Bottle Battery fault - Options

[alemanyorks]

Hi all, has anyone got a few mins to have a look at this issue:

My kit with bottle battery has just stopped working the other day, just cut out mid ride at the top of a hill climb. It has done this once before but after battery dismantling & putting back together it seemed to work again (I didn't do anything really to it).
The fault seems almost identical to this thread:
http://www.pedelecs.co.uk/forum/electric-bicycles/15522-oxydrive-battery-seems-dead-what-do-2.html

After reading d8veh's replies I tried his various suggestions & have come to the conclusion that 1 or more of the cells is dead or very low.
Voltage across the whole pack (inc BMS) is +1.5V p- to p+
Voltage across battery is 36.5V b- to b+

The voltages on the balance wires are 4.1; 3.5; 7.7; 11.8; 15.9; 20.0; 24.1; 28.2; 32.4
am I drawing the right conclusions about the cell(s) condition?
I've been trying to work out how these packs are put together, there are 40 cells in total each giving 4.1 v so is it wired 10s 4p? that doesn't seem to tally up with there only being 9 balance wires.....not sure about that.
If so taking these things apart to replace cells seems tricky & is it a good idea, not sure about the quality of the pack now as I've only done about 1000 ish miles.

Any insights or help much appreciated.





Dave W

 

[Deleted member 4366]

Interesting BMS! Do you know what thr discharge rate is?

The packs are normally 10s4p, so you need 11 wires to measure the cells. The remaining two wires must be the two thick wires from the top and the bottom of the pack. Put your black probe on the black pack wire (B-) and then probe each of the nine balance wires plus the thick red (B+) to get 10 incremental results.

The results you have given don't look right. It shouldn't be possible to go down in voltage incrementally.

 

[alemanyorks]

Thx for the reply d8veh, checked again on (B-) (its one of the yellow wires on this pack) to (B+) and that gives 36.5v, all the others are the same as before.

Not sure about the discharge rate, sorry.

 

[Deleted member 4366]

From the results you've given, one of the cell-strings is definitely faulty. All cells are at 4.1v except one, which is - 0.6v. Follow the wire to find tje group. The repair will be difficult unless it's the balance wire that's come off.

 

[alemanyorks]

Thx for your opinion & help d8veh, I may do some careful un-soldering so see what its like & also start thinking about other alternative replacements.

 

[Deleted member 4366]

This should give some idea of what's involved:
http://www.pedelecs.co.uk/forum/electric-bicycles/15289-bottle-battery-repair.html

 

[alemanyorks]

Ah that's just what I needed THX, must have missed it on a search through. Does seem pretty involved but could be well worth giving it a go as I have some new laptop cells which will fit. What sort of soldering iron power do you use? as I have a very small one which probably wont be upto the job.

 

[Deleted member 4366]

You need to check the capacity of your laptop cells match your bottle battery ones. An 8.8 ah bottle battery will have 2200 maH cells. Look at the label on your laptop battery, and then divide the total maH by the number of cells in each string. Older laptop cells have 2000 maH or less. Sometimes, a lot less.

You don't need a specially big soldering iron. Any one should do as long as it's not too small, so 30w upwards.

 

[KirstinS]

I'm finding that of the 30 or so laptop packs I've pulled apart (hp, dell, asus and I'm sure others) about 60% are Samsung cells with icr18650 22 stamped on the side. They are all green/teal though shades vary a little. On discharge testing I'm getting c2100mah depending although should be 2200mah from new. Actually they end in 22 and a letter - either a,b,e,f,h or u so far but can't find any differences that I can fathom on the spec sheets I can locate. Although the u cells perform badly I think the particular cells are just not quite salvageable for ebike use

I've got quite a few red cells with no markings that I can trace. Just batch numbers. I think these are Sanyo and they test to about same capacity- c 2050mah

If you/d8veh thinks any if these will work you are welcome to have for postage to replace your duff/duffers

Cheers

 

[alemanyorks]

I've had a look at the cells I have & think they are 2600 mah (10.8 v 5200mah 6 cell laptop pk) so looks like i'd have to do the whole lot, quite a bit bigger project than I was hoping. I may still have a go(I have enough cells) but get something else in the meantime to get me up & running again.
I think I'll start another thread about that.

Thx for the offer KirstenS but the ones I have a brand new & all the same so should be fine if/when I use them.

 

[Deleted member 4366]

I don't see why those cells shouldn't work if you just replace the faulty string of four cells. I would be more worried about using worn out cells of lower capacity.

 

[robwalley]

Bit late to this thread, but I am relating this to my oxydrive kit on a Cube Alfine 11 and d8veh's article of repairing one of these battery packs. (1) The oxydrive controller is designed to cut out intermittently if it overheats or is trying to draw to much wattage. (2) Separate to this the BMS will cut power entirely if voltage drops below a certain figure. I was getting (1) on low battery every so often as per the design, however recently I have been getting (2) more often even when battery in not too low (level 2 or 3). This would indicate to me the batteries may not be in great shape.

However, if there are now 5amp batteries available ( 10pcs Ultra Fire 18650 3.7V 5000mAH Lithium Battery Yellow - Tmart.com ) (probably exaggerating the current), d8veh can repair these battery packs and the BMS and fuses don't need changing then we end up with a 20amp pack ??

Alternatively I did find where this particular case design comes from. 36V/11.6 Ah WaterBottle E bike battery, Panasonic cell NCR18650-in Electric Bicycle Battery from Sports & Entertainment on Aliexpress.com in an 11.6amp version. Looks the right size so just swap the outer casing.

 

[Deleted member 4366]

Those Ultrafire cells are just as fakeas the description. Nobody can yet make 5000maH 18650 cells. The 2900 maH ones cost more than £5 each. How can they make 5000maH for £1.20. If they could, we'd all have them. Peel back the covering and you'll probably find recycled laptop cells.

If that 11.6aH battery is a diifferent fitting, you could swap the internals, which is very straight forward.