Removing 10s from 37.7 v EM3EV batt
- Thread starter Seya
- Start date
So you're removing one parallel section of 10 cells? If so, then that's not going to change anything about the pack except it's capacity and the total current supply it can deliver, besides it's shape and volume. The BMS wouldn't see any difference, except it's max current to protect against should be lower than it will be.
Takemehome
1 kW
Seya said:
It looks like a 10S5P pack.
If you remove 10 cells you are removing 2S5P
Your pack would then be 8S5P = 30.2V 13.7A
DON'T DO IT.
dogman dan
1 PW
To nit pick, I'd call it a 5p 10s pack. Meaning that cells are paralleled in 5p first, then the 5p sections are connected in series. 10s -5p is quite different.
If you want to split the pack into two sections, it can be done, but you have to remove portions while keeping the 5p chunks together. So you can remove 5,10, 15 cells and so forth.
Then reconnect to the bms with longer wires. Ideally, all the small wires to the bms will be the same length once done. Use very heavy thick wire to connect the two sections on the discharge wires, so you don't have too much power heating those long wires.
If you want to just make the entire battery smaller and less capacity, you are screwed, very hard to do that now.
If you want to split the pack into two sections, it can be done, but you have to remove portions while keeping the 5p chunks together. So you can remove 5,10, 15 cells and so forth.
Then reconnect to the bms with longer wires. Ideally, all the small wires to the bms will be the same length once done. Use very heavy thick wire to connect the two sections on the discharge wires, so you don't have too much power heating those long wires.
If you want to just make the entire battery smaller and less capacity, you are screwed, very hard to do that now.
mfj197
10 W
That is fine if you wish to change (reduce) the voltage, and you'd make it a 5p9s or 5p8s pack (to use your nomenclature). It's also fine to change the capacity and make it a 4p10s. You would have to make sure you take one cell out of each 5p grouping so they all become 4p groups. Whether or not the packaging would give you much benefit to doing this entirely depends on how the cells are grouped in the pack - I have to say I'd be doubtful of suitable gains as you'll probably be removing single cells from all over the pack so you can't make it smaller unless you reweld the cells to take advantage of the holes. You would make it lighter though, if that is the aim.dogman dan said:
Michael
dogman dan
1 PW
I just meant that to make the pack 4s, it won't be real easy. To get at one cell of some of the cell groups could mean breaking the entire pack into it's individual 5p sections.
But you could make the pack smaller, lower voltage fairly easy. I'm not sure if you can modify the bms smaller or not.
But you could make the pack smaller, lower voltage fairly easy. I'm not sure if you can modify the bms smaller or not.
DAND214
10 MW
Confused, :?
Are you tring to lower thr voltage or lower the Ah rating?
If you are lowering the voltage, will the controller still work?
Dan
Are you tring to lower thr voltage or lower the Ah rating?
If you are lowering the voltage, will the controller still work?
Dan
Seya
10 W
- Joined
- Feb 27, 2012
- Messages
- 81
I'm trying to lower the ah while keeping the voltage the same.
In the image you can see there is a group sticking out making the battery a " p " shape and that affects my location choices. I want to locate the battery at the bottom of the triangle.
I want to remove that 10s group making the pack a 10s 4p.
In the image you can see there is a group sticking out making the battery a " p " shape and that affects my location choices. I want to locate the battery at the bottom of the triangle.
I want to remove that 10s group making the pack a 10s 4p.
999zip999
100 TW
You want to remove 1p or one cell from each group of 5p for 4p. This would hard to get to the 5p groups in the middle of pack because of the series connections. You still need it as 10s. As 10s4p the bms will still work. Or as 10s 2p. Be careful as these little cells are live and can ez cause a Fire. Yes a fire.
dnmun
1 PW
it will be easier to just buy another battery which is only 4P wide.
otherwise you will have to use a diagonal grinder with a metal cutting wheel and cut across those wide plates to remove the end cells from the others. you will have to cut through the glue holding them in close packed formation too. some of the sense wires will have to be moved and resoldered onto the plates in a new position.
otherwise you will have to use a diagonal grinder with a metal cutting wheel and cut across those wide plates to remove the end cells from the others. you will have to cut through the glue holding them in close packed formation too. some of the sense wires will have to be moved and resoldered onto the plates in a new position.
Seya
10 W
- Joined
- Feb 27, 2012
- Messages
- 81
Ahh ok I see where I was wrong.
Removing 1 cell per parallel group is too difficult I supposed
If I had a 24 V motor.. Can I remove the whole group ( creating 30 volt pack ) and limit the controller to 28 volts.
I just want the setup to work for a protoype
Removing 1 cell per parallel group is too difficult I supposed
If I had a 24 V motor.. Can I remove the whole group ( creating 30 volt pack ) and limit the controller to 28 volts.
I just want the setup to work for a protoype
dogman dan
1 PW
Motor won't care,,, but you'll need a controller for 24v. That battery is not too heavy to just carry it on a rear rack. Sure, the triangle is ideal, but now hou have it.
Just rack it and ride. Next try, get the battery to fit your triangle better.
Just rack it and ride. Next try, get the battery to fit your triangle better.
dnmun
1 PW
or better yet, save your money and buy another battery of the same voltage and chemistry and use them in parallel. one on the rack and one in the frame. that will help both of them last longer.
tomjasz
1 GW
That just woke me up to a possibility I had never considered. I hope I don't piss anyone off by jumping in and asking about parallel wiring, but I have two battery packs form cell_man. If I can parallel them and extend my range that is a life changer. I have two packs and a spare mount I could put on my rear rack. How do I wire them? I have the 10s 36V packs in my sig.dnmun said:
Sorry for the interruption but this really got me excited! Should I start a new thread. Nor sure what's polite or proper...
dnmun
1 PW
you can wire them up in parallel and that BMS has a separate charging mosfet so when you charge them up in parallel you will have to disconnect the two P- leads from the BMS.
if the two batteries are tied in parallel while charging and one pack goes to HVC and tries to shut off charging then the charging current can flow around the charging mosfet that is turned off through the BMS of the other battery.
so one of the batteries will have to have a connector on the negative lead to the controller that you can disconnect while charging them in parallel.
if the two batteries are tied in parallel while charging and one pack goes to HVC and tries to shut off charging then the charging current can flow around the charging mosfet that is turned off through the BMS of the other battery.
so one of the batteries will have to have a connector on the negative lead to the controller that you can disconnect while charging them in parallel.
999zip999
100 TW
Or get a second 36v battery same ah and new controller @ 72v and run at a lower amp draw. Just saying. For a look forward. But very hard and a lot of time cutting up a made battery.
36v x 20a= 720watts
72v x10a= 720 watts or more.
36v x 20a= 720watts
72v x10a= 720 watts or more.
tomjasz
1 GW
Sounds like it might be easier just to put my spare mount on the rack and switch batteries. DUH another brain fart by tomjasz....dnmun said:
dnmun
1 PW
no, it is not easier.
tomjasz
1 GW
Huh? No wiring, just switch batteries. Leaving batteries free to be used on other rides. What can be easier? I am not breaking open the packs and accessing the BMS. I was looking for a way to wire the packs together as they are presently built and configured. Assuming I would have to charge them separately. OK I'm a wiring dunce and am learning, so... without a clear visualization of how I would achieve your recommended configuration, it surely seems easier.
Thanks for the lessons.
Thanks for the lessons.
