Strange Solax Battery Capacity Issue

[Mach13]

Hi Folks
Here's What Happened?
So I did a two hour evening charge on my hybrid car yesterday which put about 5KWs into the car.

Now because the sun hid itself the power was drawn from my home Solax battery (two batteries total of 11wkh)

The batteries were at 100% but had dropped to 17% before i'd noticed.. the charger had put about 5kwh into the car a very small amount of which would be solar. the only power being drawn was the car charger and nominal house stuff. Strange I thought as at the very worst i'd have imagined it to have dropped to 50%

So... i kept an eye on the home battery overnight charge and it went from 10% to 100% with a max input usage of 5.8kwh which it did within about and hour (that 5.8 will include minimal house power) That indicates to me that battery capacity has dropped to around 50% of its original. Or am I missing something?

So here's the questions
I have two batteries, ive turned the system on and off to let it reset itself and both batteries appear to be working (steady green flashing lights) and there are no faults showing on the inverter. Is there a way to test battery function/capacity?

The System (less than a year old)
Solax Inverter X1-Hybrid-G4
2 x Solax Batteries with total of 11.6kw
Solar 4Kw

Any help appreciated

 

[johnb2713]

I dont know about the solax batteries but BMS's in general can drift out of calibration, it's the BMS that will be giving the % information to the inverter. The other possibility is one of the batteries is way out of balance, that would cause the charging to stop prematurely and discharging also. The only other thought is the same as yours, capacity has dropped to 50%.

 

[Mach13]

Aha Thanks Johnb2713 Obs you're a 'gold' member for a reason... That's exactly what the tech support have said as they got back today... They said something about putting the batteries into rebalance mode so we'll see what that does

 

[johnb2713]

Aha Thanks Johnb2713 Obs you're a 'gold' member for a reason... That's exactly what the tech support have said as they got back today... They said something about putting the batteries into rebalance mode so we'll see what that does

I aim to please, rarely manage it though.

Thanks for the update, it’s good to know for future

 

[arwooldridge]

I have a Solax system and find sometimes anomalous battery states, but they seem to sort themselves out after a while, probably BMS working. Just interested though how did you get into battery balance mode?

 

[Mach13]

h how did you get into battery balance mode?

I didn't but the installer did it remotely. So sorry can't help with that,. He said the SOC would drop to 37% (which it has) whilst it rebalances and may take upto 48hrs to complete.... Its had 24hrs so far and is still at 37% so we'll see how it goes by tomorrow.

Whilst its doing this the house seems basically to be running fro the grid (Barring whatever Solar input there is) But if it works... then i can live with that..

 

[binky]

Whilst its doing this the house seems basically to be running fro the grid (Barring whatever Solar input there is) But if it works... then i can live with that..

Losing the odd day is annoying but trivial in the overall scheme of it's kifespan.

 

[johnb2713]

Losing the odd day is annoying but trivial in the overall scheme of it's kifespan.

Very true but a concern surely must be that it can get this far out of balance to reduce capacity to 50% and take days to balance?

 

[binky]

Very true but a concern surely must be that it can get this far out of balance to reduce capacity to 50% and take days to balance?

Oh definetly, does sound like the BMS is possibly slightly faulty, or just not good at recovering the situation.

 

[Mach13]

UPDATE:
The software balancing over 48hrs didn't work as a subsequent overnight charge showed that it was still only taking 5kw to fully charge to 100%

Its interesting that Solax's solution (they got back to me within 24hrs) was to disconnect both batteries then reconnect individually and charge each one to 100%. Obs I'm not going to do that myself, but the installer is going to and is currently scheduling an engineer to come and test the hardware and then try that to see if it works.

Seems the thought is that its possible that the batteries were not balanced at the time of installation and so the differential has just grown over time.
I guess to my untrained ears that's a possibility.

Will update on progress as I imagine its a useful insight into these things

 

[arwooldridge]

In my experience these batteries can take a long time to correct any imbalance, think weeks vs days. But once balanced all should be good.
It's not too difficult to measure each individual battery voltage with a meter on DC by disconnecting them, I think you need to put the short jumper link (normally reserved for the end battery of the string) on the right hand side them measure the voltage on the LHS terminals. If one is way down or too high that could be your problem. Make sure all BMS connections are fully engaged and tight.

 

[binky]

Seems the thought is that its possible that the batteries were not balanced at the time of installation and so the differential has just grown over time.
I guess to my untrained ears that's a possibility.

even then it should self balance over a few days. I've added batteries to several stacks over the years. Batteries tend to come with some charge, but never going to be the same as those already installed. I've not used Solax batteries, though I have used a Solax inverter with pylontech batteries.

 

[arwooldridge]

In my experience these batteries can take a long time to correct any imbalance, think weeks vs days. But once balanced all should be good.
It's not too difficult to measure each individual battery voltage with a meter on DC by disconnecting them, I think you need to put the short jumper link (normally reserved for the end battery of the string) on the right hand side them measure the voltage on the LHS terminals. If one is way down or too high that could be your problem. Make sure all BMS connections are fully engaged and tight.

So you only have two batteries. First get the total battery voltage of the two from the system status menu. Then isolate the batteries if you have a DC isolator, if not switch off the inverter and or master battery, and disconnect the two leads connecting the two batteries together, and measure the DC voltage coming out of the LHS two terminals of the end of string battery ( the one that has the jumper connecting the two RHS terminals, leaving that in place) subtract that from the total voltage should give you both battery voltages.Take care not to short anything and use well insulated probes. It's over 100 volts and almost unlimited current available there!

 

[Mach13]

Thanks for your comments to date.

As i'm not savvy with these things i'm not inclined to be touching the system to investigate. That said i'm sure someone else coming across this thread will find your contributions practical and useful.

So here's the update I promised.

It took a few weeks to get the engineer here as It took time for them to find a slot and then I was on holiday... But they came this week.

This is what they seemed to do.. (to the best of my knowledge)

Prior to commencing the system was showing itself to be charged to 100%.

During the following the system was put into a mode that put it offline from the home, so we were running from the grid

The lead guy disconnected the batteries and dealt with them individually. As I understand it, the slave was charged to 100% and disconnected from the system. This took quite some time.

Then the Master was connected on its own and discharged to around 37%.

Then both batteries were connected and the system was charged up to 100%.

That seemed to be it..

Then we did a forced discharge (to the grid) until the system dropped to 90% and checked to see how much had been put to the grid. With an 11Kwh system it should have pushed 1.1kwhrs and that's exactly what it did Result!!!!

Later in in the week I put a 5kwhr charge in my car and the system performed exactly as it should by dropping around to around 55% (approx figures)

Its good enough for me to feel comfortable that the system is back to normal and balanced.

I will check it again in a few months.

FYI Apparently all SolaX batteries reliably come with 46% charge. So maybe, just maybe the installer didn't carry out a balance at the start and that's why we got to where we were. Perhaps a lesson learnt. Either way I'm content that the installer fixed the problem and I learnt a lot from all this....

Thanks for your comments todate... Hopefully this will be of some use it anyone else searches on a similar problem in the future.

If anything changes I will update again