Low voltage - discharging

[Ian Whittaker]

I’m after testing my batteries for a couple of reasons - one, to test and establish the condition of two new (cheap) lipos I’ve just bought, and two, to see the state of my current ones. My charger has a Lipo discharge facility, at 10W. The cut off point is 3 to 3.3v per cell. Surely this is far too low? As I’m using 5000mAh six cell packs I’m looking at at 10 hours or more for the discharge anyhow (less than 0.1C).
I could sit and watch the voltage on the charger I suppose and stop at (say) 20% but I don’t really fancy watchkeeping on the thing for five days!
my other option is just charge the new packs, use them for a short gentle flight then use the amount replaced as a guide - this does seem much more sensible!!

[Tom Gaskin 1]

Certainly charge and use is the more convenient option. 3 volts per cell is fine for the cutoff voltage.

Tom

[Frank Skilbeck]

In some respects look at the capacity of a new Lipo isn't a great measure of how good they are, at a low discharge rate they could have a good capacity, but put them under load and the internal resistance can cause a significant voltage drop across the Lipo and heat build up.

Better to use a watt meter and test them under a real load, or onboard technology which measures current, mah and pack voltage, the Unisens E sensors are great if your radio supports them.