Frank avatar image
Frank asked

Charging batteries only with solar energy and only from grid when almost empty

Hello i have installed this system on my boat. See drawing.2022022401 - Bootschappen-1.pdf

Quattro 12/5000/220, solar MPPT’s, lithium batteries, VE.bus,Cerbo.

Purpose: To use as much solar energy as possible, and only use the shore connection or generator when no sun or too much energy needed.

Problem: When I connect the shore connection the quattro starts charging immediately to 100% SoC and keeps the batteries full, so no solar power harvested. Offcourse I disconnected the shore cable, and for a couple of days we used solar energy, but this night the alarm went of and the complete system had a shutdown at 40% SoC. When connected the shore cable, the quattro immediately charged the batteries to 100%. I have read about ESS, but it is stated in the manual that this should not be used on boats...

Solution where I am looking for:

  1. In case of shutdown due to low voltage, the quattro only charges enough to keep the 12 volt system running and keeps the batteries available for harvesting solar energy.
  2. Shore connection keeps available at all times, except when sailing, for if there’s no sun for longer periods.


  1. How come that it shuts down at 40%, lithium is supposed to be used until 5% right?


MultiPlus Quattro Inverter Chargercerbo gxoffgridsolar
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1 Answer
JohnC avatar image
JohnC answered ·

Hi @Frank

It's possible to do this, maybe in varied ways. And your needs may change in the detail, but taking them as stated..

Have a look at the Quattro's Charge Current Control Assistant, which can vary the shore sourced charge based on the status of an Aux input. Then the Cerbo's Generator Start/Stop function (Quattro has this too, but not as good as the Cerbo's). Which you could use to provide the signal to it based on (say) SOC. Add a signal wire pair between the Cerbo relay and Quattro Aux port (that one should pull up to 5V when open). With this you could set shore charge to happen only between say 45 to 50%.

If you wanted to make some room in the batts, the IgnoreAC (in Assistants) functionality can shut off both charging and loads in a similar way.

You might also want to charge up fully before leaving dock, and a manual switch could work there alongside that wire pair.

Sure you'll need to delve a little, but a great way to learn about your system. Your 40% shutdown may be a BMS/settings thing, but I'm unfamiliar so can't comment. I don't like system crashes though.

To give solar priority with both chargers on, set the Quattro's Absorb setting maybe 0.05V lower than the mppt's (DVCC on too).

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Frank avatar image Frank commented ·

@JohnC thanks I will try with the IgnoreAC

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JohnC avatar image JohnC ♦ Frank commented ·

You won't need the wire pair for just that, it can all happen in the Quattro.

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