18650 spot welding -how to- ULTIMATE REPOSITORY

LikeToRideMyBike said:
Hey guys, I've got a problem. I just hooked up my BMS. When I reached a full charge some lights came on where the balancing cables went in. It was a little warm while these lights were on. It was strange. I don't know, maybe that was normal. But overnight it lost charge from 67.2 volts down to 66.6 volts. That's definitely not normal. What is going on? Do I need to disconnect this BMS and get a new one? I scared that it's going to ruin my brand new Samsung 25r cells. What do you think?

Here is the link to the BMS I used: http://www.aliexpress.com/item/16S-Li-ion-Lipo-Batteries-Protection-Board-BMS-System-60V-67-2V-50A-Continuous-Discharge-Current/32263328170.html

thanks all
Click to expand...

Should be normal, the BMS balances the cells to the lowest cell, so it discharges all the other higher cells and will lower your pack voltage. This discharging will cause heat.
If all your cells are balanced the voltage shouldn't drop anymore and nothing should feel warm. If the voltage continues to drop then you have problems.
 
How are you suppose to size up heat shrink.
I got 14cm x 22cm x 6.5cm (140mm x 220mm x 65mm)
Basically I need to find someway to convert flat dimensions to round dimensions.
These are 2:1 or 50% shrinkage.
So I should buy something that is a diameter of ~250mm

http://stores.ebay.com/Atop-Authentic-Auction/PVC-Heat-Shrink-Tubing-/_i.html?rt=nc&_fsub=2998732015&_sid=879188535&_sticky=1&_trksid=p4634.c0.m14&_sop=2&_sc=1
 
markz said:
How are you suppose to size up heat shrink.
I got 14cm x 22cm x 6.5cm (140mm x 220mm x 65mm)
Basically I need to find someway to convert flat dimensions to round dimensions.
These are 2:1 or 50% shrinkage.
So I should buy something that is a diameter of ~250mm

http://stores.ebay.com/Atop-Authentic-Auction/PVC-Heat-Shrink-Tubing-/_i.html?rt=nc&_fsub=2998732015&_sid=879188535&_sticky=1&_trksid=p4634.c0.m14&_sop=2&_sc=1
Click to expand...

The way I figured it, they give you the flat diameter dimension. So say it is 250mm

Use one of those sewing measuring tapes and bring 0mm to the 500 mm end. That is exactly the size the shrink wrap will be when you then make a circle with the measuring tape holding it at those marks.

You can then try and circle it around your battery, or something with your battery dimensions.

They also give you the round dimensions, but you won't be going totally round so it isn't that useful.
 
Use one of those sewing measuring tapes and bring 0mm to the 500 mm end. That is exactly the size the shrink wrap will be when you then make a circle with the measuring tape holding it at those marks.
Click to expand...

I just can not envision what you are saying right now. My length is 220mm, but the diameter shouldnt be much more then that, based on my width. OK After reading it several times I see what you mean now.
You mean make a loop or circle with the measuring tape. Why did you pick 500mm?
I was trying to do it using math, but the width of the pack makes it a complex eqaution rather then the simple equation.
Your way is easiest with a "manly mans" construction measuring tape and making a loop. Better then putting a pencil of the end and randomly picking a length to scribe a circle.

From the looks of this heat shrink stuff, its like $10 USD or more for a meter (3.3') so $13 CAD per meter. If its thick PVC then it might be worth it. I have a feeling this aint thick PVC heat shrink, because thick PVC from the store I buy mine at is more expensive then this China product.

I am thinking extra wide Gorilla Duct Tape should work better!!
Perhaps with some card board type material between the batteries and the sticky tape.
I need to reopen the packs when I get a new Weller soldering tip, and another pound of solder. My current soldering job is horrible.
 
Offroader said:
Is there an easy way to remove cells that are hot glued together?
Click to expand...

Rotary tool with cut off wheel would work for the outter cans.
A hot air gun might work.
A razor blade perhaps to get into the second row/column.

You might have to do it piece meal, would be able save the holders. They are always a pain to take apart.
 
bikegeek said:
Offroader said:
Is there an easy way to remove cells that are hot glued together?
Click to expand...

Try this: https://www.youtube.com/watch?v=dNNqSXgj6DE
Click to expand...


WOW, this work amazingly well. You spray a little isopropyl alcohol on the edges and let it seep for 20 seconds in and the cell loosens right up..

I honestly didn't think there was any good way to do it but thought I'd ask anyway.

I believe this is also safe on the cells.
 
Offroader said:
Is there an easy way to remove cells that are hot glued together?
Click to expand...

Put the glued cells into the freezer (-18ºC or less) for 12h to 24h. Cover all into a semi-vacuum bag (standard plastic bag tied) to avoid a very high temperature change and humidity. Then you can very easily rip off them, even with your hands. You have only 5 minutes to do it properly, then you must put again into the freezer 4h more to have them ready again.

- Use latex gloves to avoid freeze your hands
- a screw driver help good, but you have a high risk of damage insulators (this will happen continuously depending of the quality/type of melt silicone/glue used)
- if you are ripping a piece, put the rest inside the bag while working, this makes you a greater time to work.

This is the easiest and fastest method I've tried
 
Question,

I read it is recommended not to solder cells because of the heat.

