Lifepo4 never reaching full charge - panel output ample

[solaar]

I have a relatively new lifepo4 12v solar setup which under charge is only reaching around 13.36V and then it slows down so much it may as well have stopped. It's never reaching the absorb or float stages. It seems to be very slow even getting to this point.

I've dismantled the setup and the settled battery charge is now 13.25.

It was 13.5 when it arrived from the store

The programmable Victron charger 75/15 has worked flawlessly on my SLA setup, so I'm hesitant to think this is the problem.

I am charging at 14.6 floating at 13.6, temp compensation and equalisation is off.

Battery is an EV power 60Ah with BMS and BCU

I have tested with and without the BCU - no difference.

BMS shows balanced cells

Panel is 120W with plenty of tropical sun to play with. I've tested with another panel - no change. Both are outputting above spec.

Obviously I need to test with a different charge controller and rule this out, but there aren't a lot of options where I am other than buying a new one which I would like to avoid.

Does any of this sound indicative of a known problem?

Thanks

[inetdog]

Is the BMS system you are using doing more than just monitoring? That is, is it shunting individual cells to limit the maximum voltage?

If you are using LiFePO₄ then the resting full charge voltage (after charger is removed and cell left to sit without load for awhile) should be about 3.33V/cell, which is 13.3V on a four cell battery.
You are trying to overcharge the battery by using 14.6, even though the float voltage setting is only 13.6.

In addition, for longest battery life in an application like RE where total available capacity is not as critical as in a flying vehicle use, you do not really want to go above about 80% SOC. (Around 3.2V per cell?)

I am not sure why your Victron charger is not being successful in overcharging your battery, unless the BMS is being successful in protecting it.

[solaar]

14.6 was the spec the manufacturer gave me.

I have read the post here that says to use a lower charge voltage, but I think it mentions that higher voltages may be needed for those running external BCUs - which I am. So I decided to just stick to the manufacturers spec.

I will check what the function of the BMS is, I thought it was only a monitor, but maybe it does more.

The manufacturer also says that while incomplete charges are ok, a full charge should be completed every month or two. I'm sure that's probably up for debate.

I'll post when I find out about the BMS.

[Sunking]

OK first you do not want to ever charge to 100% or 14.6 volts. The BMS is pretty much worthless and not needed for a 4S battery.. BMS will not even turn on until you reach around 14.4 volts.

OK having said that the problem could be a few things.

1. Defective Controller or improperly setup. My best guess this is the problem based on what you have said.
2. You use to much power and not enough panel wattage to get recharged before the sunsets.
3. The biggest destroyer of LFP batteries is the BMS. One of the Vampire Boards is turning on shunting a cell draining and bypassing the cell. Example a Vampire Board shorted out and draining a cell. Real easy to figure out.

1. First thing to do is get rid of the BMS and BCU. You have no need for it.

2. Next set Bulk = Absorb = Float = 13.6 to 13.8 volts. Turn everything else off especially Temp Comp. This forces your controller to operate as a CC/CV Float Charger which is exactly what you want for LFP cells. If the controller is working properly it will operate in Constant Current Mode until the pack voltage reaches 13.8 volts. When the pack reaches 13.8 volts, it will be Constant Voltage mode. At that point the battery voltage will hold 13.8 volts, and charge current wil taper off to 0 amps when the batteries are saturated. If you still have sun out, th epower will come from the panels assuming th eload is less than what the panels can supply.

If that does not fix the problem, you either have a Controller problem, using to much power, or a defective cell. Defective cell is easy to spot and feel. It will be a lower voltage than the other three and warm if taking charge current.


What Chi-Com cells are you using? CALB. GBS, Winston, Sinopoly, what? Since you used the term BCU, and a voltage of 14.6 volts sounds like you bought from EV Power and Winston Thunder Bomb cells.

[solaar]

1. Defective Controller or improperly setup. My best guess this is the problem based on what you have said.

Controller has been checked, double checked and re-checked. It works fine on my AGM with SLA settings. Lithium values entered are all correct (manufacturers specs), though I understand there is disagreement as to what the charge should be. Either way, I should still be getting the values I have entered into the charge controller which is 14.6. Right or wrong charge, it suggests there is something that is not working right.

2. You use to much power and not enough panel wattage to get recharged before the sunsets.

After I noticed there was a problem, all charging was done without any load and the charge would still stagnate for hours in full sunlight.

For the loads I use with the same setup on an AGM, I would have full charge again by 10am most days, so the panel creates surplus power for what I need.

What Chi-Com cells are you using? CALB. GBS, Winston, Sinopoly, what? Since you used the term BCU, and a voltage of 14.6 volts sounds like you bought from EV Power and Winston Thunder Bomb cells.

