8s bms using 6s + 2s

Hi,

I have a 6s-bms and 2s-bms lying around and
I was wondering if I could make a 8s BMS out of them.

How:

Each BMS has its own wiring as it is stand alone,
only difference is that the 6s-last-battery is connected to the 2s-first-battery.

Is it possible?
Any disadvantages it might have?

Thanks

Will it balance correctly? If the two BMS’s have different ideas about full charge voltage or balancing voltages you’ll be unbalancing the pack, not a good thing - however if the BMS’s are the same sort from same manufacturer I’d have thought this is OK.

1 Like

Thanks,
I am not sure where to look at in the specifications, How should I make sure of that?

Here are the details:

6S BMS:

Lampshift maximum discharge current: 15A
Instantaneous discharge current: 25A
Charging voltage: 25.5V
Charging current: 15A (MAX)
Overcharge detection voltage: 4.28 ± 0.05V
Overcharge protection delay: 0.1S
Overcharge release voltage: 4.08 ± 0.05V
Over discharge detection voltage: 2.55 ± 0.08V
Overdischarge detection delay: 0.1S
The overdischarge release voltage: 2.9 ± 0.1V
Overcurrent detection voltage: 150mV
Overcurrent detection delay: 9MS
Overcurrent protection current: 30 ± 3A
Overcurrent protection release condition: Disconnect the load
Short circuit detection delay: 250uS
Short circuit protection Release condition: disconnect negative open
Main circuit conduction resistance: ≤20mΩ
Working current: ≤30uA
Sleep current (battery over discharge) ≤10uA
Temperature range: -30 / + 80 °
Feature:
Fine workmanship and durable.
For the rechargeable (generally refers to the lithium battery) from the protection of the integrated circuit board. Lithium battery (rechargeable type) so need protection.
As the lithium battery itself determines the material itself can not be overcharge, over discharge, overcurrent, short circuit and ultra-high temperature charge and discharge, so lithium battery lithium components will always follow a protective resistor with a sampling resistor and a current fuse.

2S BMS:

Technical Parameters Model: HX-2S-D20
Size: 46203.6MM
Overcharge voltage range: 4.25V-4.35v±0.05V
Over-discharge voltage range: 2.5-3.0V±0.05V
Upper limit working current: 13A
Working temperature: -40 ° C ~ 50 ° C
Upper limit instantaneous current: 20A
Storage conditions: -40 ° C ~ 80 ° C
Quiescent current: less than 10uA
Effective life: more than 50,000 hours
Internal resistance: less than 300mΩ
Short circuit protection: protection, charge recovery
Charging voltage: 8.4V-9V

Solder Joint Description
B+: Connect the battery positive
B-: Connect the battery negative
MB: Connect the connection point between battery 1 and battery 2
P+: Charge/discharge terminal positive (common terminal/discharge terminal)
P-: Charge/discharge terminal negative (common terminal/discharge terminal)

Thanks