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mikebuoy avatar image
mikebuoy asked

24v Multiplus: Trickle Charing a 12v Starter Battery for Generator?

I have a RV with a 24v Multiplus 3000. This is used in combination with my MPPT charger to charge my 24v house batteries.

I have a generator that uses a 12v starter battery that I would like to trickle charge using the built in Trickle charge connection on the Multiplus:

The install/user guides do not provide any information other than the Trickle charger provides 4A of current. I've measured the voltage coming out of it when I attached my Starter battery and observed current ranging from 13.5v 4A to 16v .5A.

Q1: What is the nominal voltage provided by this connection? 12v 24v?

Q2: Is there any "smart charging" provided by this trickle connection? Or is it supposed to provide a "dumb" flat charge/voltage?

Q3: If this is a 24v connection, what would you suggest for charging my 12v starter battery (there is NO alternator in my system)?

Please share your solutions! I'd love to hear what you figured out.

Cheers!

-Mike


MultiPlus Quattro Inverter Chargerstarter battery
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5 Answers
Charlie Johnson avatar image
Charlie Johnson answered ·

@mikebuoy You could install an Orion IP67 24/12 DC/DC converter between the output of the Multi-Plus trickle charge port and the 12VDC genset starting battery.

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mikebuoy avatar image mikebuoy commented ·

Charlie, I ended up doing as you suggested.

I have a 12v system downstream of my 24V battery, MMPT charger and MultiPlus so I ended up needing the Orion 24/12 70 DC/DC converter anyways.

I set the converter to 13.7v output which is the float voltage for my starter battery and the ideal voltage for my 12v system. Now I have very stable voltage in my 12v system and an ideal float charge on my starter battery. Win-Win solution!

NOTE: I was surprised that the starter battery was able to back feed 12v through the Orion converter into the 24V side of my system.

So anyone doing a similar setup will want to add a battery cutoff switch between the starter battery and the Orion converter (which is a good idea anyways) so you can completely shutdown power from your system.

I may add a diode into the system to prevent back flow past the DC/DC converter in the future but will manage it manually with the battery cut off switch for now.

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Paul B avatar image
Paul B answered ·

On the 24 volt Multiplus the trick charge is also 24 volt


best way is to buy a small 220 or 110 volt 12 v battery charger and connect it to the inverters output and then to the 12 volt battery

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JohnC avatar image JohnC ♦ commented ·

Yeh, I do that with a $5 power point timer set for a few hours of best sun. So doesn't trickle 24/7.

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Paul B avatar image Paul B JohnC ♦ commented ·

Good idea re the timer

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gyrogypsy avatar image
gyrogypsy answered ·

Could this be done by using a simple 13V Zener diode to the 24V bus?

I like the cheap AC powered trickle charger idea too.

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gwbn avatar image
gwbn answered ·

well, i dont have an answer, but sit with the same situation.... Would like Victron to answer this from their tech side. or at least explain what the thinking was to have the trickle charge point

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jaime-garcia avatar image
jaime-garcia answered ·

I also have the same questions. I do have the orion 24/12-70 converter as well but would prefer a smarter device to charge my 12v gen batteries as well as my 12v chassis batteries. I was thinking of going with the 24/12-20 Orion but all these components keep adding up to be way too expensive in the end. Also, I wanted to be able to charge the 24v system via my 12v chassis/alternator so I suppose I would have to get the 12/24-10 Orion as well?

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kevgermany avatar image kevgermany ♦♦ commented ·
Basically you need chargers in each direction. Preferably isolated.
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