Post by speakertom on Feb 1, 2022 12:24:00 GMT -5
For those of you working with power tools using lithium batteries you will probably have to replace them at some time. I have several tools using them and have had some failures after many years. What I discovered is that most of the batteries are based on some combination of 18650 cells. Also, some of the “compatible” batteries don’t seem to last long. I decided to make up some replacement batteries using the original housings and control circuits.
The two major factors were finding a source for reliable cells and also a way to assemble them. Soldering directly to cells is a bad practice because there is a high probability of damage to the cells. Commercial packs have the cells connected with nickel straps that are spot welded to the cells. So how do you spot weld them at home?
Apparently, there is a big business in DIY battery repair using 18650 cells. I went on line and found a home spot welder specifically for these cells. The welder is essentially a high capacity lithium battery in a housing with circuitry to control both charge and discharge. Here is a link to the one I bought on Amazon.
www.amazon.com/dp/B091BY3L6L?ref=ppx_yo2_dt_b_product_details&th=1
It comes complete with a hank of nickel connecting strip that can be cut to length with ordinary scissors. You should use this supplied material because the welder will not work satisfactorily with heavier strips.
For cells, there are lots of suppliers and I picked the company called of all things, 18650 Battery Store. Here is a link to the cells I bought:
www.18650batterystore.com/collections/molicel-all-products/products/molicel-p26a
Since I bought 10, the price was $4.50 each. The Makita pack I was repairing used two banks of 5 cells each in parallel to give 18V and 3 AH. These cells had higher capacity so the battery wound up with 18V at 5.2 AH. A genuine Makita 18V 5 AH battery currently costs $115 on Amazon if you buy one. That was a savings of $70 which more than paid for the spot welder.
In addition to the one repaired battery, I also had enough good cells left over from formerly defective batteries to make another one having only one bank of 5 cells for 1.5 AH. The Makita 1.5 AH battery sells for $75 and mine was essentially free using the cells I had plus another old housing. So if you have some old battery housings around and want to resurrect them, consider this approach. When working with any of these batteries, be very careful not to short them. They are capable of very high currents and you can burn things up quickly.
I haven’t run life tests on the repaired batteries, but both run my Makita tools very well.
Tom
The two major factors were finding a source for reliable cells and also a way to assemble them. Soldering directly to cells is a bad practice because there is a high probability of damage to the cells. Commercial packs have the cells connected with nickel straps that are spot welded to the cells. So how do you spot weld them at home?
Apparently, there is a big business in DIY battery repair using 18650 cells. I went on line and found a home spot welder specifically for these cells. The welder is essentially a high capacity lithium battery in a housing with circuitry to control both charge and discharge. Here is a link to the one I bought on Amazon.
www.amazon.com/dp/B091BY3L6L?ref=ppx_yo2_dt_b_product_details&th=1
It comes complete with a hank of nickel connecting strip that can be cut to length with ordinary scissors. You should use this supplied material because the welder will not work satisfactorily with heavier strips.
For cells, there are lots of suppliers and I picked the company called of all things, 18650 Battery Store. Here is a link to the cells I bought:
www.18650batterystore.com/collections/molicel-all-products/products/molicel-p26a
Since I bought 10, the price was $4.50 each. The Makita pack I was repairing used two banks of 5 cells each in parallel to give 18V and 3 AH. These cells had higher capacity so the battery wound up with 18V at 5.2 AH. A genuine Makita 18V 5 AH battery currently costs $115 on Amazon if you buy one. That was a savings of $70 which more than paid for the spot welder.
In addition to the one repaired battery, I also had enough good cells left over from formerly defective batteries to make another one having only one bank of 5 cells for 1.5 AH. The Makita 1.5 AH battery sells for $75 and mine was essentially free using the cells I had plus another old housing. So if you have some old battery housings around and want to resurrect them, consider this approach. When working with any of these batteries, be very careful not to short them. They are capable of very high currents and you can burn things up quickly.
I haven’t run life tests on the repaired batteries, but both run my Makita tools very well.
Tom
