PINNED - Lithium battery conversion/info

[rustyjames]

Where are you going to buy your cells Hotwheels?

[hotwheels_75]

I went with evassemble. Took the plunge last night. now I have to order the charger, cables & a power supply.

[snaker]

Could someone please recommend for me the right ring terminals? I am having headache in this problem. I did not know there are too many types. I spend 2 days for searching but cannot find them.

The battery cells are as underneath. The hole/screw size is M6 (6mm diameter). I need both insulated (terminals with adhesive heat shrink tubes) and non-insulated ring terminals.That's because a friend advises terminals should be soldered after crimping (is he right?). Insulated ones will be used for crimping only, non-insulated ones for crimping+soldering. I will try the non-insulated ones first, If soldering is not properly done, I will switch to the insulated ones.

So my needs are:
1. Insulated ring terminals M6 for 6/8/10/12/22 AWG wires.
2. Nom-insulated ring terminals M6 for 6/8/10/12/22 AWG wires.

I can buy from digikey.com or mouser.com. Or I just need to know the code names or pics of them.

[Burgerman]

eBay has every size in the universe.

Crimping, on these commonly available terminals is a joke. There is inadequate wall thickness. Once its crimped, air can get in and cause corrosion. Worse you can pull the crimp off and often with little effort. They are just made from a bit of thin soft copper tube.

You want: 10 sq mm cable, 6mm stud. http://www.ebay.co.uk/itm/Crimp-or-Sold ... MNxFyXH0QA

Or for 5mm cable you want these, with 6mm stud. http://www.ebay.co.uk/itm/6mm-Battery-S ... NXL0dSXYDg

Then buy adhesive heat shrink, that covers every bit but the whole you put the bolt in!

SMALL wires can be crimped securely in a professional system that is in a production environment http://www.easternbeaver.com/Main/Elec_ ... -crimp.jpg

Unless you can find some real heavy crimp terminals, like this http://static.baxters.com.au/media/cata ... 0/00sp.jpg and I never could! Those can be crimped airtight on heavy wires.

You need a small gas torch, and a crimper to close it up tight to solder with capillary action well.

http://www.wheelchairdriver.com/crimp-solder.htm this is what I do.

[snaker]

Now I know their technical name "battery lug" and I found some Molex Eyelet ones for each size. Thank you soooooooooo much, BM.

[shirley_hkg]

It will easier to do the parallel and series connection in one go , by using a copper strip . 0.5mm thick copper strip with 4 holes . Easily diy .

[snaker]

The batteries arrive without connection bars. My next step is to implement copper bars. There will be 1x2, 1x4, 2x2 holes bars. A local workshop has a CNC machine, I could ask them doing the bars. I can buy 1mm or even thicker copper sheet (plate?). Shirley, do you think if I should use 1mm bars? Or are 0.5mm bars already adequate?

[Burgerman]

1mm brass is easier to work with and physically stronger. And easy to get. Copper is horrible to work/drill.

[snaker]

Each of my batteries is wrapped by a blue nylon as the image below. I intend to remove that nylon so I can put batteries close side-by-side in the battery box and precisely measure the connection bars. Is there any problem if batteries are naked without nylon wrappers.

[shirley_hkg]

Smoke & fire for sure .

Look closely what other people do .

[snaker]

So they will get burned if ... naked. Fortunately, I have not unwrapped their nylon yet. Thanks Shirley.

[shirley_hkg]

. I intend to remove that nylon so I can put batteries close side-by-side in the battery box and precisely measure the connection bars. Is there any problem if batteries are naked without nylon wrappers.

Instead , additional insulation should be induced .

The blue shrink wrap is very vulnerable .

Seller asks user to put at least 0.5mm barley paper around cell , to avoid short circuit

Never forget to insulate the bottom of your battery box too .

[Burgerman]

Interestingly the headway style cells casing does not appear to be connected to the plus or minus. And the calb/winston/thundersky/etc type cells are already plastic. So these are the only cell types that have this danger. I would be very careful! Heatshrink an extra layer, and wrap in a layer of duct tape too!

Or Wrap each neatly in duct tape, then, use some of that plastidip stuff on every one to hide it, seal it, and add extra insulation.


youtu.be/DwHglysGMDE

[snaker]

Is it safe enough if I insert these thin 0.1-0.3mm silicon sheets between cells?

https://world.tmall.com/item/5244464044 ... 1087688462

[Burgerman]

As long as the base is insulated with something a little thicker, I would say ok. But .3 is very thin... 1mm better. On all 4 sides of each cell. Leave the blue heatshrink too.

[Burgerman]

Better to add 2 layers of this to every cell all over neatly.

Then slip each into a accurately fitting plastic bag.
And then tape the whole pack tightly together.
Use an insulating layer of plastic on the base too.

[Gnomatic]

Interestingly the headway style cells casing does not appear to be connected to the plus or minus.

Scraping the blue coating of a Headway cell on chair bolts on each side of a Headway pack simultaneously, is not something you want to happen. Don't ask me how I know this.

[Burgerman]

So they are connected.The can is neg or pos? I measured one here and it showed otherwise! Maybe I had a bad connection.

[snaker]

My battery box is too small. If adding just a couple of mm tape, the pack cannot fit the box.

Here are my thoughts, please check if where I am wrong?

I see the electric only goes out from 2 holes on each battery. And these 2 poles are isolated from the metal shell (through a rubber ring). So if a battery stands alone, it is completely safe. Even if all the blue nylon covers are removed and the batteries are put side by side, they are still safe as long as they are not connected. The problem only comes when they are connected. That's because after connected, the top of screws or the copper bars might touch the box. If the box is not well insulated, that causes a short circuit and the pack gets burned. To prevent this danger, I only need to wrap the pack by a thick duct tape after connecting batteries. I have to ensure no metal part is open to the outside.

[Burgerman]

No. One of the poles (the terminals) is also the case. So every cell casing, is 3.4V different to its neibour once connected in series.

Use a multimeter. See if the case is the same as the negative. It will probably be so, according to shirley.

[Gnomatic]

So they are connected.The can is neg or pos?

Not sure. Just know if you do what I described, lots of sparks, and the cell on each side of the pack that got scraped will have a small hole in the casing where the aluminium was melted through! With electrolyte bleeding out of it.

I think the casing is the pos but don't quote me on that.

[shirley_hkg]

My battery box is too small. If adding just a couple of mm tape, the pack cannot fit the box.

You are doing 2P8S right ?

An 2P pair can be regarded as 1 , so need no EXTRA insulation .

I only put thin paper cardboard between adjacent cells , and stuck stuff in , to fill up any excess void in battery box . That prevents the cells rubbing each others .

[snaker]

Yes, the pack was planned to be 2P8S. But it seems I have to wrap each battery by thick tapes and accept 1P8S 75Ah@24V.

I just meter the batteries, the metal case is positive. I cannot understand why they can invent this danger. The batteries must have thick plastic or at least durable silicon covers instead of thin and weak nylon.

[Burgerman]

Yes thats what I expected. Its what you expect with cheap chinese cells. Just wrap in 2 layers of duct tape. And about 4 layers at the bottom.

[shirley_hkg]

75Ah is too small that the cell will be stressed to 1C discharge most of the time . That's too hard for these cells and they won't last long .

Take a breath and think thoroughly what can be done ; anything on the battery box / compartment .

[Burgerman]

Just to scare you, my brushless chair takes a measured 175A + initially from the battery to turn left or right on the spot. Thats 2.2C from a 75Ah battery...

This is why I and Shirley always stress that its important to maximize Ah or at least use high C rate cells.

[steves1977uk]

Headway cells are rated 10C for a single cell, so it would've been better to use 40 of the 15A cells to make a 75Ah pack. Trying to do it as cheap as possible ends up costing you more since the cells are stressed under load.

Steve

[Burgerman]

Looking at the voltage drop under load, and feeling the temp with my hand I would say the 10C rating is best thought of as pulse or short term. Theres no standards to say how these 1, 2, 5 or 10C ratings are measured. So while its definitely higher than the prismatics, and can also cool better I think 10C is a little exadurated. Even so, if you compare to the prismatic cells its at least double.

That said, all lithium cells prefer to be charged and discharged at a lower rate. The 1500 cycles testing is done at 0.2 or 0.3C typically. Likewise for best service life a charge rate of around 1/5th to 1/3rd capacity is best.

So when charging you CAN charge at up to 5C on a headway. So that would mean max charge rate on a 50Ah pack would be 250 Amps! But a 50Ah battery is still going to thank you with a longer service life if charged at 0.2C to 0.3C or 10 to 15A.

So if time allows, charge slowly. If you are in a hurry, dont fret, turn the charger up to max. 40A isnt that high.

[snaker]

You want: 10 sq mm cable, 6mm stud. http://www.ebay.co.uk/itm/Crimp-or-Sold ... MNxFyXH0QA
Or for 5mm cable you want these, with 6mm stud. http://www.ebay.co.uk/itm/6mm-Battery-S ... NXL0dSXYDg

BM, your recommended ring terminals are zinc plated. I cannot find sellers of that zinc plating type. I only find Molex ones which are tin plated. Can I apply your soldering style on tin plated ones? I mean if there is any problem when heating tin plated terminals through a gas torch?
http://www.mouser.vn/ProductDetail/Mole ... TpMGITs%3d

[Burgerman]

You can solder any of them easily. When using a flame you only heat just enough to see the solder run. Then stop. Adding more heat will ruin the joint and oxydise everything. Just enough only!