Pylon Batteries not charging to 100%

[SolarPhil]

Hi all

I have a Solis RHI-6K-48ES-5G inverter originally installed in March 2021 with two Pylontech 2000C batteries which I charge overnight on Octopus Intelligent Go. I’ve recently installed an additional 6 2000C batteries, but the whole 8 battery setup only charging to 91-92% - whereas previously the two battery configuration was regularly charging to 100%. The installer put the original batteries first in the series - would this make any difference? The installer is coming back to look at the system, but I would appreciate any help anyone can give. Many thanks

 

[DIYrich]

You have 20kwh of batteries. How fast can the octopus charge, and how long is the cheap tarrif window?

Any solar panels?

For a 6 hour charge window, that would be about 4kw charge rate, which seems reasonable. Check your settings on the Octopus that you are requesting 22kwh to allow for some charging loss.

Also, the charge rate tapers at high soc. Maybe octopus assumes a more linear charge rate. Make sure you are charging at 4kw during the first 4 hours. And that gives you 2 hours to charge the last 20%

 

[AshleyL]

......8 pylontech batteries in parallel? You gonna need a busbar for that.....

 

[DIYrich]

The installer put the original batteries first in the series - would this make any difference?

The batteries are 24v, and the inverter is 48v. They need to be in pairs (series) to provide 48v to the inverter.

 

[KnobCountry]

......8 pylontech batteries in parallel? You gonna need a busbar for that.....

I believe the pylontech batteries have their own semi proprietary connection studs and a communication hub to keep them balanced.

Phil mentions series but I suspect the 48v batteries are in parallel as it's a 48v inverter.
Pylontech 2000c show as 48v on the website.

Phil did they install the lv hub unit as well? The lv hub acts as a full system balancer.

The system may need more time to balance out as that is a lot of cells. How long have the additional batteries been in place?

If the pylontech lv hub was not installed then your state of charge is being determined how? Voltage at the inverter?

 

[SolarPhil]

You have 20kwh of batteries. How fast can the octopus charge, and how long is the cheap tarrif window?

Any solar panels?

For a 6 hour charge window, that would be about 4kw charge rate, which seems reasonable. Check your settings on the Octopus that you are requesting 22kwh to allow for some charging loss.

Also, the charge rate tapers at high soc. Maybe octopus assumes a more linear charge rate. Make sure you are charging at 4kw during the first 4 hours. And that gives you 2 hours to charge the last 20%

18 340w panels - graph below shows steady charge until 75% soc - then tapers off.

 

[SolarPhil]

I believe the pylontech batteries have their own semi proprietary connection studs and a communication hub to keep them balanced.

Phil mentions series but I suspect the 48v batteries are in parallel as it's a 48v inverter.
Pylontech 2000c show as 48v on the website.

Phil did they install the lv hub unit as well? The lv hub acts as a full system balancer.

The system may need more time to balance out as that is a lot of cells. How long have the additional batteries been in place?

If the pylontech lv hub was not installed then your state of charge is being determined how? Voltage at the inverter?

Here’s a picture of the installation - sorry for my ignorance but I don’t know what an lv hub is.. Additional batteries been installed 3 weeks - I’m reading the SOC from the Solis monitoring app.

 

[AshleyL]

I believe the pylontech batteries have their own semi proprietary connection studs and a communication hub to keep them balanced.

Phil mentions series but I suspect the 48v batteries are in parallel as it's a 48v inverter.
Pylontech 2000c show as 48v on the website.

Phil did they install the lv hub unit as well? The lv hub acts as a full system balancer.

The system may need more time to balance out as that is a lot of cells. How long have the additional batteries been in place?

If the pylontech lv hub was not installed then your state of charge is being determined how? Voltage at the inverter?

Here’s a picture of the installation - sorry for my ignorance but I don’t know what an lv hub is.. Additional batteries been installed 3 weeks - I’m reading the SOC from the Solis monitoring app.

View attachment 210431

Well.......no wonder they said a picture is worth a thousand words..........this is exactly what I am trying to say with those two videos.....

 

[SolarPhil]

Well.......no wonder they said a picture is worth a thousand words..........this is exactly what I am trying to say with those two videos.....

Very informative videos, but as my system is under warranty for 10 years don’t think I’ll be installing bus bars - I’ll have to live with the inefficiency of daisy chaining.. I did look up the Pylontech lv hub, only needed if you want to connect more than 8 batteries.

 

[jgh]

The installer put the original batteries first in the series - would this make any difference? The installer is coming back to look at the system, but I would appreciate any help anyone can give. Many thanks

Pylontech say to have the newest unit "first" (ie. master for the stack).

I suspect that's to get the latest firmware version being in control, to the extent that it matters.

 

[DIYrich]

Add a battery voltage line. Maybe you need to reset the SOC.

 

[rpdom]

They look to be wired correctly (I have 2xUS2000C and Solis S5-EH1P3K inverter). My batteries tend to "stick" at around 93% for ages when charging, then suddenly jump to 100%. This is because the batteries are balancing themselves internally.

As some of your batteries are new, it may take longer for them to all balance out.

Make sure your inverter has the latest firmware (your installer should have had it updated for you) as the older firmware had some sub-optimal settings for Pylontech batteries.

 

[SeaGal]

I have a Solis RHI-6K-48ES-5G inverter originally installed in March 2021 with two Pylontech 2000C batteries which I charge overnight on Octopus Intelligent Go. I’ve recently installed an additional 6 2000C batteries, but the whole 8 battery setup only charging to 91-92% - whereas previously the two battery configuration was regularly charging to 100%.

That behaviour is exactly what I would expect with your configuration.

The Solis RHI range has a maximum of 3000W / 62.5A battery charge / discharge rate - probably a bit less as Pylontech batteries are lower voltage than regular ones, being only a 15S architecture.

In the 6h charge window you will not achieve full charge of 8 US200C's.

The solution will be to swap to the newer Solis EH1P 5kW or 6kW inverter, which can charge/discharge at 5000W / 100A.

 

[SeaGal]

Further thought, having seen the charge rate drop off after about 2 hours charging...

Can you monitor the inverter's temperature? One other reason for the charge rate dropping (i.e. apart from the Pylontechs specifically requesting a lower charge rate) is the Solis will reduce the rate if it is getting too hot.

If the charge rate is being limited by the Solis, rather than the Pylons, check that it has been installed with the necessary ventilation around the big heatsink; this should be minimum of 300mm unobstructed space on either side, 300mm above and 500mm below, with free air movement (e.g. not in a cupboard).

Failing that, it may be necessary to install additional external fans as I and others have done - e.g. see:-

Solis S5: Various issues

Let us know if it powers up automatically when get PV again. Also, have you measured how much battery consumption reduces by when you put it in sleep mode? Results: Yesterday at midnight, battery SOC was 11%. I turned the inverter off using the GUI. This morning at 8AM, battery SOC was still...

diysolarforum.com

 

[SolarPhil]

An update after a visit from the installer this week - all the batteries were checked showing normal behaviour, firmware on batteries and inverter at correct levels. The installer charged each battery individually to 100% from grid, then reconnected the entire 8 battery array in series, but made the master one of the latest batteries installed (which is the Pylon recommendation) - previously the master was one of the original (3 year old) batteries. Batteries are now all balanced and charging to 100%. Many thanks for all the replies