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msmith1199's avatar
msmith1199
Explorer II
Jul 24, 2023

Electrical/Battery issue.

Question about electrical issue.
I have two 100 watt LiPo batteries. Been dry camping for 7 days now. The first 3 were on the road so batteries were charged by alternator for the first three and the generator only for the last 4. Everything has been going fine until last night. I turned the generator off at 10pm and it had run at least 5 hours during the day, maybe more. But at 1am my batteries died. I knew they died because my CPAP tried to suffocate me! :).

I have a residential fridge and my Satelite receiver was on, but other than those and CPAP there wasn’t much other electrical draw. So the only thing I can conclude is for some reason the batteries didn’t fully charge. They are charging today and I can get power out of the inverter so I know the charger is working.

I’m not much of an electrical guy but I check the voltage at the converter with the generator running and it’s at 14.5 volts. The voltage at the batteries both with the generator running and without is 13.6 volts. I think those numbers mean it’s should be working fine.

The only thing I did different yesterday over any of the other days is whenever I had the generator running I had the A/C on. Is it possible all the power was taken by the A/C and wasn’t going to the converter to charge the batteries? That’s the only thing I did different yesterday over the others.
  • 3_tons's avatar
    3_tons
    Explorer III
    Jul 26, 2023
    You didn’t say how you are determining state of charge…Determining SOC with lithium (LiFePo4) batteries can sometimes be problematic due to what is an uber flat voltage discharge curve, and I would think that running a CPAC is mission critical…Do you have a lithium capable SOC (state of charge) meter such as a Victron Smart shunt, or a BMV-12 or equivalent?? …If not, then it’s gonna be difficult for you to know what your true SOC is - voltage alone may not be telling you the whole story…

    Outside of that, when your battery is undergoing a charge, you’ll need to see a voltage at the terminals of somewhere around 14.2 to 14.6 v and holding to achieve a full charge, yet this will occur prior to a passive internal cell-balancing regime which can usually take (depending on number of less than full charge battery cycling) say another 15-30 min or so - this phase can be readily monitored on your SOC meter via intermittent amps vs volts until holding at near zero amps (assuming no load)…After this, it is best to discontinue longer term charging to avoid the possibility of dreaded dendrite formation that may occur due to such overcharging…

    3 tons

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