Scalable BMS

[Supersleeper]

Hi folks,

I've built a 48v 12s 6p battery out of 18650s and am extremely happy with the performance. Now I'm looking for a simple way to charge and scale up as I am intending on going 8p soon. So I'm thinking a 12s 2p PCB BMS would be ideal as I link the batteries in 2p banks. I'm having a heck of a time trying to find a PCB for this. I prefer not to make my own, and the only ones I can find are already integrated into complete battery packs.

My other solution is to just integrate a hobby charger inside my battery pack, but I'm not sure about splitting each ballance wire 6 ways (6p) and likely not scalable to 8p. Is this safe/effective? I know that most Li-ion packs I pull out of laptops have 2p ballance and sometimes 3p.

 

[Supersleeper]

Bump

 

[jonescg]

Put two 6s JSTs on it and balance the pack periodically.

Alternatively, buy yourself a 12s BMS from Cell_Man www.em3ev.com for a set and forget BMS.

 

[friendly1uk]

48v 12s ?
I'm not sure that is possible, So advising how to change it is beyond me.

 

[dnmun]

here are some 12S lipo BMSs. all very cheap:

http://www.bestekpower.com/444v12spcmbmspcbforli-ionli-polymerbatterypack/

 

[knighty]

48v 12s ?
I'm not sure that is possible, So advising how to change it is beyond me.

lithiumm ion laptop cells, 4.1v fully charged ? (4.2 if you want to push em a bit harder)

 

[dnmun]

no, i think the guy thinks of the battery voltage as 4V/cell. so he used 48v when most people would use 36v for a 12S pack.

 

[Supersleeper]

no, i think the guy thinks of the battery voltage as 4V/cell. so he used 48v when most people would use 36v for a 12S pack.

My motor/controller is 48v rated and accepts 52v fully charged battery like most 48v systems do.

 

[dnmun]

but you said 12S so that was why i gave you the link to 12S lipo BMSs.

you said there were none available so i pointed to the guys that agnius found who do make lipo BMSs.

controller voltage ratings are established for SLA batteries and 12V of SLA is considered the equivalent of 4S of lithium and by extension to lipo. even though lipo charges to 4.2V and a 12S lipo pack is 50.4V DC.

 

[Supersleeper]

So I'm a little confused, because 36v divided by 4 is 9. 36v pack would be 9s wouldn't it? 12 times 4 = 48 so 48v would be 12s. So fully charged my pack reads about 51v. I would think u would grossly undercharge a 12s pack for a 36v system.

 

[dnmun]

So I'm a little confused, because 36v divided by 4 is 9. 36v pack would be 9s wouldn't it? 12 times 4 = 48 so 48v would be 12s. So fully charged my pack reads about 51v. I would think u would grossly undercharge a 12s pack for a 36v system.

nominal battery voltages refer back to the time when people used SLA batteries. so a 4S lifepo4 series is equivalent to one 12V SLA. so 4x12V SLA is 48V or 16S of lifepo4.

but some people who sell batteries now use the 3.2V for lifepo4 and say a 16S pack is 51.2V but in fact it still charges up to 58.4V DC.

 

[Takemehome]

So I'm a little confused, because 36v divided by 4 is 9. 36v pack would be 9s wouldn't it? 12 times 4 = 48 so 48v would be 12s. So fully charged my pack reads about 51v. I would think u would grossly undercharge a 12s pack for a 36v system.

14s of 3.7V = 51.8V close to 4 X 12V = 48V NOMINAL VOLTAGE
14s at 4.2V = 58.8V close to 4 X 14.4V = 57.6V Fully charged