Rebuilding Li-Ion power tool batteries

[rslaback]

I'm the type of guy who gets a thrill from fixing junk. I'm starting down a road of rebuilding bad cordless tool battery packs. I have the spot welder, a tester charger on the way and I've salvaged quite a few 18650 cells from old laptop batteries.

I know that in most cases, the issue with a pack dying is either in the charge controller or a single cell. I plan to salvage cells from dead packs to reuse to build new batteries. However, I also know that I need to start down the road of finding a good source of all new cells. The idea would be that if I have a 5 cell pack with one bad cell I would use all 5 new cells and then salvage the other 4 to put into either smaller packs or wait until I have another pack and turn two into one.

I'd appreciate any guidance in determining the actual discharge rate needed for a cordless pack. So far both of the Milwaukee and Ridgid packs I have been inside of use a NLA Samsung 15M cell which has a 23 amp discharge rate. I've seen mention of using the Samsung 30Q cell which only has a 20 amp discharge. What is the actual minimum that you need the cells to be able to support for normal use?

 

[jkeyser14]

The rigid pack I replaced a cell in last month was a 20A cell. It is important to only use the same cell model or replace all cells at once, otherwise the impedence mismatch and capacity mismatch can cause uneven cell loading which leads to rapid failures.

 

[PhysicsDude]

My understanding is that 3-5 years ago most manufacturers started using 30A cells in most of their battery packs, and many started using 21700 cells for their higher discharge ratings.

I'm sure a 20A cell is fine for most uses (drill/impact/light, etc). I would be weary about using them on higher power draw tools.

The cells should have their ratings written on them when you take the battery apart.

 

[yatg]

What kind of spot welder did you get?

 

[jkeyser14]

What kind of spot welder did you get?

Not the OP, but I have a cheap Chineese ebay unit. It works ok, but occassionly trips my 20A breaker due to the inrush since it just charges and dumps some large capacitors.

 

[rslaback]

What kind of spot welder did you get?

I bought a 737G. It is definitely not the top of the line but the reviews I've read indicate it gets the job done.

 

[rslaback]

My understanding is that 3-5 years ago most manufacturers started using 30A cells in most of their battery packs, and many started using 21700 cells for their higher discharge ratings.

I'm sure a 20A cell is fine for most uses (drill/impact/light, etc). I would be weary about using them on higher power draw tools.

The cells should have their ratings written on them when you take the battery apart.

I've never found one with the actual ratings on it. I've always had to look up the battery specs based on the model info on the wrapper.

 

[PhysicsDude]

I've never found one with the actual ratings on it. I've always had to look up the battery specs based on the model info on the wrapper.

Oh, yeah, you're right. Now that I think about it they usually have the capacity written on them, but not usually the discharge rating. Either way I think you should be able to find some way what the discharge rating is of the cells you're replacing.

 

[timm1]

Oh, yeah, you're right. Now that I think about it they usually have the capacity written on them, but not usually the discharge rating. Either way I think you should be able to find some way what the discharge rating is of the cells you're replacing.

When removing the bad batteries how do you disconnect them without damaging the thin contack that is spot welded to them.

 

[slow]

I have bought from https://www.18650batterystore.com/ they are legit, but not cheap from my research. I only needed a half dozen so cost was not a real factor, but did not want knock off or used cells.

 

[flyingwolf]

When removing the bad batteries how do you disconnect them without damaging the thin contack that is spot welded to them.

You can be really careful and use a pair of pliers to gently tease it off there, but the simple truth is they were not made to come off, so just expect to have to replace them.

The link that @slow dropped has the nickel tab material you will need.

 

[trs71]

What kind of spot welder did you get?

Waste of money for batteries to buy a cheap one, you can DIY cheap, that way when the china cheap one goes, you can build or fix another one....or use a car battery and some wire (hey it works, if your only doing it a few times.)

I used to solder it on way back, I recently saw a video on it on how much more even a few seconds of soldering heats it up compared to a spot welding system,

 

[vwpieces]

Liion Wholesale Batteries | Li-ion battery/cell distributor

Liion Wholesale is a US-based wholesale distributor specializing in authentic high quality lithium ion batteries, fast shipping, and expert customer support.

liionwholesale.com

I have bought cells from them, all genuine. The 30Q is the most Faked battery out there. So, avoid ebay and amazon when buying cells. Customs will confiscate cells that are imported and not shipped properly "Hazmat"
30Q will do fine in the packs, have seen them in OEM packs too. You might be limited to the mosfets in output current long before the batteries max out.

Are you just replacing one cell or building entire packs with new cells?
Ask because if you should at least be matching pairs, if not replacing the entire pack.

Just checked and all Samsung 18650 are out of stock

Here is another popular USA distributor of cells.

IMR Batteries | Premium Rechargeable Batteries & Power Solutions

Shop IMR Batteries for high-quality, reliable power solutions. Explore premium rechargeable batteries for flashlights, tools, and devices. Trusted by professionals!

www.imrbatteries.com

 

[timm1]

Liion Wholesale Batteries | Li-ion battery/cell distributor

Liion Wholesale is a US-based wholesale distributor specializing in authentic high quality lithium ion batteries, fast shipping, and expert customer support.

liionwholesale.com

I have bought cells from them, all genuine. The 30Q is the most Faked battery out there. So, avoid ebay and amazon when buying cells. Customs will confiscate cells that are imported and not shipped properly "Hazmat"
30Q will do fine in the packs, have seen them in OEM packs too. You might be limited to the mosfets in output current long before the batteries max out.

Are you just replacing one cell or building entire packs with new cells?
Ask because if you should at least be matching pairs, if not replacing the entire pack.

Just checked and all Samsung 18650 are out of stock

Here is another popular USA distributor of cells.

IMR Batteries | Premium Rechargeable Batteries & Power Solutions

Shop IMR Batteries for high-quality, reliable power solutions. Explore premium rechargeable batteries for flashlights, tools, and devices. Trusted by professionals!

www.imrbatteries.com

I am just replacing bad cells. I use a welder I made using a 12 volt battery a solenoid and a button and 2 wires.

 

[flyingwolf]

I am just replacing bad cells. I use a welder I made using a 12 volt battery a solenoid and a button and 2 wires.

You can't just be saying that and not showing your work!

 

[trs71]

Hey I've got 6 old Ryobi yellow battery packs, I'd like 1 or 2 fixed where is a good place/brand to purchase battery cells from nowadays?

 

[AP514]

Hey I've got 6 old Ryobi yellow battery packs, I'd like 1 or 2 fixed where is a good place/brand to purchase battery cells from nowadays?

Two good sources in the post above.....