RV solar and alternator question

[Wy_White_Wolf]

Sunking - my batteries are brand new. 180AH 12V. Im trying to run a 7amp fridge off them and the 190w panel. I expect to be able to suck at least 90ah from the battery after sundown, but the battery goes flat (the regulator disconnects it at 10.5v) about 2 hours after sundown. So I must conclude the battery was not fully charged by solar. Ok fair enough BUT if I have been driving all the day, the result is the same. So I conclude the alternator is not charging the battery. Why? I assume because the solar panel lifts the battery voltage up enough to confuse the alternator not to charge it.

Wy_White_Wolf - yes if we assume both solar and alternator charges the battery by presenting 13.47 volts to it, then if the solar is doing that, but only pushing small amps, then the alternator wont push amps, even though it has lots more available.
I am assuming that with charging happening, the battery voltage reads 13.47 volts, BUT it is not necessarily fully charged. Am I correct?

No. You need to quit assuming and learn. Reread what was wrote before.

Your system is shutting down after 2 hours because it is undersized for your load. 7amps at 50% duty cycle is over 1000WH a day. Your panel cannot supply that.

Your solar is not shutting down the alternator. Your battery does because it's reach the SOC/voltage that the alternator is designed to charge it to.

Actually it sounds more like you have a loose connection or something in between the battery and alternator that is causing a voltage drop so it can't properly charge the battery. Your alternator puts out 13.47 but only 12.5 or so is reaching the battery from it. That is why you can drive all day and still have the problem that night. Your solar panel is to small to handle the load by itself. But it is not what is shutting down the alternator.

WWW

[Wy_White_Wolf]

Are you running a diode type battery isolator? If so, that is causing the problem.

WWW

[SimonHiluxGalaxy]

The isolator came standard in the Hilux motorhome. I'll do some research/testing on it !

[Sunking]

You need an Isolator that replaces the Voltage regulator in your alternator like Sure Power. The diode types and mechanical should be avoided. But your battery is way too small for the job, and the panel is way undersized making it useless.

The fix is a 12 volt 400 AH battery and a good Isolator. Want solar? Think 500 to 750 watts.