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Old Dec 05, 2012, 05:35 AM
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These smoked traces were most likely the effect of wrong polarity.

I strongly doubt that the equalisation current can reach such high values, but I will make a test to be sure.
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Old Dec 05, 2012, 08:59 AM
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Unfortunately, not true Julez. Equalization current can easily smoke traces.

Quicky math with a fully charged 5000mAh cell with 1mOhm IR and a discharged cell of same specs:

2mOhm (aggregate cell resistance)
30mOhm (aggregate balance tap / connector resistance)
1.5V differential

1.5V / 32mOhm = 47A at connect.

Wimpy traces don't have a prayer. Suggest you use large packs with low IR and large voltage differential in your test to replicate the real world conditions of our RC Groups friends.

Agreed that with small packs with high internal resistance and low voltage differential (.1V/cell) there won't be an issue. However, with large capacity cells and larger voltage differential, making a universal recommendation without a disclaimer will alienate some folks as there will unquestionably be more smoked traces. The most disturbing part is many may never know since they're charging in parallel and could experience a lipoly fire as a result.

Mark
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Last edited by mrforsyth; Dec 05, 2012 at 10:39 AM. Reason: correct typo in units.
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Old Dec 05, 2012, 09:50 AM
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It is really a best practice to parallel charge packs with a 1.5v voltage differential?
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Old Dec 05, 2012, 01:25 PM
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Quote:
Originally Posted by mrforsyth View Post
The most disturbing part is many may never know since they're charging in parallel and could experience a lipoly fire as a result.

Mark
Wow, I have many parallel boards, and never ever thought about that possibility. I guess I would have smelled something if any traces burned away, but sure enough, I'll get the multimeter out tonight, and check them up just in case (and everynow and then after that). I'm a bad boy, and while you're discussing which one to plug first, I randomly plug mine, depending on which wire get in my fingers first when I grab a battery. Though, I always use a timer, and if for any reason, one battery is not used until the timer goes off (ex.: crash), then I charge that battery by itself. Otherwise, I know my batteries are always very close to each other. But it only bad management once, and take a full battery to make a mess I guess. Thanks for the tip!
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Old Dec 06, 2012, 01:53 AM
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Quote:
However, with large capacity cells and larger voltage differential, making a universal recommendation without a disclaimer will alienate some folks as there will unquestionably be more smoked traces.
Ok, I will add a warning until my tests are finished.
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Old Jan 28, 2013, 06:24 AM
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hi all.

just stumbled across parallel charging. didn't know it could be done.
this will save me a bunch of time charging big 6S 8000 packs !

i have 4x zippy 6S 8000 packs, wired up for 12S 16000 for use on my ebike.
what i want to do is permanently wire up 2x 6s packs in parallel using these parallel adapters from Hobbyking
http://www.hobbyking.com/hobbyking/s...arch=ec5%20par
and permanently parallel the balance taps using this http://www.hobbyking.com/hobbyking/s...=6s%20parallel

then parallel charge the pack as one 6S 16000 pack.

i would have 2x 6S 16000 packs and series connect them before the controller, giving me the required voltage for the controller.
i would split the series connection for charging.
and charge each 6S 16000 on a separate charger

as these would be permanently paralleled packs, as long as i make sure that the packs are within 0.050 volts (per cell)
it shouldn't matter if i connect the balance leads of the main leads first ?

this will save a boat load of time, as i currently charge each of the 4 packs on it's own.

now ill be able to charge 2 at a time, and having 2 chargers (now) means i can charge them all at the same time.

for reference, my chargers are the turnigy fatboy 8 chargers, and i have a meanwell 1000w PSU.
i know i wont get the maximum rates from the chargers with this supply, but it's still way quicker than what i have been doing till now.

i will also run a lipo alarm on each 6s 16000 pack for low voltage warning, set at 3.5v / cell.

can anyone see any major issues with this setup ?

Jason.
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Old Jan 28, 2013, 08:58 AM
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Hi Jason!

Everything is fine as you describe it! Even 0.1V difference won't be a problem.

You could even charge all your packs at once on one charger using such a parallel adapter:

http://www.progressiverc.com/adapter...arallel-boards

I charged my 16s 16Ah ebike battery with less than 4A current, and it was always fully charged in the morning.
So unless you are in a hurry, I wouldn't take higher charge currents than neccessary.
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Old Jan 28, 2013, 06:46 PM
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thanks for the confirmation.

Jason.
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Old Feb 03, 2013, 02:35 PM
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Can we have this thread stickied? Very valuable info here, couldn't find it again to recommend to someone
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Old Mar 01, 2013, 11:00 AM
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I didn't realized that different lipo capacity of the same Voltage can be charge in paralleled i always thought that it all needs to be the same capacity. Thanks Julez.


Just would like to confirm that charging this packs in paralel is safe (same state of charge)

2 x 6000mah 2S
2 x 5800mah 2S
1 x 5000mah 2S

in total there are 5 packs in total of 33600mah capacity in 2S configuration. Since my charger only got up to 10A (icharger 106) i'll set it to 10A and still saves charging time compares to charging them individually?

Thanks
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Old Mar 01, 2013, 11:43 AM
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Quote:
Originally Posted by rizky_p View Post
Since my charger only got up to 10A (icharger 106) i'll set it to 10A and still saves charging time compares to charging them individually?
Assuming that you'd normally charge at 2C or more (most modern batteries can take at least 2C), with "only" 10A capacity you wouldn't really save all that much time, except for the fewer unconnect/reconnect periods.

Even your smallest battery - the 5000mAh - could max out your charger at 2C, so by connecting them all together (33600 mAh), your max charge rate drops down to around 0.3C, and that's not going to save significant time.

Now if you had a bigger charger, say 30 or 40 amps, yes, you'd certainly be saving time to charge all that in parallel.
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Old Mar 01, 2013, 11:58 AM
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Quote:
Originally Posted by H2SO4 View Post
Assuming that you'd normally charge at 2C or more (most modern batteries can take at least 2C), with "only" 10A capacity you wouldn't really save all that much time, except for the fewer unconnect/reconnect periods.

Even your smallest battery - the 5000mAh - could max out your charger at 2C, so by connecting them all together (33600 mAh), your max charge rate drops down to around 0.3C, and that's not going to save significant time.

Now if you had a bigger charger, say 30 or 40 amps, yes, you'd certainly be saving time to charge all that in parallel.

I normally charge @1C and no higher.


Thanks,
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Old Mar 02, 2013, 09:31 AM
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Then it would safe you some time, and quite a bit of hassle.
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Old Mar 02, 2013, 10:05 AM
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Quote:
Originally Posted by Julez View Post
Definitely not. The lower the power electronic components have to deal with, the longer their lifespan will be. It is even an exponential corellation, like half the power gives you 4 times the lifespan.
New to this

Looking at the PL6, Are you saying that useing it at it's 30 amp rating will shorten life? And does charging battery's at 3c to 5c makes a measurable difference in battery life.

It was my understanding that it made no significant difference.

Dennis
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Old Mar 02, 2013, 10:09 AM
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Your understanding is correct Dennis.

My iChargers have been run at full current on nearly every charge since the day I bought them several years ago and they're trucking along just fine. All well-designed electronics have headroom built into the design so I would not worry at all here.

Also, there's zero conclusive evidence that demonstrates that 3-5C charging has any deleterious effect on the usable life of a lipoly.

Mark
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