My wife had trouble with the connector for the rechargeable battery for our lawn mower, she wasn't able to easily disconnect it so it defeated the purpose of having an easy to start lawn mower.
I found a male to female DC extension for $3 at a local electronics store that I used to hack in a quick connect so now my wife can easily disconnect the mower whenever she wants to mow the lawn instead of having to wait for me to come home to disconnect it.
The equivalent part on Amazon would be something like this:
or cheaper on eBay if you're willing to wait:
The key is to find a cable where the male and female ends are the same size. Alternatively if you have multiple cables that you can salvage with a male plug that fits in a female socket you can use those, but I will assume you've found or salvaged an extension cable like the above.
Step 1: Cut the Cords
The extension cord is meant to have other things plugged into each end, but we need to cut the extension cord so that we can splice into the charging cord and have the ends plug into each other.
Depending on the length of your cord you may want to just cut it in the middle, or different lengths depending on your need, but make sure you leave at least a couple inches from the connector in order to work with the wires comfortably. If you cut them too short it will be difficult to do some of the next steps.
You'll also need to cut the original cable. You'll want to cut this a couple inches from the end of the plug that plugs into the lawn mower. This is the end that will stay plugged into the lawn mower so you won't want a long piece dangling while you mow.
Step 2: Time to Strip
Strip off the black outer casing with wire cutters or a wire stripper. Be sure not to nick the inner wires, we just want to expose about a half inch of the two inner wires.
You may have two separate insulated wires in the outer casing, or more likely as shown in the attached picture one insulated wire and bare strands of another wire around it.
If you have two insulated wires they will either be different colours or there will be some indicator on one of the wires so that you can tell them apart. You'll also notice on the original cable that one of the wires is marked in some way (white dashed line like in the picture above). It is important that you can tell the difference between the wires since we will need to make sure we do the same thing on both ends.
If you have two insulated wires strip some of the insulation off of both of them, or if you have the same as pictured above strip one and pull all the strands of the other together and twist a couple times to pull it into one.
Do the same thing with the other end.
Step 3: Extra Protection With Heat Shrink Tubing
This step is optional although you will need some sort of insulation between the wires to prevent a short.
I used heat shrink tubing as insulation. It makes the end result nice and tight, but if you're using heat shrink tubing you need to slide it onto the wire before you make any connections.
If you don't have heat shrink tubing or just would prefer to use electrical tape you don't need to do it at this stage, it can wait until after the connections are made.
I slid a wider piece of heat shrink tube down the cable and then added two thinner ones for each connection. This will make sure the wires are insulated from each other and then the larger one will hold everything together the way the original black casing did.
Step 4: Connection Time
Making note of the marked wires pointed out earlier, connect one wire of the connector to one of the original wires and the bunched up wires twisted together to the other. Connect the other connector to the other end of the original cable in the exact same way.
It is optional to solder the wires here, but it will make the connection even stronger, I recommend doing it if you can, but don't worry about it if you can't.
Step 5: Insulate
If you used heat shrink tubing, slide the smaller tubes down over the connection so that there is no wire showing and heat them up with a heat gun or lighter and they should shrink around the wires to insulate and strengthen the connection. Then slide the larger piece of tubing over both of the wires and heat it up to secure everything together.
If you didn't use heat shrink tubing you can use some electrical tape to do the same thing. Wrap each wire and then secure them both together.
Step 6: Final Cable
You should now have something similar to the pictures here. The original cable should now work exactly the same as before when it is connected, but the new connector should be much easier to disconnect and reconnect as whenever you need.
You can leave the shorter cable plugged into the lawn mower and secure it with a twist-tie so it stays out of the way and doesn't flap around and vibrate.