sailing-cat avatar image
sailing-cat asked

Slow charging on Shore Power from Multiplus with Lynx BMS and Victron Smart Batteries

System is Victron Batteries, Lynx BMS, Cerbo GX and dual 24v 3kva Multiplusses. The batteries are 4 330AH 12V batteries in two strings of 2 for a 24v nominal voltage.

This is on a boat with a solar array and connected to shore power.

We drew the batteries down to about %75 SOC before connecting shore power. While connected to shore power the solar was not being used at all. So we installed ESS onto the Multipluses following advice.

Now when connected to shore power, the Solar produces its max energy (it seems) and the Multiplus is inverting and charging as necessary.

But at night. the Multiplus charges VERY slow. Took something like 12 hours to put in 4kwh which could have safely been done in 2 hours?!

For example, nothing from PV, input limit from shore power set at 18A (2kw) and the battery at a %75 SoC the Multiplus only charges at a few hundred watts, like 200w. This took forever to bring the battery back up to %100. The Multiplus shows "absorption" light as on.

The Lynx BMS has CVL set at 27v and that's the voltage so I think the batteries are maybe at 27v and so there's not much current flowing.

The batteries didn't get down to the %70 threshold set in the Lynx BMS so it didn't start a "new cycle".

So, I guess I understand what is happening, I'm just not sure I like it. I would have hopped the batteries would be charged at 1500w or some reasonable percentage of the shore power current limit unit they were near full.

Maybe I should set the threshold in the BMS to %95?

I do like the idea of fast charging to %95 then trickling from there.

multiplus in parallellynx bms
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kevgermany avatar image kevgermany ♦♦ commented ·
Victron say no ESS for mobile applications like boats.

Did the charge on shore power behave as expected before ESS?

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sailing-cat avatar image sailing-cat kevgermany ♦♦ commented ·
No. Before ESS the batteries would charge slow, no solar production would happen and all power supply to satisfy power demand would come from the shore power. That's why we installed ESS.
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1 Answer
Stefanie (Victron Energy Staff) avatar image
Stefanie (Victron Energy Staff) answered ·

Hi @Sailing Cat

This is normal behaviour. If you discharge below the set SoC threshold, the CVL changes to 28.4V (check parameters in your GX device - Device List > Lynx Smart BMS 500 > Parameters - or on VRM), which in return should increase the charging current of the Multi to the maximum until 28.4V is reached.

If the CVL is at 27V and the battery voltage is close to it, the charging current is reduced.

And I agree with @kevgermany, you should not install and configure as ESS. You easily can get into trouble because your system may feed the grid. If you want a quick charge, change your SoC threshold.

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Kevin Windrem avatar image Kevin Windrem commented ·
I think Victron needs to address this scenario. That is, wishing to prioritize solar over grid in mobile applications that disqualify ESS. The charge management that is part of ESS can be useful in many applications that otherwise would not require ESS to be activated.

Either there should be a way to active ESS and disable all grid feed-in or the features that are part of ESS should be broken out into separate assistants, etc so that they can be activated without enabling grid feed-in. Maybe a "No feed-in" grid code would make this possible/legal.

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Stefanie (Victron Energy Staff) avatar image Stefanie (Victron Energy Staff) ♦♦ Kevin Windrem commented ·
@Kevin Windrem AFAIK something like this is coming, but no details yet.
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