On Wednesday, September 11, 2019 at 5:19:03 AM UTC-7, wrote:
On Wednesday, September 11, 2019 at 7:15:06 AM UTC-4, Jim White wrote:
At 00:23 11 September 2019, 2G wrote:
? The only way to know with any certainty the energy content of a battery
i=
s to do a discharge test. This can be done very easily with an FES - you

Coulumb counter should do it. Count the coulumbs in and out.

Jim

A Coulomb counter counts electrons, not energy (Coulombs times voltage) - some energy is lost to internal resistance, thus the output voltage is lower. Also some Coulombs are lost to internal self-discharge. The energy coming out is always less than the energy going in. That said, as long as the battery is behaving consistently these losses are predictable, albeit variable with time since charge, temperature, discharge rate, etc. And the prediction will be wrong once some deterioration happens inside the battery.

And the device would have to be calibrated anyhow by doing a discharge test.. That said, it would be useful to have an accurate battery fuel gauge in the cockpit. I would not, however, recommend that the average glider pilot install any instrument that requires modifying high voltage/current circuitry. Doing a discharge test, on the other hand, only requires a stop watch.

Tom