Lifepo4 Charging confusion

[datsolardude]

I have been charging my life chins 12v 300ah lifepo4 battery With my newly installed renogy DC to DC charger. I have a 200 watt panel up top and a switch to turn off the solar to maximize my alternator charging. My question and confusion comes from Seeing my battery at 12.8 V or lower before charging. I start charging at max of 50 amps my battery will top off like pretty fast within a few minutes and cut off my current and start boosting. I'll adjust the charging down to 40 amps or even 30 and it will eventually do the same thing even though I know my battery is not that full. Why does this happen? Is there something wrong with my battery or charger? I'm always adjusting the charging even switching on and off the solar for combined charging of 20 amps which seems to work but I want To get maximum efficiency and wondering what's going wrong. Can anybody help me put on this one? Any input would be great thanks

 

[webbbn]

What voltage are you charging at?

 

[datsolardude]

12 volt system

 

[Supervstech]

12 volt system

So... what voltage are you charging at?
What are the voltage settings on your equipment?

 

[datsolardude]

Which settings are you asking for? Like boost?

 

[hwse]

What is your max charge current that the BMS will allow and are you hitting it with the combination of charger and solar?

 

[datsolardude]

 

[MisterSandals]

You realize that your BMS right there says max charge current 10? Yet you are throwing 50A, 40A,… at it and expecting it to work?

 

[datsolardude]

No incorrect I can change that, it will go 10 20 30 40 50, my battery can handle 50 amps, that's just the setting I currently have it set to from the charger

 

[MisterSandals]

So what are your (current) charge settings?

 

[datsolardude]

It depends when I'm driving down the road. I keep an Eye on it with the renogy app and if it's charging low when I drive I increase it. It will reach 14.5 and cut off current go into boost mode I'll make a video and upload it

 

[MisterSandals]

Sorry I mistook your settings as BMS settings.
I would try changing battery type to “user defined” and put reasonable charging on it to ~14.0V to see if that helps.
I suspect your battery is not perfectly balance at 3.65Vpc to 14.6V and your BMS curtails charging.
Can you see individual cell voltages somehow?

 

[datsolardude]

So what are your (current) charge settings?

I made a video, but it's like, 14 minutes long. Basically, my battery was nothing charging is at 13.1 V. I start up the engine and Set the parameters for 50 amps which it usually doesn't get that high but it is capable of it. It reaches about 30 amps, and after a couple of minutes of driving, it hits 14.5 and goes into boost mode. It says my battery is at Is fourteen point five

Sorry I mistook your settings as BMS settings.
I would try changing battery type to “user defined” and put reasonable charging on it to ~14.0V to see if that helps.
I suspect your battery is not perfectly balance at 3.65Vpc to 14.6V and your BMS curtails charging.
Can you see individual cell voltages somehow?

It's a sealed LIFEPO4, how does one test individual cells?

 

[webbbn]

If it's hitting 14.5 when charging, and staying high (14+?) after, then I think your battery is fully charged. That's 3.5-3.6V / cell. It may be that the SoC calculation in your battery is not calibrated. Have you tried fully discharging it and seeing how much you get out if it?

 

[datsolardude]

I have fully discharged it a couple of times a while ago, but it's been a while. Might try that, It's just weird because I know it's not fully charged. The battery is sitting at 13.1 V before I turn on my engine and start the initial charge. Within like, 3 or 4 minutes, it's hitting 14.5 even at 30 amps. I'm no physicist but I highly doubt that's my 3800+ W hour. Battery can go from being half discharged to fully charged in the amount of minutes.

 

[Tomthumb62]

It's a sealed LIFEPO4, how does one test individual cells?

To see the voltages of individual cells, you need either a Bluetooth-enabled BMS on the battery, or you must cut open the battery (not recommended) to place multimeter probes on each cell and read the results. The cheapest lifepo4 batteries are glued shut and have no Bluetooth. Paying a bit more money will get you a better battery that has Bluetooth and/or a removable screw-top lid to access the internals.

Without knowing the voltage of the individual cells, you can only guess. It's helpful to diagnose what's really going on, instead of guessing. But as others have said, most likely your cells are out of balance and it can take weeks/months to coax them back into better balance. Someone suggested charging boost to 14.0v and see if that helps. If not, then charge at 13.8v for 24 hours at a time (set both boost and float at 13.8v), then try again at 14.0v. If it's still not acting right, charge again for 24h at 13.8v. I ended up leaving my charger at 13.8v for over a week before it would finish a charge cycle at 14.0v, but my cells were not that out of balance (according to what I saw on the bluetooth app).

 

[datsolardude]

I don't really have the option of doing that. I can only charge when I'm driving my car or the sun is out.

 

[Tomthumb62]

I don't really have the option of doing that. I can only charge when I'm driving my car or the sun is out.

Then you can just live with the unbalanced cells. You'll still get 95-98% capacity, but it will get worse over time unless you place the battery on a constant charging source and do a re-balancing process. Don't worry about it unless you use the battery every day for a year or more.

 

[mikefitz]

I guess the BMS is closing down the charge path. When this happens the battery volts seen at the terminals is around 0.6 volts less than the Internal volts due to BMS volt drop. So your battery at 13.1 at the terminals is actually at a full charged voltage of 13.7
Lowering the charge volts will help preventing the BMS from entering protection. You don't have to charge to 14.6 volts together the battery fully charged, any voltage over 13.8 will charge.

The battery is sitting at 13.1 V before I turn on my engine and start the initial charge. Within like, 3 or 4 minutes, it's hitting 14.5 even at 30 amps

When the BMS shuts down the charge path, no current flows and the charger will reach full boost voltage.

You don't have a serious issue, unbalanced cells are common in many batteries and your battery is charging OK.

When you see the battery in its 13.1 volt state after charging, stop tyring to charge and apply a load of a few amps. The BMS will wake up a you will see actual battery volts in the region of 13.4 to 13.5.

Mike

 

[hwse]

This is one of the reasons that I would not get a battery without a Bluetooth BMS or a serviceable case. It sounds like your battery it badly out of balance but without knowing with the actual cell voltages are we are just guessing. As a worst-case scenario, if it were my battery and it got to the point where I cannot get a usable capacity, I would not hesitate to cut open the case and replace the built-in BMS with a JK.