Reduced Charge Rate Above 90% SoC

[eml2]

I have 2 Powerwalls, and have a 9.24 kW PV system. With 2 Powerwalls, max charge rate is 10 kW. In the past, all the excess solar were charging PW all the way up to 100% SoC. Nothing exported to the grid until PW recahed 100% SoC. However, today, when it reaches 90%, it throttles down to above 3 kW and exports the rest to the grid. I haven't seen this before. My PW recently updated to 1.25.0. Is this new to this version? Have anyone seen this before.

Here is the PVOutput of today. My 2 PW's have been charged at about 7 kW starting around 11:15 am. There are some clouds around 1:30 pm which drops the excess solar to around 4.5 kW (SoC is ~88% at that point). However, when SoC reaches 90% around 1:50 pm, PW doesn't accept all the excess solar anymore. Only about half goes to PW, the other half goes to grid.

 

[JHellow]

I have seen the same behavior, but mine started with 1.23.0. Not sure that the reduced charge rate kicked in at 90% on mine. May have been earlier. Since 1.23, my discharge rate when 10kw is called for also kicks down to 5-6kw, and reverts to grid for the remainder until the batteries hit their 30% reserve floor.

 

[Bigtanuki]

Seeing similar behavior after 1.23.0 . I'm on TBC and I noted that since 1.23.0 I'm seeing discharge patterns changing also with discharge starting during partial-peak with SOC at 70% or above. Definitely not the behavior I want. Now on 1.24 with change.
I've started running the units in Self-powered mode until the solar outputs drop late in the day then swapping to TBS so that vehicle charging will be from the grid after 11 pm.

JHellow - with respect to the diminished discharge rate; I saw the same issue with my first two PW units. Check if one of your units has a higher fan flow than the other. That's an indication that the cooling system isn't working which causes the battery management system to reduce output to keep the unit operation in it's temperature band. You should be able to get a continuous 10kW out of two PW units.

 

[eml2]

It happens again today, at around 88% SoC. One of the 2 Powerwalls is warmer than the other one. None of the fans are turned on though.

About 9 months ago, I already had one of the Powerwalls replaced due to coolant pump failure. Now, it is the other one that is acting up. Maybe it's time for another warranty exchange.

I haven't seen any problem with the discharge yet. Charged my car @ 40 A and my 2 PW's can discharge a total of 10 kW at that time.

 

[Shygar]

I'm on 1.25.0 and I noticed yesterday that around 70% SOC to 85% it dropped my charging rate on my single powerwall 2 to less than 1kW:

Shygar-A 7.500kW | Live Output

I can't figure out any reason for this other than the powerwall decided to charge like this. I went outside when it was happening and I couldn't see or hear anything obviously wrong with the powerwall.

 

[JHellow]

[QUOTE="JHellow - with respect to the diminished discharge rate; I saw the same issue with my first two PW units. Check if one of your units has a higher fan flow than the other. That's an indication that the cooling system isn't working which causes the battery management system to reduce output to keep the unit operation in it's temperature band. You should be able to get a continuous 10kW out of two PW units.[/QUOTE]

Thanks for this. I have an open ticket with Tesla support. They have not been very helpful, but
I’ll ask this specific question on Monday.

 

[ewoodrick]

That's the way batteries work. The charge currents decrease as the battery charges.

 

[montreid]

Something changed over the past week. Soc often maxs between 80-90% without reason. Yesterday noted discharge during SUPER OFF PEAK TIMES despite cost savings setting. Not good. Then again, love our model 3 update, so that balances things out this past week

 

[cwied]

Something changed over the past week. Soc often maxs between 80-90% without reason. Yesterday noted discharge during SUPER OFF PEAK TIMES despite cost savings setting. Not good. Then again, love our model 3 update, so that balances things out this past week

Double-check your TOU schedule. My weekend settings got messed up around the time I was upgraded to 1.25.0. I don't know if it was Tesla fixing the weekend/weekday schedule setting bug that was causing issues earlier or just a random glitch.