I've just got myself a lovely new LED up-lighter, but look where I'm testing it - under a desk in the office, where there are plenty of plug sockets!
I'm going to convert it to battery power, so I can take it wherever I want.
A build like this would work on just about anything that runs from a main socket mounted transformer.
Step 1: Step 1: Gather Your Tools
At the back of the table there I have my LED up-lighter, and a large (15 Amp/hours - which is like half a dozen decent mobile phone batteries!) battery pack. Battery packs like this sell as "power banks". I chose one which can take a cylindrical DC plug, and which has a wide range of voltages selectable - partly for future compatibility, and mostly because I couldn't find the information I needed about the lamp before I bought it and didn't want to wait until it arrived to order the battery pack.
The information is actually on the plug, but it's very difficult to find detailed pictures of plugs. They're all low resolution on Ebay, or cut from official promotional material so as not to offend people who don't like to see another nation's mains plugs. I, however, have no such problem. Feel free to tell me what you think of my massive, three-pinned plug.
In any case, I'm not ready to believe the 24V I'm seeing here. For that reason, there's a multi-meter on the table. There's also a workbench power supply, so I can check the lamp is also happy running at the stated voltage!
I've bought a male and female DC connector. They're at the bottom right. I want to be able to swap the battery and the original power supply easily in the future. One's a solderless type, the other isn't. That's all they had, and - as we've already established - I don't like waiting.
I've also got a load of cutters and heat-shrink and the like. You may notice I'm doing this build inside. It's November. I don't want to go back out to the garage if I can help it, so I've probably got more than I need here (no electrical tape or lighter for the heat shrink though, but I haven't noticed that yet).
Step 2: Step 2: Remove the Transformer
Cut the wire. I don't do enough electrical work to do this confidently, so I've not put the cut too close to the lamp. I wouldn't want to have to take it apart because I've accidentally cut through the copper, and haven't left myself enough room to try again (although it's only rated IP20, so I could probably just walk straight in).
Fasten the wires back together. Just loosely though. I'm using the crocodile clips from my power supply here. They're actually (not shown, because I struggle to use three hands at once) connected to the multi-meter. Plug the original power supply back in, making very careful not to short it where you made your incision, and read the voltage across the lamp.
I knew it! 22.8 to 23.1 volts. I have a strong feeling the battery I bought will get much closer to the target 24, so it's best to test this thing.
Plug the leads back into the power supply and take it from the minimum the original power supply gives out, up to your target voltage. Good. It works.
In truth, I doubt this would ever be a problem. If you don't have a power supply like this, or a multi-meter, skip this step. I have them though, and if it's going to fail, it may as well happen before I've wasted my precious, precious heat-shrink.
Step 3: Step 3: Attach the New Plug and Socket
You're dealing with DC here, so be careful to follow that red wire! Not that I would ever condone you getting them the wrong way round with AC, but... you know. Don't mix them up.
You can see here that I've slipped some heat-shrink on before I've fit the socket. The socket's pretty wide. I've got some more to slip over, but I don't think it'll shrink down to the cable size so this should bridge the gap. I don't know what sort of connectors are available to you, but this one is easily removed without tools, so I'm happier covering it up.
Once the socket is on, you can test your battery. I works! Time to get that heat shrink shrunk. As you can see, it didn't quite tighten up, so I had to use some electrical tape.
Note shown - repeat this process for the plug.
Step 4: Step 4: Tidy Up
Look ma - no mains sockets!
At the bottom right of the first image you can see the plug I added. I'm pretty happy with the red heat shrink and no electrical tape. Full disclosure - it's less tidy inside. Safe though.
It looks good behind that chair. It's not staying there though; that's just for this instructable.
I get about ten hours of run time from it, at full brightness.