thenamshow123

i have a great planes polycharge lipo charger. and it refuses to charge my lipo, which is a greatplanes lipo 1500mAh 11.1 volt battery, the batters voltage is 8.59 and when ever i plug it in, the charger wont charge it...any help would bre great, i need it working by saturday, either batter or charger?


thanks, billy

jdetray

Hi Billy-

Your charger is behaving correctly. You've allowed your lipo to be discharged too far. The charger correctly recognizes that fact and refuses to charge it.

A lipo should never be discharged below 3.0V per cell under load, or about 3.6V resting. For a 3-cell lipo, that's 9.0V under load or 10.8V resting. At 8.59V resting, your lipo is over-discharged and may be damaged.

There are techniques that sometimes work for restoring over-discharged lipos, but I have not tried them. Personally, I would not attempt to use or charge a lipo that was discharged as far as yours. Others may have different opinions.

In any event, there is probably no way to force the PolyCharge to charge that pack. Your charger is doing you a favor!

- Jeff

thenamshow123

alrighty, so all i need is a new battery....and a non expensive one...cause we need four and my friend has 3...are GWS lipos any good...i guess its worth me putting 30 dollars into...


thanks
billy

jdetray

Whichever brand of battery you purchase, be sure it has sufficient capacity and a high enough "C" rating to fly your plane.

For example, GWS makes a 3-cell lipo rated at 1300 mAh and an average discharge rate of 8C. So that battery can supply:
1.3 x 8 = 10.4 Amps

If your plane needs 10A or less, then this GWS pack might be OK. If your plane needs more than 10A, this pack is probably not suitable.

- Jeff

thenamshow123

i have no idea whats going on with Amps and such...its a foamie with a himaxx 4100 and a cc phoniex 35 and a 64 tooth gear and a 10x4.7 prop

jdetray

I don't know how much current that power system draws. The proper way of determining it would be to measure it with a wattmeter.

If your plane flew well with the original (now dead) battery, I'd recommend replacing it with one that has at least the same capacity and "C" rating. Great planes sells two different 3-cell 1500mAh batteries. Which one do you have, their regular lipo or their "Power Series?"

- Jeff

thenamshow123

mine was rated at 8C discharge...so is that good?

jdetray

Hi Billy-

A rating of 8C is neither good or bad. What it tells you is that your old 1500 mAh battery could provide up to 12 Amps.

This is calculated as follows:
1500 x 8 = 12000 mA, which is 12 Amps.

So to be sure your new battery can power your plane, it should also be capable of providing 12 Amps.

- Jeff

thenamshow123

do i want a higher or lower C rating

jdetray

A higher "C" rating is better. It means the bettery can provide more current than one with a lower "C" rating.

For any amount of current that your power system needs, there are many ways to achieve it. For 12 Amps, any of the following batteries would work.

1000 mAh, 12C
1200 mAh, 10C
1320 mAh, 9C
1500 mAh, 8C
1800 mAh, 7C
2000 mAh, 6C

In other words, you need a combination of capacity (mAh) and "C" rating that will give you 12 Amps.

Of course, the larger batteries like the 2000 mAh will be heavier, which can cause problems for some planes. The smaller packs like to 1000 mAh will be lighter but will also have shorter flight times.

The point is that there are many answers. The best one is usually a compromise between cost, battery weight, and flight time.

- Jeff

thenamshow123

ok ill stay between 8-12 "C"s...until my next plane....

jdetray

Remember, it is BOTH the "C" rating and the capacity of the battery that determine how much current it can provide.

For example, an 800 mAh battery that is 12C can not provide 12 Amps. Its limit is:
800 mAh x 12C = 9600 mA, or 9.6 Amps

So pay attention to BOTH values: "C" rating and battery capacity.

- Jeff

thenamshow123

so i know my system has to pull less then 12 amps...cause i always had it at full


-billy