Newbie feeling lost 😞 Battery Balance issue

[Dannyg2325]

Good morning folks!

Hoping for some advice if I may please.

I have 2 x pylontech batteries, I believe maybe a 1st gen as they don’t communicate with my charger (me3000)

I had these setup on a lead acid format, dod around 70%, everything running great for a year or so until one day I noticed no lights on the batteries and the charger off.

Turned out the batteries had discharged too far resulting in a full shut down.

Lids off and multimeter out, I started checking the 4 packs within each cabinet. The first pack on both batteries had the same reading of approx 9v, the other 3 packs on both were in and around 11v each. So I’m guessing that’s them all out of balance now.
I had a small 4a 12v charger that I used to lift the packs back up enough to bring the charger back on, but appreciate this is not ideal.
What’s my best course of action from here on?

I have limited tools, and errm…. Knowledge haha so go easy on me

Many thanks in advance

Danny

[nowty]

Hi Dannyg2325, I do something similar with my lithium batteries and don't worry, we all start somewhere on our renewable journeys.

So first question, have you got the pylontechs operating again at least with charging with the solar (or grid) ?

If they are still operational then the pylontech calls should self balance over time. You say you set them for lead acid and have set the DOD to 70%. If thats how you are controlling the low end cut off thats where you are going wrong because the ME3000SP will simply not really know the true SOC of the batteries in lead acid mode so you need to set the discharge cut off voltage setting appropriately.

When lithium batteries get very low, their cell voltages drop off a cliff and some cells may become deeply discharged or even go into reversal. From what I understand and from my own experience, lithium cells can be deeply discharged, even completely flattened for a limited length of time. If they go into reversal, once the reversal on a cell get to -12% of the nominal cell voltage, copper bleeds out of the cathode and migrates through the electrolyte and eventually short circuits with the anode in the affected cell which is a terminal event. The fact that you have voltage on all cells is a good thing and the battery did the correct action and shut itself down.

Have you changed any of the other charging parameters on the ME3000SP ?, can you list what they are all currently set to shown below.

Set min discharge voltage
Set max discharge current
Set min protect voltage
Set battery capacity
Set discharge depth
Set max charge voltage
Set empty discharge voltage
Set max charge current
Set full charge voltage
Set max protect voltage

Do you have a datasheet for your 1st generation pylontechs ?, if not I'll assume their spec will be same or similar to the latest ones and I will offer a set of parameters which should work safely for you.

[Tinbum]

I think your going to need a charger (60v) to be able to get the voltages high enough to be able to then use the ME3000 unless you open the pylontechs and charge each pack separately.. You must make sure that you dont take a cell above its designed max voltage though.

[Dannyg2325]

Hi Nowty,

Thanks for your reply!

Yes I managed to get the cells lifted enough to power everything back up, it’s been connected to grid/panels again and is taking charge from the ME3000.
Currently the voltage is showing 53.4v on the sofar, but also says it’s only 35% charged.

I set the the Sofar based on the values here :- https://www.greenengineering.com.au/pdf ... mation.pdf

Hopefully you are right in what you’re saying that they will balance themselves out again.

I had to disconnect the system to make room for a new boiler installation, so it has been off for a couple weeks now, maybe it’s rectified itself.
My original configuration on the Sofar has reset though, so I’ll need to program all the values in again

Thanks for your input

Hi Dannyg2325, I do something similar with my lithium batteries and don't worry, we all start somewhere on our renewable journeys.

So first question, have you got the pylontechs operating again at least with charging with the solar (or grid) ?

If they are still operational then the pylontech calls should self balance over time. You say you set them for lead acid and have set the DOD to 70%. If thats how you are controlling the low end cut off thats where you are going wrong because the ME3000SP will simply not really know the true SOC of the batteries in lead acid mode so you need to set the discharge cut off voltage setting appropriately.

When lithium batteries get very low, their cell voltages drop off a cliff and some cells may become deeply discharged or even go into reversal. From what I understand and from my own experience, lithium cells can be deeply discharged, even completely flattened for a limited length of time. If they go into reversal, once the reversal on a cell get to -12% of the nominal cell voltage, copper bleeds out of the cathode and migrates through the electrolyte and eventually short circuits with the anode in the affected cell which is a terminal event. The fact that you have voltage on all cells is a good thing and the battery did the correct action and shut itself down.

