Hello all.
5kw Sunsynk inverter, two Sunsynk 100ah L5.1 batteries in parallel. Inverter shows battery setting is Li BMS 14.

Number 1 battery is working well, and number 2 not responding to discharge settings, and would drop till empty if I let it (no way of telling if it is over charging).

Master no'1, and slave no'2 battery.
I have tried no'2 master and no'1 as slave, but no'2 always has the same problem.

Obviously a BMS problem.

Q1) Does anyone know what make the BMS is? A Sunsynk / Deye own manufacture?

Q2) Saying the bms is totally dead, how hard will this be to change it to another more common bms make?

Q3) And will the Sunsynk SG01LP1EU 5kw inverter recognize the new bms?

Thank you for any help you can give.

 

Edited May 2, 20251 yr by Bear
Forgot to add photos

Panic over. 😀

I have just ran each battery separately, no problem at all.

In the inverters menu system, in the battery section there is a check box, BMS error stop, if there's a problem with the bms it will shut down, it hasn't which is a big relief as these batteries cost me £2000 each!

I'm 100% sure the problem is with the bms bios, although the batteries have been used for only eight months until the problem, the batteries were made in 2022, and the bios has not been updated.

I have been reading on the net that there has been various problems with batteries, bios updates going wrong and parallel vs series etc.

I've come to the conclusion that's exactly what it is, my options are update the bms bios (can't do that as sunsynk uk will not release the update to the public or even communicate with them) , or take it out of parallel and put it into series.

New cables ordered for series.

Not sure if series is what you want, it will push the total voltage to over 100v.

Changing out the bms to a known one, is a relatively easy task, you might just need to find a way to mount it, if the mounting holes do not correspond. Suggestion would be a JK Bms.

If both are working apart, perhaps try a new ethernet/comms cable between the BMS's. This is most likely your culprit. Just read the manual as well to make sure a dipswitch wasn't accidentally changed, and correct it.

If all else fails, try running them in voltage mode.

Edited May 3, 20251 yr by Pho3niX90

You know what, I've been using the wrong terminology.

Parallel: Live and neutral cables coming off each battery to it's own breaker then joined with a bus bar, and on to the inverter.

Series: Live and neutral from battery no 1 running to battery no 2 (live to live & neutral to neutral) then on to a breaker then on to inverter.

Totally wrong terminology, what should it be?

I've been away from solar for some time and in to other things, how easy it is to forget.

Here is a nice pciture showing the difference