Scale Soaring UK

Peter Balcombe wrote:
I wonder if the batteries were 'run in' at all, as I understand that higher power LiPo batteries need a few initial gentle charge/discharge cycles before they learn what their real capacity is. Maybe, a failure to do this can shorten their effective life.

Thanks Peter

No, sadly they weren't. I was not aware of that issue at the time but will certainly do so with any new batteries.

Chris - for 25 to 35C, read 12.5 to 17,5C, which is probably much closer to the truth for those batteries. As John said, better batteries required.
It's OK to leave Lipos fully charged for a day or two, but every day more than that will shorten their life. Discharge to 3.8V per cell for storage. I keep all my batteries in a beer fridge at a constant 5C, winter and summer. In a steel cabinet in a garage, the temperature is going to vary quite a bit. The cooler the better really, but you don't want to freeze them.

Gordon

Chris - fully charged Lipos will normally hold their charge for years. However, if left fully charged, their internal resistance slowly increases, which will reduce their capability to deliver current. You may also find some loss of capacity goes with this and some puffing up of the cells. Store them at 3.8Volts if you possibly can. Most modern chargers have a storage mode which will bring the batteries to the correct level.

Mark - This happens with all Lipos, just that the more expensive ones will probably take longer. The new Turnigy Graphene cells may be less prone to doing it, but they're too new at the moment to know for sure. Li-Ion - not sure to be honest.

Many thanks everybody for the various thoughts. I will progress this over the next few months and let you know where we get to.