Battery Charger. Victron Pallas 12/25

DIY
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Hello,

I am writing to ask you a question about one of your products.

On my boat I have installed a Victron Pallas 12/25 battery charger connected to two 12v 105 amp batteries (VMF VDC31M). This means that the capacity connected to the Victron charger is 210 amps. These batteries are charged by the Victron charger when shore power is available and by the engine alternator (Volvo Penta 2002, 18 HP) when the boat is underway.

These two batteries are connected via a 1/2/BOTH switch, so one would be the engine starting battery and the other the house battery.

However, the person who sold me the boat recommended that when using the batteries I should always keep the switch in BOTH. And that in the event of accidentally discharging these two batteries, there is a third 12v 76 amp starter battery on the boat completely separate from the rest of the electrical system, which is only connected to a small solar panel that keeps it charged.

As this system does not seem to me to be very suitable and I would like to know precisely what the level of all the batteries is at all times, I have purchased a Victron BMV 712 Smart Monitor.

I would like to redesign the battery layout to include the 76 amp battery (another new battery of the same capacity) as the starter battery and monitor it with the BMV 712 Smart.

So I would have one 12v 76 amp battery as the starter battery (switch position 1) and two 12v 105 amp batteries in parallel as the house battery (switch position 2), plus the Victron BMV712 monitor.

My question is: can I redesign the electrical system in this way and keep the Victron Pallas 12/25 battery charger? Because in the user manual of this model it says that “The maximum charging current is 25A and the recommended battery capacity is 100-200Ah”.

Therefore, if I add the capacity of the three batteries in the new distribution (105 + 105 + 76 = 286 amp) it would be somewhat higher than what you recommend in the manual.

But, although in the new layout the 76 amp starter battery would be connected to the main system (and thus also monitored by the BMV 712) it would not be used as a house battery, only as a starter battery, and therefore would not need to be recharged as frequently as the two 105 amp batteries.

How should I redesign the
Would this be possible, would it only affect the charging speed or would it be something that could damage the system? In case it is not possible to charge all three batteries with the Pallas 12/25, could I charge only the domestic batteries and assume that the starter battery is charged only with the engine alternator? Could I in the latter case monitor the starter battery with the BMV 712?

Please let me know your opinion on this. Thank you very much for your help.

Best regards,
Marcos

2

Good system, keep it.

3

Hello Ludo,

Thank you for your answer. Just one last question. When you say it’s a good system, do you mean the one I currently have (Pallas 12/25 + 2 x 105 amp batteries) or the modification I want to make (Pallas 12/25 + 2 x 105 amp batteries + 1 x 76 amp battery + BMV 712 Smart)?

Thank you very much for your help.
Marcos

4

Imho what you have makes more sense then your proposed modifications.

5

Hi Ludo,

Ok, thanks for the advice. I will leave it as I have it then.

And do you know how I should install the BMV 712 (which I have already bought) to monitor the two 105 amp batteries? Because I don’t know if it would be like in figure 11 or 12 of the “Quick Installation Guide” of the BMV 712. Because depending on if the switch 1/2/BOTH is in one or another position I think it could be considered as a house battery and a starter battery (fig. 11) or two batteries in parallel (BOTH fig.12) isn’t it? So how should I connect it to have all the information of both batteries?

Thank you very much for your help Ludo.

Best regards,
Marcos

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Insert them in the “minus to ground” wire of both batteries seperately.

Connect one of the aux wires to monitor the small battery.