question

0xana avatar image

Sources combined exceeding max charge current - solutions?

Hi,
I am putting together the electrics for a camper van. I currently have the following items:

- Multiplus 12/1200/50
- SmartSolar 100/30 with a 350 Wp solar panel
- BMV-712
- SOK 206 Ah Lithium Battery (Max charge current 50A, max discharge 100A)

I have two points that I need some help figuring out:

(1) I realized that the max theoretical charging current (shore power + full solar) would be 80A, exceeding the battery's charge current of 50A. Would this be a problem? I found that a Cerbo device can be used to limit the charge current to the battery. I feel like this a relatively advanced device for my simple system (and it adds to the costs as well). Would it be highly recommended to get one, or are there other options?

(2) I would also like to be able to charge via the (smart) alternator. Initially I thought I could use a cyrix-ct, but with the 120A rating this would not work with my battery, correct? (Even disregarding the fact that solar charging wile driving would even add more current). I am trying to figure out a solution that could charge my batteries without killing them, and prioritizes solar over alternator. I came across the Orion DC-DC charger, but because it does not connect with a Cerbo device I would not be able to prioritize solar, correct? Any other methods?

Thanks!

battery chargingalternator
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6 Answers
kevgermany avatar image
kevgermany answered ·

You need to check, but I think your battery has a built in BMS which will limit input current.

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It indeed has a BMS, but I'm not sure if it will also limit the charging current when the battery has not reached full charge yet. Couldn't find anything Googling around so I'm going to try to check with the manufacturer.
0xana avatar image
0xana answered ·

I've contacted the manufacturer and the BMS will noot limit the input current, put simply shut off at ~70A. Any advice regarding my initial questions?

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bluejeans avatar image
bluejeans answered ·

I am barely just figuring all of this out, trying to switch from a hodge podge of devices to full Victron. . But if you have determined the Cerbo GX can fix/regulate your issue, I have about $50 in my DIY Cerbo with a Raspberri Pi, Venus OS, and a screen hacked out of a laptop. A screen is not even necessary. You can do everything on line on the Victron VRM

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shaneyake avatar image
shaneyake answered ·

You would need a GX and a BVM or Smart shunt, the GX would then control the charge current via DVCC.
https://www.victronenergy.com/media/pg/CCGX/en/dvcc---distributed-voltage-and-current-control.html

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shea avatar image
shea answered ·

You can limit shore power input amp on the MultiPlus via Cerbo/Touch, etc. Get a 2nd battery. Use the jumper to make a switch for the possible Orion. I just kill my solar for a week or so until I hit 30%, charger back up around 20 Amps in 4 or 5 days. solar only This is with minimal draw, just a frig, some occasional lights, phone charging etc. Don't want to bounce at the top of the charge, so forcing a gentle cycling.

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kevgermany avatar image
kevgermany answered ·

If you want to keep it simple, get the VE bus to usb cable, this takes a standard Lan cable which must be fully wired from the multiplus and goes into a computer/laptop. Install VE configure on your PC (free download). Wire up. You can configure all the settings. Including max charge current. But although this keeps you below the battery limit, it will penalise you when there is little sun and you have a mains hookup.

You should install an isolator switch between the solar panel and the MPPT. This can be used to switch off the panel on mains hookup.

If you fit smart Orion, these can be switched by the ignition, alternator voltage, or external switch.

But with all of these you're manually switching the panels.

Second battery is another option.



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