JK BMS Overvoltage Protection Delay

[Delta Sierra]

Hi all, I recently replaced my Overkill 4s 120A JBD BMS with a JK B2A8S20P-H BMS.

Just putting it through its paces today and I noticed it takes roughly 4-6 seconds to shut off charging when the over voltage protection value is met. (Did some screen recording so I could go back frame by frame to sort it out)

Charging at about 23 amps with a 3.649 overvolt cutoff value in BMS settings I get to around 3.68 before it finally cuts off. I noticed the JBD shuts down charging almost instantly once value is hit.

My absorption target was going to be 3.625 per cell (14.5 for pack), but I may take it a bit lower after finding this out.

My main concern is- can I rely on this BMS to protect my cells? What other protections are there that it is supposed to provide which take much longer to engage then they should?

Does anyone have experiences with both the JK BMS brand and JBD that might provide some insights as to me possibly reinstalling the JBD and calling it quits with the JK or vice versa? I really love the balancing this JK provides & higher amp rating though I would hate to give that up!

 

[Steve_S]

You are Over-charging the pack for one !

LFP "Allowable Voltage Range" is 2.500-3.650. This is the voltage range the cells can be used without Harm/Degradation. This is NOT the actual "Working Voltage Range" which is from 3.000-3.400 with Nominal Voltage @ 3.200 (50% SOC). That 0.400V is where all your AmpHours actually come from. Generally even with B-Grade cells one can use 2.900-3.450 without creating runner cells. ALL BATTERIES regardless of chemistry have an Allowable Range & Working Range, allowable is there as a safe No-harm buffer and not intended to be used regularly.

Set your charging profile to:
Divide Values X2 for 12V. Multiply X2 for 48V.
Absorb: 27.6 for 45 minutes (3.45vpc) (some call this boost)
Equalize: OFF
Float 27.5V (3.437vpc)
MIn Volts: 21.2 (2.650vpc)
Max Volts: 28.6 (3.575vpc)
Rebulk Voltage: 25.6 (3.200vpc)
End Amps/TailCurrent: Depends on your battery pack. 100AH x 0.05=5A, 280AHx0.05=14A

JK Advanced Settings:
Cell OVP(V) 3.600 volts
Cell OVPR(V) 3.525 volts or even 3.550
....
Charge OCP Delay(s) 30 This is in seconds to delay
Charge OCPR Time(s) 60 Release time

Refer to Manual, "5.3.2 参数设置/ Parameter Settings"

i) Single Under-voltage Protection, Single Under-voltage Recovery

"Single under-voltage protection" refers to the cut-off voltage of the cells. When any single Cell within the battery pack is lower than this value, a "single under-voltage alarm" is generated, and the BMS turns off the discharging MOS. At this time, the battery cannot be discharged and can only be charged. When the alarm is generated, only after all the individual voltage values exceed the value of "single voltage recovery", the BMS removes the "single under-voltage alarm" and turns on the discharge MOS.

j) Monomer Overcharge Voltage", "Monomer Overcharge Recovery"
Single Overcharge Voltage refers to the saturated voltage of the battery. As long as any single Cell voltage within the battery pack exceeds this value,'Single Overcharge Alarm' will be generated, and the BMS will turn off the charging MOS. At this time, the battery can not be charged but can only be discharged. When the alarm is generated, only after all the individual voltage values are lower than the "single overcharge recovery" value, the BMS removes the "single overcharge alarm" and turns on the charging MOS at the same time. While not being able to charge, the Active Balancing will transfer the higher voltage cell to a lower voltage cell.

k) Auto Shutdown Voltage
The automatic shut-off voltage indicates the lowest voltage at which the BMS operates. When the lowest cell voltage in the battery pack reaches this value, the BMS shuts down. This value must be lower than "Single under-voltage protection"

l) Maximum Charging Current", "Charging Over-current Delay", "Charging Over-current Release"
When charging the battery pack, the current exceeds the "maximum charging current" and the duration exceeds the "charging Over-current delay", the BMS generates the "charging Over-current alarm" and turns off the charging MOS. After the alarm is generated, after the "charging Over-current relief" time, the BMS relieves the charging Over-current alarm and turns on the charging MOS again.

