Motorhome - 2 Batteries

DIY
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1

Can I have 2 batteries connected to a single Cerbo GX system?

My motorhome, like most has 2 batteries. Chassis battery (standard lead acid) and a house battery (Li-ion)

My set up uses all victron equipment and works great, but I want to add a second solar array and mppt charge controller for the chassis battery.

My current set up has a solar array and mppt controller charging the house battery. The house battery has a smart shunt. The mppt and smart shunt communicate with the cerbo GX via VE.Direct. The smart shunt gives me battery voltage / current and temperature.

There is also an Orion XS that charges the house battery from the chassis battery when the motor is running (or when I’m connected to ac - see below). The Orion also communicates with the cerbo GX via VE.direct.

There is a IP22 AC charger that charges the chassis battery, but this does not communicate with the Cerbo GX or anything else. Thus when I’m connected to a 240v shore connection the ac charger charges the chassis battery, which in turn charges the House battery via the Orion XS.

All works fine. I can see the House battery voltage and temperature via the VRM portal and by looking at the Orion XS input voltage I know what voltage the chassis battery is at.

Now the question.

If I fit a second MPPT charger and solar array to charge the Chassis battery and leave it stand alone all will be fine, but I won’t be able to see it via the VRM portal.

If I connect this second MPPT charger to the Cerbo GX via a VE.Direct to USB cable how do I tell / configure the system i.e. the Cerbo to know that there is a second battery and the battery monitoring provided by the Smart Shunt does not apply to this second battery (i e. The chassis battery).

I want to be able to remotely monitor everything, hence the desire to connect the second mppt and thus chassis battery to the Cerbo GX.

Apologies that that took soooooooo many word.

Les

2

No, a cerbo can manage only one battery, it can show the voltage of another.

All features only regard the main battery

3

Hi Ludo. Thanks for replying.

I’d kind 9of come to that conclusion, but hoped someone with more knowledge might show me a workaround, hence asking the question. It would have been nice to be able to get charge stats and control the second mppt for the second battery via VRM.

Just out of curiosity, am I right in saying that the second mppt for the second battery (chassis battery) would receive battery info (voltage in particular) from the Cerbo via VE.Direct and that this info would override it’s own voltage measurements thus it could thus over charge the chassis battery.

This is especially likely in my setup as the house battery is a 3S NMC with a max charge voltage of 12.6v (I actually use 12.3v most of the time) whereas the chassis battery is lead acid thus 14.4v Absorbsion charge V.

Would the 2nd mppt for the chassis battery see the 12.3v from the smart shunt via the Cerbo and then keep ramping up its bulk charge voltage trying to achieve 14.4 and of course never getting there, thus cooking the chassis battery?

4

Probably yes.