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timmermc avatar image

How to charge additionaly your car battery from solar.

I installed a Victron 200w Bluesolar panel and a Smartsolar MPPT 100/20 in my Campervan, charging one Victron AGM 110Ah/12V battery (I'm not a heavy consumer on power).

I used the 'Gel victron deep discharge (2)' presetting on the MPPT for this battery. This looked fine to me for my Victron AGM battery specifications.

Until now I was completely dependent on two Victron wallchargers, one 15A used for the AGM battery and a small 4A charger I installed nearby the lead-acid battery of the car.

But now that I am no longer dependent on fixed power and love to stay for weeks at the same location without moving or using the engine, I have to find a way to keep the car battery also fully charged. And this is especially important for the following winter.

Unfortunately, the roof of the campervan is not very large, and together with the 200w panel, roof domes, etc. I see no way to install an extra small solar panel on the roof to topup my car battery.

Another option would be to use my Victron Phoenix inverter and connect the small 4A charger to this inverter outlet to topup the car battery, or is this a stupid idea and not possible

I would appreciate very much your suggestions.

MPPT - Solar Charge Controllerbattery chargingSolar Panel
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Charging job well done, needed some 12Ah for a full car battery according to the BMV monitor. No other loads were connected at that time and most of the charging was done after sunset.

2 Answers
JohnC avatar image
JohnC answered ·

Hi Tim. I like your Phoenix/charger idea. I do that myself on my boat, and I added a $5 powerpoint timer to confine the charge times to when the solar feeding the main house bank is in excess of needs.

Works for me, and the cheap option always holds some attraction. Try it.

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thanks for your quick response. Awesome, I connected the small charger to the Phoenix inverter and it works and charges just fine. I was a little reluctant at first to try it by myself, but it does indeed work flawlessly. Using a timer is now also on the schedule. Great tips, thank you very much.

avs_power avatar image
avs_power answered ·

On my van I have used the Cyrix-I, which is the Victron version of a normal voltage sensitive split charge relay... but the interesting bit is the fact its Bi-Directional.

So if your second battery is being charged by another means (mains charger, solar...) as soon as the voltage is high enough on the second battery the relay will click in, and also charge your starter battery.

Its also got other functions like a extra pin on the relay you can energise to manually combine both batteries for 30 seconds... so if you have been somewhere and left your lights on, but you have a full second battery... you can pop a bit of wire on (or ideally attach a little momentary push button dangling under the relay) and you can combine both batteries for 30 seconds, to shove some charge from your second battery into your starter battery.

I think its an amazing relay, and not enough people know about them.

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Would by using a Cyrix-i the lead-acid car battery not being overcharged by the solar?