Hello All

I have a system with a conversol vm4 5 Kw inverter, 7x 420 watt panels and 2 US 5000 pylontech batteries.

I am not grid tied so I only use the power in the batteries for my off grid sockets etc. I have been using them quite happily for a couple of years now and I use watch power and smart ESS to keep an eye on the system.

Whilst checking the power going into the system yesterday I noticed I have had a couple of weak battery warnings in the past few weeks and I was wondering what could cause this?

I Have bulk charge at 53.00V, Float at 52.5V, Re charge set at 49.00V and the Re discharge at 54.00V. The sytem is set to USER for the battery as the PYL setting puts a much larger charge into the batteries than I have been advised is good for them.

The BMS has not shown any issues with the batteries over the time it has been working and when I check the batteries they are both charged to the same level and over the day they both ccharge to 100% and sit there happily on standby with the single light flashing to say it is full.

I was wondering if the free software is looking at these batteries as lead acid and therefore showing this error when a large load is drawn or the solar goes down as the day ends and a load is pulled causing the voltage to drop in the event. The weird issue is that this seems to happen at no set time in the day and sometimes the warning is un handled over a short time or a long time with no obvious reason why. I am going to check each battery with a multimeter later but in the meantime I thought I would ask if anyone has any ideas as to what may cause such a warning to occur. The system is working fine and the batteries stay charged fully with the sun and drain down to no less than 50% on any normal day sometimes even higher.

Any advice or suggestions would be welcomed please.

Regards

Bony 999

Edited March 26, 20251 yr by bony999
spelling edit

1 hour ago, bony999 said:

Hello All

I have a system with a conversol vm4 5 Kw inverter, 7x 420 watt panels and 2 US 5000 pylontech batteries.

I am not grid tied so I only use the power in the batteries for my off grid sockets etc. I have been using them quite happily for a couple of years now and I use watch power and smart ESS to keep an eye on the system.

Whilst checking the power going into the system yesterday I noticed I have had a couple of weak battery warnings in the past few weeks and I was wondering what could cause this?

I Have bulk charge at 53.00V, Float at 52.5V, Re charge set at 49.00V and the Re discharge at 54.00V. The sytem is set to USER for the battery as the PYL setting puts a much larger charge into the batteries than I have been advised is good for them.

The BMS has not shown any issues with the batteries over the time it has been working and when I check the batteries they are both charged to the same level and over the day they both ccharge to 100% and sit there happily on standby with the single light flashing to say it is full.

I was wondering if the free software is looking at these batteries as lead acid and therefore showing this error when a large load is drawn or the solar goes down as the day ends and a load is pulled causing the voltage to drop in the event. The weird issue is that this seems to happen at no set time in the day and sometimes the warning is un handled over a short time or a long time with no obvious reason why. I am going to check each battery with a multimeter later but in the meantime I thought I would ask if anyone has any ideas as to what may cause such a warning to occur. The system is working fine and the batteries stay charged fully with the sun and drain down to no less than 50% on any normal day sometimes even higher.

Any advice or suggestions would be welcomed please.

Regards

Bony 999

Just a comment on your settings. You have re-discharge at 54V yet your bulk is to only bulk charge to 53V. In theory it means you never reach the re-discharge after you started re-charging.

PYLTECH specs give a maximum charge up to 53.5V. If the inverter is slow to stop charging at 53V it could reach the 53.5V level. These batteries are prone to give problems if over charging I guess from the posts on the forum.

Also it seems it is using lead acid levels for these lithiums. The fact that it worked well with your USER settings for years and now gives weak warnings looks like they are suffering with quick discharge levels that are a new warning and worth investigating if there are not weak cells causing this warning.

Not a user of these batteries but just some general comments based on your information provided.

One would need to see the per cell voltage levels when you get this weak warning.

Hi Scorp007

Thanks for the reply, from your comments, do you suggest setting the back to re discharge to the same as the bulk charge voltage?

I understand your comment regarding the pylontec and over charging the battery voltage and it has always struck me that the settings for any of the inverters should not allow this to happen if they provide a specific setting for the battery type.

I will have a look into how to get a cell voltage from a battery as I have no idea how to do that.

Thanks again Regards Bony999

10 hours ago, bony999 said:

Hi Scorp007

Thanks for the reply, from your comments, do you suggest setting the back to re discharge to the same as the bulk charge voltage?

I understand your comment regarding the pylontec and over charging the battery voltage and it has always struck me that the settings for any of the inverters should not allow this to happen if they provide a specific setting for the battery type.

