My newly set up system was working more or less fine until last night, I had the EV plugged in and was programmed to start charging at 24.00hrs. I had previously set up the ESS to use the grid from 11.30 to power house loads and charge battery on cheap rate and done that a few times with no issue. Except the car charging started at 11.00pm takin 7kW and seemingly has upset the system. The battery has drained to 50v as measured by external voltmeter and locked it on idle. System says it is 80% and 59V but it isn’t, I thought the setup would have stopped that happening must have a setting wrong somewhere. The VRM dashboard is showing the MPPT trying to charge, but battery is not accepting it. I tried powering everything down and having a restart, that did not work, how do I rectify issue.
Since it is battery related, you may have to consult with the manufacturer help.
Is their nothing in their manual about how to unlock it?
Although at 50V is should not be too depleted for a total cut off unless you have a really bad cell.
Have you tried just switching the inverter into charger only mode?
Thank you for quick response much appreciated.
No but there is mention of a service tool software and a manual for it so suspect that is what is needed, it is a separate entity to the manual I have. BMZ battery has been subject to a takeover recently and they have been notoriously difficult to make contact with.(i.e.no reply) I have this morning found a completely different email address and sent a query which has resulted in a ticket number from them by return,
No I have not what else will need doing in addition to switching inverter on if anything?
I have never used your battery brand at all. Does it communicate charge current and discharge to the GX?
My other thought since the voltage in your system is so different on each device is to check fusing between everything.
If your battery is talking to the gx then cap charge current at 20A.
I found one manual for a bmz not even sure if it is yours, says to charge it from deep discharge at 20A with bench power supply from 46 to 50v.
But you are already at 50v.
Switch the inverter either on the gx or with the rocker switch to the charger position.
Yes normally but not now it is idle. The MPPT is trying to push 55v but A is 0 as effectively no load as battery not taking it.
No I have not what else will need doing in addition to switching inverter on if anything?
Ok but everything else looks ok battery BMS showing up in devices no hint of anything amiss apart from battery locked out. It is communicating with the system
Yes will try that will it react instantaneously, do I need to turn off MPPT seeing as that is trying to charge? At moment have got everything on and been exporting and using solar but the current on the MPPT is up and down because it keeps trying to charge battery but failing and trying again. I will switch system down this evening maybe that might make a difference. Not much point having it on when battery cannot supply the juice for the inverter.
If you switch off the solar and the ac in does the system invert?
I suppose you would face the issie of your 12v jump start if it has also disabled discharge. Does it have a relay inside it (the battery?)
I would imagine so is that not the UPS. it might not do so if battery is signalling it is low
Yes it has it mentioned in the context of parallel connection of additional batteries for which a service tool is needed. The relay is engaged when energising the inverter capacitors. A constant greenlight indicates the battery is on which it is at the moment. There is a click when battery comes on presume the relay.
I tried switching over to charge and the battery immediately switched off and the relay could be heard. So I tried the 12v power to the Cerbo to power that on and switched on the battery. The on light and relay activated but battery did not deliver any volts but the Cerbo detected a BMS battery and the values as before but no volts to the bus bars. So the comms is there so that is not the issue. It seems that the BMZ has a particular type of BMS causing a hard lockout.It looks like I need the BMZ service tool or some inspiration otherwise I am in a new battery purchase scenario. I gleamed the following from an Ai Q.
To wake up a BMZ ESS X specifically, you must address the fact that the battery has likely entered “Service Mode” or “Deep Discharge Protection,” and the 50V you see on the bus bars may be “ghost voltage” or the inverter’s own capacitors rather than the battery’s active output. [2]
The specific use of a BMZ ESS X battery changes the recovery procedure slightly because these units utilize a high-performance integrated BMS that is known for a “hard lockout” once the voltage drops below its safety threshold. At 50V DC on the bus bars , the battery is sitting at approximately 3.12V per cell (assuming a 16-cell configuration), which is the critical “empty” threshold where the BMZ internal relay may remain open to prevent cell inversion.[1]
I think the ghost voltage scenario is correct and the voltage on the battery was not 50V. The value shown on the Cerbo of 80% SOC and 59.5V is probally correct. The VRM widget information confirms this as being what the battery value was when it locked down. So it looks like the battery locked down in a safe condition. Just needs waking up.
Did not mention the system gave a low voltage alarm so that contradicts what BMS said it was,
What is puzzling me is, if the system i.e. grid and battery were delivering 7kW to the EV charger and 1kW to the house why no DC fuses were blown. The battery is Mersen fused to 80A so could never deliver more than 5kW so what was the mechanism for battery to shut down, but BMS is still showing 80% and 59V and got the low volts alarm.
Often happens when the relay disconnects in a battery, the inverter notices, the bms probably reads its pack voltage in the power chain long before that point.
The bms is still live and reporting.
Does it say on the gx if it is blocking charge or discharge?
Thanks again.
I have not noticed that where would I find it? Only alarm is low voltage.
I have shut down the system for now hoping will get a response from BMZ this week.
I powered up this morning for a look see again and the Cerbo is still communicating with the battery if I switch the battery on but I am only getting 4.5 volts from the bus bar after I have removed power from the Cerbo. I think the battery is completely shut down. From what I can make out BMZ have gone OTT with it, typical Germanic approach I guess. Meanwhile doing some research into a replacement in case I can’t resolve.
venus.local or on your Cerbo device → Under BMS → Details
Thank you
Will take a look.
Could not get to it yesterday was away. I have only powered up the Cerbo to get the information. There is nothing reported under BMS details that looks all normal. But I cannot be confident because the battery does not come on. The green LED is lit which says it on, it communicates to the Cerbo but only 4.5 volts on terminals. The BMZ manual table of error lights states that a single green LED there is no error.
Since last posting I managed to get a diagnostic tool from BMZ and have run that and it is showing that the battery is healthy, cells all good and the report confirms what the Can bus is telling the Cerbo. When I start up I have confirmed that the battery is switching on providing the volts but is not accepting charge. I think the BMS has locked the contactors in safe modeThe MPPT display as it cycles through the Strings is showing volts but no current so battery not accepting charge. Won’t charge of the mutltiplus either.The battery info on the MPPT states battery is idle so it is still asleep. I will be ordering Pytes batteries next week to replace the BMZ but I would like to get it working before temporarily mothballing it as I have another use for it.