For example, set the "maximum charging current" to 10A, "charging Over-current delay" to 10 seconds, and "charging Over-current relief" to 50 seconds. When the charging current exceeds 10A continuously for 10 seconds during the charging process, the BMS will generate a 'charging Over-current alarm', turn off the charging MOS at the same time, remove the 'charging Over-current alarm' 50 seconds after the alarm is generated, and turn on the charging MOS again.

m) Maximum Discharge Current", "Discharge Over-current Delay", "Discharge Over-current Release"​

When the battery pack is discharged, and the current exceeds the "maximum discharge current" and the duration exceeds the "discharge Over-current delay", the BMS generates a "discharge Over-current alarm" and turns off the discharging MOS. After the alarm is generated, after the time of "discharge Over-current relief", the BMS relieves the "discharge Over-current alarm" and turns on the discharge MOS again.

Examples include setting maximum discharge current to 100A,'discharge Over-current delay to 10 seconds, and discharge Over-current relief' to 50 seconds. When the discharge current exceeds 100A continuously for 10 seconds during the discharge process, the BMS will produce a 'discharge Over-current alarm', turn off the discharge MOS at the same time, remove the 'discharge Over-current alarm' 50 seconds after the alarm is generated, and turn On the discharge MOS again.​

 

[Delta Sierra]

You are Over-charging the pack for one !

LFP "Allowable Voltage Range" is 2.500-3.650. This is the voltage range the cells can be used without Harm/Degradation. This is NOT the actual "Working Voltage Range" which is from 3.000-3.400 with Nominal Voltage @ 3.200 (50% SOC). That 0.400V is where all your AmpHours actually come from. Generally even with B-Grade cells one can use 2.900-3.450 without creating runner cells. ALL BATTERIES regardless of chemistry have an Allowable Range & Working Range, allowable is there as a safe No-harm buffer and not intended to be used regularly.

Set your charging profile to:
Divide Values X2 for 12V. Multiply X2 for 48V.
Absorb: 27.6 for 45 minutes (3.45vpc) (some call this boost)
Equalize: OFF
Float 27.5V (3.437vpc)
MIn Volts: 21.2 (2.650vpc)
Max Volts: 28.6 (3.575vpc)
Rebulk Voltage: 25.6 (3.200vpc)
End Amps/TailCurrent: Depends on your battery pack. 100AH x 0.05=5A, 280AHx0.05=14A

JK Advanced Settings:
Cell OVP(V) 3.600 volts
Cell OVPR(V) 3.525 volts or even 3.550
....
Charge OCP Delay(s) 30 This is in seconds to delay
Charge OCPR Time(s) 60 Release time

Refer to Manual, "5.3.2 参数设置/ Parameter Settings"

Thank you so much Steve for the great information! You have provided a wealth of info for your other posts as well I really appreciate it!

I will make those adjustments they sound good. I was mainly using the other values just in my testing, not planning on them being for everyday use.

I suppose with using the 3.6v ovp value with the jk, this will give enough breathing room for the strange 5s delay for it to shut the charging off before cells reach 3.65? (Just case something in the system decides to not behave and start climbing in volts?) I suppose it would also depend on the amps it is charging at as well.

 

[Uksolarguy]

You are Over-charging the pack for one !

LFP "Allowable Voltage Range" is 2.500-3.650. This is the voltage range the cells can be used without Harm/Degradation. This is NOT the actual "Working Voltage Range" which is from 3.000-3.400 with Nominal Voltage @ 3.200 (50% SOC). That 0.400V is where all your AmpHours actually come from. Generally even with B-Grade cells one can use 2.900-3.450 without creating runner cells. ALL BATTERIES regardless of chemistry have an Allowable Range & Working Range, allowable is there as a safe No-harm buffer and not intended to be used regularly.

Set your charging profile to:
Divide Values X2 for 12V. Multiply X2 for 48V.
Absorb: 27.6 for 45 minutes (3.45vpc) (some call this boost)
Equalize: OFF
Float 27.5V (3.437vpc)
MIn Volts: 21.2 (2.650vpc)
Max Volts: 28.6 (3.575vpc)
Rebulk Voltage: 25.6 (3.200vpc)
End Amps/TailCurrent: Depends on your battery pack. 100AH x 0.05=5A, 280AHx0.05=14A

JK Advanced Settings:
Cell OVP(V) 3.600 volts
Cell OVPR(V) 3.525 volts or even 3.550
....
Charge OCP Delay(s) 30 This is in seconds to delay
Charge OCPR Time(s) 60 Release time

Refer to Manual, "5.3.2 参数设置/ Parameter Settings"

Hi Steve outdoor it be possible to pick your brains over a solar set up please ?
trying to work out some inverter settings on a user defined battery ?

 

[upnorthandpersonal]

suppose with using the 3.6v ovp value with the jk, this will give enough breathing room for the strange 5s delay for it to shut the charging off before cells reach 3.65?

Why go that high? Make it 3.55V (which I use as well). There is nothing to be gained by going to 3.6V per cell.