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Li-poly life and charge rates

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Li-poly life and charge rates

Old 08-26-2004, 01:53 PM
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scottm
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Default Li-poly life and charge rates

I have bought 9 li polys in the last year, and some are down to half capacity after 40 to 50 cycles. They have never been discharged to 3.0 v or less, and I charge them on a Triton at 1C. What is the recommended cycle frequency - how may flights/recharge cycles per day? I sometimes charge mine 2-3 times per day, but I let them cool off before recharging.

Also, what is normal life for a li-po, in charge cycles? 100? 1000? Will charging them at less than 1C improve life?
Old 08-29-2004, 11:22 PM
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Foamaholic
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Default RE: Li-poly life and charge rates

You aren't exceeding their maximum amp draw rating in flight are you?
You seem to be doing everything else right.
I've heard charging at less than 1C extends their life, but not all that much.
I don't think cylcing them will help like it does nicads.
Old 08-30-2004, 07:40 AM
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Matt Kirsch
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Default RE: Li-poly life and charge rates

I've always thought that the "X cycles/day" thing is poppycock. The cells have no sense of day or night, or of time for that matter. As long as they don't get too hot, you should be able to charge them as many times per day as time allows.

40-50 cycles? Sounds like you're pushing them too hard in flight to me. What cells and what are you running them in?

Be aware that just because a 1500mAh cell is rated at 8C (12 Amps) for example, that does not mean you can draw 12 Amps from beginning to end in all situations. Poor cooling, which can happen even if the cells are hanging out in the open air, will allow the cells to get too hot, and cause damage. Encouraging good airflow with baffles and properly proportioned inlets and outlets, and limiting static running to a few seconds will do much to extend any battery's life.
Old 08-30-2004, 08:28 AM
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scottm
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Default RE: Li-poly life and charge rates

Thanks guys. I ran them mostly on a Wattage Live wire with a gws 350c with c gears and a 1047 prop, with amp draw around 7-8. The ones that have lost capacity are 2 cell Thunderpower 1320's and a Kokam 1500. I now have an Insanefoamies.com Edge with a Park 370-4100 and 3-cell Etecs, drawing 8 amps. I have had no trouble with 5 E-tecs - they are excellent!

Matt, I always thought it was silly too, but allegedly ni-mh batts have the most trouble. The e-tecs have spacers between the cells, so I set them on a fan and cool em off before recharging. I think most of my problems were with cells that can't take 5C rates. Even the yellow stripe TP's don't like 5C, despite the claims.

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