Bottle Battery Repair.

[Arbol]

If you've got a faint heart, don't read this thread because it has graphic pictures of major surgery.

I was given a bottle battery to have a look at, which wouldn''t charge. I checked the voltage on both the charge socket and the main connector, which both showed about 36v.
Charger showed 41.7v -- time to open it up.

Opening is easy enough: Undo the screws in the bottom and top; remove the LED board from the top, and slide everything downwards and you then have the contents to look at:



This battery has 40 cells on a 10S4P configuration. Lets say 10 strings of four cells.

I pulled the plug on the BMS and checked the string voltages. This battery only had 10 wires to the BMS connector, which means either the red or the black main wire is the 11th. You need 11 wires to measure 10 strings. In this case, the 11th was the black wire. All strings were OK except number six, which showed 0v. This means four individual cells are scrap.

I followed the balance wire down, and it led to the middle of the pack somewhere. Oh well, time to ripit apart. It's scrap as it is, so nothing to lose.


I had to unsolder several wires because they're put on at the end, and hold it together. Then I was able to break out the middle section to see the problem. There was one cell showing signs of leakage. I had some spare cells, but the ones in this battery are welded together after being assembled into the plastic holders. The only way to get them out is to cut all the welded strips, but you can't get cutters on them because the plastic holder prevents you from getting cutters on them. I therefore had to use my trusty Dremmel to remove plastic at every cutting point. Here it is all cut and ready to pull apart. You have to do both ends. It's a lot of work:

This post is great, thanks d8veh. Just one question: you say the configuration is 10s4p. But if I look at the picture, I do not see 10 strings of 4 (vertical) cells, since it seems there are 14 cells in each "horizontal" base. As a consequence, it seems as if there could be 56 (=14*4) cells maximum. So, there have to be some "bases" with less than 14 cells, in order to make the 40 cells in total.

What is the solution to the riddle?

 

[Arbol]

There's one for each string of four cells that goes from the top of the cells and the BMS. The BMS is monitoring the difference in voltage between each wire plus the difference between the first one and ground, like this:

Mmm maybe I can reply to my own question (please correct me if I am wrong): it does not matter the physical position of the cells, what matters is which cells are soldered (with a spot welder). In the picture above, a spot welder has soldered the cells in groups of four, giving a total of ten groups of four. In effective terms, the four soldered cells become a single, "bigger" cell (four cells in parallel, with the same voltage as a single cell, but four times the Ah of a single cell).

When one speaks about balancing cells, in this configuration one should have ten balance tabs, one for each "big" cell. So, one should have at least a RC charger of 4s (or bigger).

The only limitation with the physical distribution of cells is the cells in the same "group" should be in the same "horizontal base" (I guess one cannot solder cells in different "horizontal bases").

Have I got it right?

 

[Arbol]

This is a similar battery to yours (externally) This photo shows the cylindrical cells onside. The ones marked had leaked, so had to be replaced. I had three like this, so I made a serviceable one out of the three. I could probably have made three, which would have involved much more cutting and shutting.



This one shows a complete string about to be soldered in:

In relation to my previous post, I see these metal pieces connecting the cells. I believe this is called "tabbing" the cells.

Has this "tabbing" anything to do with the "groups" in the post above? I mean, the "tabbing" connects cells in groups of fourteen cells. Are these 14 cells the equivalent of the 4 cells above (in the 10s4p configuration)? Or in fact they are the equivalent of the 10 cells, i.e. 10 cells in series?

In other words: the spot welder will soldier the 14 cells together? Or the spot welder will solder the cells in "groups of four"? (where it can be four or another number X, with X being the chosen in the YsXp? (is Y=14?).

 

[Deleted member 4366]

The individual cells can be located anywhere. and joined by wires or tabs although those in the same string of four tend to be next to each other where practical. In the bottle battery, they're arranged 14, 14 and 12, so the most you could get in is 42. There are 48v bottle batteries with an extra segment, so 56 should be possible, but they use only use 52. The extra segment makes them too long for most bikes.

 

[Arbol]

Mmm interesting. So in fact what one could do in order to have a quite compact and stealthy distribution would be the following:

- Buy say 36 good 18650 cells for a 12s3p configuration
- Buy a 12s BMS in a shape amenable to a bottle, such as the 15A of bestech: http://bestechpower.com/444v12spcmbmspcbforli-ionli-polymerbatterypack/PCB-D128V1.html
- Buy a S06P controller for a bottle battery http://www.bmsbattery.com/controller/578-36v-s06p-integrated-controller-for-new-bottle-case.html
- Buy a plastic water bottle of 900ml or 1l
- Buy three of these http://www.bmsbattery.com/battery-case/621-18650-cells-protection-cover.html

Since plastic water bottles have a smaller diameter than the battery bottles, one cannot put 14 cells horizontally. But possibly 12 can be put there. Put three "towers" of 12 cells each. Put the controller on the bottom. Put the BMS above the controller and below the cells. I have a big plastic water bottle and it measures 21cm of height. Three towers of 18650 are 19.5cm. A BMS maybe 1cm. Really close, I do not know if in real terms everything would fit.

One could cut the bottom of the water bottle with a cutter and insert the whole package. Maybe one could throw away the bottom and use the controller instead as a "new bottom", reducing the problems of total height.

I believe it would be better to anchor directly the bottle to the bike instead of using a water bottle holder. If one cuts the bottom of the water bottle, I believe one can screw the bottle directly to the bike.

Is this feasible? I believe it would be really stealthy.

