Finding quality 18650 cells to repair Dremel 1100?

[timg11]

I would like to repair two Dremel 1100 tools, which are no longer made. There is nothing similar in size and form factor, so I want to repair them.

When the first one's battery failed a couple of years ago, we tried replacing it with this kit from Amazon. Unfortunately, the replacement cells lasted only a few months.

Since this kit is only providing the raw cells, and all the work of tab soldering etc still has to be done, I believe any quality 18650 cells could be used. But the assortment of cells from sketchy companies and with various alleged mAh capacities found on Amazon are challenging to sort through.

Can anyone offer advice on identifying reputable suppliers and sourcing cells with capacity at least as good as the original?
Should I use Digikey (that seems to be reselling Sparkfun and other suppliers)
Or directly from Sparkfun?

[edavid]

Do you have a local Batteries Plus store?  If so, they can make a new pack for you.  They sell quality cells and have all the tools.  It's not that expensive compared to getting tabbed cells by mail order.

BTW, battery tabs should be spot welded rather than soldered.  Maybe that's why your replacement batteries failed so quickly.

[thm_w]

The cells lasting only a few months is suspicious, even if they are not quality parts. Do you have a dedicated 18650 tester/charger you can pop the cells out and test them with? These cost about $20 so its worth having one around.
It looks like there is no balancing circuit so if the cells were not reasonably matched, this could cause problems. Can you measure the existing voltage across each cell?

You can buy directly from sparkfun or digikey, or many other 18650 suppliers that sell quality cells. Though I would go with the sparkfun ones as they have the tabs already welded on.

BTW, battery tabs should be spot welded rather than soldered.  Maybe that's why your replacement batteries failed so quickly.

The kit includes tabs so that would have not been the issue. Soldering to tabs is fine.

[edavid]

BTW, battery tabs should be spot welded rather than soldered.  Maybe that's why your replacement batteries failed so quickly.

The kit includes tabs so that would have not been the issue. Soldering to tabs is fine.

If you look at the photos in the Amazon listing, they seem to be asking the buyer to solder the tabs from the old batteries right on top of the tabs on the new batteries.  That seems almost as bad as soldering to the batteries themselves.

[Haenk]

If you look at the photos in the Amazon listing, they seem to be asking the buyer to solder the tabs from the old batteries right on top of the tabs on the new batteries.  That seems almost as bad as soldering to the batteries themselves.

It seems you should solder to the tabs already spot welded on the new pack (as seen in picture one), not the battery. Nothing wrong with that, I guess.
However you do not know the sketchy brand of the cells, so I would not use that pack.

[Mechatrommer]

buy good charger that can show mAh when fully charged. I use nitecore um4.. all type of batteries can use.. so i know who sells good battery who sells crap.. i can also know the status of my old battery whether to repurpose, or into the trash.. i may look like a tight ass but i hate overpriced fancy colorful brands. In the end i usually bought samsung or panasonic flat colored brand, i figured grey color is bang per buck more than 2Ah specified.. i have soldered battery working until it rusted on outdoor usage for years, so i dont see problem with soldering tabs.. we dont have local spot welder here, if i rely on them, i will still in stoneage by now. fwiw.

[edavid]

buy good charger that can show mAh when fully charged. I use nitecore um4.. all type of batteries can use.. so i know who sells good battery who sells crap.. i can also know the status of my old battery whether to repurpose, or into the trash

Kind of irrelevant to OP, who is going to be charging the batteries inside the tool.

i have soldered battery working until it rusted on outdoor usage for years, so i dont see problem with soldering tabs.. we dont have local spot welder here, if i rely on them, i will still in stoneage by now. fwiw.

Look at the photos, they seem to be wanting the user to solder the tabs from the old battery right on top of the new tabs.  That seems like a recipe for overheating the batteries to me.  Of course we don't know how the OP actually soldered them, maybe he did something more sensible.

[BILLPOD]

Believe it, or not......there IS a 18650 store:
https://www.18650batterystore.com/
 

[thm_w]

buy good charger that can show mAh when fully charged. I use nitecore um4.. all type of batteries can use.. so i know who sells good battery who sells crap.. i can also know the status of my old battery whether to repurpose, or into the trash

Kind of irrelevant to OP, who is going to be charging the batteries inside the tool.

