Segway X2 battery

[agniusm]

Hi. Was looking for more info on segway X2 battery pack. So far i figured out that they are 73.6V, 5.3Ah per pack and uses Valence 1.4AH cell. My math shows me that there are 4 cells in parallel groups, 23 groups in series or 4P23S.
Max continuous discharge on these is 2C and cycle life at .2C at 100% DOD is something like 5000 cycles to 80% capacity and ~7200 cycles to 70% capacity. Cells are 40g each making 3.68kg per pack.
I was asked to rebuild battery packs on rented segways but somehow it does not fit in my head how 5K cycle life cell died in two years? If they would be charged 7 times a day they would be at 80% capacity after 2 years which is not possible with charging time of 10hrs. Only explanation i can think of is incorrect use. I was told that one winter they were hooked up to a charger all the time and they are charged fully when they are not used as well.
Is there some wanky electronics like on makita chargers that disables someone swapping cells in the pack? Any sources for Valence cells?

 

[agniusm]

So nobody had any info on these batteries. I got one, got it apart for you guys to see. So it has Valence IFR-18650EC cells, 92 to be exact in 4P23S configuration. Cell specs are:
Nominal voltage: 3.2V
Minimum voltage: 2.0V
Charging voltage: 3.45-4.2V
Capacity: 1.4AH
Max continuous current: 2.8A or 2C
30S pulse current: 7A or 5C
Charging: 0.7A or 0/5C
Max charging: 1.4A or 1C
Cycle life at 10% DOD, +23C, C/2: ~93% after 2000 cycles; ~85% after 4000 cycles; ~77% after 6000 cycles

The box is welded so i got my dremel out, easy enough.

To take out the board, you need to cut all sense wires and main wires. there is some insulation and glue under the board.

After the board is taken out, cells are glued at the bottom as well. It is almost impossible to pull them out but i have managed afte .5h of work:

First half weight:

Second half weight:

Damaged cells:

Tab material:

Naked cell:

To sum up this battery:
I think battery is built indestructible. Battery box is made out of PP or similar, it has double bottom, and double sidewalls with bracing.
The bad things:
Cells are touching, thermal runaway?!
No temp sensor
No cell level fusing
Cells don't have extra padding on positive terminal and some PVC wrap was cracked
Inconsistent and some bad spot welds, brakes of by hand.
For those who want to reuse these cells you will need to cut them out as per last photo as they are glued inside out with some stuff that is hard to pierce or cut. Additional ring insulators could be reused.

 

[dnmun]

will you try to rebuild them with parts from each other or buy some similar cans to restore the packs?

looks like one of them shorted the anode to the case through the nickel contacting layer in spite of the insulation but it might have jammed up against the case or on a wire.

i really think this kinda maintenance is gonna be crucial to keeping lotsa EVs going in the future.

 

[agniusm]

will you try to rebuild them with parts from each other or buy some similar cans to restore the packs?

looks like one of them shorted the anode to the case through the nickel contacting layer in spite of the insulation but it might have jammed up against the case or on a wire.

i really think this kinda maintenance is gonna be crucial to keeping lotsa EVs going in the future.

Yeah, i think it shorted out on the can and perhaps gassed out as there is running lines of corrosion on the can.
They have a gap around the case and are very sturdy mounted. The whole BMS board is coated with some sort of silicone so the only issue i see is tabs wearing through over time.
They are nothing special except cycle life. 40g per can is a lot for 1.4Ah cell. LG, Panasonic, Sony are double or more at 47.5g and with 2C max, that's good enough for assisted bike. Getting the cells fixed is some job. Getting them out of the middle is a job and half.

 

[agniusm]

Oh, and the cells are LiFeMgPO4. Its sorta iron phosphate, but you could charge them to 4.2V
Who else makes these cells?

 

[blisspacket]

Interesting autopsy, Agniusm. LiMg2O4 batteries are Nissan Leaf, Torqeedo batteries for their electric outboard, and I think even the Chev Volt. LiMg2O4 seems to be a pretty safe chemistry.

 

[agniusm]

i don't think its the same chemistry as LiMg2O4 (or LiMn2O4)

 

[velias]

What are the white stripes on the side of the cells? are they just the color of the wrap around the cells or is it a rubber like spacer/bumper to keep the cell bodys from rubbing together and wearing thru & shorting to each other?

 

[agniusm]

Same material as cell wrap, pvc is it?! The cells has no chance of rubbing, they are as solid as a brick.

 

[circuit]

Have you succeeded rebuilding this? Have the same issue here and wondering what kind of protocol it uses, and if BMS will work straight away when connected to new cells (no Permanent Fault flag).