16s2p BMS

harrisonpatm

Moderator
Staff member
Joined
Aug 8, 2022
Messages
1,425
Location
Michigan, USA
You'll want a NO contactor. Take a look at this thread for suggestions.

 
Is it possible to configure a JBD BMS

HP32S001, 3s-32s​

to monitor a lifepo4 16s2p pack?
Seems like it would be easier than dealing with the issues associated with running two 16s. It is for a 48v “golf cart”. Thanks for any direction in advance.

 
Yes that is one of the configurations it will work for.
Later floyd
 
Is it possible to configure a JBD BMS

HP32S001, 3s-32s​

to monitor a lifepo4 16s2p pack?
Seems like it would be easier than dealing with the issues associated with running two 16s.

You don't use two BMS to monitor a pack that is 2p.

The 2p are wired in parallel together at the cell level, so they are both monitored by the same BMS.

The only time two separate BMS are useful or required would be if you have two separate 1p packs that are then wired in parallel *only at the main + of the cell block and the BMS discharge negative.
 
Great! I just need to figure how to wire a contactor in for the hv/lv cut offs. Time to search.
One of the motorcycle threads (or the battery for it) has some info on that; I *think* it was harrisonpatm's, was a year or two ago?
 
How I wired mine:

 
You don't use two BMS to monitor a pack that is 2p.

The 2p are wired in parallel together at the cell level, so they are both monitored by the same BMS.

The only time two separate BMS are useful or required would be if you have two separate 1p packs that are then wired in parallel *only at the main + of the cell block and the BMS discharge negative.
I’m going with the 16s2p configuration for the higher discharge rate. (Off road Ev) I would have to go 2p16s for one BMS.
 
I’m going with the 16s2p configuration for the higher discharge rate. (Off road Ev) I would have to go 2p16s for one BMS.
Both use a single BMS
1 BMS to control the entire battery, (you make your parallel groups)( then series the 16s) (2p)cells you created when you paralleled the cells can be written 2p16s or 16s2p

negative 2p-2p-2p-2p-2p-2p-2p-2p-2p-2p-2p-2p-2p-2p-2p-2p positive
later floyd
ps I prefer series first then parallel cause you chose the voltage first.
 
I’m going with the 16s2p configuration for the higher discharge rate. (Off road Ev) I would have to go 2p16s for one BMS.
There's no difference regarding discharge rates.

If you parallel two sets of cells, you get the same discharge whether you series them first or parallel them first, assuming your series interconnects are the same and the cells are the same.

If by 2p16s you mean that you have two completely separate 16s1p packs, that you connect only at the main + and -, then that's the situation I posted that uses two BMS.

Otherwise, you only use one, because the cells are connected together in parallel at the cell level, and one BMS monitors all of them.
 
There's no difference regarding discharge rates.

If you parallel two sets of cells, you get the same discharge whether you series them first or parallel them first, assuming your series interconnects are the same and the cells are the same.

If by 2p16s you mean that you have two completely separate 16s1p packs, that you connect only at the main + and -, then that's the situation I posted that uses two BMS.

Otherwise, you only use one, because the cells are connected together in parallel at the cell level, and one BMS monitors all of them.
I meant the added discharge rates from using two BMS. It probably would be easier to go 2p16s (16 pairs of cells)and use one contactor style BMS. It’s for a 650 amp controller but it’ll realistically pull 150, short burst to 400.
 
Battery Hook up has a beast of a BMS JBD 7s-21s 300 A continuous for cheap should be able to handle anything your cart would throw at it bms .
later floyd
 
I meant the added discharge rates from using two BMS. It probably would be easier to go 2p16s (16 pairs of cells)and use one contactor style BMS. It’s for a 650 amp controller but it’ll realistically pull 150, short burst to 400.
You don't get more discharge from a pack by using more BMSes on it.

The cells themselves have a limit to what they can do, and the BMS should be chosen so it's shutdown current limit is *below* that. As much below as is practical, because as the pack ages, the cells become less capable of delivering current, so if you are pushing that limit to begin with, then it won't be too long before you are at the limit, then past it, and the pack starts to perform badly, or even start to be damaged by that and rapidly go downhill from there.

If you are using a contactor to pass the current, then the BMS has nothing to do with the discharge rate (other than whatever current limit it is built for or programmed as, and you would choose that as noted above). The contactor's limitations would be important, however.

2p16s (16 pairs of cells)
Normally, using the p before the s means that you are using two separate series strings of 16 cells, that are not paired at the cell level.

Using the s before the p usually means that you are using one block of cells that is first wired as 16 sets of 2 parallel cells that are then put in series. That's how almost all batteries >1p are built, for a variety of reasons.

It's very uncommon to build them the other way, as separate series strings connected only at main + and -, for a variety of reasons that seriously complicate monitoring and safety.

There are advantages and disadvantages to both methods; there are a few threads detailing all these, mostly in hte battery technology subforum.
 
Battery Hook up has a beast of a BMS JBD 7s-21s 300 A continuous for cheap should be able to handle anything your cart would throw at it bms .
later floyd
That might work perfect! The balance is a bit weaker than the Jk’s but the cells are all new so it shouldn’t be an issue. Appreciate it.
 
You don't get more discharge from a pack by using more BMSes on it.

The cells themselves have a limit to what they can do, and the BMS should be chosen so it's shutdown current limit is *below* that. As much below as is practical, because as the pack ages, the cells become less capable of delivering current, so if you are pushing that limit to begin with, then it won't be too long before you are at the limit, then past it, and the pack starts to perform badly, or even start to be damaged by that and rapidly go downhill from there.

If you are using a contactor to pass the current, then the BMS has nothing to do with the discharge rate (other than whatever current limit it is built for or programmed as, and you would choose that as noted above). The contactor's limitations would be important, however.
The cells are rated for 180a continuous/600a short burst so I probably could’ve skipped the contactor with two BMS. The Jk’s combined would’ve been good for 400 continuous/700 peak. The BMS Floyd recommended would probably be sufficient without a separate contactor also. 300 continuous/600 peak.
 
Wasn't a recommendation as I haven't installed one yet. But it is a beast I have one need to find a use for it. Note it weighs 4lbs. if you get one be sure to grab the appropriate file for your phone.
later floyd
ps I have no affiliation with battery hookup they just take my money. sorta my candy store
 
Back
Top