I am getting a random shutdown and have not been able to figure out why. System will work flawless for weeks then all of a sudden will get an OFF warning with no reason codes
Thought it was happening on a high amp,draw but did not have a high amp draw this time
Imhave included all vrm pics happened at 1535 this time
Type of Battery and BMS or Monitoring ?
I see a midpoint Voltage … maybe some 12V Batteries in series
300 ah of eco worthy with internal bms
Checked individual cells and all are balenced and working properly
Was thinking about getting a victron bms
48v system 8 total 12v batteries
4S then connected in parallel
A Victron BMS or others will not work because you would then have to open all the batteries and completely rebuild them in order to be able to monitor the individual cells.
How high are your cut-off voltages in the multi’s configuration? and what voltage do you measure at the terminals of the multi at this moment if you were to stress it?
Stress the system and then measure all the batteries … You may have a cell in between that is sagging too much …
A 4S2P configuration is of course very demanding in terms of maintenance, evaluation and balancing
My cut off voltages are
.0005c 46.75
.25c 46.5
.7c 46
2c 45
Im not seeing a high amp draw at this time of shutdown
I see a firmware update needed for cerbo and multi
Was planning to do the cerbo but saw some people posting problems with the latest multi update and was not sure about that one
What kind of shutdown was it?
Only short ones or again and again in quick succession?
Output Voltage L1 just 40.6V ???
Im thinking that low output voltage was after the shutdown
You might also consider trying a 2P1S configuration.
I’ve built 24V and 48V systems by connecting 12V lithium batteries in series, and I’ve encountered a strange but important phenomenon when using batteries with built-in BMS.
In a 2S (24V) setup, for example, if one of the 12V batteries disconnects due to undervoltage (say it drops to 10V and the BMS cuts off), it can actually appear as -10V at the terminals. The other battery might still be reading +12V, and when you measure across the full 24V system, you only see 2V instead of 22–24V. This shuts down the multiplus, no error it’s like flipping the battery breaker.
This happens because the disconnected battery is floating there’s no solid ground reference, and depending on system wiring or leakage paths, it can “flip” polarity from the multimeter’s perspective.
It’s a reminder that using individual 12V lithium batteries with separate BMS units in series can be unpredictable and even unsafe, unless the batteries are explicitly designed for series operation. Without proper coordination between BMS units, you can run into all sorts of weird behaviour, reverse voltages, false readings, or worse, over-discharge and potential damage.
Do you have a balancer? I use one of these, they work well.
Just found out these shutdowns are happening when the house air conditioner is coming on so high amp draw is the culprit.
I have two balencers (eco worthy) each connected to 4 batteries.
Im running the 48/5000 inverters wired in split phase.
I have the batteries wired 4s2p according to wiring unlimited recommendation
Is there a better way to connect these for 48 volt? Maybe bus bars?
Woukd power assist help with compressor startup?
Also your recommendation of 2p1s not sure how this looks with a 8 battery 48volt system
