Solar panels and lithium batteries

prstlk wrote:

We are boondocking and run the generator until the panel shows full but we run out of power in the middle of the night. Both of us have to use CPAP machines so this is not a good thing. We make sure that everything else is shut off even unplugging the coffee pot and TV.

This is a very common practice and also the biggest mistake many make when charging their Lead/Acid batteries. Generally a converter (powered by generator or shore power) can charge a discharged battery to about 90% in a few hours. The catch is that the last 10% can take the same amount of charging time (or more) to finish replenishing that last 10%.

The LED indicators supplied by most RV manufacturers are responsible for more battery deaths because they lull people into thinking the battery is charged.

A good battery monitor like those from Victron or a Trimetric will prevent a lot of early battery deaths from partial charging and the resulting sulfation that eats away at the battery's capacity.

If changing to LiFePo4 batteries one of these monitors is almost essential as the LED gauges will show a fully charged battery until the LiFePo4 battery is almost dead. All due to the battery voltage curve during discharge.

Yes, the mentioned Battery Monitors are more expensive than the LED "gauges" and some of the cheaper monitors on the market but they give a far more accurate display of battery State of Charge. Properly set up (which is easy) one can see with great accuracy when it's time to shut off the generator.

As for Lithium batteries, I have two of them I charge with a portable 240 watt solar kit (self built) that has cut my generator run time to only days when it's too overcast and raining to get a full charge. My last week long trip resulted in NO generator time at all, even with watching movies in the evening and using the microwave several times per day.

BTW, 5 year old Lead/Acid batteries are pretty much at end of life. Fact they won't last the night is a good indication.