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rhinoman avatar image

MPPT 75/15 charging vehicle battery ? How ?

I Have the smart solar MPPT hooked up to my van leisure battery, works a treat. The Van also has a Sargent ECU for Mains hook up. Can I use the "Load" output on the MPPT Victron to somehow charge my vehicle battery when off grid ?? At present Solar panel goes into MPPT and then MPPT to leisure battery. Many Thanks !

MPPT - Solar Charge Controller
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4 Answers
kevgermany avatar image
kevgermany answered ·

If your house battery is the same voltage as the starter it's easy. Assuming you just want to keep the starter charged on a trickle charger.

I installed a basic Orion to cut the house battery down from 24V to 12V. You need a diode between the house side and starter battery. Also resistors to limit current. I was going to build one, but found a German non Victron battery to battery trickle charger designed for this. As I needed the Orion for other 12V consumers, the box and wire were all that was needed. Cost less than 30Euros. The voltage output on the Orion is adjustable, do I set this below 13.5 to avoid overcharging the starter. The trickle charger resistors prevent overloading the circuit and house battery when you start the engine. Works a treat. When first installed the starter battery was a little down. It charged at about 2A. Since then it's never been above about 0.2A and the starter battery sits around 12.7V.


The risk is, of course, that you flatten the house battery. So if you're off grid and no solar, make sure you can switch the trickle charger if needed.

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antiguasky avatar image
antiguasky answered ·

I inserted a 100/20 between my 48V house system and my 12V chassis battery. It’s worked without flaw for the last two years. All primary sources charge the house (except the chassis alternator) and the 100/20 maintains the chassis.

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drlbradley avatar image
drlbradley answered ·

I looked into this too, its not an easy thing to achieve. On shore-power I have an IP22 that charges my vehicle batt, and a multiplus that takes care of the leisure charging. Rumour has it that other manufacturers sell MPPTs that split the solar charge between leisure and vehicle but Im not sure we're allowed to talk about them here?

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dazey77 avatar image
dazey77 answered ·

There is no easy way to do this as far as I know (this question comes up quite a lot and I am in a similar situation to you)

You can have a DC-DC converter to do it but you need to watch creating a loop if you have an existing link to charge the leisure from the alternator.

I went the route of using a second 75/15 with some portable panels for topping up the van battery (but I had this anyway as a portable system)

I have considered a system to allow me to switch the charge output to the vehicle battery but as its lithium and lead acid I think its too open to accidental damage.

I am still considering a changeover system to let the solar input from the main pannels to be switched to my mobile 75/15 for charging the vehicle battery.

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The switch idea is a good one, expensive but workable. Just need to find a suitable switch. Similarly a portable solution might be the way to go. Will have a think on next steps ! Cheers