diy solar

diy solar

220ah 4s bank @ 12v with only 60ah useage

Saxk

Saxk

New Member
Joined
Apr 24, 2023
Messages
11
Location
Germany
My lifepo4 4s batteries in my camper are at sub 12v after just 66ah of discharge, they are 220ah batteries.

I know i wouldn't get 220ah use from them, but id have hoped for at least 150, not 66ah. Does this mean one cell is dead?
where do i start testing? i plan to let them run down again and then check the cells individual voltages, to see if one is extra low.

Checked volts
C4 3.25
C3 3.24
C2 3.27
C1 2.21
So it's clear that cell 1 is not holding it's own against the rest. Is it simply dead, can I fix it? It is pretty swollen.

What else can i do

60a DCDC charger
4 x 220ah Lifepo4s
Daly 80a BMS

Brad
 
Last edited:
rodrick said:
Is this a diy battery can you check each cell voltage it sounds like you need to top balance
Click to expand...
Yes it's a diy build.
They ran one year without a bms, I fact I just fitted the bms, but it's not charged through it yet, I haven't driven anywhere.

I'll check out a top balance routine.
 
If you ran for a year without a bms you may have damaged a cell, top balance and see what you have when you run a capacity test but with a swollen cell and low voltage you probably have a damaged cell which will need replacing
 
Yeah i figured. I had a Daly, but couldn't get it to work, so kinda gave up and thought ill look over winter, i didn't get round to it.

so to top balance, I'm familiar with the procedure, but not familiar on what i need to do it, i cant seem to find many 3.2/3.65v chargers in Europe and i don't want to wait 2 months from china. Can i use a lab power supply like this?


1682752902349.png
 
Yes make a good set of leads with 10 gage wire the ones included with them are garbage

set your voltage before connecting to the cell then do not adjust while charging
 
Brilliant, i ordered a even better one. I'm sure the battery is damaged regardless, but ill find other uses for this charger. ive often considered buying one

1682756923259.png
 
ok so i top balanced them all to 3.55v, put them back in the van, with no bms, as they're not getting a charge, its also disconnected, its just the easiest place to run them down with the fridge for a few days.

C4 3.35
C3 3.35
C2 3.38
C1 1.24

So is that it, is C1 just trash. why did it give all of its amps up and the rest barely got used. This time I got down to 130ah remaining, so a bit better at 70ah usage.

is a new cell the only option, a single cell is hard to buy.
 
Saxk said:
ok so i top balanced them all to 3.55v, put them back in the van, with no bms, as they're not getting a charge, its also disconnected, its just the easiest place to run them down with the fridge for a few days.

C4 3.35
C3 3.35
C2 3.38
C1 1.24

So is that it, is C1 just trash. why did it give all of its amps up and the rest barely got used. This time I got down to 130ah remaining, so a bit better at 70ah usage.

is a new cell the only option, a single cell is hard to buy.
Click to expand...
You see that C1 isn't holding its charge, but you may have damaged other cells too, charging them without a BMS.
In short, the other cells might not pull the capacity you expect either.

If you are able to source another cell (same brand, type and Ah, etc...), I would first do a capacity test on each cell individually, to see if it's worth replacing just one. You may be surprised of the outcome (heavily degraded cells).
You will need some sort of capacity tester for this though. A few good options are the DL24 and the EBC A20.
 
meetyg said:
You see that C1 isn't holding its charge, but you may have damaged other cells too, charging them without a BMS.
In short, the other cells might not pull the capacity you expect either.

If you are able to source another cell (same brand, type and Ah, etc...), I would first do a capacity test on each cell individually, to see if it's worth replacing just one. You may be surprised of the outcome (heavily degraded cells).
You will need some sort of capacity tester for this though. A few good options are the DL24 and the EBC A20.
Click to expand...
To be fair they're all a bit bloated. but they seem to hold well, so far. But yeah, I'm not holding my breath that they're still 100%
The cell I found is 200ah, not 202 and a different brand, is that not ok to mix brands?
I'm really not in the market to buy a machine for 200 euros to check if my probably dead batteries are infact, dead. Can I DIY something, a lmap with a 3v dra etc and record how long it lasts, with a camera over an ammeter? Sorry if this sounds not clever, I'm really new to this, as you can tell. But I'm good and cameras, so I could rig something up to run for days like that.

Thanks for the help

Just seem the DL24 is not so expensive.
 
I find the DL24 to be cost effective and pretty handy. It helps testing many kinds of batteries and simulating loads in general (up to its limits). If you do choose to get one, make sure you get the newer models with color screen. The older ones were somewhat inaccurate.

I guess you could DIY something... But I think it will be hard to simulate a true constant current load.
You would need a load/resistor that is between 10 and 40 amps (depending on the time you have).
 
meetyg said:
I find the DL24 to be cost effective and pretty handy. It helps testing many kinds of batteries and simulating loads in general (up to its limits). If you do choose to get one, make sure you get the newer models with color screen. The older ones were somewhat inaccurate.

I guess you could DIY something... But I think it will be hard to simulate a true constant current load.
You would need a load/resistor that is between 10 and 40 amps (depending on the time you have).
Click to expand...
Thanks. I ordered last night a dl150§ or some ting, the new one.
 
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