Powerwall charge rate materially impacted by temperature?

[sk00]

I had a few issues that were stuck in tier-2 hell for several months that finally got resolved with a service visit yesterday.

But 1 issue still seems to persist. It looks like the Powerwall charge rate is capped, and the rate that it's capped at seems to fluctuate during the day.

As an example, attached screenshot shows 2.3kw solar generation, of that 0.6 going to my home, 0.7 charging Powerwalls, and 1.0 sold to grid. This is odd because all the excess solar after home usage should be entirely used to charge the Powerwalls until they reach 100pct charge. But in my particular situation, the charge rate seems to be capped at 0.7kw.

I asked the service tech about this and he said this is actually normal behavior due to the cold whether. For context, it is quite cold here right now with temps dropping to the teens during the night and in the 30s during the day.

Can someone confirm that this is in fact correct -- that the cold weather does in fact limit Powerwall charge rate? Thanks.

 

[GtiMart]

Assuming the battery chemistry is similar to the batteries in the cars, that would be expected. A battery in a Tesla model 3 / Y, and probably the other models as well, will not accept any charge under freezing. Even slightly above freezing, the maximum charge rate is severely limited, so as to not hurt the batteries, until they heat up. Does the powerwall have any capacity to heat itself?

 

[jhn_]

I had a few issues that were stuck in tier-2 hell for several months that finally got resolved with a service visit yesterday.

But 1 issue still seems to persist. It looks like the Powerwall charge rate is capped, and the rate that it's capped at seems to fluctuate during the day.

As an example, attached screenshot shows 2.3kw solar generation, of that 0.6 going to my home, 0.7 charging Powerwalls, and 1.0 sold to grid. This is odd because all the excess solar after home usage should be entirely used to charge the Powerwalls until they reach 100pct charge. But in my particular situation, the charge rate seems to be capped at 0.7kw.

I asked the service tech about this and he said this is actually normal behavior due to the cold whether. For context, it is quite cold here right now with temps dropping to the teens during the night and in the 30s during the day.

Can someone confirm that this is in fact correct -- that the cold weather does in fact limit Powerwall charge rate? Thanks.

View attachment 757923

Yes, the cold will have this effect especially if your Powerwalls are outside. Mine are in an unheated garage but we keep it the doors closed nearly all the time in the winter and this seems to help quite a bit. We ‘be noticed that if you can keep the ambient temp even a few degrees above freezing it makes a big difference.

Really we see the drop you describe when the temps get into the 20s. Rarely does our garage get colder than that. We had -4 outside and single digits in the garage with Powerwalls for the first time since install two years ago about a week ago. The Powerwalls were so cold soaked that the gateway just exported to grid for the day. Next day, the PWs were happily back to normal.

 

[ptdusn]

Assuming the battery chemistry is similar to the batteries in the cars, that would be expected. A battery in a Tesla model 3 / Y, and probably the other models as well, will not accept any charge under freezing. Even slightly above freezing, the maximum charge rate is severely limited, so as to not hurt the batteries, until they heat up. Does the powerwall have any capacity to heat itself?

Yes, the PWs have an internal heating system to precondition themselves prior to charging.

 

[sk00]

Yes, the cold will have this effect especially if your Powerwalls are outside. Mine are in an unheated garage but we keep it the doors closed nearly all the time in the winter and this seems to help quite a bit. We ‘be noticed that if you can keep the ambient temp even a few degrees above freezing it makes a big difference.

Really we see the drop you describe when the temps get into the 20s. Rarely does our garage get colder than that. We had -4 outside and single digits in the garage with Powerwalls for the first time since install two years ago about a week ago. The Powerwalls were so cold soaked that the gateway just exported to grid for the day. Next day, the PWs were happily back to normal.

That's good to know.
Unfortunately ours had to be installed outside the garage (on the northside, and completely shaded, so probably even colder) because of regulations that would have forced us to re-sheetrock the entire garage if we were to install them indoors.

 

[scdoubleu]

I raised a support ticket with Tesla regarding the charging rate drop off in low temps. The response was that it's behaving normally.

Even with my PW2 in an unheated detached brick garage, it still drops close to freezing this time of year, resulting in the PW charging at around 1 kW until it warms up. In the meantime, we could be exporting a couple of kW to the grid for an hour or two. Here in the UK, we don't have net metering (our export rate is 3p/kWh, vs 20p/kWh import cost), so this is just lost energy as far as I'm concerned.

I'd much prefer if the PW was smart enough to use that wasted energy to heat its batteries.

 

[jhn_]

I raised a support ticket with Tesla regarding the charging rate drop off in low temps. The response was that it's behaving normally.

Even with my PW2 in an unheated detached brick garage, it still drops close to freezing this time of year, resulting in the PW charging at around 1 kW until it warms up. In the meantime, we could be exporting a couple of kW to the grid for an hour or two. Here in the UK, we don't have net metering (our export rate is 3p/kWh, vs 20p/kWh import cost), so this is just lost energy as far as I'm concerned.

I'd much prefer if the PW was smart enough to use that wasted energy to heat its batteries.

It is using some of that energy to heat its batteries, your solar is just generating more than it can use for a period.

 

[charlesj]

That's good to know.
Unfortunately ours had to be installed outside the garage (on the northside, and completely shaded, so probably even colder) because of regulations that would have forced us to re-sheetrock the entire garage if we were to install them indoors.

An option is to consider an insulated enclosure around it?

 

[tfan2018]

What amperage is set for charging and what is actual amperage indicated in Tesla app?

 

[jjrandorin]

What amperage is set for charging and what is actual amperage indicated in Tesla app?

Im not sure I understand this question, because we do not "set amperage for charging" on powerwalls. nor is charging amps displayed in the tesla app for powerwalls like it is for cars.

 

[sk00]

Today was absolutely frigid (teens to low 20s all day) and the Powerwalls didn't charge at all. From what you all are saying, that's likely normal behavior.

Honestly I don't mind that as long as these low temps aren't actually causing damage to the Powerwalls. There are probaby only 30 days during the entire year when low temps will materially impact charge rate.

Curious though how effective the Powerwall's heating/condition system is as it seems like temps in the teens will basically block charging.

 

[ucmndd]

Curious though how effective the Powerwall's heating/condition system is as it seems like temps in the teens will basically block charging.

There's little risk to batteries basically sitting in cold temps like that - you don't start talking about "damage" to cells until you're down near or below 0F. Charging very cold cells is a problem and can cause them to rapidly degrade, which is why your system is protecting itself and limiting the charge rate (or stopping it entirely).

Powerwalls do have internal heaters to protect from extreme temperatures, but I doubt they're used much to support charging (I imagine it's rarely if ever economical to expend 1-3 kw in heating to bring the cells up to temp for charging in the dead of winter).

 

[Tardis5]

That's good to know.
Unfortunately ours had to be installed outside the garage (on the northside, and completely shaded, so probably even colder) because of regulations that would have forced us to re-sheetrock the entire garage if we were to install them indoors.

I have three PWs installed indoors and am looking to get another but new regs mean we would have to put ours in what sounds like the exact same location as yours. Being in NH means temps below zero Fahrenheit a number of days. Local solar firms refuse to place them outside. Does your PW have a weather kit installed? Have you since this post tried building an insulated enclosure around your PW? Any updates appreciated.