Hi 

My 8kw Sunsynk inverter varies my SOC on my 5kwh Freedom Won battery between 99 & 100% during the my PV is on, the rest of the time my SOC is constan at 99%. Why would that happen?

I suspect it denotes battery cell balancing.

We can see your PV is dipping very slightly into your battery; balancing then happens thereafter briefly.

It happens after running during load shedding as well, right?

I see the same behaviour from my Hubble AM5:

99% is the default “full state;” but after the battery SOC drops, the battery hits 100% at the end of each charge (presumably indicating battery cell balancing) for a little while before reverting to 99% and staying there.

My Goodwe with a Freedom Won 10/8 can show this.

I suspect it is the Freedom Won BMS at work. When it gets to 99% it starts balancing the cells. When the balancing is complete it reports 100%. Then some thing comes along to take a bit of load out of the battery, then it must get back up to 99% and do the balancing again. This doesn't happen when there's no PV because when there's no PV, there's no PV to charge from and so, in my case, the battery is discharging.

Thing to remember: If you have comms between the BMS and the inverter, then the BMS tail is supposed to wag the inverter dog. 

This is particularly the case with the FW (I'm not complaining here). Their BMS does a very good job of setting things up on the inverter as it wants them set, and it doesn't let go. So the inverter is constantly being directed and reported to by the BMS.

Edited July 2, 20233 yr by Bobster.

Also have the same setup. Does the BMS have temperature compensation voltage for the battery? If the battery is at 20degreesC does the charge voltage be the same as at 25degreesC?

Edited July 2, 20233 yr by Jakac

Thanks for all the comments. Does it matter when a battery cycles by 1%, what counts as a cycle on a battery: how far does it have to drain (SOC) and be recharged before it counts as a cycle on a battery? 

4 minutes ago, Francois Taljaard said:

Thanks for all the comments. Does it matter when a battery cycles by 1%, what counts as a cycle on a battery: how far does it have to drain (SOC) and be recharged before it counts as a cycle on a battery? 

Nope: a single cycle is typically 100% (so on a 5kwh-capacity battery, a single cycle is the full 5kWh). If this is indeed the BMS balancing, it’s not going to contribute!

5 hours ago, Francois Taljaard said:

 

Deleted by author 

Edited July 2, 20233 yr by Bobster.
Duplication

2 hours ago, Francois Taljaard said:

Thanks for all the comments. Does it matter when a battery cycles by 1%, what counts as a cycle on a battery: how far does it have to drain (SOC) and be recharged before it counts as a cycle on a battery? 

Read the warranty. 

Freedom won define a cycle as 100% SoC to 20%. BUT additionally say that lower discharges will be counted cumulatively. I take that to mean that if you go down to 60% two days running, that counts as one cycle. 

Really the number of cycles is what the BMS says it is. 

13 hours ago, Bobster. said:

Read the warranty. 

Freedom won define a cycle as 100% SoC to 20%. BUT additionally say that lower discharges will be counted cumulatively. I take that to mean that if you go down to 60% two days running, that counts as one cycle. 

Really the number of cycles is what the BMS says it is. 

From the warrant I read, "Discharges deeper than 80% DoD and less than 80% DoD are also counted into to the total number of cycles on a pro rata basis."  I interpret your example as being two by 50% cycles, i.e. one full cycle over two days. However, a discharge to 10% will be 90/80 cycles or 1,13. In my case, I set my on grid limit to 35% DOD and force charge back to 100% if I have inclement weather so theoretically my battery is only cycling around 300 times p.a. Do you concur?

24 minutes ago, Peter V said:

From the warrant I read, "Discharges deeper than 80% DoD and less than 80% DoD are also counted into to the total number of cycles on a pro rata basis."  I interpret your example as being two by 50% cycles, i.e. one full cycle over two days. However, a discharge to 10% will be 90/80 cycles or 1,13. In my case, I set my on grid limit to 35% DOD and force charge back to 100% if I have inclement weather so theoretically my battery is only cycling around 300 times p.a. Do you concur?

I agree with your first example. I was talking about 60% remaining SOC, which is 40% used, thus half of the 80% cycle.

I think you have your DODs and SOCs mixed up. It's easy to do: "Discharges deeper than 80% DoD and less than 80% DoD". I think that should read "Discharges deeper than 80% SoC and less than 80% DoD". That's the territory I live in.

14 hours ago, Bobster. said:

Read the warranty. 

Freedom won define a cycle as 100% SoC to 20%. BUT additionally say that lower discharges will be counted cumulatively. I take that to mean that if you go down to 60% two days running, that counts as one cycle. 

Really the number of cycles is what the BMS says it is. 

For FW the BMS cycle count still has a calculation attached to it to get to their warranty count.  You take the BMS cycle divided by 2 divided by 0.8 and that is what FW work with.  In practice it comes down to a discharge from 100% to 20% SOC and charge to 100% counts as 1 cycle.  Which also comes down to 160% of the battery capacity (in a combined charge/discharge view) is 1 cycle.

Will the 1% cycles x say 100, eventually also make up a cycle?

 

 

Thanks

 

4 minutes ago, Francois Taljaard said:

Will the 1% cycles x say 100, eventually also make up a cycle?

 

 

Thanks

 

Probably, but will it make any real difference?

On 2023/07/03 at 9:29 AM, Bobster. said:

I think you have your DODs and SOCs mixed up.

I did )-;

It’s almost definitely related to balancing: if you take a look at my attachment you can see my battery drops from 100% to 99% whilst absorbing power (this is after charging post-load-shedding). It happens every time. I’m certain it just indicates that battery cell-balancing is completed.

 

Happens during PV cycling day-time as well; even when the SOC for the time slot is at 100%.

 

I run an unlimited-cycle-warranty battery - but even then, I’d be extremely surprised if this contributed to the BMS cycle counter…

 

As a side-note, OP would be an excellent candidate for setting his SOC System-Mode settings below 100% to smooth out those peaks and troughs (and hence capitalise further on that glorious PV!); at the expense of a few extra (legitimate) battery cycles!

Edited July 4, 20233 yr by JayMardern