 

[trex]

I would have thought you would be better off using a square bottle battery (Chinese call them flat bottles) - the case can pack 50 cells or 40 cells + controller. Why 48V? 36V with more Amps will do the same job with a lot less hassle (eg a 36V battery cannot kill you but a 48V battery can)

 

[Arbol]

Thanks. Is this a square bottle battery?

http://www.b-t-n.cn/product/1690030056-210753991/36v_10ah_electrical_bike_battery.html

I would prefer a typical plastic water bottle for two reasons:

1. It is more stealthy
2. A plastic water bottle can be anchored to the seat tube, while the above battery I believe has to be anchored to the bottom tube. With for example an Abus Bordo, one could try to secure the plastic water bottle, the wheel and part of the frame at the same time. But if you have the battery at the bottom tube, I believe this is not possible

You ask: "Why 48V?"

Answer: d8veh said the S06P / S06S works well at least up to 12s. The more voltage, the more speed. With a 12s3p of 18650 cells rated at 10A or more, a 3p would give 30A. Applying the rule of thumb that in the real world, the max to be delivered is half the amount promised, a 3p would give 15A. This fits with a 15A BMS and a 15A controller.

Why can a 48V kill?

 

[Deleted member 4366]

I have a couple of comments regarding what you're trying to do.

36 cells still occupies a lot of space. There aren't many bottles big enough to house them, especially if you use those cell-holders.

You could save a lot of space by packing the cells directly to each other. Three segments of four layers of three cells will occupy a lot less space.

The BMS doesn't have to be located with the cell pack. As long as it's joined by the 12 thin sense wires and the two power wires, it can be anywhere - like with the controller.

Rather than a bottle battery, you could make something like this out of GRP, which is high on the stealthiness scale:

 

[trex]

The xootr battery case is spendid, made for the job. A square bottle is possibly a next best thing for standard diamond bike frame. It has better occupancy rate than a cylindrical bottle. Like this one:
http://www.ebay.co.uk/itm/2014-Model-48V-10-4ah-bottle-holdermount-lithium-Li-ion-electric-bike-battery-/141198150930
With regard to speed, I think you can shop around for a suitable winding, more or less any speed you like or pay a little extra and buy the xiongda XD motor.
Can 48V kill you?
http://answers.yahoo.com/question/index?qid=20110222124745AAKkkP5
SHOCK HAZARD: As defined in American National Standard, C39.5, Safety Requirements for Electrical & Electronic Measuring & Controlling Instrumentation: A shock hazard shall be considered to exist at any part involving a potential in excess of 30 volts RMS (sine wave) or 42.4 volts DC or peak and where a leakage current from that part to ground exceeds 0.5 milliampere, when measured with an appropriate measuring instrument defined in Section 11.6.1 of ANSI C39.5.

 

[Arbol]

I have a couple of comments regarding what you're trying to do.

36 cells still occupies a lot of space. There aren't many bottles big enough to house them, especially if you use those cell-holders.

You could save a lot of space by packing the cells directly to each other. Three segments of four layers of three cells will occupy a lot less space.

The BMS doesn't have to be located with the cell pack. As long as it's joined by the 12 thin sense wires and the two power wires, it can be anywhere - like with the controller.

Rather than a bottle battery, you could make something like this out of GRP, which is high on the stealthiness scale:

OK, so then I consider 30 cells in 10s3p, to make a "safer" 36V.

The cell holders then would not be needed. I could pack three "towers" of 10 cells each tower. And instead using those cells holders, just to pack them with some kind of elastic plastic band.

The xootr idea is great for that bike. But it has a very special geometry. For a "normal" bike that method would not be so ideal. I continue believing that for a "normal" bike (either MTB or road) a 900ml plastic water bottle anchored to the seat post is the stealthiest thing you can have to combine a small battery and the controller.

One could also consider a big controller case such as:

http://www.elifebike.com/peng/iview.asp?KeyID=dtpic-2013-7W-BAXN.27YMM

Possibly it has enough space for a S06S and 30 cells. And it could be anchored to the seat post. But then, it is not so stealthy: burglars could ask "why a box instead of a water bottle?"

 

[trex]

it's a shame that Lishui stops making this integrated controller + LCD:
http://www.lsdzs.com/e/ProView.asp?ProId=341

that would simplify the wiring so much.

"why a box instead of a water bottle?"

I would prefer using off-the-shelf components - you can buy the box today, no need for soldering iron.

 

[Arbol]

Yes, and why not the LCD, the controller and the BMS combined at the same place. And batteries and cables inside the frame.

I am surprised it has not been tried for a "normal" bike (apart from your example, and Keyde attempt to put batteries inside the seat post, and of course, the different "monsters" appearing mostly at ES).

Room for entrepreneurs?

 

[twinkle]

How did I miss this excellent thread ? - thanks for sharing D8veh

regards emma

 

[Ajax]

There's one for each string of four cells that goes from the top of the cells and the BMS. The BMS is monitoring the difference in voltage between each wire plus the difference between the first one and ground, like this:

Do you require any special kit for measuring and/or balancing the voltages?

 

[Deleted member 4366]

To measure, you need a voltmeter, which means a standard multimeter from Ebay, Maplin or any DIY shop:
http://pages.ebay.com/link/?nav=item.view&id=271649617604&alt=web

To balance, it helps if you have the right equipment. You can do it with any old phone or USB charger.

It helps if you can solder because you might have to fix some wires to charge it.

The BC168 charger is the tool of choice for balancing batteries because it can charge and balance directly to the cells without any special leads. It costs about £60.

 

[Lee]

I just bought a bottle battery with a dead BMS with the intention of pulling them all out, and following a tutorial I found where I'd have them taped in rows of 3, top to toe, and copy the wiring in the tutorial (even bought exact same BMS to be sure). Might have to give this post some more time and have a crack though, as the bottle casing is pretty handy and would rather not have to go down the DIY "tape it up and put it in a case" route.