Hi all I have been browsing through the site for some time and got a lot of useful tips and solutions. 

I now have a headache which I cannot seem to get the correct answer to. I installed a 3kw system with 4 x 24v 100ah lifep04 batteries.  I quickly realised it was not big enough and then upgraded the 3kw to a 5kw Sun pay unit. Took the batteries which at that stage was about a month old placed them in series to make 2 x 48v 100ah batteries. I draw about 1100w at peak of the system at night which is basically just lights on a farm.  System worked fine for the last couple of months until somehow the Mppt burned. (Solar panels run half of them through mppt and the other half through the inverter due to size difference in the panels). Replaced the Mppt. If I measure the batteries they are all 25.9v (approximately) and linked one by one to the 3kva system the inverter switches on. Put the batteries in series they measure about 51,9(approximately) but the inverter does not switch on and the batteries read 26.9v. take the terminals of the inverter and we are back at 51.9v. 

 

Changed the inverter with exactly the same model I have spare, does the same. 

 

I am out of ideas and solutions on this. Does anyone have a answers on how to fix this. The batteries charge on the 3kva inverter to 100% so I  don't think the batteries are the problem

 I also swapped the batteries around when doing the series setup with the same answer everytime.

 

 

 

 

 

 

3 hours ago, kobus123 said:

24v 100ah lifep04 batteries

What brand are your batteries and are you sure they can be hooked up in series (not all of them can)?

Have you checked what classifies as over voltage on the battery input of the inverter? Try drawing the batteries down by a few volt.

The overcharge voltage is 54.6v and the floating charge 54v. 

Voltage on the batteries in series is 51,9v. Which puts it about 20 to 25%. 

I can charge the batteries up to a higher voltage bit it does the same

4 hours ago, jumper said:

What brand are your batteries and are you sure they can be hooked up in series (not all of them can)?

Hi yes can be hooked up in series. Had them running like that for about 3 to 4 Months. Make is Pylon 

@kobus123 it sound like when series one of the bms is shutting down thus giving you 26.9v .Does the batteries have Bluetooth monitoring to check?

6 hours ago, kobus123 said:

Hi yes can be hooked up in series. Had them running like that for about 3 to 4 Months. Make is Pylon 

Hmmm, so if they are measuring 52V in series with a multimeter and then 26V when connected to the inverter I would think the inverter is the problem, but maybe it could be one of the BMS switching off for some reason as @Raj35says. If it was working for months and isn't working anymore and the batteries work on their own then that would also point me towards an inverter issue, but you say the batteries do the same thing on another spare inverter which then points to the batteries being the problem because surely both inverters can't be faulty... I can see your frustration, but unfortunately I have no experience with these batteries.

Hopefully some pylontech users on the forum can help out.

12 hours ago, kobus123 said:

Hi yes can be hooked up in series. Had them running like that for about 3 to 4 Months. Make is Pylon 

I've not heard of any 24v Pylon that can be used in series. What model are they? Are you using CAN / RS485 communication between them and the inverter?

 

From the 24v UP2500 manual.

Edited April 4, 20231 yr by Tinbum

On 2023/04/04 at 11:38 AM, Tinbum said:

I've not heard of any 24v Pylon that can be used in series. What model are they? Are you using CAN / RS485 communication between them and the inverter?

 

From the 24v UP2500 manual.

The earlier question if the batteries can be used in series gives a yes answer yet the manual clearly indicates NO. 

Further the BMS should not be able to use comms via the inverter If they are in series. The inverter will not be able to tell which battery needs charge if the are indeed at different SOCs. 

My assumption of using them in series. In 24V in parallel via the 3kW they will work happily together. 

Cannot explain how they worked right up to where the MPPT blew up and got replaced. 

Edited August 12, 20231 yr by Scorp007