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Sending power to the grid when battery is not charged

Sending power to the grid when battery is not charged

For some reason, my new power wall is sending a substantial amount of power to the grid (2.5kW out of 3.6kW) rather than using it all to recharge the Powerwall (even though the PowerWall is only 54% charged). Is there some sort of limit on the amount of power the Powerwall is able to receive at one time? Or is this a configurational error of some sort?

Gregg

sashton | 5 December 2017

In some locales the inverter capacity is reduced to comply with local power distribution requirements but your limitation appears excessive. E.G. by default in the UK under G83 rules the PWII is limited to charge and discharge at 3.6kW.
The second possibility is that your import/export sensor is misreading the current but that would only make sense if your figures posted above are gleaned from a third party meter. If you are using a WiFi connection between the import/export sensor and the Gateway it is also possible that an unreliable signal (distance/thick walls) between the two could affect the system.
It is also worth noting that the system, on occasion, takes a while to come out of standby and during this period the above symptoms can be seen but this should be transient.

Beyond this I am only guessing... part of the commissioning script involves some self tests. These may be required for accurate performance of the PWII. It is possible to skip them. I do not know the consequences if your installer decided not to wait for them to complete.

None of the above really explain your symptoms so I would advise getting your installer back.

harrye | 7 December 2017

Also, check you have the latest version of the mobile telephone application. It was recently updated from v3.2.1 to v3.2.2. The former giving gross misreadings and unacceptable response times to change.

Tony163 | 13 December 2017

If you want the solar panels to exclusively charge the powerwall, you need to set the powerwall to 100% backup mode. Keep in mind it only charges at 1.7 Kwh. I set the 100% backup mode about 11 PM when my time of use rates drop and then I set it back again after the powerwall is charged or if it's late in the day, even if it didn't get charged all the way. That way I'm running off battery at night until 11. All this manual work is necessary until they get time of use built into the powerwall itself. Also keep in mind it takes 10-20 minutes for the powerwall to respond to your input on the phone application.

erikpk | 17 December 2017

@karynshaun is there any way to have the grid charge the PW? I was reading a few folks manually flipping the breaker which how i interpreted what they then wrote is the grid would charge their battery. I'm in the same TOU plan with PGE. I have had the PW live for about a week and have already been doing exactly what you just described. Thanks for the advice.

Largs Bay | 18 December 2017

I am having the same problem as gregg. It's really annoying as the Powerwall is not fully charged at the end of the day and we then have to purchase power from the grid for a much higher cost than we got for exporting it during the day. I have called Tesla about this twice but nobody has ever gotten back to me.

KarynShaun, where did you find out that it only charges at 1.7 Kwh? I'm pretty sure that I've seen it charge at a higher rate than that before.

Tony163 | 19 December 2017

For my part, as part of the SGIP rebate program, you are not allowed to charge directly from the grid when you have solar. I have never seen my powerwall charge over 1.7 Kwh. If it does, I'd like to know how to configure it to do so. I have a 4.5 kwh solar system, so with the battery being solely charged by the panels during the day, I usually get to 100% or close. It's only on very cloudy and rainy days where I have issues.

ekim909 | 27 January 2018

There is a very similar problem as the above poster, with my system as well, installed end November 2017. My system consists of 6kW of solar panels feeding a Fronious 5KW inverter with a single Powerwall 2 for storage. In Australia as far as I am aware the Powerwall should accept up to its maximum of 5kW. My system initially starts with around 3.8kW of power charging the Powerwall for around an hour. It then exponentially decrease its charge acceptance to about 1.4kW when the power from the solar panels reduces to less than this. I have noticed the fan which initially could be heard working, now doesn't work at all, so I am thinking the Powerwall is running into an internal temperature limitation. Whether this is because of a hardware fault or is software driven I don't know. Having read some threads here that suggest power cycling the system restores "normal" operation, I will try this next to see if there is any change in the charging level.

eml2 | 1 February 2018

My experience is that if I set it to Backup-only mode, each PW will be charged up to 1.7 kW. If PV is generating more power than 1.7 kW, any extra power will first go to house load, then export to grid.

