48volt 280ah battery pack

[offthetop04]

Woke up to this this morning.
Disconnected the busbars and the #1&#2 cells read 3.30v. When I was re-installing the busbars I stripped the thread of the #1 cell.
The nut is somewhat snug but not tight.
Any advice on where to start would be extremely appreciated.
48volt 280ah 16s battery pack.
Daly 250amp BMS
Daly active balancer.
I disconnected everything and reconnected and it didn’t do anything different.

 

[Xhumeka]

Any damage to the BMS sensing wires? If individual cells read 3.3, but are reporting those crazy numbers in your BMS software I'd think either the wires have shorted or the BMS is defective.

Have you tried testing the BMS connector (with the sensing leads attached to cells) to see what is being reported there?

 

[offthetop04]

I have not. I broke down the battery pack and put it in parallel on charge/balance. I’m going to order a different bms that’s not Daly. I’m going to need to figure out how to unstripe this terminal stud too. I’ll rebuild in series when the new bms gets here.

 

[sunshine_eggo]

Pics of the stripped stud might help.

If the thread is good at the top, you could simply add spacers/washers to raise the nut to the area where you have good threads. Obviously, spacers/washers go on TOP of the busbar/BMS sense wire - not in the current path.

 

[Texas-Mark]

I'd think either the wires have shorted or the BMS is defective.

I would have checked the sense wire voltages at the BMS end of the harness before ordering a new one. An open on one sense wire can give squirrly readings too.

 

[Quattrohead]

Some of the studs and nuts I have received on cells have been pretty sloppy so you might be able to go to your local store and get a decent M8 or whatever size nut it is that will tighten up properly. Just double check your cell voltages at the BMS end of the wires in case that connection between one and two isn't good.
Unfortunately the Daly BMS seem to have more problems then JBD or JK for example.

 

[sunshine_eggo]

When the sum of two adjacent cells divided by 2 is pretty close to what you would expect, it's almost always a wiring/crimp/connection issue.

I’m going to order a different bms that’s not Daly. I’m going to need to figure out how to unstripe this terminal stud too. I’ll rebuild in series when the new bms gets here.

I support this even if there's nothing wrong with it... for this reason...

Unfortunately the Daly BMS seem to have more problems then JBD or JK for example.

 

[offthetop04]

Do you have a preference on JBD or JK?

 

[sunshine_eggo]

JBD if I'm good with passive balancing and/or want to easily connect to a Victron GX device with UART to USB adapter.
JK if I want active balancing. 99% sure you can do the Victron thing too, I've just never done it.

 

[offthetop04]

I would have checked the sense wire voltages at the BMS end of the harness before ordering a new one. An open on one sense wire can give squirrly readings too.

To do this i would unplug the harness from the bms one lead on the #1 cell - and the other lead on #1 slot of unplugged harness. Repeat to # 2 cell ?
If yes that’s what I did and I got 3.2v on each.
That would probably be a bad bms?

 

[offthetop04]

Well I put the pack back in series checked the bms side of the harness and all the voltages added up to 52.7.
Did not install the active balancer this time due to the stripped terminal. The bottom of the stud is still on the top is trashed.
Ordered a tap and die set to try and make it a M4 lol
Turned everything back on and things seem to be working again.
The two JK bms’s will be here Friday. Hopefully this will work in this Texas heat till then.

 

[Texas-Mark]

Turned everything back on and things seem to be working again.

If possible, I would wiggle and jiggle the sense cable harness to see if it wigs out again. Would hate to toss a BMS because of a bad harness wire.

I know some here don't like Daly, but I have like 7 of them and they all work fine.

 

[sunshine_eggo]

Yuck. You basically have near empty cell with a bunch of nearly full cells. If you get 20-30% of the rated capacity from that battery in that state, I'll be shocked.

A die on that may twist the terminal out of the cell itself.

Could something like this work?

https://www.amazon.com/Inserts-Stainless-Reducing-Industrial-Hardware/dp/B09L5KJ6Y2

 

[cs1234]

Could something like this work?

https://www.amazon.com/Inserts-Stainless-Reducing-Industrial-Hardware/dp/B09L5KJ6Y2

Those look nice, but they are stainless. What are the the battery terminals normally made of?

 

[sunshine_eggo]

Those look nice, but they are stainless. What are the the battery terminals normally made of?

The studs are stainless.

 

[offthetop04]

Well I have no idea what went wrong but things are petty on point as of today.
I jiggles all the wires and nothing changed’
Going to try and rethreade the stud with a m5 when the tool set arrives. But for now alls we’ll. .

 

[offthetop04]

Those look nice, but they are stainless. What are the the battery terminals normally made of?

I’m going to try and rethread the stripped stud with a m5 I might order a m5 set of these as well. Great find.

 

[cs1234]

I’m going to try and rethread the stripped stud with a m5 I might order a m5 set of these as well. Great find.

It was @sunshine_eggo that found them. I only asked a dumb question about them.

 

[offthetop04]

It was @sunshine_eggo that found them. I only asked a dumb question about them.

I was outside in the glaring sun trying to post lol

 

[offthetop04]

The studs are stainless.

Great find, I’ll grab some and see about joining over the stud once i thread it to a m5.