RV solar and alternator question

[sdbuck]

Thanks guys! Your answers are the same as I got when I called an RV Solar Installer...the MPPT controller can figure it out...best to keep it all connected.

My batteries are 82AH @ 8hr Rate AGM 12V (two of them). Float charge is 13.5 +/- .06 V. I'm still not exactly sure what 100% fully charged Voltage should be. I've looked at charts online and some say 12.7, others 12.6 or even 12.5 for AGM.

I think my batteries actually go down to about 12.2V without anything draining them (a rear view camera is the only thing I leave on all the time, can't imagine that would drain .3V-.4V off a 164AH battery bank...)

I guess I'll bring the batteries to an auto store to have them tested. I should have 984 watts to play with before draining them past 50% [(82AH x 2 batteries x 12 volts)/2 for 50%) and they seem to be closer to 12.1 after just ~300 watts which doesn't make sense. Unless they're shot. Even then, they function pretty well, just doesn't seem to be as good as they should be if my math is correct.

[Leehamrick]

Boats have two batteries one is for starting the boat and one is for using the running lights at night
when your just floating around at night parting or fishing or what ever. And they work this way.
I'm not sure but I think some how it does it by it's self. I don't know if a switch is used hooked to the
ignition switch or if a diode is used. But yes I would think this would work fine.

[Sunking]

Do not disconnect the alternator/solenoid circuit. The alternator can do more in 15 to 30 minutes than the panels can do in a week. If anything get rid of the panels as they are not contributing much of anything.

[Mike90250]

in a word NO, the alternator and solenoid will not confuse the MPPT controller.
5 minutes of running the engine will put a days worth of solar charge into the battery. So it's likely that

a) the battery is getting old/tired/ruined from being older than 3 years, or not enough sun to recharge it.

b)

Batteries are 6 months old but were constantly under charged before I got the solar panels - they were below 10.5 or 10V once.

That will do them in.


Make sure the solar parts are working well before investing in the new batteries.

[sdbuck]

My RV's (VW Rialta) house batteries are connected to a solenoid that connects to the vehicle's alternator. The solenoid enables the house batteries to be charged while driving, but also disconnects when the vehicle's off so the house batteries don't drain the engine's battery.

My charge controller is the Tracer-3215RN. It's MPPT and has 4 charging stages (I think).

QUESTION:

Should I disconnect the house batteries from the solenoid or alternator so that they're only charging from my solar panels? I feel like the alternator is disrupting the charging phases of the MPPT controller and giving it false voltage readings (while I'm driving and for a little while after, the batteries are at 13.5-14V, even though they're actually between 12-13.5).

The only advantage I see to keeping them connected to the alternator is when the batteries are low, the alternator can probably initially charge the batteries faster than my panels because it's much higher amperage. Also, if my batteries are low at night and I'm driving somewhere, I can charge the batteries a little more. Maybe I should install a switch?

ALSO, my AGM batteries are at 13.5-13.7 and I'll disconnect everything that would drain them. When I come back a few hours later, they're around 12.5V. Is this because they aren't being charged properly (alternator is getting in the way of the MPPT function and not fully charging them) or because my batteries are shot? Batteries are 6 months old but were constantly under charged before I got the solar panels - they were below 10.5 or 10V once.