Power tool batteries are expensive, there is no getting away from that. If you use your tools regularly, like we do here, then you will go through batteries at a reasonable pace. This has led us to wonder whether it is possible to make your own batteries, after all the 18650 cells are available at a decent price. So can you build your own batteries?
*Note, I am no expert when it comes to electronics and this is not intended to be a follow-along guide. Lithium batteries can be dangerous and have caused many fires. This is for entertainment purposes only, I am just a muppet with a soldering iron.*
So here are all the tools I used to create my own Makita battery. A spot welder, soldering iron, solder and screwdriver.
I used a spot welder to connect the nickel tabs to the 18650 cells as it is easier and safer. You can use a soldering iron and solder to do this but you do run the risk of getting the batteries too hot and damaging them.
Laying Out The Pack
To start with I laid out the batteries into the order they would take in a pack. The batteries will be arranged in a 5 in series 2 in parallel arrangement.
The cells I will be using are Molicell P26A Cells. The stats for these cells are below.
- Capacity: 2600mAh
- Maximum Discharge: 25A
- Nominal Voltage: 3.6V
So because we have 5 in series the voltage will be multiplied 5 times, this gives us the 18v needed for the tool. Then because we have 2 in parallel the Ah will also be doubled. So this pack will be a 5.2Ah 18V battery pack.
The only thing you need to remember when laying your pack out in the holder is to get the positive and negative sides the right way around. You can accidentally assemble the pack upside down so this is very important.
Connecting The Battery Together
The battery kit comes with nickel tabs that go onto the battery and then connect to the main board. You can see the positive connection on the battery below.
To connect the tabs to the cells themselves I will be using a little battery-powered spot welder. You can solder these on but you need to be really careful as the heat from the soldering iron can cause severe damage to lithium-ion cells if not done correctly.
Built-in high-rate polymer power cell, the maximum output current is up to 639A, and it can continuously weld thousands of points after being fully charged.
This spot welder is really easy to use and allows you to connect up the cells without worrying about damaging them.
The connecter strips have a set layout and will only go over the correct cells. This makes this step a lot easier as you know you are doing everything right.
Once all of the nickel tabs have been spot welded on it is time to solder them to the main circuit board of the battery.
Connect to the circuit board
So now it is finally time to crack that soldering iron out and get to work. The nickel tabs come up and under the circuit board and then need to be soldered into place.
You can see this in the image below where I have soldered the nickel to the main board on the B1 marked connection.
I then went around the board and soldered all of these together. The board is now technically done but there is one additional step that needs to be done if you want to get everything you of your battery.
Connecting up the LED indicator
So this kit that I bought comes with a separate led indicator that sits in the usual place on the front of the battery. This needs to be wired up to the mainboard, which is easy enough. There are just a + and – connections that need to be soldered.
The only annoying thing here is that the kit doesn’t come with these wires. I didn’t have any small gauge wire lying around at the time I did this so I had to go steal some from a redundant USB cable.
And there we have it, one DIY Makita battery. I have to say this kit made it really simple to do.
So let’s talk about the reason why you might want to do this, that is cost. This battery came in substantially cheaper than an official Makita battery.
The cells themselves cost me £30 and the kit cost around £8 from AliExpress, you can find them here.
So for a total cost of £38, I got a 5.2Ah battery. A genuine 5Ah Makita battery is currently around £75. The genuine Makita battery will have Samsung cells in, usually 25R cells. These are probably a little better than the Molicell i used but Molicell make really good cells themseleves, they ar enot just cheap imitations.
I actually wanted to use Samsung cells, and this would have cost roughly the same, but they are really hard to get hold of for consumers at the moment. Samsung really dont like there cells being sold to end users so have made it a lot harder to get hold of them at a reasonable cost.