Battery build 18650 cells

[Rodney64]

I've decided to document my battery build.

The battery will be made with Samsung 25r cells

The battery is going to be 16s 10p.

My spot welder is one of Ribas.

My components


http://m.aliexpress.com/store/storeHome.htm?sellerAdminSeq=221052922

Nickel, battery holders and shrink wrap that I purchased from aliexpress

My ballance leads are 4s which I purchased from hobby king

My BMS will be the adaptto

Ill post picks as I start the build.

Current status I still need to purchase the clamps to go onto the battery and connect to the welder and electrodes.



I've started assembling the holders and arranging the cells.

The holders come in 2 and 3s and just push together.

 

[quackstar84]

Thank you. I'm planning to sell my 1000 watt hub and dismantle my vpower 48v 10ah and change it to an 24v 20ah battery or just an 10ah so this will help me a great deal.

 

[fullonoob]

where to solder the 4s balance lead

 

[Rodney64]

where to solder the 4s balance lead

That's what I'm not sure about. I'm confident in the rest of the pack build.

The 4s ballance lead has 5 wires with the last one being black. So I'm assuming that this goes to negitave. But where I'm not sure.

 

[Rodney64]

I have decided to stop the build until my gaskets arrive.

I've decided to start a different configuration. 20s 8p. I've also decided to glue the cells. (No gap)



My first 2s 8p group

I'll post tomorrow the 3s, 4s and so on.

Before I start spot welding the 3s group tomorrow I'll be taking some measurements. Mainly to prevent this below.

The positive end of the pack in the middle of the battery (the button). So it's important to get the Nikel strip centred and I will mark it out so I don't short another battery. By the looks of it all the rest of the battery is negative.




Anyway a good lesson on what not to do and why it's important why you need to wear safety glasses.

Looking good so far. 2s 8p so fat looks good.



I'm using the Bosch glue gun. Another thing that I'm doing is taping the top of the positive end and using a hole punch 6mm to expose the button. This will add extra protection to the top of the negative end. Between the nickel strip and the positive side of the cell.




This is the bottom of the pack.

 

[Hyena]

It's probably too late now Rod but you can avoid that little shorting incident you had by using these little gasket type insulators that go on the top of the cells around the positive terminal. They're a good idea anyway as with any slight moving or rubbing over time, as you found, there's only the slightest gap between the -ve and +ve of the battery. Likewise if the thin insulation on the side and top of the cell was to rub through the +ve straps could short to the -ve case

http://www.aliexpress.com/item/two-double-joint-hollow-solid-insulation-red-paper-adhesive-high-temperature-pad-cushion-gasket-for18650-18500/32477472336.html?spm=2114.01020208.3.27.cFxyW6&ws_ab_test=201556_3,201527_3_71_72_73_74_75,201409_1

If you get this longer, joined style they ever so slightly help with pack construction too by holding the cells together while you weld them.

 

[Rodney64]

Yes maybe too late for me but for anyone following then it's good insurance.

Thanks Hyena.

 

[Mammalian04]

I get the feeling there will be a suspension coming.....

On a separate note, did you decide not to offset the cells for simplicity of construction or for cooling purposes?
I have the same dilemma. I would like 20s (in 4s groups for the Adaptto) but I would rather have the structural rigidity of the cell holders. Unfortuantely, 6 wide seems to be the magic number for making 20s fit nicely. I will play more when the cells arrive.

 

[Rodney64]

I get the feeling there will be a suspension coming.....

On a separate note, did you decide not to offset the cells for simplicity of construction or for cooling purposes?
I have the same dilemma. I would like 20s (in 4s groups for the Adaptto) but I would rather have the structural rigidity of the cell holders. Unfortuantely, 6 wide seems to be the magic number for making 20s fit nicely. I will play more when the cells arrive.

I decided not to offset because of space. At the moment the controller will be on end beside the pack.

3rd and 4th S parallel groups now finished.



This will be my BMS wiring diagram.

I'm numbering the cells now. So I am gaining confidence. The pack as it is now is 10.99 volt.

 

[Rix]

I like this thread, the heart of our machines is the battery, Subscribed.

 

[markz]

Rodney - Do you got riba's tab welder?

Hyena - Whats the delivery time like for SuPower?

 

[Rodney64]

Rodney - Do you got riba's tab welder?

Hyena - Whats the delivery time like for SuPower?

Yes it's Ribas tab welder.'

 

[ridethelightning]

del. from supower is pretty fast, a couple weeks max to australia, i just got some of those ring gaskets.
its going to be a whole lot faster waiting for those to arrive then repairing the aftermath of a dead short/cell fusion/plasma explosion incident :wink:

 

[Rodney64]

del. from supower is pretty fast, a couple weeks max to australia, i just got some of those ring gaskets.
its going to be a whole lot faster waiting for those to arrive then repairing the aftermath of a dead short/cell fusion/plasma explosion incident :wink:

Ok, I've decided to stop the build and disassemble what I have already soldiered together and wait until the tabs arrive. I will also order 5,6 ml wide nickel strip.'

