Why is my Batrium allowing low current charging when Charge state is off?

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snoobler asked Nov 1, '22

Why is my Batrium allowing low current charging when Charge state is off?

Custom NMC 14S 48V bank.

Successfully configured WM5 to control system for a few months. Relatively happy with it.

Issue is with cold temp charging. Obviously, I want to restrict charging to 0A below freezing. To give myself some margin, I have specified 5°C as a limit, i.e., if below 5°C, charge is not permitted.

When below 5°C, the MPPT 250/100 will power loads, but "charge" is throttled to between 0.2 and .05A (starts at 0.2A and increases to 0.5A as temperature approaches 5°C).

The Batrium Shunt and my BMV-702 report identical values.

Consistent with their poor support as of late, Batrium says, "not our problem, contact Victron."

It's my understanding that when my MPPT says "External control" it's ONLY doing what the BMS is telling it to do, so if it's sending 0.2-0.5A to the battery, this is a result of whatever criteria the BMS is feeding it.

Any ideas?

MPPT Controllers CCGX Color Control batrium

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Stefanie (Victron Energy Staff) ♦♦ commented · Nov 01, 2022 at 02:59 PM

Tbh, I have no idea about Batrium. But one idea that comes to mind is that it could be a balance current rather than a charge current. Otherwise it's as you said, the MPPT is fully controlled by the BMS (assuming Batrium implemented its driver well).

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snoobler Stefanie (Victron Energy Staff) ♦♦ commented · Nov 01, 2022 at 08:00 PM

No idea about Batrium? You and me both! :)

The Batrium is a passive (resistive) balancer, and balancing is inactive almost all the time - definitely during the period in question. I have some active balancers installed, but at the 0.02V difference between cells, they only pass about 20ma between adjacent cells.

I haven't completely ruled out that something might be pulling current on the battery side of the shunt. It's remote, and I'll be visiting it this weekend. I'm 99% sure everything is pulling on the load side of the BMV. Batrium shunt is between BMV and battery. The BMS is a comparative battery hog, but it should NOT be the 20-30W seen going to the battery - should be closer to 3-5W due to a 5V, 2W cooling fan.

Thank you for confirming the MPPT is only doing what it's being told to do.

Lastly, if the BMS wasn't in the mix, and the MPPT was engaging low temp charging protection based on the BMV-702 temperature sensor, would the MPPT completely cease all production, or would it power loads, but not allow charging?

Given the 450Ah of the battery, the high grade Panasonic PHEV cells, and the very low C rate, I'm not too worried about Lithium plating, but... I'd be way more happy seeing a slight drain to the battery vs. a slight charge. :)

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Answer 1 · 2022-11-02T16:05:53Z

hardy-tuner answered · Nov 02, 2022 at 04:05 PM

I‘ll change soon from rec-bms to battrium wm5 and can try this Config, but the other Question is: how is your dvcc configured?

Which power source using WM5, contactor and infrastruce of your installation?

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snoobler commented · Nov 03, 2022 at 06:30 AM

Given Batrium's supply and support woes as of late, I'm not too keen on them. I've been having issues with cell voltages jumping up or down 0.1V (sometimes WAY lower - 0.5V) long enough for VRM to capture it The upper ones are squashed by Autolevel set to 0.10V, but the lowers linger. You can see when I have Autolevel off:

They claim this is related to the balancing method, and it will be fixed in a future patch. The majority of the time, balancing on the affected cell is inactive at the time of occurrence.

ANYWAY...

BMS power taken at:

1) battery (+) and load side of BMV.

2) USB cable from a battery powered Mini PC

Batrium WiFi has been completely unreliable for me.

DVCC:

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Answer 2 · 2022-11-04T16:58:06Z

snoobler answered · Nov 04, 2022 at 04:58 PM

I'm pretty sure this is a Victron issue. I went into DVCC and set the charge limit to 0A. I'm still getting up to 0.5A of charging:

DVCC is at 0A:

Batirum is commanding 0.0A:

So the question is now, why is my GX allowing up to 0.5A of charge current to the battery when it's set to 0A?

This is a concern for ANYONE with Lithium batteries.

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