Lab PSU + universal battery charger for minimalists.

Just like many electronics hobbyists out there, I don't really have a dedicated workshop room. That's why the space is at a premium for me. Take a look at the room I used to do electronics work in my previous apartment and you'll get what I mean:

Having accumulated a heap of store-bought as well as handmade tools over the years, I started thinking lately if there's a way to minimize the number of tools I'm using to do electronics-related work. Then I moved to a new apartment in a different country without any extra space at all, and those constrained conditions finally forced me to start acting upon those thoughts.

Here's one outtake from this ongoing process that you might find useful. In your hobby you'll certainly need those 2 tools: laboratory power supply (lab PSU) that can crank out some good amps at commonly used voltages (12V, 5V and 3.3V) and a multi-chemistry battery charger.

Back in my old workshop those were 2 separate tools: lab PSU made out of a huge tote with computer power supply and some additions inside and banana plug terminals outside (you can see how to make one on the cheap in my blog as well), and an Imax B6 with a noisy power supply.

Here's how I merged those into one, saving lots of space and manual work.

You'll need the following parts:
1) Computer PSU. You can source one from any old computer that's about to be thrown into the garbage (or already thrown away - if you enjoy a good ol' dumpster dive).

2) (Aliexpress) ATX Power supply adapter.

3) (Aliexpress) IMax B6 multichemistry battery charger. With it you'll be able to charge lead-acid, LiIon, LiPo, NiCd and NiMH battery packs (or individual cells). This covered 100% of my charging needs. You need just the basic configuration without power supply provided.

4) (Aliexpress) One of those multi-size battery chargers with spring connection that fits for every battery size. Don't look for a good quality of charging - they are all crap for that. We only need the body with the spring connector for cheap.

5) (Aliexpress or your local electronics store) 5.5x2.1 DC barrel jack: plug and panel-mount socket.
You can do with a board-mount socket (it's easier to find) but mounting it is going to be much trickier.

Making it

You have already guessed that the whole "universal lab PSU from ATX power supply" deal is replaced with one board easily sourced from China. It does not have a variable voltage output, ammeters and all those fancy features, but over the years I found myself using those advanced features only once or twice.

This combo is as easy as "plug one thing into another" and covers 90% of custom power supply use cases. I'd advice this combination to beginners and veterans alike.

What about the charger? IMax has all kinds of useless connectors aimed for RC use:

If you're not an avid fan of RC models, you'll never need anything out of those except crocodile clips.
We'll cut off one of those charging leads and solder something more commonly used in place: a simple 5.5x2.1mm barrel jack:

Fits like a glove! I'd think it's all factory-made if I didn't know any better.

Now, the charger has to be modified to accept that plug. Disassemble the charger, desolder/take out everything except the battery spring connector, melt a hole in its side and solder the battery terminals directly to the DC jack socket.

Mind the polarity! The most widespread connection in those jacks is the one where the central pin is positive, and sleeve is the negative.

Assemble the charger back together. Now you have an implement for your charger that will accept any battery size from AAA to 18650:

AAA NiCd cell firmly in place and charging.

The regular 18650 LiPo cell during charging process.

That's all! All this combo takes up the space equivalent to less than one drawer rack, costs 25 USD in parts, takes an hour to cobble up and can be used as both lab PSU and multichemistry charger.

This charger covers all cylindrical cells from AAA to 18650, and most other types of cells thanks to crocodile clips (lead-acid for example). If you ever find yourself missing a connector for the battery you'd like to charge, just chop off one of those RC hobby connectors and make your own.

Enjoy and most importantly, keep DIY!


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