 

[ridethelightning]

probably a good thing, even just for a good night sleep

the nice wide nickel you are using is good though. id stick with it, as with the cell protectors, it really doesnt matter how wide it is. it will give better current flow, unless you plan to double up the narrower stuff.

 

[Rodney64]

probably a good thing, even just for a good night sleep

the nice wide nickel you are using is good though. id stick with it, as with the cell protectors, it really doesnt matter how wide it is. it will give better current flow, unless you plan to double up the narrower stuff.

I will use the 7ml nickel strip on the positive and 12ml on the negative.

One cell has shorted and burnt. So yes a good move to wait for the cell protectors. I like the idea of using the 7ml strip for the positive, just easier to get the nickel positioned and less error for incorrectly welding the negative by mistake.

I've left all the cells in 1s 8p groups. So when the new nickel arrives this will cut the build time down.

 

[macribs]

*Subscribed"

Great work Rod, documenting the build.
Looking forward to read and learn. The balancing part is what turns my head into mush.
Now we get a step by step guide.

 

[riba2233]

Yeah, be careful, whole can is negative.

Also, you should put isolation between series groups, in here:

Original wrapping could wear out with time, and then the cell can short out. Although glue should help with preventing chaffing, but still...

 

[Rodney64]

Thanks for the feedback Riba.

Insulation tape on the ends be enough between the series?

Another option is fibreglass G10-FR4 sheeting between the series.

This maybe a good option for the top and bottom of the pack as well prior to heat shrinking.

 

[Hyena]

Insulation tape on the ends be enough between the series?

Nope, the whole length of the can. As Riba said the entire battery case is -ve so if the insulation breaks through anywhere on the cell at all it could short. If it's within its parallel group it doesn't really matter, but if it shorts to a neighboring group it will short out.
Worst still, if the pack is arranged such that 2 cells with a big voltage differential end up side by side and come in contact, it's fireworks time.
I actually had an 18650 pack explode like this. The pack stopped working after a few cycles and when I poked it with the multimetre probe it was enough to set off the short - showers of fireworks like sparks which then must have welded to 2 cells together, which proceeded to erupt into flames and set my bench alight before I could grab the fire blanket and hurl the whole thing outside. 18650 cells are safer than lipo but anyone who tells you they're safe and can't blow up are having themselves on.

Not that I'm trying to deter you or anything :lol:
I think waiting for the insulators to arrive is a good call though.

 

[Rodney64]

Insulation tape on the ends be enough between the series?

Nope, the whole length of the can. As Riba said the entire battery case is -ve so if the insulation breaks through anywhere on the cell at all it could short. If it's within its parallel group it doesn't really matter, but if it shorts to a neighboring group it will short out.
Worst still, if the pack is arranged such that 2 cells with a big voltage differential end up side by side and come in contact, it's fireworks time.
I actually had an 18650 pack explode like this. The pack stopped working after a few cycles and when I poked it with the multimetre probe it was enough to set off the short - showers of fireworks like sparks which then must have welded to 2 cells together, which proceeded to erupt into flames and set my bench alight before I could grab the fire blanket and hurl the whole thing outside. 18650 cells are safer than lipo but anyone who tells you they're safe and can't blow up are having themselves on.

Not that I'm trying to deter you or anything :lol:
I think waiting for the insulators to arrive is a good call though.

Chris said he has plenty of fibreglass .8 ml. So I'll use this to put between the series the whole length of the cell.

The safer way would be two stay with the holders and in hind sight I should have done this. But I've ordered the nickel strip and the gaskets so I'm confident in building a reliable pack.

 

[Hillhater]

Yes, easily overlooked Is the fact that not all negatives are at the same potential !
One benefit of using those plastic cell holders to keep the cans from touching.

 

[ridethelightning]

you can still build a pretty safe pack without the holders, and its a whole lot more compact.

as long as there is some good insulating material between the series groups, there should be no possibility of the wrap chaffing through and shorting between cans at diff volt potential.

insulating material could be fibreglass tape, thin leather, or some other heat resistant tough material. iv even seen just gaffa tape used for this.
ill post some shots of my latest pack build when i get a mo..

 

[amberwolf]

I actually had an 18650 pack explode like this. The pack stopped working after a few cycles and when I poked it with the multimetre probe it was enough to set off the short - showers of fireworks like sparks which then must have welded to 2 cells together, which proceeded to erupt into flames and set my bench alight before I could grab the fire blanket and hurl the whole thing outside.

And your camera wasnt' running why?

 

[Hyena]

And your camera wasnt' running why?

well, what I didnt say above was that things got rather out of hand WHILE I was reaching for the camera :lol:
Rest assured, I captured all the action! I just have to edit it a little so it's fit for public viewing. My wife was woken at 11pm by screeching fire alarms, then looking out the window and see a lithium blaze in the driveway that I was unable to put out. Her verbal response was a little... aah.. colourful :lol: