Hi Everyone, 

Current setup 1x Kodak OG-Plus 5.48 with 2x US2000 Pylontech batteries.

My questions is regarding the battery equalization setting available within the inverter settings.

Reason I'm looking into this is because I recently noticed that my batteries don't run down to the same SOC before switching back to grid supply.

e.g. battery 1 would be @ 18%SOC while battery 2 would be @28%SOC. My inverter will then switch back to Grid due to battery 1 being below the critical threshold however there is still some charge left in battery 2 which could be used.

Even when charging you can see the 10% difference in SOC (attached)

Any advice would be appreciated. 

On 2024/06/26 at 5:20 PM, WernerM said:

Reason I'm looking into this is because I recently noticed that my batteries don't run down to the same SOC before switching back to grid supply.

The equalisation facility is intended for flooded lead acid batteries only.

It can sometimes be repurposed to overcome the premature float bug. But it is definitely not suitable for this sort of balancing.

Is it possible that your two US2000s are not connected correctly? The inverter's positive lead should connect to one, and the negative lead to the other inverter. Otherwise, one of the US2000s does more of the work, discharging more fully.

Are they of different ages? In that case, the internal resistance of one may be higher than the other.

Was one added recently? If so, were they at close to the same SoC?

I note that one reads as 15 Ah and the other as 20 Ah. These figures seem very low, unless those figures represent present capacity, not capacity when fully charged.

You might be able to charge the battery fully, then disconnect one module (leaving the one with the lowest capacity), then charge it fully. Finally recombine the modules.

Edited June 27, 20242 yr by Coulomb

Hi Coulomb,

Is it possible that your two US2000s are not connected correctly? The inverter's positive lead should connect to one, and the negative lead to the other inverter. Otherwise, one of the US2000s does more of the work, discharging more fully.            I attached a photo of how they are connected.

Are they of different ages? In that case, the internal resistance of one may be higher than the other. Same age, both been running for about 2 years. About 2 months ago I found that my 'bulk charge voltage' was set to 56v for some reason, so I brought that down to 53.1v and float charge volts to 52.5v. 

I note that one reads as 15 Ah and the other as 20 Ah. These figures seem very low, unless those figures represent present capacity, not capacity when fully charged. Yes, these figures are for present capacity based on the SOC as seen in the image as well. 

Both batteries charge to 100% daily without any issues. I also swopped the two batteries around making the secondary the master and vise versa, but had the same results. Their SoC differ by about 10% when they are at 80% DoD.

On 2024/06/27 at 7:36 PM, WernerM said:

I attached a photo of how they are connected.

Those are connected correctly.

On 2024/06/27 at 7:36 PM, WernerM said:

About 2 months ago I found that my 'bulk charge voltage' was set to 56v for some reason, so I brought that down to 53.1v and float charge volts to 52.5v. 

Assuming that you have battery type set to PYL, this should not matter. The BMS overrides those settings.

On 2024/06/27 at 7:36 PM, WernerM said:

Their SoC differ by about 10% when they are at 80% DoD.

Then consider my last suggestion:

Quote

You might be able to charge the battery fully, then disconnect one module (leaving the one with the lowest capacity), then charge it fully. Finally recombine the modules.

By "lowest capacity", I mean that one that shows the lowest SoC when the battery is at a high state of discharge.