 mAh however.

n and eggs, for breakfast.

e connection blocks.

trands together,

limit to 4.2 V.

Tplugs ?

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T_Plugs.html

-Lasse

Reply to
Lasse Langwadt Christensen

On a sunny day (Sun, 24 Jan 2016 12:14:29 -0800 (PST)) it happened Lasse Langwadt Christensen wrote in :

Not sure, do not see these:

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?

Reply to
Jan Panteltje

s-X=

9.JPG

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looks like these: ?

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rs_20pc_.html

-Lasse

Reply to
Lasse Langwadt Christensen

T-connector. Most RC batteries came with those because they're cheap. There are others, so I just ordered a collection of adapters: Notice that the contact area of the T-connectors is much smaller than the contact area of the XT60 connectors.

To reduce weight, some fanatics drastically shorten the battery cable and re-solder the connector. That's another nice thing about XT60. The connectors can easily be re-used.

Right. LiIon batteries do not like high temperatures, low temperatures, low voltages, overcharging, high humidity, and tight packages: The tight package problem is where the battery will swell when charged. This is normal: and must be accommodated in the packaging design. Apparently, it's a lesson not easily learned by consumer electronics packaging designers: and Boeing 787 Dreamliner designers:

Get a better charger. According to the data sheet on the 2200 ma-hr battery I buy from Hobby King: You can charge at up to 5C or 22A. Of course, that assumes that you have some method of keeping the battery (and the charger) cool. I've done some testing and found that a zip-loc bag around the battery, while immersed in cold water, is sufficient. However, even if you use a reasonable charge rate of something like 2A, your battery should be charged in about an hour.

I recommend a (genuine) Imax B6 5A charger. I have two of these: Beware the clones. There's also a later model with more features, and one with an internal AC power supply. Plan on wasting a day decoding the documentation.

If you continue to discharge the battery to nearly zero, I predict that this will be a very short time.

I made the mistake of not clearing the associated cookies and logging in with my login/password so I could grab the products mentioned from my purchase history. Since I was a previous customer, no bargains. You'll find that if they think you're a first time buyer, they'll give you a discount on most everything. Also, you have to sit on the page for a while for the discount offer to appear.

Oops. For the battery, I paid $11.80 in June 2015 with some kind of discount. It's now $11.80 or the same price. I could swear that I've paid less, but I suspect it might have been from another vendor.

The Imax B6 charger is currently priced at $28.41. The discounted price offer is $26.88 or an 18.6% discount.

There are scorch marks on the Formica bench top, where various batteries have either caught fire, spewed hot caustic chemicals, or simulated a volcanic eruption. They are one reason I gave up on my super-fast charger product idea. It can't be done safely. Pliers and water are insufficient. I suggest a bucket of sand and a hand axe to cut the wires quickly. If it does catch fire, you would be able to get close enough to move it outdoors or disconnect the wires.

The cutoff voltage is largely determined by the current drain. For your 20A cooking load and a 2.2A-hr cell, that's about 9C. That's for a 1000 ma-hr battery, but is close enough. 3.5V will work at 9C but any more current drain, and you'll go below 3.5V during normal operation. I usually cut off at 3.2 or 3.3V so that it works at all discharge rates.

Ferrule. However, they don't really add much surface area. If you try one, and look at it from one end, you'll find that there is plenty of air space and gaps in the stranded wiring, which reduces the contact area. Even if you use a ferrule, and solder it to the wire, you'll still have a minimal contact area because the compression screw pushes the ferrule away from the screw. At best, you'll have about a

90 degree contact surface on the side opposite the screw, and nearly a point contact from the screw.

With me, it's "Learn by Destroying(tm)".

Yeah, I saw that. Good idea and methinks it should work.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
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Reply to
Jeff Liebermann

On a sunny day (Sun, 24 Jan 2016 15:12:17 -0800) it happened Jeff Liebermann wrote in :

OK, it looks like I will have to replace with those round ones.

Yes copper is heavy.

That is a very clear and easy to read site.

Designed to scare... that red graph, it is true however...

Yea, there were some postings about that here in those years, I may have said something about that too.

Right this has already been discussed and i have the parts now. But remember the solar panel power can fluctuate a lot. And, you only need breakfast once a day.... OK say twice.

More like: 'Shall I take the picture first, or move it outside first?' That famous 1 second decision window, I go for bringing it outside, my 'pliers' are maybe bigger than you think, But again, I do not go for max charge current like you do. Mistakes are normal for human neural nets though. This is what I did to some single cells:

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That charge protection baord is this one:

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the fuse is also from ebay, slow blow, so far it did not blow at rated value after 1 minute... :-)

Aha, so basically battery Ri?

Thanks.

When I was very small I used to rip toys apart so only gears etc was left... Just to understand how it worked. Putting it back together was not always that interesting,, if at all still possible.

Reply to
Jan Panteltje

On a sunny day (Sun, 24 Jan 2016 12:59:30 -0800 (PST)) it happened Lasse Langwadt Christensen wrote in :

Great, yes, thanks a lot, finally know what they are called. Jeff Lieberman says the round ones are better?

That is a bit like EU mains plugs (round pins), versus UK and US mains plugs (flat pins). I dunno. ;-)

Reply to
Jan Panteltje

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