JK BMS - can anyone explain this?

I enclosed details of my LiFePo4 battery( 3.2V 280Ah, 16 cells) status
As you can see
JK BMS says Remain battery 98% but Remain capacity 274
I think the 100% capacity should be 13,44kWh
Can you please explain?

Besides Cycle count 5356 seems nonsense. The cells should be new ( from the beginning BMS reported cycle count from 0 but later in few next days started showing nonsense.
When I disconnected
JK BMS it started working in a correct way but later ( few days later ) worked in faulty way again.
Is there a firmware bug?

Is it possible to upgrade firmware?

Thank you for help

Your battery is empty.

The JK BMS will not accurately report % charge until it is fully charged.

Battery Capacity is set to 280Ah so that is the units of measurement you will see. 274/280 = 97.8%. This is obviously incorrect because the cell voltages indicate a discharged battery. It needs to be put through a full charge cycle so the BMS can calibrate the SoC. Sunshine beat me to that point.
BTW, the nominal cell voltage of LiFePO4 is considered as 3.2V. Your 16S battery would then be 51.2V.
Lastly battery capacity in Wh is as follows: 51.2V x 280Ah = 14,336Wh

Jane, I may have not explained this to you previously.
LFP Cells have an Allowable Voltage Range of 2.500-3.650 which is the voltage range that the cells can be charged/discharged. Above or Below that range is causing harm to the cells.
Their "Working Range" is actually from 3.000-3.400 Volts per cell and that is where your Stored Energy comes from, ie the AH's.

At present your cells are 3.04V per cell and essentially at 0% SOC.
The JK BMS will require a couple of proper cycles to fully calibrate (this is normal) so you need to charge that pack up to 3.425Volts per cell - 55.2V with Amps taken reaching down to 14A which is your Endamps / Tailcurrent for that pack. I say 3.425Vpc because the moment you stop applying charge the cells will settle (as expected) to just over 3.395 +/-

Jane said:

Is it possible to upgrade firmware?

Click to expand...

I am not sure if the FW can be changed.


As already stated by others, your cells are practically 0% SOC, not 98%.
JK's current sensing/measurement SUCK, it is inaccurate even when calibrated.
I bet your battery was being charged/discharged between 20% and 90% so much so, it was not given the chance to reset itself periodically.

Periodically (once a week) fully charge your cells to 3.500V ~3.600V of which JK will reset SOC to 100%

Finally, judging with the cycle count, I bet your JK experienced a glitch.

Any luck,so far?

Please post a pic of your screen 2 , Basic and Avanced Setttings, that may help solve the puzzle,if you haven't yet.

Also give us the model of your BMS and the number of versions on it;
--for instance, mine is JK_ B2A8S20P , bought in Aug/2022 ans it comes already with 121 update versions,go figure,from V1.0.0 all the way to V4.8.4 (click on the 3 dots on any os the 3 screens to see it), so there WERE problems along the way,probably there still are.

My jk bms does something just amazing to me,in order for it to calculate the SOC (state of charge) instantly: it reads Volts (to the millivolt, that is needed given the relative flatness of the lifepo4 curves) and Amps, and it knows when they are In or Out, and it knows it's Lifepo4,you selected it on screen 2; armed with that and with a lot of time and work elaborating charts and tables by the engineers at jikong bms, the software instantly calculates the SOC on percentage; the SOC reading on Ah is not real,it is just a calculation,it can be anything, depending on YOUR input of the total capacity of your pack, on line 2 of screen 2, so that should be near the real Ah of your pack.

Do verify the tightness of all terminals( you need to pull on them to be sure...) and all their locations, double check that,before condemning the BMS; also it transmits via bluetooth,a radio, i don't think so,but still, do verify that there are no heavy electrical nor magnetic interferences along the way.
Keep us posted,good luck.

I have 72v 49Ah lifepo4 battery. 1st time jk bms shows accurate percentage and remaining capacity of battery. But after recharging and then discharging. Jk bms shows 0 percentage and 0 remaining capacity. Then I emailed jk bms company. They replied and told me to discharge battery to zero. Change it to 20 times higher for example 72v 49Ah to 72v 69Ah. Then recharge and it will fix my problem. But its not. Please guide me.

My BMS also has a glitch: After it goes into undervoltage protection for one of my 15 cells, the SOC drops to 0%. I then have to manually set the pack capacity to a different number and set it back again and then the SOC goes up again.

Normal behaviour after UVP should be that it goes back to where it was before UVP.