What do people think about Lipos? (racing packs) in parralell for EVs

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colin9876
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What do people think about Lipos? (racing packs) in parralell for EVs

On ebay there were some 14.4v 4000mah Lipos going for £9 each. I ordered 4 so 2s2p will give me 29v and 8amph
Given these are 15C that will give me more than enough Amps. Im going to try them on an old scooter.
#Just was thinking this is very cheap in comparison to LIFEPO4. It will cost me more to by a charger though, plus Ill have to then charge up all 4 packs!
Has anyone else tried this route?

NeoScootersDotCom
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Re: What do people think about Lipos? (racing packs) in ...

Let me know how you make out with the LiPo's. We also own www.bigrcmodels.com and can get anyone that's interested great pricing on bulk orders of LiPo products. Here's an easy to use chart to match up volts to mah and see what inventory we have that matches up. http://www.bigrcmodels.com/lipo_batteries_launch.asp

Iccarus
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Re: What do people think about Lipos? (racing packs) in ...

you might want to check your website. I checked the price on the 10AH 22.2v 6cell and it came up $9,999.00 a little steep, I payed $300 each for mine. Must be a misprint.

2008 XM3500li Mods/Kelly KBL12251/84v 28cell 40AH pack/ Variable regen brake trigger on left brake handle/Givi/Cycle Analyst/Homemade BMS

KMX Typhoon Home build (recumbent pedelec) with two Astro Brushless 3220motors/twin castle Phoenix ICEHV 160/ Cycl

Iccarus
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Re: What do people think about Lipos? (racing packs) in ...

Colin, Yes we have used these to raise the voltage on an xm3500li to 93v.(4 10AH 22.2v wired parallel to create a 40AH 22.2v added battery) The drawback as you said is you need a different charger. These batteries have much more power to weight and space than the LIFEPO4 batteries but are usually more expensive. I figured I could fit 80AH@72v nominal(88v full charge) of lipo batteries in my 3500li that would give me about 50mph top speed and about an 80 mile range at 35mph. Does anyone know if you can charge these type of batteries with the TSL series chargers from thundersky?

2008 XM3500li Mods/Kelly KBL12251/84v 28cell 40AH pack/ Variable regen brake trigger on left brake handle/Givi/Cycle Analyst/Homemade BMS

KMX Typhoon Home build (recumbent pedelec) with two Astro Brushless 3220motors/twin castle Phoenix ICEHV 160/ Cycl

colin9876
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Re: self balancing batteries?

Well the Lipos arived - great price $15 each 14v 4ah but I had trouble getting a charger Ended up paying about 66pounds (100$) for a Hobby one but even though the pack connector seemed to fit, the charger said no connecion. Really annoying that none of these conectors are to any Standard?
So I had an idea - Brainwave. why not make a self balancing battery by charging all the cells in parrallel from a 4.2v charger!
Anyway I disassembled my Lipo pack and it caught on fire - so Im giving up with them

Still gave me an idea - rather than these electronic bms, why dont batteries have a button that conects all the cells in parallel for a minute or two, that would even out all the cells

Surely someone has thought of this? It would only need a line of contacts that could be pressed on tho all the -ves and +ves of the cells to allow a bit of charge movement to level out the imbalances?

antiscab
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Re: self balancing batteries?

you are correct, parralleling all the cells when under charge will balance out their SOC (absolutely wont work when the cells are not under charge, and will cause all kinds of balance issues).

however, before the cells are parralleled, they must first be taken out of the series circuit (if you dont you short *all* the cells which results in smoke fire and other bad things)
this requires a switching mechanism on *each* cell thats rated to full discharge current (but not necessarily voltage).

if going the solid state route (mosfets and such) you need devices rated to *full* pack voltage and current.
the on resistance easily double the voltage drop of the pack under load.

if going the contactor route, the contacts need to be sized big enough not to cause to much voltage drop.

both approaches increase weight size and cost of the pack while reducing performance.

Matt

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km

colin9876
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Re: What do people think about Lipos? (racing packs) in ...

Yes I was thinking that too, that you would have to take them out of series when you balance them in paralel.However I didnt know you couldnt do this when it wasnt on charge?
Why doesnt a 4.2 volt cell start charging a 3.7v cell if they are just paralelled up (not with a charger?) yoiu would think they would both end up at say 4v??

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Re: What do people think about Lipos? (racing packs) in ...

Colin, did you check the votage on the batteries when you got them? $15 is a great price for those batteries. I keep hoping the price will come down on these. Then we'll be talkin some range and speed with these electric motorcycles. They can be very volitile though as you found out. Don't feel like the lone ranger on that one. At least you didn't pay to much for them. Anyway the charger you bought, was it a balancing charger? From the sound of it your batteries were 4 cells. hyperion makes good chargers, check out thier website. Sorry for your loss...don't give up.
Bill-

2008 XM3500li Mods/Kelly KBL12251/84v 28cell 40AH pack/ Variable regen brake trigger on left brake handle/Givi/Cycle Analyst/Homemade BMS

KMX Typhoon Home build (recumbent pedelec) with two Astro Brushless 3220motors/twin castle Phoenix ICEHV 160/ Cycl

Iccarus
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Re: What do people think about Lipos? (racing packs) in ...

I forgot to say, sometimes if the batteries have been drawn down to low it will say no connection or if the balance lead isn't hooked up. Can you still get those for that price?
PS Don't have anymore brainwaves man.