Will hot glue cause any heat issues to the cells? Should you limit the temperature on the hot glue gun?
 
Neither hot glue/ melt silicone or spot welding will make an appreciable harming heat. The important thing is the capacity of the cell to spread the heat quickly so the chemicals have not an increased temperature. All the cells is covered with a metal that will spread the heat quickly over all its surface and insides, making the temperature lowered very quick
 
Thanks Nobou, I would like to ask you another question.

When you build a pack with the cells touching each other. Is it important to put something between the cells touching each other that will be in a difference series group?

I know that if cells next to each other in a different series group short together (with the outside negative case) that will be bad.

Is using Hot glue and welding tabs good enough that a short will not happen? If it isn't, what do you recommend to put between the cells in a different series group?
 
Depends closely with your detail level construction. Cells are perfect cylinders, if you make good shapes and patterns where cells are very exactly placed, the weight will perfectly distributed if the battery have an impact for example, and is almost impossible that both insulators of two consecutive cells will be punctured making its cathodes electrically in contact. However if while making the battery you left a grain of sand or any sharp metal between two cells, you could have a strange cathode short before a hard impact

Also the glue/silicone, if it is used in the right quantity (in the way if makes even a small film between cells in contact, will absorb an important part of the energy on any impact.

It depends also about your battery size, use, installation, etc.

Only you could answer if you need serial separators, anode spacers, cell holders, active cooling..
 
Overclocker said:
nice thread!

gotta restock my nickel. now using 7mm. but the vendor also offers 12mm.

so which one is better for "all-around" use? 7mm or 12mm width?
Click to expand...

To be honest I would recommend the 12mm wide.

15 mm x 7 mm has a 1.05 mm² cross section, .15 x 12 mm has a 1.8 mm² cross section. So you get 70% more current capacity with the .15 x 12 mm.

.15 x 12 mm is similar to .2 x 9 mm strip.

That is a large increase in current capacity and you can use 12 mm wide on 18650 cells and they will not be wider than the cell. The only issue is on the positive side when welding you will slightly overlap where you need to weld and will have to be a little careful to make sure you weld in the center, but this is easy to solve with placing a gasket or template before welding to see exactly where you need to.

Welding the 12mm side strip to the negative side of the batter is easy.

Most people want to go thicker like .3 nickel, but I say go wider as it is so much easier to weld.
 
DVDRW said:
My first 18650 pack plan. 22s18p
Wish me luck! :D
Click to expand...
Pardon the expression but, "holy crap" - that's an enormous battery for a bike 352 cells - what are they?

...good luck! :lol:
 
Random questions... Does anyone have any tips on soldering the balance wires and discharge/charge wires to the nickel. Techniques or type of solder. I've pretty much tried every technique I can think of. It's just hard to get the big wires to stick. I just use regular electrical solder from the local hardware store. 10AMW wire is extremely hard the solder to these thin strips of .7mm nickel. I'm having the damnedest time. Any help would be appreciated.

Thanks everyone
 
LikeToRideMyBike said:
Random questions... Does anyone have any tips on soldering the balance wires and discharge/charge wires to the nickel. Techniques or type of solder. I've pretty much tried every technique I can think of. It's just hard to get the big wires to stick. I just use regular electrical solder from the local hardware store. 10AMW wire is extremely hard the solder to these thin strips of .7mm nickel. I'm having the damnedest time. Any help would be appreciated.

Thanks everyone
Click to expand...

Need more information.

Are you pre tinning the wire?
How many watts is your soldering iron?
How big is your soldering iron tip?

You need a high wattage soldering iron with a big tip for the 10 gauge wire.

Have you been trying to solder the wire over a cell? I bet you are overheating the cells if you are having difficulty.
 
Offroader said:
LikeToRideMyBike said:
Random questions... Does anyone have any tips on soldering the balance wires and discharge/charge wires to the nickel. Techniques or type of solder. I've pretty much tried every technique I can think of. It's just hard to get the big wires to stick. I just use regular electrical solder from the local hardware store. 10AMW wire is extremely hard the solder to these thin strips of .7mm nickel. I'm having the damnedest time. Any help would be appreciated.

Thanks everyone
Click to expand...

Need more information.

Are you pre tinning the wire?
How many watts is your soldering iron?
How big is your soldering iron tip?

You need a high wattage soldering iron with a big tip for the 10 gauge wire.

Have you been trying to solder the wire over a cell? I bet you are overheating the cells if you are having difficulty.
Click to expand...

Yeah, for the bigger wires I suppose I'll get an 80watt fat tip weller solder iron. Someone recommended one of those earlier. And some of that tinning paste as well. I just learned about that stuff today. And yes I most definitely have heated up some of the cells. I hope that I have not caused any permanent damage. Ughhhh :arrow: I'm most definitely losing sleep over this battery.

thanks again offroader
 
80 watts is way too big to be honest, even for 10 gauge. It'll get too hot. Probably should have soldered the wire to the nickel before welding.

tinning paste? I don't think you need that, just get solder with flux in it.

Soldering takes lots of practice to get good at it. You probably shouldn't hold that soldering iron on the nickel strip attached to a cell for more than like 5 seconds max.
 
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