Pylontech US5000 rapid discharge when not in use

[Maikysupra]

I’ve just set up my first solar system with 9 x 540W JA solar panels and two Growatt Spf5000 investors in parallel. A week ago I received the first Pylontech US5000 battery (second arriving next week). Everything seems to be working fine apart from the fact that I noticed that the battery seems to loose around 30% of its charge when NOT being used in about 14h period. My inverters are set up to start using the battery when I reach 60% charge and stop at 30%. What had been happening for the first few days of the use is that I would discharge the battery down to 30% around 6pm when my inverters would switch back to the grid. However by about 11pm I would get a low charge fault code (battery below 20%) and around 1-2am my inverters would start charging the battery from the grid up to about 43% (despite the fact that they are set up to only charge the battery from Solar) I assume as safety measure?. Yesterday was the first day when I didn’t manage to reach 60% charge during the day (bad weather) so the inverters never switched to the solar/battery mode (grid off) meaning that around 5pm I was only on 56% charge. By this morning 7am, my battery was down to 28% despite not being used (to my knowledge and data). I’m attaching screenshots of the system over time to show how the battery discharges over time. Does anyone have an idea why this might be happening?

 

[Don B. Cilly]

Have you tried laying the battery case flat - or in another orientation - to see if it gets better?

 

[timselectric]

I’ve just set up my first solar system with 9 x 540W JA solar panels and two Growatt Spf5000 investors in parallel. A week ago I received the first Pylontech US5000 battery (second arriving next week). Everything seems to be working fine apart from the fact that I noticed that the battery seems to loose around 30% of its charge when NOT being used in about 14h period. My inverters are set up to start using the battery when I reach 60% charge and stop at 30%. What had been happening for the first few days of the use is that I would discharge the battery down to 30% around 6pm when my inverters would switch back to the grid. However by about 11pm I would get a low charge fault code (battery below 20%) and around 1-2am my inverters would start charging the battery from the grid up to about 43% (despite the fact that they are set up to only charge the battery from Solar) I assume as safety measure?. Yesterday was the first day when I didn’t manage to reach 60% charge during the day (bad weather) so the inverters never switched to the solar/battery mode (grid off) meaning that around 5pm I was only on 56% charge. By this morning 7am, my battery was down to 28% despite not being used (to my knowledge and data). I’m attaching screenshots of the system over time to show how the battery discharges over time. Does anyone have an idea why this might be happening?

It's going to use some battery, any time it's on.These units can draw up to 70w when idle. So two will draw a total of 140w continuously. Over 14 hrs that's almost 2kwh. Which is 40% of your single battery. If you can switch to SUB mode when using grid. It won't pull from the battery to run the electronics.

 

[Maikysupra]

Have you tried laying the battery case flat - or in another orientation - to see if it gets better?

View attachment 120450

I haven't. Based on the Pylontech manual, the vertical orientation (and the horizontal one) are the only two orientations that are recommended. However I will try lying the battery flat (horizontal) tonight and see if this changes anything. Thanks for the tip!

 

[timselectric]

I haven't. Based on the Pylontech manual, the vertical orientation (and the horizontal one) are the only two orientations that are recommended. However I will try lying the battery flat (horizontal) tonight and see if this changes anything. Thanks for the tip!

It won't make any difference.
LiFePo4 batteries are not using liquid electrolyte.
The only orientation not recommended is vent down.

 

[Maikysupra]

It's going to use some battery, any time it's on.These units draw about 70w when idle. So two will draw a total of 140w continuously. Over 14 hrs that's almost 2kwh. Which is 40% of your single battery. If you can switch to SUB mode when using grid. It won't pull from the battery to run the electronics.

That's interesting. I have the inverters set up in SBU mode. However I assumed that once they switch to 'Grid mode' due to batteries running low, the inverters then power themselves from the grid too, not the batteries..

 

[timselectric]

That's interesting. I have the inverters set up in SBU mode. However I assumed that once they switch to 'Grid mode' due to batteries running low, the inverters then power themselves from the grid too, not the batteries..

Sadly, that's not the case.
It would be nice though.

 

[Maikysupra]

It's going to use some battery, any time it's on.These units can draw up to 70w when idle. So two will draw a total of 140w continuously. Over 14 hrs that's almost 2kwh. Which is 40% of your single battery. If you can switch to SUB mode when using grid. It won't pull from the battery to run the electronics.

 

[Maikysupra]

If this really is the expected behavior, should I then increase my cut off charge level from 30% to about 40-45% to allow for running these inverters overnight from batteries? Otherwise I end up using the grid charging those batteries due to hitting the critical low battery state..

 

[Don B. Cilly]

LiFePo4 batteries are not using liquid electrolyte.

So what do they use, solid electrolyte?
And how does that leak out when they rupture?
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[timselectric]

If this really is the expected behavior, should I then increase my cut off charge level from 30% to about 40-45% to allow for running these inverters overnight from batteries? Otherwise I end up using the grid charging those batteries due to hitting the critical low battery state..

Probably

 

[timselectric]

View attachment 120474
So what do they use, solid electrolyte?
And how does that leak out when they rupture?
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They're not full of liquid like led acid batteries. It's more like a wet paste.
You can check out some being opened on YouTube.
There aren't plates like in your pictures. It's more like a jelly roll.

 

[Don B. Cilly]

Right, but the gel/paste will settle over time, won't it?
Those Pylons usually have pouch cells in them, so it's possible that in that orientation they could eventually get "starved"... probably worth a try, for what it costs :·)
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[Quattrohead]

The bottom line is that the inverter standby is killing him.

 

[Don B. Cilly]

It's a 5kWh battery. 30% of that is 1.6kWh. Over 14 hours it would take more than 110Wh to discharge it that much.
My (AIO, 3kW) inverter uses some 25Wh idle. I'd say unlikely.
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[timselectric]

It's a 5kWh battery. 30% of that is 1.6kWh. Over 14 hours it would take more than 110Wh to discharge it that much.
My (AIO, 3kW) inverter uses some 25Wh idle. I'd say unlikely.
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110w for 14 hours is 1,540 wh.
But his AIO's are drawing somewhere between 60 and 70 watts each. With these lower priced AIO's, it's just something that you have to work with.