I’ve had my system for around 8 years, installed during a house build and installed by a supplier who is no longer available. I have 14 PV panels on my roof and runs through to an inverter that has a BMS controller attached and is then hooked up to 3 batteries. Due to the house being quite power hungry, I have the batteries only wired into the RCD board running the house lighting as if it was to everything in the house, the batteries would get drained very quickly.
I’m on a cheap overnight tarif so have a scheduled charge between 11.30pm and 5.30am to charge the batteries to 100%, then they will decline a little during the morning, possibly charge up if the PV’s are active but then sit waiting for the evening when the sun goes down, the lights come on and the battery power is required.
MY ISSUE - As we head into Autumn in the UK, I’ve noticed that my batteries are draining during the evening as lights are switched on but only to 68-70% after which the inverter then starts charging them up 1% or 2%, then they discharge 1% or 2%, then charge again, then discharge, generally doing this and sitting at around 68%-70%. Just at the point it stops discharging and starts charging, a message shows saying #4 BMS has deactivated charging. I’ve googled this message but can’t find what is causing it. I have the SOC set at 25% so I’d expect the batteries to drain down to 25% before requiring any recharging. I’ve searched all the settings and cannot find why this behaviour is happening. Any thoughts anyone?
I thought about screen shotting a load of settings but as there are so many options and menus, thought I’d wait and see if anyone wants anything in particular.
I’ve also been wondering if there are people out there that provide a service where they can remote into my console panel, and almost do an audit to check everything is set correctly.
If these are lead acid batteries, then they are probably sulphated, at end of life.
Performance will be better determined from the battery voltage, not the reported SOC. If you have a VRM connection for the system, then look at the battery voltage during charge and discharge. If the voltage on charge rises very quickly, then the batteries have a high internal resistance, due to age and sulphation.
Good shout @MikeD, never gave it a thought that the batteries could be end of life. 8 years in and many discharges and charges.
Volts and amps are all alien to me but took some screen shots. First one whilst it was discharging, then the second after it started charging. The third one was whilst it was discharging this morning having fully charged overnight during the cheap tariff. Not a huge difference in voltages being reported.
It would be interesting to see what your battery voltage settings are in the Multiplus, given that you are getting low battery warnings at 13V. Bot the charger settings and the inverter voltage settings - for low volt warning / cut out.
For a 12V system (Sealed or wet?) typically a low voltage warning would not come on until 11.5V.
Read the label, these are lithium batteries. The Settings you want to get at are in Victron connect. Also look up the battery data sheet to see what the recommended settings are.
Being the amateur that I am, I didn’t realise that LiFePO4 meant lithium batteries but now know that. I looked up the datasheet and with having 3 batteries, checked the settings including the absorption rate. I’ve put some screen shots below.
No matter what I try, I cannot get the batteries to drain below 70% SOC despite it being set to 15%. I’ve even tried trickle charging the batteries up to full (despite them being charged every night to 100%) but they still only discharge to 70% and then commence a continual cycle of charge up 1% then discharge 1%, charge 1% and then discharge and so on.
Something isn’t charging right as once it gets to 70%, I get the low voltage alarm and it all starts playing up. Whilst that is probably the reason, I’m unclear on how to resolve it.
Is that Charge Efficiency of yours (0.95%) really part of the datasheet for your batteries? Mine is set to 99%. I wonder what would happen when I set it to something below 1%. Nah. Not going to happen.
Victron Connect suggests the default value of this would be 1 and so not sure its a percentage value, or at least if 1 is the whole number, then 0.95 is 95% of that.
Your system stops discharging because the battery voltage is just 11.4V. This is the voltage of an empty battery, so the protection is activated to prevent damage from total discharge. What is the voltage when charged to 100%? It should be around 13.8V.
I eventually found this setting under a Virtual Switch tab but on clicking it, a warning pops up about any existing assistants being deleted or removed. I don’t know if this is right, wrong or irrecoverable so didnt’ have the confidence to press continue.
There definitely is something wrong with the batteries holding their volts, so maybe one or all are damaged.
During today, I fully charged the batteries, both with a trickle charger and forcing the inverter to charge batteries. Once they got to 99%, it went into absorption charging and then I put the inverter back to Optimize with Battery Life. Volts were sitting at 14.21v.
Then moments later, the Inverter started charging the batteries and then discharging and then charging and going round in cycles every few minutes!
It doesn’t like being below 12.3v or 12.4v. And it doesn’t seem to want to hold the volts whilst the battery discharges, deciding to then start it up 1% which boosts the volts and then discharges for 1% till the volts drop too low again.
I hadn’t changed these, partly because I didn’t realise they were wrong nor can find what the right settings should be. I found what I thought was a datasheet for the batteries I have but couldn’t find these settings. Also confused that they are for lead batteries as if I’ve not changed them, they must be from what the original installer set them too and I’d have hoped they knew what they were doing (unlike me!). That is unless they can reset somehow to a default setting.
