On Friday, May 8, 2020 at 3:21:11 PM UTC-4, John Silverberg wrote:
Hi,

I'm hoping someone with experience with K2 batteries can help determine if mine are due for replacement. I have dual K2 batteries wired in parallel to supply avionics power. I have an LX9000, S8 and V8 varios, trig transponder, FLARM core, and becker com radio running off them. I'm not sure how old they are but they're at least 3 years old as this is my 3rd season with the ship. Yesterday, after a little over 5 hours I got a low battery warning with the batteries at 11.3 volts. I had all the above avionics on but did virtually no transmitting on the com, just listening. They were fully charged at takeoff.

I'm not sure if this normal endurance for these batteries or not, any advice would be appreciated.

Thanks,

John S.

John: At 3 years of age the batteries (I assume they are LiFePO4 type) should hold almost as much charge as new ones, assuming they were stored under reasonable conditions (not in a hot trailer). You know from your experience what is normal endurance with your avionics, so compare with that. If this is way lower than normal then that's bad news. But try recharging them and trying again, perhaps the capacity will return. Was this the first use after the winter lay-over? Some types of batteries need "exercise" after a long rest, although LiFePO4 are less prone to that AFAIK. If there is still an issue, try using one battery at a time, perhaps one is bad but the other still good.