5w 15v solar maintainer

Interesting point. Around 90 degrees out and the battery box was in the sun when I measured it.

That's one of the reasons I cannot bring myself to mount the Deka AGMs on the TT yet. Parking spot faces south and it seems wrong to leave them there to cook.

Jim

Brand new battery maintained by a low max volt low power solar panel to avoid sulfation having a resting voltage of 12.9 if ambient temperature is high seems reasonable.

My boat batteries disconnected for 3 months in winter typically still read 12.8 when put back in service. They are maintained by a small solar system during the season (30 watt with morningstar sunsaver) but disconnected for winter storage

At any rate, don't count on the suspect reading of 12.9 volts to add up to any more minutes of useful time.

It is a decent but not great meter. An Amprobe AM240 with auto off to conserve battery. It agrees to within 3/100ths of a volt with 2 turnigy and 2 watts up meters. The odds of a surface charge after a month are pretty much 0 I think.

Jim

I would put a load on the battery for about 5 minutes, and recheck the voltage.

A surface charge would disappear. The same reading means your meter is reading high. I would replace the meter, or at least the meter's battery. If it's still 12.90 volts, get a better meter.

By the way, if you remember back in March we were discussing upper limits of voltage for charging batteries under different temperatures. My Schumacher SC-12000A Speed Charger reached 16.1 volts while finish charging between 90% and 100% (full cutoff) when charging @35F ambient temperature.

Last week I got chances to recharge the battery twice. The first time the charger reached 15.7 volts after 90% @ 65F ambient temperature. The second time the charger reached 15.3 volts after 90% @ 82F ambient temperature.

While the charger does not have a thermistor to read temperature, it does use programing to limit the maximum force (voltage) output to keep the battery from over-heating (per the manual).

Mark B.