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customfab asked

Adding addt charger to Multiplus 3000 for 2nd solar battery bank?

Need some advice and recommendations. I have a Multiplus 3000 120V with MPPT 100/50 Solar charger. I have two Deka 8c6V batteries currently configured in the system for 660 AH. This is not enough power when we are boondocking. I was to add two additional Trojan batteries (L16 series) so I can add another 780 AH to the system.


I know the Multiplus offers a 2nd built-in trickle charger. I want to hook-up a quicker 5-stage charger to the new batteries (ideally). The trickle charger won't cut it as I'll be waiting days for the battery to reach full charge via solar. I have 3 large residential solar panels on my RV.


Suggestions on best path forward? Can a seperate Victron charger be configured within the system? Or better suggestions?

One of my issues is that my existing Deka batteries are 3-4 years old. I also prefer to go with the Trojan L16s as I have two different battery banks.


battery charging
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kevgermany answered ·

The trickle charger is only really useful for keeping something like a starter battery charged when the vehicle isn't in use e.g. boats/campers.

You can use any of the Victron chargers in parallel with the multi, but make sure all have the same settings.

The concern is the battery mix. Two things, they may require different settings and the old/new mix. This will lead to uneven charging and load distribution.

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customfab avatar image customfab commented ·

Thanks. It has been about 4 years since I originally installed this system so my head is a bit fuzzy on all the features and cross-capatilibility.


So yes, I would defintely prefer not to have the main charging (5-stage) tied to my original battery bank (4 years told....660AH combined) + a new battery bank (780AH). Same battery chemistry but different manufacturers and sizes of batteries. And 4 yrs old vs new.


Is there a way to get the Multi 3000 to control a charger like the Smart IP43 charger which can put out at much at 50As. I'd like to ideally have the IP43 charger wired / tied into the Multi 3000 so I'm utilizing the solar current for charging. Versus plugging the unit into a 120V socket and then relying on the inverter to draw the charging power from the existing batteries. Hope that makes sense. I feel it is inefficient setup this way.

If I recall correctly, my panels can put out about 60A per hour with maximum sunlight. So in a ideal situation, the Multi 3000 is providing that solar current to both 5-stage chargers.




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kevgermany avatar image
kevgermany answered ·

The ip43 has a VE.direct interface, can connect to a GX device for integrated charge control with the multiplus. But that doesn't solve the unbalanced battery situation.

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JohnC answered ·

Hi @customfab

Not sure why you think a '5 stage charger' is needed for the new batts.

I'd put them all in the same bank and charge them together. You only have a 100/50 mppt to charge them all, so 50A into 1440Ah is a very mild charge rate. And indeed your system's inherent weakness, a lack of solar power. A common design yardstick for Pbs is 10% A/Ah, so you're well short there.

Each string of 2 batts the same type, similar chemistry, they should just follow each other up in V without any detectable signs of charge rejection or string preference.

And when you can find an external ac charge source, just use the Multi for both strings together as well.

If it makes you feel better, perhaps ease back on Vabs from (say) 14.4V to 14.2V. No real reason for saying this though.

Note though, never mix different batts in the same series string, that's a definite nono.




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