2 or more bms in series, charging in paralel

edyxrp said:
i already saw that i have 3 direct short circuits

Yeah that's the problem.
Here's some ideas:
- have the batteries in 3 separate modules, you could charge each separately when disconnected from the system.
- have 3x separate chargers (isolated,not grounded outputs, etc) you could charge the pack in circuit.
- step up the existing 12V charger (depending on type)to 36V with a boost switching supply device.

If you tried having the batteries in tree separate "equal" packs & disconnected from bike & motor but then attempted to parallel them to use one charger, you would likely have issues with imbalanced voltages causing uncontrolled current flow until they equalized.
 
edyxrp said:
i want to build an e-bike using a 36v 1000W motor but i face a problem that im not sure about the solution i want charge my battery pack with a 12v power supply so i will be using 3*3s bms that have to output in total 36v but im not sure about my wiring or if its possible
https://image.noelshack.com/fichiers/2019/10/7/1552256627-20190310-232230.jpg
edit: i already saw that i have 3 direct short circuits
Additionally, you face the problem that the BMS usually are not designed to cut-off 3 times the voltage.
 
10s bms and use stepup Converter.
 
Agree 10s BMS is ideal with a step up converter to use with your 12v supply.

Alternately, easy to find a 36v charging supply from all those hoverboards, I would just get that and simplify the setup.
 
CrimpDaddy said:
Agree 10s BMS is ideal with a step up converter to use with your 12v supply.

Alternately, easy to find a 36v charging supply from all those hoverboards, I would just get that and simplify the setup.

Absolutely.
 
thx i will use a 48v battery because i already ordered th bms for one and will vary the speed using pwm to activate a mosfet but my motor is 36v and 1000W.Do you think the motor can handle that tension or should i figure something out to lower the tension?
 
Get your self a DC/DC buck converter for the motor that can do 1kW. that one can also if variable vary the motor speed. Easier and you get correct max voltage directly
 
daromer said:
Get your self a DC/DC buck converter for the motor that can do 1kW. that one can also if variable vary the motor speed. Easier and you get correct max voltage directly
not sure about this one first its rlly expensive and i cant find any powerfull buck converters
 
CrimpDaddy said:
Agree 10s BMS is ideal with a step up converter to use with your 12v supply.

Alternately, easy to find a 36v charging supply from all those hoverboards, I would just get that and simplify the setup.

that'd be a '42V' [lithium! CC/CV] charger.

10s is the key. (3*3s != 36V nominal).

is your motor brushed, or unbrushed? if its two-wire (brushed) this is all somewhat easier. I prefer unbrushed myself, as they are 'waterproof' and the work is done / onus is on the controller, much more than the motor.
 
DCkiwi said:
CrimpDaddy said:
Agree 10s BMS is ideal with a step up converter to use with your 12v supply.

Alternately, easy to find a 36v charging supply from all those hoverboards, I would just get that and simplify the setup.

that'd be a '42V' [lithium! CC/CV] charger.

10s is the key. (3*3s != 36V nominal).

is your motor brushed, or unbrushed? if its two-wire (brushed) this is all somewhat easier. I prefer unbrushed myself, as they are 'waterproof' and the work is done / onus is on the controller, much more than the motor.

Im confused 3x3 = 9s?

Generally speaking, when someone says 36v battery pack or 36v charger, they are generally referring to a 10s system. 10 x 3.7 = 37v nominal, lithium max = 42vdc.

Even if compared to lead acid, 12v x 3 = 36v nominal, still has a max charge voltage of 43.2vdc

A 36 volt charger is generally ideal for a 10s lithium setup.
 
It looks like somebody calculated wrong, 3*3 equals 9, not 10. But nobody else realized that.... we are specialists here, ROTFL.
 
CrimpDaddy said:
Generally speaking, when someone says 36v battery pack or 36v charger, they are generally referring to a 10s system. 10 x 3.7 = 37v nominal, lithium max = 42vdc.

[...]

A 36 volt charger is generally ideal for a 10s lithium setup.

um .... yes, and no. yes, I agree with you Crimp Daddy, it is 36V nominal, BUT if one was to do a websearch for a suitable supply ... then '42V' is a better keyword to use for that search.

EVERY electric skateboard/e-scooter 10s chargers I have EVER seen (including the ones I own and use) labels itself as 42V.

some dont even put out 42V (like ~41.5V) ... just to get even funnier.

reminds me of Ireland ... Ive been told they use Miles for distance, and Kilometers for speed signage ... lol.
 
DCkiwi said:
CrimpDaddy said:
Generally speaking, when someone says 36v battery pack or 36v charger, they are generally referring to a 10s system. 10 x 3.7 = 37v nominal, lithium max = 42vdc.

[...]

A 36 volt charger is generally ideal for a 10s lithium setup.

um .... yes, and no. yes, I agree with you Crimp Daddy, it is 36V nominal, BUT if one was to do a websearch for a suitable supply ... then '42V' is a better keyword to use for that search.

EVERY electric skateboard/e-scooter 10s chargers I have EVER seen (including the ones I own and use) labels itself as 42V.

some dont even put out 42V (like ~41.5V) ... just to get even funnier.

reminds me of Ireland ... Ive been told they use Miles for distance, and Kilometers for speed signage ... lol.
That is all correct - and it is correct !!

10s "Blocks" is 36 Volts because the NOMINAL Voltage of LiIon is 3.6 Volt.

10 s Charging is 42 volt because the the top Voltage for Charging is 4.2 Volts....... :D
 
DCkiwi said:
CrimpDaddy said:
Agree 10s BMS is ideal with a step up converter to use with your 12v supply.

Alternately, easy to find a 36v charging supply from all those hoverboards, I would just get that and simplify the setup.

that'd be a '42V' [lithium! CC/CV] charger.

10s is the key. (3*3s != 36V nominal).

is your motor brushed, or unbrushed? if its two-wire (brushed) this is all somewhat easier. I prefer unbrushed myself, as they are 'waterproof' and the work is done / onus is on the controller, much more than the motor.
it's a brushed motor
 
edyxrp said:
i want to build an e-bike using a 36v 1000W motor but i face a problem that im not sure about the solution i want charge my battery pack with a 12v power supply so i will be using 3*3s bms that have to output in total 36v but im not sure about my wiring or if its possible

updates?
 
emuland-metroman said:
what will do first pack if second/third will cut?

Mosfets will be overstressed by reverse voiltage.
 
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