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captainmagnus avatar image
captainmagnus asked

MPPT and DC-DC in parallel?

Hello,

Is it OK to connect Orion-Tr (12-12-30) and MPPT (100/20) to the (second) battery in parallel or do I need to have a switch so they don't both connect at the same time?


Cheers

MPPT ControllersOrion DC-DC Converters not smart
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3 Answers
JohnC avatar image
JohnC answered ·

Hi @CaptainMagnus

Yes, you can do that. They can't hurt one another.

You may want to fiddle with their settings so that one takes charge priority, but that shouldn't be too hard to work out.

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captainmagnus avatar image captainmagnus commented ·

Awesome thanks. I just found this one as well so all good!
https://www.victronenergy.com/upload/documents/1.6KVA-12V-MultiPlus-230-Volt-system-example-4-PIN-VE-Bus-BMS-Lithium-Orion-Tr.pdf


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mdbrown avatar image
mdbrown answered ·

What's the best way to have one Victron charging device "take charge"? Offset the absorption voltages?


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JohnC avatar image JohnC ♦ commented ·

Yeh, for this particular instance, that's what I was thinking. Float too.

Not saying there's not 'cleverer' ways with more serious kit, and there the imagination rules..

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motorhomer avatar image
motorhomer answered ·

Interesting this one. I have same setup currently with an AGM battery. I found the B2B would go into float setting but the solar MPPT would still be in absorption mode keeping voltage at 14.8v. The second issue is with charge current. On a sunny day your solar charger could deliver 20 Amps and your b2b 30 amps. This would be to high for AGM battery. I end up disabling the solar in setting when on the road if the battery is fully charged.

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JohnC avatar image JohnC ♦ commented ·

@Motorhomer

It's all in the settings. If your B2B's are lower than the mppt's then it will complete it's charge cycle first and the mppt will then complete it's own. 14.8V is quite high and probably unnecessary. If you don't like the Absorb cycle, then change it to something that you prefer, maybe a fixed time or even none at all.

Your batts are only fully charged when they can't accept current (or very little). So switching off the mppt when it's already wound itself back to hold to a V profile seems somewhat futile. Victron mppts can be power limited anyway, but a typical solar day starts slowly and winds up, and it would be a rarity for a balanced system to exceed the max recommended charge rate. It can be done though in certain circumstances, but usually V will take over and the system will self limit.

If you ever see excessive charge into the batts, then reduce the charge V's to where it doesn't happen. The batts will still charge, just slower.



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