Have you changed any of the other charging parameters on the ME3000SP ?, can you list what they are all currently set to shown below.

Set min discharge voltage
Set max discharge current
Set min protect voltage
Set battery capacity
Set discharge depth
Set max charge voltage
Set empty discharge voltage
Set max charge current
Set full charge voltage
Set max protect voltage

Do you have a datasheet for your 1st generation pylontechs ?, if not I'll assume their spec will be same or similar to the latest ones and I will offer a set of parameters which should work safely for you.

[Dannyg2325]

Hi Tinbum,

Yeah I lifted the lids and and charged each pack back up.
As they are 12v, was just concerned that possibly one of the smaller cells within the 12v pack was too far out of balance and would not rectify.

I need to check the 12v cells again to see what voltage they are at now and I will know better as to what’s happening.

Cheers

I think your going to need a charger (60v) to be able to get the voltages high enough to be able to then use the ME3000 unless you open the pylontechs and charge each pack separately.. You must make sure that you dont take a cell above its designed max voltage though.

[nowty]

Hi Nowty,

Thanks for your reply!

Yes I managed to get the cells lifted enough to power everything back up, it’s been connected to grid/panels again and is taking charge from the ME3000.
Currently the voltage is showing 53.4v on the sofar, but also says it’s only 35% charged.

I set the the Sofar based on the values here :- https://www.greenengineering.com.au/pdf ... mation.pdf

Hopefully you are right in what you’re saying that they will balance themselves out again.

I had to disconnect the system to make room for a new boiler installation, so it has been off for a couple weeks now, maybe it’s rectified itself.
My original configuration on the Sofar has reset though, so I’ll need to program all the values in again

Thanks for your input

Thanks for the datasheet, I'll try and go through it and get back to you with what I think your settings should be, especially at the lower end as you don't want a repeat of the problem.

I do have a ME3000SP so I know how the parameters work.

As I said previously, because you have it set to lead acid, you wont get sensible readings from the SOC indicator on the ME3000SP, its the voltage you need to watch and work it out from a graph.

Example this is for a generic lithium cell with the same chemistry, those pylontecs have 15 cells in series, so you multiply the voltage on the graph by 15. Or divide the voltage showing on the ME3000SP by 15 to get the individual cell voltage, then look it up against the graph.

[Tinbum]

Currently the voltage is showing 53.4v on the sofar, but also says it’s only 35% charged.

That battery goes to a high voltage 57v though compared with other more modern Pylontech. It also shows min charge voltage as 54v though.

[Tinbum]

Example this is for a generic lithium cell with the same chemistry, those pylontecs have 15 cells in series, so you multiply the voltage on the graph by 15. Or divide the voltage showing on the ME3000SP by 15 to get the individual cell voltage, then look it up against the graph.

I have a feeling they are not 15 cells as the charge voltage is higher from the manual but max cell voltage is 3.7v. 16 cells probably.

[Stinsy]

Example this is for a generic lithium cell with the same chemistry, those pylontecs have 15 cells in series, so you multiply the voltage on the graph by 15. Or divide the voltage showing on the ME3000SP by 15 to get the individual cell voltage, then look it up against the graph.

I have a feeling they are not 15 cells as the charge voltage is higher from the manual but max cell voltage is 3.7v. 16 cells probably.

Definitely 15 cells.

[nowty]

Example this is for a generic lithium cell with the same chemistry, those pylontecs have 15 cells in series, so you multiply the voltage on the graph by 15. Or divide the voltage showing on the ME3000SP by 15 to get the individual cell voltage, then look it up against the graph.

I have a feeling they are not 15 cells as the charge voltage is higher from the manual but max cell voltage is 3.7v. 16 cells probably.

I thought that as well at first but I still think they are 15 cells and the datasheet is just badly written.

From part of the datasheet shown below, look at lines 2 and 3, shows over voltage protection for cell and pack 3.75v and 57v respectively.
57v / 3.75v = 15.2 so much nearer 15 than 16.

So I think the datasheet saying you can charge it at up to 57v is insane unless your going to cut it off at a set current value like fast lithium chargers do. But if your charging in lead acid mode with constant voltage, the max charge setting needs to be much lower.

My Covid is giving me a touch of brain strain at the moment so I need to look at it properly tomorrow to give a full set of settings in lead acid mode.