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don-b asked

Varying output voltage from Multiplus Compact!

Once the Multiplus is in float mode, its output is set to be 13.60v. My motorhome is on shore power. When the DC load on the Multiplus drops from 15A to 5A, the Multiplus' output voltage rises to 13.65v (as measured by the BMV-712, and a Fluke DVM). It will eventually get back to 13.60 but very slowly. And then when the DC load current increases from 5A to 15A, the Multiplus output voltage drops to 13.55v. Again, it will eventually, slowly, find its way back to 13.60v. But these voltage fluctuations cause current to go in and out of the LiFePO4 battery (as per the BMV-712), which affects the BMV-712's capacity algorithm. Is there something wrong with the Multiplus that it can't hold a solid 13.60v output? My old power supply / converter could. Any insights would be appreciated... if it's defective, I'll make an exchange.

MultiPlus Quattro Inverter Charger
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Stefanie (Victron Energy Staff) avatar image
Stefanie (Victron Energy Staff) answered ·

Hi @Don B.,

nothing to worry about. This is absolutely normal.
DC power is coming from your batteries and it takes a bit of time for the MultiPlus to react and regulate for the sudden decrease or increase of DC power. The capacity algorithm of your BMV is only affected by a very little percentage in the decimal range.

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don-b answered ·

Thanks Stephanie. Yes, this behavior does cause the % remaining figure to slowly decrease over time even though I'm on shore power. The reason I didn't think this was normal is because my previous charging system (with an AGM battery) didn't exhibit this behavior. When the % remaining sync'd to 100% when absorption changed to float, it stayed at 100% for many days if plugged in. And 0.0 amps went in or out of the battery during that time, with the same loads and load usage behavior. So I guess the Multiplus isn't as "solid" as I would have assumed with regards to holding its DC output voltage steady. Sad, because otherwise it's a high-end product. I only wish I could discuss this with Victron tech support (maybe a large capacitor across the output would help), but I discovered that they're only available for distributors and not the end-user.

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Stefanie (Victron Energy Staff) avatar image Stefanie (Victron Energy Staff) ♦♦ commented ·

Don,

>So I guess the Multiplus isn't as "solid" as I would have assumed with regards to holding its DC output voltage steady. Sad, because otherwise it's a high-end product.<

It still is a high-end product and as solid as I can think of. You most probably will see the same behaviour with other brands.

About Victron Tech Support. Yes, you're right. To get tech support, in first line you should discuss things with either your Victron dealer or Victron installer. Other chances are the community here with some really knowledgeable and experienced people around. Some of them are official Victron Dealers and Installers at the same time and spend some of there free time here to share their experience.

Sorry, that I couldn't be more of a help.

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