Why aren't my batteries discharging below 18%?

Rheumatoid · 30 July 2022 at 9:05AM

The inverter on my panels has gone down so for the first time since they were installed in April I expected my batteries to discharge completely (or at least down to 5% which I believe the newer Pylontech 2400's go down to). However, the Solis Cloud app says they have 18% and it is not going any lower. I have 4 x 2400 batteries.

Is this to be expected? It seems odd if this much capacity is not accessible.

QrizB · 30 July 2022 at 9:19AM

I don't know your system, but is there a setting in the inverter to limit the battery depth-of-discharge?

Rheumatoid · 30 July 2022 at 9:24AM

QrizB said:

I don't know your system, but is there a setting in the inverter to limit the battery depth-of-discharge?

I'm not sure. Its a Solis inverter and I guess that might make sense. Is it usual to have it set so high though?

QrizB · 30 July 2022 at 9:58AM

Rheumatoid said:

QrizB said:

I don't know your system, but is there a setting in the inverter to limit the battery depth-of-discharge?

I'm not sure. Its a Solis inverter and I guess that might make sense. Is it usual to have it set so high though?

I think a max discharge of 80% is a common default.

Rodders53 · 30 July 2022 at 10:25AM

Be grateful the system is preserving the lifetime of the batteries. e.g. Lead Acid batteries should not be discharged below 50% without degrading the charge cycles available.

From a Solis manual (do find and read yours)

Only two parameters need to be defined: * OverDischg SOC (10%~40%, default 20%) --Inverter will not discharge the battery when the OverDischg SOC is reached. Battery self-discharge is unavoidable, SOC may go lower than the limit if the battery can't get charged for a long period of time.

Rheumatoid · 30 July 2022 at 11:11AM

Rodders53 said:

Be grateful the system is preserving the lifetime of the batteries. e.g. Lead Acid batteries should not be discharged below 50% without degrading the charge cycles available.

From a Solis manual (do find and read yours)

Only two parameters need to be defined: * OverDischg SOC (10%~40%, default 20%) --Inverter will not discharge the battery when the OverDischg SOC is reached. Battery self-discharge is unavoidable, SOC may go lower than the limit if the battery can't get charged for a long period of time.

Will dig out the manual now I know its an inverter issue and something that is probably desirable.

Thanks both.

Alnat1 · 30 July 2022 at 4:24PM

If your Pylontechs are US2000C they are supposed to be able to go to 5%. My system has been set so they go to 10% though

Rheumatoid · 30 July 2022 at 5:44PM

They are C's that's why I thought only letting them down to 20 was overly protective. What is the general view on a lower limit?

Reed_Richards · 30 July 2022 at 6:07PM

In the summer I have my minimum charge set to 10% but it rarely gets that low. In winter my electric heating drains the battery as fast as I can charge it so I change my inverter setting to make the minimum charge 50% in the hope that the battery likes that better.