Maybe, if OP plans on using 18650's or refurbishing packs in the future it is a very useful tool to have. It would have allowed them to check the amazon cells upon receipt.
Though for $12 you get two new genuine cells which will basically be guaranteed to be good, so its not really as relevant here when the charger is $20.

Look at the photos, they seem to be wanting the user to solder the tabs from the old battery right on top of the new tabs.  That seems like a recipe for overheating the batteries to me.  Of course we don't know how the OP actually soldered them, maybe he did something more sensible.

Yeah you are right the amazon instructions are garbage. So hopefully they did not follow those.

[Mechatrommer]

Kind of irrelevant to OP, who is going to be charging the batteries inside the tool.

remove from welded spots, file until both end flat, and then charge and discharge like normal single cell 18650... if battery ok, resolder back, if not ok, throw into trash and buy new from known good seller and solder again into the tool. this is the best known method to diy specify a battery, no need to rely on sweet promises...

That seems like a recipe for overheating the batteries to me.

there is technique, you dont use underpowered soldering iron, i dialed my iron to max when soldering the tab and use fair amount of flux to quicken the process. too long underpowered iron on the tab is not good practice, yes overheating lithium thing is not good. 5 to 10 seconds solder iron on each tab is about the right timing figure, ymmv.

[KE5FX]

Also a good idea to use a rotary burr or similar tool to prep the battery contact surface for soldering, if you go that route. 

That, plus extra flux, plus a very hot iron with a well-tinned tip makes it possible to solder to 18650s directly, if not altogether wise.  They are scary enough when used as directed. 

[Mechatrommer]

Also a good idea to use a rotary burr or similar tool to prep the battery contact surface for soldering, if you go that route. 

yes good idea, in fact i did this always whenever removing each cell from the pack, just using sanding disc, deburr tool bit is a bit slow and rough for me.

and one thing i forgot to mention, i usually remove the batteries in order, from most positive to the most negative, and when soldering back, reverse the order, ie solder the most negative first, just in case, who knows controller may get wacky if you dont use the order. in my recent cheap china battery powered tools, after installing batteries in to the pack, you need to charge the pack with provided charger for just a moment to "activate" the controller, you cant right away use the soldered pack. the batteries came with the cheap tools are crap that i have to replace them all the first few weeks of using them, now they all in tip top condition. ymmv.

[timg11]

Believe it, or not......there IS a 18650 store:
https://www.18650batterystore.com/
 

Hi all - thanks for all the great comments. I selected the "Molicel P28A 18650 2800mAh 35A Battery" from the 18650batterystore.  They shipped the same day and had reasonable shipping (unlike Sparkfun ...  wow...)

They are not tabbed, so I'll have to figure out the best approach for connecting.  Unfortunately, my "rotary burr" tool is the Dremel 1100 that I'm in the process of repairing...

[Mechatrommer]

today there are many descent dremel knockoff at cheap..

[J-R]

A top method for obtaining quality batteries is checking out flashlight forums where cells are regularly tested and and sellers are discussed.

Personally, I can recommend the following online retailers:
https://www.mtnelectronics.com
https://liionwholesale.com
https://illumn.com
https://www.imrbatteries.com
It's up to you to determine what cells might be appropriate for your application.  For example, high capacity vs. high discharge rate.

[timg11]

@J-R, thanks for the additional sources. I have completed the repair with the Molicel P28A from 18650batterystore.com.

It was easy. I did have to solder to the cells, but did it very quickly so hopefully no issues.  Time will tell what the lifetime is. The original tool worked for over 7 years. I re-assembled and ran it briefly through it's speed range, it it seemed as good as new. I'll let it charge for a while and test again.

I wanted to ask if anyone has researched acquiring a spot welder for batteries? This is something I do regularly, having a preference to repair, especially when a suitable replacement is not available as in the Dremel 1100.

[J-R]

Molicel P28A is a great cell.  I have a bunch of the predecessor P26A cells in my high-drain flashlights.

https://lygte-info.dk/review/batteries2012/Molicel%20INR18650-P28A%202800mAh%20(Gray)%20UK.html