Gateway does not keep PW charged

[Boatguy]

I've set my system to have the small solar array keep the two PWs at 93% and use the remainder to buffer solar.

I originally set it at 90%. The solar all went to the battery until it reached 90%, then started going to the house (too small a system to feed back to the grid in winter). The vampire loss in the PWs is 2-3% and the PWs started to decline each day. I changed it to 93% and it charged the PWs up to 93%, but now the PWs have started to decline again.

Is the Gateway too stupid to monitor the PW status on an ongoing basis once the PWs reach the specified charge level? Tesla in denial about vampire loss?

It's raining today and I have a small system, but the attached tell the story.

 

[miimura]

I also have a small solar system. I have seen that when the solar production is very low, like 0.2kW or less, it may not activate charging.
You can see in the morning, it did not start charging until the solar output exceeded about 200W. Even when it was producing 300W, it was only charging with 100W.

 

[aesculus]

I assume you are running Cost Saving based. Today it's totally cloudy and light rain so I am only producing 400 W from the ambient light. My reserve is set to 70%. This AM is started at 69% (not sure if that's 1% VD or just the temp differential overnight. I think the temp). Anyway ever since I could produce at least 100 W it has been in charge mode (right now in partial peak). In another hour it will go to peak and discharge the 4-5% I have been able to sock away today.

 

[cwied]

My observation is that the Powerwalls don't start charging up to the backup reserve level until they're 3% below. I'm guessing this may be a buffer to prevent them from flipping back and forth from charging to discharging when the state of charge is riding the reserve level.

 

[Boatguy]

I am not in Cost Savings mode, not a TOU rate plan. So we have conflicting experiences here.

@miimura does not see charging until 200-300W of output. @aesculus sees charging with only 100W.

I'll try cost savings mode and see if that forces it to keep it charged.

 

[Boatguy]

My observation is that the Powerwalls don't start charging up to the backup reserve level until they're 3% below. I'm guessing this may be a buffer to prevent them from flipping back and forth from charging to discharging when the state of charge is riding the reserve level.

That may well be the issue. If I leave the car plugged in for 3-4 days, but don't drive it, the vampire will pull it down at least 15-20 miles before it will charge again.

 

[Boatguy]

I switched to the Balanced Cost Savings mode and juggled the TOU so it mostly charges the PW during the day, drains it down to my reserve at night and repeats the next day. The net effect is to preserve my backup capacity and be more self powered, never using the net metering which is financial nothing from PG&E anyway.