Yep, EV Power. I think they are GBS.

http://www.ev-power.com.au/-EV-Powerpak-Custom-LFP-Batteries-.html

BMS will not even turn on until you reach around 14.4 volts.

Do you mean it will only shunt charges to balance the cells on voltages above 14.4? It must still monitor at all times - my ones have green indicator lights on each cell to suggest the balance is fine.

I'd prefer to just keep the modules on and keep an eye on the issue you mention, otherwise it's more work to pull them off and figure out how to reconnect the cells. I'm sure it's easy, but I don't want to waste my time and more money if it's not overly necessary.


This is all for a camping setup, so a lot of the time when I am charging/discharging, I am there to monitor what is going on. It's not on 24/7 unattended.

[solaar]

Is the BMS system you are using doing more than just monitoring? That is, is it shunting individual cells to limit the maximum voltage?

It looks like the BMS monitors and shunts cells, according to the modules EV power sell on their website.

[Mike90250]

What are the specs of your PV panels ?
Have you been able to push your lead acid batteries to 14.6V ?

[solaar]

What are the specs of your PV panels ?
Have you been able to push your lead acid batteries to 14.6V ?

What are the specs of your PV panels ?
Have you been able to push your lead acid batteries to 14.6V ?

120W panel is what I usually use.

Max. power: 120W
Rated voltage: 12V
Voltage at max. power: 21.6V
Current at max. power: 7.75A
Open circuit voltage: 17.2V
Short circuit current: 6.68A

I set the controller to 14.8 and 13.8 float for the AGM, and I get there no problems

[SunEagle]

120W panel is what I usually use.

Max. power: 120W
Rated voltage: 12V
Voltage at max. power: 21.6V
Current at max. power: 7.75A
Open circuit voltage: 17.2V
Short circuit current: 6.68A

I set the controller to 14.8 and 13.8 float for the AGM, and I get there no problems

Something is not correct with those panel specs. Usually the rated wattage is equal to multiplying the Vmp x Imp. In your case that would be 21.6v x 7.75a = 167.4watts but you state it is 120W

So either you have posted incorrect values for the Imp and Vmp as well as Voc and Isc or your panel label is bogus.

Usually the Voc is less then the Vmp and the Isc is larger then the Imp. You have those values reversed.

[Sunking]

Do you mean it will only shunt charges to balance the cells on voltages above 14.4?

Yes that is how it works except it triggers at 3.55 volts, not 14.4. That is why they are called Vampire or Bleeder Boards. They are the number one cause of LFP battery failures. If you have GBS cells you should set the controller to 14.4 volts, but has nothing to do with your problem.

If you are certain the controller is working properly then you either have a bad cell and/or defective Vampire Board. Real easy to find with a volt meter. If you are lucky it is a Vampire Board and the solution is easy, get rid of the BMS. I suspect if you measure cell voltage you are going to find 3 cells above 4-volts and one hanging out around 0 to 1 volt. If you find one with low voltage, your Vampire board killed it.

That is it report back cell voltages. If they are healthy all should be within .05 volts when charged up reading 3.6 volts per cell.

[Sunking]

Something is not correct with those panel specs. Usually the rated wattage is equal to multiplying the Vmp x Imp. In your case that would be 21.6v x 7.75a = 167.4watts but you state it is 120W

So either you have posted incorrect values for the Imp and Vmp as well as Voc and Isc or your panel label is bogus.

Usually the Voc is less then the Vmp and the Isc is larger then the Imp. You have those values reversed.

He flopped Voc and Vmp

[littleharbor]

I have some J-Sky, Indonesian made, J Sky 150 watt.jpg 12 volt 150 watt panels with the same error on the data label.

[SunEagle]

I have some J-Sky, Indonesian made, J Sky 150 watt.jpg 12 volt 150 watt panels with the same error on the data label.

Hmm. I guess they do not have any quality control department. One wonders even if that panel will produce 150watts.

[solaar]

Something is not correct with those panel specs. Usually the rated wattage is equal to multiplying the Vmp x Imp. In your case that would be 21.6v x 7.75a = 167.4watts but you state it is 120W

So either you have posted incorrect values for the Imp and Vmp as well as Voc and Isc or your panel label is bogus.

Usually the Voc is less then the Vmp and the Isc is larger then the Imp. You have those values reversed.

Copied and pasted straight off the Jaycar website where I bought it. Doesn't surprise me at all that it's wrong.

[solaar]

That is it report back cell voltages. If they are healthy all should be within .05 volts when charged up reading 3.6 volts per cell.

Will check them tomorrow, thanks.