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Old Jul 04, 2003, 01:39 AM
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LiPo's - what rate to charge at?

I'm all set to try out my new LiPo's... a 2s4p configuration comprised of four packs of the Kokam 2s 1200HC cells. I gather that I should charge them at 1C, but I'm not sure what that means in terms of amps. I am using a Triton charger. Any input would be greatly appreciated!

John Webb
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Old Jul 04, 2003, 03:10 AM
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Stavanger, Norway
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You have 4x1200mAh in parallell = 4,8Ah at 1C
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Old Jul 04, 2003, 09:38 AM
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Thanks Haldor -

The max charge rate on the Triton is 2.5V, so I assume I can't go wrong using that rate.

The max volts charging rate on the Triton is 14.8v... Can anyone advise me if I am safe to use that with my 2s4p configuration?

Happy 4th to all

John Webb
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Old Jul 04, 2003, 10:05 AM
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Deland FL
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Set it for Li-ion charge, 7.4 v, 2.5 A. Should charge in about 2-3 hrs from a discharged (3.0 v per cell) condition. It would be instructive for you to watch the screen while charging - you will figure out what it is doing.

With li-pos you can get about 70% charge at 1c in 1 hr. (since the triton is limited to 2.5A for li-ion (5A for other chemistries), this is true for packs up to 2500 mah. Yours are bigger, so will take longer with this particular charger.

BTW the triton will charge up to 24 cells (Nimh or Nicad), somewhere around 30 volts when needed. But for your lipos, it will top out at 8.40 volts exactly. It will do up to 4s packs (14.8v) on li-ion).

Another interesting limitation with the triton is it is only a 90 watt charger or 20 watt discharger. So you might put in to discharge a 10 volt pack at 3A, but it will only do it at about 2A (10x2 = 20 watts).

John
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Old Jul 04, 2003, 10:24 AM
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John, I think you may have Amps (I) and Volts (V) a little mixed up in your post.

First, It isn't safe to try to charge a 2S4P Li-Ion up to 14.8V. This is the chargers capability for a 4S configuration. For a 2S pack it would be 1/2 that amount. I don't know if you can override the Tritons default constant current charge termination voltage but if you can don't set it to 14.8V for a 2S pack.

In general a Li-Ion charge termination voltage should set to the number of cells in series times somewhere between 4 to 4.3 volts. So for a 2S configuration it should be between 8 and 8.4V. Check the manufactures web site for their recommendations.

Just checking the Tritons manual (I just got one but it's unused so far) it appears they use 3.6V as the basis for setting up the charger times the number of series cells in the pack. So for a 2S configuration you should be setting the charger to 7.2V. I assume the charger uses this as the mid-point for the charge termination voltage but as I said, my charger is still in the box and I haven't got any Li-Ion cells to charge, yet.

What these chargers do is operate in a CCCV (constant current constant voltage) mode. They charge at a constant current until they reach a preset voltage and then provide a constant voltage so they don't overcharge the cells. There is much written in other posts here and on the web regarding Li-Ion safety so I would encourage you to check these before charging/experimenting. Herb
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Old Jul 04, 2003, 04:47 PM
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Herb -

You are right, I meant to say 2.5 amps for the max Triton charge rate, not volts.

I'll proceed with 2.5A; 7.4 volts. Tomorrow I'll finally find out if this LiPo mania is worth it!

thanks for the input.

John
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Old Jul 04, 2003, 06:40 PM
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Let us know, I'm curious too.
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