antone avatar image
antone asked

My auxiliary battery died after i installed solar system, is my installation is wrong ?

Hello everybody.

6 month ago, after installation of my solar system on my camper van, I observed an unexpected phenomena on the Bluetooth monitoring : engine off, after a sunny day charging, the regulator was floating. But as soon as i turn engine on, regulator show a high charging current as the battery needed bulk charging. I could observe that the current was directly linked to the sun exposure (instantly lower when driving in tunnel or under a bridge).

At first, i thought it was normal, perhaps with engine on and engine battery + alternator entering the system, the solar controller was kind of lost.

But few weeks ago, my auxiliary battery when totally dead. It can't keep the charge.

So now i try to understand why my battery died before i replace it.

my configuration is :

- SmartSolar 75/15

- Backcontact solar panel 210W

- Pb auxiliary battery 100Ah

- Pb engine battery 110 Ah (link between the two battery is the original VW T5 system made with a simple relay the connect "on contact" or "engine running", not sure

- 12v Dometic cooler, Led lights, etc. Yet not connected to the load output but directly to the battery (planned to connect to load later because i didn't finish global wiring)

Ideas to explain battery death :

- fridge connected to battery while controller trying to charge messed up the process ?

- problem with alternator charging and messing up with controller ?

- normal end of life for the battery. Strange because i used it for one year using fridge and only charging with engine, and it didn't seemed to be damaged.

So thank you very much even if you managed to read all my message ;P and i would be glad to have your point of view on this problem.


MPPT Controllersbattery chargingalternator
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2 Answers
asea avatar image
asea answered ·

Is the solar controller connected to the Aux battery or start battery. It should only be connected to the Auxiliary battery. The house systems and Auxilary battery need to be isolated from the start battery. There also needs to be a charging circuit from the Start battery to the Auxiliary so the alternator can charge the auxiliary battery and isolate the batteries when the ignition is off.

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antone avatar image
antone answered ·

Yes Solar Controller is connected to Aux Battery. Aux and Start battery are disconnected as soon as the engine is off (simple relay).

I also saw yesterday that the Aux battery is a standard start battery type, not AGM or Gel. Perhaps the cause is here

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