question

dhoodhat avatar image

Low battery voltage when not under load and low solar yield

Inverter Multiplus48/5000/70-100

4 batteries Victron AGM 12-230 Super cycle

12V210ah @10h rayte

12v230ah @20h rate

MPPT solar charge 250 I 100 - tr

20 solar panels @300w each.

The system worked great from May2019 till current where low voltage battery was becoming a problem even when not on load. Even a 300w load now when low solar yield cuts the battery to 46volts and shuts down. This never happened before. Only occurs when usage is greater than pv yield

Are the batteries the problem?

We have been having load shedding on a regular basis.

battery system voltage
2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

4 Answers
JohnC avatar image
JohnC answered ·

@dhoodhat

It all helps, and being able now to put it all in context clears the mysteries somewhat.

You seem to have some quite massive loads (>300W!, ha), and grid-tied in parallel to your solar mppt. Does the system export, or is it all incoming? That may be important if you're exporting.

I doubt your batts are faulty, but that's a helluva load on them when solar is tapering and the grid fails. And a spurient 46V isn't of concern, unless it shuts you down of course. I run a similar size system, and 37V (the minimum) set as the shutdown point. So I never get shutdowns, just the alarms. You could do the same..

Overloads on ac-out are a concern if they last long enough for VRM to graph them. So you're using your system to the edge, which is ok if you understand that - and get away with it.

A side observation - your solar doesn't do the 'Absorb' thing, but the grid does. There may be a reason for that, but it's something that may deserve further thought.

I doubt you have much to worry about really. Just big loads on limited batt capacity & charge..

2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

dhoodhat avatar image
dhoodhat answered ·

Don't know if this helps


2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

dhoodhat avatar image
dhoodhat answered ·

Don't know if this helps


2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

JohnC avatar image
JohnC answered ·

Hi @dhoodhat

Agreed that a 300W load shouldn't do that. But the issue could have a number of causes, from dicky wiring/fuse/isolator to maybe even the batts not being charged correctly.

Have you more info you could provide, like screenshots of relevant VRM graphs or Connect history?

Are you grid-tied or offgrid? Using Assistants?

Can you check the V of each of the batts in the string independently with a multimeter?

2 |3000 characters needed characters left characters exceeded

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.