1st cell exceeding voltage / charging too fast
- Thread starter denmek
- Start date
MisterSandals
Participation Medalist
All i can say is that all the weird shit always happens to cell #1. Try swapping cells 1 and 2 if you can and try again.
Label your cells so you can take notes and keep track of this particular cell. If this problem follows this cell then it may be your weakest cell and will limit your overall battery capacity by being the limiting factor in how high your battery can be charged to keep this cell below 3.65V. Similar for discharging, it may be your limiting cell for discharge.
Label your cells so you can take notes and keep track of this particular cell. If this problem follows this cell then it may be your weakest cell and will limit your overall battery capacity by being the limiting factor in how high your battery can be charged to keep this cell below 3.65V. Similar for discharging, it may be your limiting cell for discharge.
mikefitz
Solar Wizard
- Joined
- May 28, 2020
- Messages
- 2,987
Often where its the end cell thats showing issues, either the BMS leads are incorrectly attached or the termination is suspect. As sugested swap round the cell and at the same time check that the cable and BMS lead terminations, buss bars, are making correct contact with the cells. Verify with a meter if possible on the cells that the BMS is giving correct readings.
Mike
Mike
Bud Martin
Solar Wizard
- Joined
- Aug 27, 2020
- Messages
- 4,844
Did you perform parallel top balancing the cells?
Cells were all top balanced, same votlage, same inner resistance. Checked terminal temperature, finally replaced the cell and problem become better. So it looks like cell had some internal issue. Will have a look further. Thanks for the suggestions.
I also recognized that the problem occurs above 3.35V which is already quite close to 90% or even above. So workaround would be to stop charging earlier. I belive that might be a solution too. Is there any degradation to expect by not fully charging ? There is no memory effect, and lifetime should be even longer. What do you think ?
I also recognized that the problem occurs above 3.35V which is already quite close to 90% or even above. So workaround would be to stop charging earlier. I belive that might be a solution too. Is there any degradation to expect by not fully charging ? There is no memory effect, and lifetime should be even longer. What do you think ?
Steve_S
Offgrid Cabineer, N.E. Ontario, Canada
Few points... btdt many many times... I suggest avoiding jumping to conclusions based on assumptions, it rarely works out that way.
1) Check all busbars for ridges & burs around the holes, file them OFF so they are smooth and make full contact.
2) Clean ALL Contact points to remove oils/greases & waxes (yes everything get's a coating of one or the other) this is normal. Cutting oil, waxes to protect the raw aluminium etc. (you would be shocked to know how much that can affect readings).
3) Check all your BMS Leads from ring-terminals to connector to ensure they are all GOOD !
* NOTE * Always disconnect BMS when Futsing with wires, easiest way to fry a BMS.
An overly aggressive Charge Profile will also trigger a RUNNER cell and result in what you are seeing, having one cell go up or down faster than its companions. Nominal Voltage is 3.200, Working Voltage Curve is 3.000-3.400 Volts per cell. Anything above 3.500 or below 2.875 are cliff edge and represent <5% of capacity. Charge cells to 3.650 till they take 0A, within one hour of charge stop they will settle to 3.550 +/- and two hours to 1.490+/- which is NORMAL.
Here is my 24V Charge profile for a Midnite Classic 200 SCC, try to match your SCC Charge profile and you will not have runner issues and the batteries will top up and level out quite nicely.
All equipment MUST BE Voltage Corrected & Calibrated (VERY IMPORTANT) see link in my signature on how to do it.
Divide Values X2 for 12V. Multiply X2 for 48V.
Absorb: 28.2 for 15 minutes (3.525vpc) (some call this boost)
Equalize: OFF
Float 27.9V (3.4875vpc)
MIn Volts: 22.0 (2.750vpc)
Max Volts: 28.7 (3.5875vpc)
Rebulk Voltage: 27.7 (3.4625vpc)
End Amps: 14A (*1)
(*1): End Amps is calculated from the Highest AH Battery Pack in a Bank. IE: 200AH X 0.05 = 10A 280AH X 0.05 = 14A.
NB: Victron Forum discussion says EndAmps = TailCurrent
This get's the bank charged to full with high amps (Constant Current) and then float (Constant Voltage) tops off so the cells are on average between 3.475-3.500. I am running 7/24/365 so float is used up by the Inverter + provides whatever the packs will take to top off.
** Coulumbic Efficiency for LFP is 99%
1) Check all busbars for ridges & burs around the holes, file them OFF so they are smooth and make full contact.
2) Clean ALL Contact points to remove oils/greases & waxes (yes everything get's a coating of one or the other) this is normal. Cutting oil, waxes to protect the raw aluminium etc. (you would be shocked to know how much that can affect readings).
3) Check all your BMS Leads from ring-terminals to connector to ensure they are all GOOD !
* NOTE * Always disconnect BMS when Futsing with wires, easiest way to fry a BMS.
An overly aggressive Charge Profile will also trigger a RUNNER cell and result in what you are seeing, having one cell go up or down faster than its companions. Nominal Voltage is 3.200, Working Voltage Curve is 3.000-3.400 Volts per cell. Anything above 3.500 or below 2.875 are cliff edge and represent <5% of capacity. Charge cells to 3.650 till they take 0A, within one hour of charge stop they will settle to 3.550 +/- and two hours to 1.490+/- which is NORMAL.
Here is my 24V Charge profile for a Midnite Classic 200 SCC, try to match your SCC Charge profile and you will not have runner issues and the batteries will top up and level out quite nicely.
All equipment MUST BE Voltage Corrected & Calibrated (VERY IMPORTANT) see link in my signature on how to do it.
Divide Values X2 for 12V. Multiply X2 for 48V.
Absorb: 28.2 for 15 minutes (3.525vpc) (some call this boost)
Equalize: OFF
Float 27.9V (3.4875vpc)
MIn Volts: 22.0 (2.750vpc)
Max Volts: 28.7 (3.5875vpc)
Rebulk Voltage: 27.7 (3.4625vpc)
End Amps: 14A (*1)
(*1): End Amps is calculated from the Highest AH Battery Pack in a Bank. IE: 200AH X 0.05 = 10A 280AH X 0.05 = 14A.
NB: Victron Forum discussion says EndAmps = TailCurrent
This get's the bank charged to full with high amps (Constant Current) and then float (Constant Voltage) tops off so the cells are on average between 3.475-3.500. I am running 7/24/365 so float is used up by the Inverter + provides whatever the packs will take to top off.
** Coulumbic Efficiency for LFP is 99%
