help with single cell overvoltage and BMS overvoltage at 100% capacity

[sunshine]

I see your problem very clearly.

Maybe there are other issues.
In the original question- "so every time my battery gets fully charged and left to float at a certain time after a while of it fluctuating between charge and discharge once at 100% the inverter begins to get set off to say OV (over voltage) "\

....and there have been other posts with similar issues.

I have similar issues since I've emptied the spa, unplugged the heating elements and pump and unless I disconnect most of the panels, the voltage just rises beyond the pwm settings until the inverter goes over voltage at .15v. Lucky I have 12v panels with a voc of 21v and with the 12v loads present, and with a few smaller over voltage loads cutting in the v won't go above this.

There seems to be saturation of voltage in no load situations with the pwms. Maybe this is the reason with other CC's?

 

[Tecnodave]

@sunshine,

The OP does have a MPPT controller and they do not have a “PWM” mode. when the battery reaches full charge the MPPT controllers will unload the panels to reduce the output, but the issue with the OPs situation is the controller is set to the wrong battery profile, he has FLA selected which does have equilization but lithium batteries do not need or want equilization

 

[sunshine]

The OP does have a MPPT controller and they do not have a “PWM” mode. when the battery reaches full charge the MPPT controllers will unload the panels to reduce the output,

I did see the op having a mppt cc. The previous poster had pwm and the scenario was very similar and probably the wrong charging levels as you have pointed out.
Do you have any thoughts on maintaining the voltage settings once the system is fully charged, no load, full sun and charge controllers are mosfet based?

 

[Tecnodave]

The controller that i charge my lithium batteries was designed for lithium batteries, it shuts off when batteries are full.

I do not use limited controllability controllers, gave up on them after they were not able to maintain my batteries.

I still have not decided how i will control my large set of pouch cells but i will charge them up to set point then have charger disable itself internally. My cc has the ability to shut down from external command , as to exactly how i will do that is to be determined by expereince. I am here on this forum and other forums to learn and share...

My controller does have user defined battery type but does not have a defined lithium program. Other users have developed a method to safely charge lithium types, i will rely on their expereince.

 

[Tecnodave]

@sunshine

I think the best way to equilize most lithium types is to connect all cells in parallel, let them sit for several hours then use a good quality CC/CV power supply to slowly bring them up to terminal voltage. It may well take several cycles to achieve balance between cells.

Personally i use the Junsi iCharger i208b which is really targeted to the model airplane industry. It is way too small for full time use in large format cells but its best to take it slow and easy rather than trying to shove a full charge all at once.

Pictured is the Junsi iCharger i208 balancing a set of 16 pouch cells connected in 2P8S configuration. this model of charger/discharger/balancer/tester is rated max 8S for lithium at 20 amps. It may take a week to charge/discharge/cycle the batteries. This will be replaced with a true BMS and balancer, have ordered JBD 8S LFP BMS from high tech /current connected

 

[fratermus]

I’ve tried multiple times to reduce the charge limit but the mt50 I’m using continues to say para. Error for parameter error

Sorry for the necropost, but for onlookers this PARA error means the logic of the various setpoints is being violated. Float cannot be higher than Absorption, for example.

Page 26 of the manual (pdf) lays out the requirements

The following rules must be observed when modifying the parameter's value in user battery type

Over Voltage Disconnect Voltage > Charging Limit Voltage ≥ Equalize Charging Voltage ≥ Boost Charging Voltage ≥ Float Charging Voltage > Boost Reconnect Charging Voltage.

Over Voltage Disconnect Voltage > Over Voltage Reconnect Voltage

Low Voltage Reconnect Voltage > Low Voltage Disconnect Voltage ≥ Discharging Limit Voltage.

Under Voltage Warning Reconnect Voltage>Under Voltage Warning Voltage≥ Discharging Limit Voltage

Boost Reconnect Charging voltage >Low Voltage Reconnect Voltage.

 

[littleharbor2]

Are you using a BTS,(battery temp sensor) on the CC? This will raise the charge voltage in colder temps.