Andonstar AD208 battery compartment fix

For a long time I wondered why my Andonstar AD208 wouldn't keep time, even though I placed an 18650 battery in the battery compartment. If it couldn't do that, then what was even the use of the battery that could clearly be placed in the microscope?

At the time I got the microscope, somewhere last year, I shrugged it off. Well, not entirely; I searched the manual (no mention of a battery whatsoever) and emailed support@andonstar.com but never got a response. The only place the battery was mentioned was at the AliExpress product page. Since all I was "missing out on" was the date and time in the display (who needs that anyway?) and in my recordings (that IS actually quite useful in some situations) I figured I'd look into it later. Well, today was that day.

Clear mention of a battery, but not what for...

I unmounted the microscope from the base and unscrewed the four screws in the corner. I then carefully took both halves apart (be careful not to break the plastic clips keeping the two halves together!) and started my investigation. There were clearly two wires coming from the battery department; black and red. So I put my multimeter probes on it and measured the voltage. Zero. Naught. Nil. Zilch. Bupkis.

Well, that's weird. I checked the 18650 battery again... it was fine: 4.15V. Put it back in: nada. Well then, it must be a loose contact or broken wire I gathered. Nope. It took a while of probing and searching and then it lead me back to the battery-side of the battery compartment and I took my new flashlight (what a beast!) to take a closer look at the contacts. They seemed fine. What the... I put in the 18650 and then lit the contacts again. BINGO.

🤦‍♂️

Well... D'uh. For those maybe a little less eagle eyed or those who left their glasses on another floor and are too lazy to get them, like me usually:

🤦‍♂️🤦‍♂️🤦‍♂️

Well, I don't know about you, but I am used to my 18650's being flat like a pancake on both ends and since on first inspection I saw a 'nub' in the compartment on the positive side I thought it should contact fine. I didn't notice, however, the nub being recessed as much and the plastic obstruction being in the way...

I could've gotten another 18650 with a nub on the end. I could've stuffed some aluminum (or, as we say, aluminium) foil or other metal in the gap but that felt wrong and maybe even dangerous. However, I did have some useless 18650 'holders' gathering dust and they had exactly what I needed:

Metal tabs. So I desoldered the battery holder from the PCB and took out the tabs.

Tab with a little nubbin' snipped off (dotted line on the right)

And when that was done, all I had to do was jam it in between the original battery contact and the battery. Since it's a pretty flimsy piece of metal (strong, but not very thick) I gathered with some work I could jam it behind the plastic holder. And. It. Fit. Perfectly.

Tab jammed in

And that's about it. Pretty easy fix. The only easier fix I can think of is using an 18650 with a nub on it. As you're probably supposed to do 😅😇 Oh, as a bonus for you making it this far: it turns out the battery can also be used to power the microscope! 🤪 🥳 All you have to do is hold the power button for somewhere between 3 and 5 seconds.