I will have a look into how to get a cell voltage from a battery as I have no idea how to do that.

Thanks again Regards Bony999

Normally one will use a back to re-discharge as the battery has received quite a bit of charge but not to wait until it is nearly full. Around 50-51.5V is a possible starting point.

Hi Scorp007

Regarding the value stated above, I am somewhat confused as regards my original post you said the battery would not reach the re discharge if my bulk was 53v and the re discharge was 54v. How would setting the re discharge to 50-51.5V not make this worse?

It may be I don't understand the precise term or re discharge but I thought this was the value to set the inverter to stop the battery being charged and to start using the battery again. Is it then the value that the battery starts discharging along side using the inverter together? I am quite new to this stuff and perhaps I have got the wrong idea as to the exact meaning of the term re discharge.

Regards

Bony999

47 minutes ago, bony999 said:

Hi Scorp007

Regarding the value stated above, I am somewhat confused as regards my original post you said the battery would not reach the re discharge if my bulk was 53v and the re discharge was 54v. How would setting the re discharge to 50-51.5V not make this worse?

It may be I don't understand the precise term or re discharge but I thought this was the value to set the inverter to stop the battery being charged and to start using the battery again. Is it then the value that the battery starts discharging along side using the inverter together? I am quite new to this stuff and perhaps I have got the wrong idea as to the exact meaning of the term re discharge.

Regards

Bony999

I will try to explain. Your post indicated when the battery was say down to 51V you will start discharging once you hit 54V.

Yet your bulk charging is below this value. Thus you will never reach 54V to start the discharge cycle. The re-discharge should thus be lower than the bulk charge where charging would stop and you start discharging again.

Thus my previous reply was to start discharging when below the bulk (max) charging level.

Hello Scorp007

Thanks for the reply. After looking at a number of battery related topics in this forum and following your comments I have now changed some of the settings.

I have the re charge at 48V, the bulk down to 52.5V, the float is now 49.8V and the re discharge is 52.0V. I read that the pylontec batteries do not like being floated at full voltage and that lowering this as well as the bulk will be better for the batteries overal performance over time.

I must say, I could probably spend all day on line and still find many more things that may or may not be better or worse for the batteries but I am happy to take any advice people have, if it will do the batteries good over time. The cost of replacing them is the biggest issue these days and given the rise in the sales of them, you would have thought the prices would have come down a little by now.

Thanks again

Regards Bony999

3 hours ago, bony999 said:

Hello Scorp007

Thanks for the reply. After looking at a number of battery related topics in this forum and following your comments I have now changed some of the settings.

I have the re charge at 48V, the bulk down to 52.5V, the float is now 49.8V and the re discharge is 52.0V. I read that the pylontec batteries do not like being floated at full voltage and that lowering this as well as the bulk will be better for the batteries overal performance over time.

I must say, I could probably spend all day on line and still find many more things that may or may not be better or worse for the batteries but I am happy to take any advice people have, if it will do the batteries good over time. The cost of replacing them is the biggest issue these days and given the rise in the sales of them, you would have thought the prices would have come down a little by now.

Thanks again

Regards Bony999

The current settings seems to be in the right direction. As lithium does not need float the float being 2.7V lower being quite a large portion of the capacity.

Just my 2c.

Hi Scorp007

Following on from my previous, I had an email from Plylontec that said setting the bulk and the float to 52.5v was satisfactory so I have now got them both at the same value. I guess this will restore some of the capacity of the pair. Currently still showing 100% when at 52.5 V and am currently working through an email and PDF sent from Pylontec with instuctions on setting up comms with pc so I can update the software and bug check as well as check the cells and their condition.

Thanks again

regards

Bony999

1 hour ago, bony999 said:

Hi Scorp007

Following on from my previous, I had an email from Plylontec that said setting the bulk and the float to 52.5v was satisfactory so I have now got them both at the same value. I guess this will restore some of the capacity of the pair. Currently still showing 100% when at 52.5 V and am currently working through an email and PDF sent from Pylontec with instuctions on setting up comms with pc so I can update the software and bug check as well as check the cells and their condition.

Thanks again

regards

Bony999

If you read the battery topics on Pylontech you will see if for any reason the battery reached 53.6V they will not honour a claim.

How can this happen? Inverter perhaps slow to react, switching off a high load or the inverter accuracy not spot on. Not a train smash but just to know how they treat a single high voltage as recorded by the log files.

We tend to feel the BMS should play it's part in disconnecting before such an event. But having said this 53.5V could work for you for a long time.