Good day to all,

I have this stupid question........

Pylontech UP5000 SOH shows 93%. Is it wise to tell the Inverter (Sunsynk 5kw) that the capacity is 93ah or leave it at 100ah?

Edited May 24, 20251 yr by Warlok
added info

1 hour ago, Warlok said:

Good day to all,

I have this stupid question........

Pylontech UP5000 SOH shows 93%. Is it wise to tell the Inverter (Sunsynk 5kw) that the capacity is 93ah or leave it at 100ah?

Not sure if there is a CORRECT way. Personally I would leave it at 100Ah as when the inverter reports 50% then you have 50Ah available to zero SOC. Easier to calculate than to get what is 50% of 93 than 50% of 100. It could mean that you will never see 100% SOC. The inverter sums the Ah going in and out of the battery.

My own view.

9 hours ago, Scorp007 said:

Not sure if there is a CORRECT way. Personally I would leave it at 100Ah as when the inverter reports 50% then you have 50Ah available to zero SOC. Easier to calculate than to get what is 50% of 93 than 50% of 100. It could mean that you will never see 100% SOC. The inverter sums the Ah going in and out of the battery.

My own view.

Do the sunsynks not adhere to the SOC from the BMS?

Im my view SOH is just a FYI measurement. Everything else is handled by the BMS, which informs the inverter what charge it wants, and how much the inverter can still use.

3 hours ago, Pho3niX90 said:

Do the sunsynks not adhere to the SOC from the BMS?

Im my view SOH is just a FYI measurement. Everything else is handled by the BMS, which informs the inverter what charge it wants, and how much the inverter can still use.

I agree with how you put it. I would not think the BMS is always correct and for this reason we sometimes need to fully charge/discharge the battery to get the BMS to sort of reset upper and lower SOC.

Got this explanation on the internet...

SOH represents the overall condition and remaining useful life of a battery, reflecting factors like capacity fade and internal resistance. A 93% SOH means the battery has lost 7% of its original capacity.

My take-away here is "capacity". So when it reaches 74% SOH, the battery will have the same capacity as a us3000 pylontech and the parameters should be changed accordingly.

So, charging a battery (us3000) that charges/discharges (recommended 37a) max 74ah charging and telling the inverter its a 100ah battery could cause damage?

My logic brings me to this conclusion, or am I looking at this the wrong way and will the BMS sort it out?

On these Pylons SOH is a very crude, hard-coded estimate.

For the first 1000 cycles: for each 100 completed cycles the SOH is decreased by 1%.

Thereafter, for each 167 completed cycles the SOH is decreased by 1%.

SOC is calculated based on Coulomb counting (from full) using the current SOH.

The exception to this is when charging above 89%, or discharging below 11%, SOC is based on a lookup table using the lowest cell voltage. That is why, when charging, the SOC seems stuck at 89% and then suddenly shoots up.

A further exception is that, when discharging, if any cell voltage gets into the values contained in the lookup table, the SOC reported for the pack is that value. This is why SOC will suddenly drop very quickly if there is a weak cell in the pack.

I have the full set of voltages and corresponding SOC values available if anybody is interested.

9 hours ago, Warlok said:

Got this explanation on the internet...

SOH represents the overall condition and remaining useful life of a battery, reflecting factors like capacity fade and internal resistance. A 93% SOH means the battery has lost 7% of its original capacity.

My take-away here is "capacity". So when it reaches 74% SOH, the battery will have the same capacity as a us3000 pylontech and the parameters should be changed accordingly.

So, charging a battery (us3000) that charges/discharges (recommended 37a) max 74ah charging and telling the inverter its a 100ah battery could cause damage?

My logic brings me to this conclusion, or am I looking at this the wrong way and will the BMS sort it out?

I wouldn't change anything manually. The BMS is there to protect the battery, and it will tell the inverter what the max discharge and charge amps are.

When you manually adjust things around, you might just inadvertently change the behavior of the inverter, which might already account for this since it knows what the SOH is. Even with that, it just simply doesn't care. It only cares about tbe voltage, the SOC, and what the BMS tells it. If the BMS says no more discharge, then there is no more discharge. Same with charging. If the BMS thinks the power draw is too much, it will send the inverter a warning etc. You get the point.

Thank you for all the replies. I have a better understanding now.