Charging Batteries

[Ed Hardin]

I got my Multiplex charger and 1300mhr 8.4V battery packs in the mail this week. I figured out the fast charge stuff ok (0.7A charged them first time). The instructions talk about charging/discharging cycles for up to 5 cycles. So my question is: do I need to discharge the batteries before charging or will the flight discharge them enough. The batteries feel pretty warm after the flight. I am talking now about contest conditions. Is it desirable to do the charging/discharge cycles at any time? Does that make the batteries any better or give longer life.
Thanks,
Ed

[Jim Jennings]

Ed, Chuck Groth is the guy that should answer this. I cycle mine a couple of times a year depending on how often I fly (RC) without a noticable difference. Perhaps Chuck will chime in. The NMiH cells that I use in Electric B get hot at charge and discharge. They will only get used twice in a years time so cycling once a year is enough.

[CHARLES C GROTH]

Hi,

You say this is an 8.4 volt 1300 mah pack so I assume it is 7 NMH cells of 2/3 A size weighing about 21 grams per cell. If this is so, 3/4 to 1.5 amps ought to be about right. It should take between 30 minutes and 1 hour to charge an empty pack, the potential across the pack should not exceed 1.65 volts per cell (11.55 volt for the pack), and the pack should not be hot when charging. At the end of the charge it should be pleasantly warm. Cycling occasionally helps but is not neccessary every flight — just top it off to peak. A slow C/10 charge is advisable the first time you charge to prevent overheating the weakest cell. I wouldn’t completely empty the pack either — take it down to 7 volts (1 volt per cell). When you cycle it, about 3 amps is good — I use two 1156 auto bulbs. If your pack is lithium, disregard this.

Thermals,
Chuck

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