To charge my PW at max rate (5 kW per PW), I have to set it to Self-Powered mode.

ekim909 | 3 February 2018

eml2 I have now had a bit of a play with the system (Including setting it to Backup-only mode) and agree that my system does indeed only charge at a flat 1.7kW when in Backup-only mode. I do not use this mode though so it was just out of interest that I tried it.

Just in case it was a software type issue that could reset itself I have tried powering off the system, both at the battery on/off switch and completely removing power to the PW using the 3 installed breakers, but there is no change. Has anyone on the forum had any comment from Tesla about this issue? I am sure I have a problem that seems to be mirrored by others on the forum, so would expect some comment from Tesla about a solution. It would be nice to know if the lack of hearing the PW fan running was a software/configuration type issue or in my case a failure of hardware. Please wake up Tesla!!

ekim909 | 6 February 2018

Thank you Tesla...........

Have now heard from my installer that Tesla have decided the cooling system is faulty and will replace the Powerwall 2 under warranty. Just have to wait for the unit to arrive now. Hope Greg and Largs Bay have some success with their situation.

psusi | 10 February 2018

sashton, what does "distribution requirements" have to do with power you generate and use locally?

sashton | 11 February 2018

psusi, Here, and possibly by other power companies, a battery system is considered to be a generator like a PV array or a wind turbine. To prevent over-voltage scenarios and possible damage to your neighbours equipment the power company here defaults to 3.6 kW until surveyed and a higher limit is agreed.
The PW will accept that as a generating limit as part of its initial config but it also appears to limit the battery charging to the same level.
So it is quite possible to have, for example, a PV system generating 5 kW; a house consuming 1 kW but the battery only accepting 3 kW of the excess, resulting in an export of 1 kW.
I have found recently that the PW will also restrict the charge rate in cold conditions. A couple of days ago I saw mine limiting charging to 1.7 kW when the battery was just above freezing.

psusi | 12 February 2018

Weird... over-voltage isn't a thing that can happen. And silly that the PW also limits the power it will charge the batteries with.

kirk_nason | 18 February 2018

@karynshaun will give your tips a try, but this is sure a lot of work. As you indicated, my goal was to charge up and not use to PEAK rates late in the day starting at about 4:30pm or later. My PW filled by ~noon (from 10%) and then started discharging at about 2pm. Not what I want....

ekim909 | 23 March 2018

My PW2 was replaced under warranty and it will now charge at up to about 4.2kW from the solar panels. Thank you Tesla, a great result. The PW2 may accept more but my house normally consumes about 0.8 - 1kW and my solar array can only produce 5kW.

Just FYI - I sometimes set the "Reserve" to 80 - 100% after 10pm when my Time of Use cost drops, if I know from the forecast that the following day will not be sunny. This enables me to charge at 1.7kW overnight until the PW2 is full. The following morning I set the reserve back to 10% and use the PW2 power for the rest of the day. Hope that info can help someone out there.

dborn @nsw.au | 4 April 2018

Ekim909 - I am in Sydney. How do you set your unit to charge from the grid overnight? I only got time of use today and have it set to cost saving. It is also only charging at under 2kw and is exporting to the grid despite being only 20% charged!
Not happy with that!

barondebeaumont | 5 April 2018

dborn- I am on the Central Coast with 11kw Solar and 1 powerwall.

At present I run my system the same way as ekim909.

The customised setting is at Self Powered.

Depending on your excess solar should charge the battery to a max of 5 kw imput before sending it to the grid. From the grid the charge rate is 1.7kw.

With regards to the time based control.

This link should help.

https://www.tesla.com/support/energy/learn/powerwall/time-based-control

This was just activated on my system yesterday so have yet to work that out.