2008 XM3500li Mods/Kelly KBL12251/84v 28cell 40AH pack/ Variable regen brake trigger on left brake handle/Givi/Cycle Analyst/Homemade BMS

KMX Typhoon Home build (recumbent pedelec) with two Astro Brushless 3220motors/twin castle Phoenix ICEHV 160/ Cycl

colin9876
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Re: What do people think about Lipos? (racing packs) in ...

Yes theyre 4 cells and still for sale on ebay.
U know what I blew another pack yesterday, accidentally shorted one out and it smoked in seconds.
Im working on a new project so had to revert to a string of AA NiCd batteries just to give me my 24v to do some testing and I realised for current draw and sturdiness NiCds are good. Granted I only got a couple of km range but strong!

Back to my Lipo charhging problem (not that Ive got any packs left to test lol) the Hobby charger had a Lipo charger, and a Lipo Balancing charge mode.
The Lipo pack had big RED, BLACK output wires -I guess u use those for standard Lipo Charge?
The Lipo pack also had a small connector with 4 small leads, It was that I connected into the port on the Hobby charger to try the balancing charge but it said no connection. I wasnt supposed to connect the big RED / BLACK Leads to the charger too was I???

antiscab
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Re: What do people think about Lipos? (racing packs) in ...

when one of the cells is at an extreme end of the charge spectrum (ie almost fully discharged or charged), then it will sort of work. but the two cells will only balance voltage, not state of charge.

It is only when the voltage of both cells are held at an extreme end, that both are at the same state of charge.
normally this is done while on charge, rather than discharge.

voltage at no load is a *very* deceptive way of determinig state of charge, yet parrallel balancing relies on voltage balancing.

so two cells at 3.65v each, can be a good 20% SOC apart from each other.
this is actually worse with good quality cells, as the charge and discharge curves are so flat at the middle.

parrallel balancing is also *very* slow when the voltage isnt far above the chemistry reaction voltage.
so the current flowing between a cell at 3.65v and a cell at 3.6v will be minute.

the amount of energy (and AH) a cell at 4.2v can give before it falls back to 3.7v is insignificant relative to its capacity. its just surface charge, caused by the capacitive nature of the two electrodes near each other absorbing the charge due to the reaction side of things going open circuit due to running out of reactants (ie fully charged).

Matt

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km

colin9876
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Re: What do people think about Lipos? (racing packs) in ...

Brilliant answer Matt - are you a Chemist or something lol! Thanks

Still want to know whether I should have connected the main RED BLACK leads as well as the balanicing 4 lead connector when I tried a balancing charge with the Hobby charger. Im now wondering if that was why it didnt work?

antiscab
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Re: What do people think about Lipos? (racing packs) in ...

hi colin,

not a chemist, but an electrical engineer in the making (im 2/3s the way there :p) who spends alot of time talking to the pros in the EV field.

not sure how the RC chargers are made, but yes, i think you should connect the big red and black leads as well as the 4 lead connector.

the 4 leads allow the charger to vary the current applied to each cell to keep the voltages balanced (which when the cells are near full charged will allow the charger to make sure the cells are at the same SOC, 100%).

the two big leads provide the charging current.

i must admit i havent played around with RC balancing chargers before, since all my lithium batteries are either single cells or come with a BMS that does the balancing.

if that doesnt work there is another solution.

you could put a 4.3v zener diode across each cell, such as this one:
http://www.jaycar.com.au/productView.asp?ID=ZR1401&CATID=33&form=CAT&SUBCATID=359

and use a lab powersupply to charge the pack.
just limit current to 0.25A, and wait for the voltage of each cell to reach 4.3v

Matt

Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km

Iccarus
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Re: What do people think about Lipos? (racing packs) in ...

yeah colin matts right, and I'm still sitting here with my mouth hanging open try to get all of what he said. I've used these chargers alot and thats right you have to plug both in. There are some that charge through the balance lead but they are all very low amp chargers. You'll be amazed at the performance of lipo. Yeah I learned the hard way to only have one lead exposed at a time myself. I wish these batteries came with standard connectors already soldered. Not everyone is a solder wiz. You should check out the balance pro cards at commonsense rc. Each card can monitor and balance up to 6cells, they are $39 each.

2008 XM3500li Mods/Kelly KBL12251/84v 28cell 40AH pack/ Variable regen brake trigger on left brake handle/Givi/Cycle Analyst/Homemade BMS

KMX Typhoon Home build (recumbent pedelec) with two Astro Brushless 3220motors/twin castle Phoenix ICEHV 160/ Cycl

Iccarus
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Re: What do people think about Lipos? (racing packs) in ...

Thanks Matt, that explains something. I noticed that at full charge my 3500li had some cells up in the low to mid 4.2os with most around 3.38v average. After a quick run up and down the road they become very balanced and all line up. I guess that burns off that surface charge. I tried riding a little(half mile at full speed) to bring the cells in good balance and then charging again and it seemed to help my range. Is it possible that helps bring the low cells up? Unfortunatly I realize that isn't very scientific. Now I can monitor as I ride with the balance pro cards and realize the value of seeing whats going on under load. I guess now if I see any dropping way below the rest, I know they are going. I think ultimately a computer is needed to record the data and control charging. I guess the pak trakr keeps tack of that data but doesn't balance, it would be nice to have both.

2008 XM3500li Mods/Kelly KBL12251/84v 28cell 40AH pack/ Variable regen brake trigger on left brake handle/Givi/Cycle Analyst/Homemade BMS

KMX Typhoon Home build (recumbent pedelec) with two Astro Brushless 3220motors/twin castle Phoenix ICEHV 160/ Cycl

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