If you're getting into the hobby or trying to refresh one of your old MiniDisc players, you may have learned that batteries aren't always that easy to come by.
Many MiniDisc players come with, or support, battery "sidecars" that allow you to use a single or double AA battery to power the device. That's a nice option because AAs are readily available and you can use rechargeables! For my players that do have sidecars, I'm using Eneloops and Amazon Basics AA rechargeables which are both working fine.
TL;DR - These are great for replacing an old MiniDisc player/recorder's battery (compatible models, of course), BUT use a less powerful charger (maybe 500ma or less)
What about different battery shapes?
The challenge comes when you have a device that requires a different type of battery. There are different "gumstick" batteries, round batteries, and even some that were encased in a custom plastic cartridge of their own.
In this case, we'll look at the round battery that came with the Sharp MD-MS200-S (AKA Denon DMP-R70, Kenwood DMC-G7R, Pioneer PMD-R2). I happen to have a very nice, clean one that came with the original 3.6v Li-Ion battery. It's in great shape, but doesn't hold much of a charge (even when using a proper voltage adapter).
Note - these models were also very similar, and I believe use the same battery:
Googling around led to the dimensions:
70.70 x 19.70 x 19.70mm
There are plenty of people selling replacement batteries, but I felt there was a bit of a markup since it's for a niche/classic device so I started looking on my own.
My initial searches for batteries of that power/capacity/size led me to an unlikely source: vape/e-cigarette batteries! Apparently, there are many models of those devices with varying sizes and power requirements, and I found some that were VERY close in size. I figured I could use a small metal spring or other shim to get a perfect fit. The choices were all a bit narrower and I didn't want to deal with any "knocking" in the battery compartment so I kept looking.
While continuing to shop for something else on Amazon, I decided to see what was out there. I started to go down the path of rechargeable 18650 batteries since they were very close in size. Again, I noticed that they were all a bit short and I would have to accommodate for that. I kept looking and finally found something that looked and sounded like it would fit perfectly!
Streamlight is known for making good flashlights for outdoors or firearms, and they have also been providing batteries for those devices.
Size-wise, at 70 x 18.9 x 18.9mm, it's SUPER close to the original. Even though it isn't a flat top, I figured the if the measurements were correct, it would fit and work.
And yes, it's certainly just a battery/cell with a charging circuit on top (note the indentation around the top of the battery/wrapper), but because of that, it seems just the right size.
Not only that, I could recharge it via a separate USB (I know, it's micro-USB...) cable and it's available on Amazon with a limited lifetime warranty through Streamlight.
But wait, there's more - for the price, you get TWO batteries! That's right, it's a 2-pack! Charge one and use the other!
In typical Amazon fashion, I received the batteries quickly and did a quick fit test...
It drops in perfectly and just as flush as the original. There was no extra pressure to close the door and there's no movement when the door is closed. I think the Streamlight battery is still a tiny bit narrower, but the spring tension from the battery terminals is holding it just fine.
They work perfectly! Closing the door (again, no extra pressure or force required), I slotted in (love that slot-in design!) a disc and seconds later, I'm soaking in the sounds of late 90s J-pop!
Now I get more battery life, easy charging (though micro-USB...), and TWO batteries for under $30 USD.
There's always a "but", isn't there? When I initially connected this to my multi-port charger with a micro-USB cable, the top (where the charging mechanism is) got hot. Really hot. It was uncomfortable to have my finger on there for more than a fraction of a second.
We should all know that heat is the enemy of electronics, not to mention what can happen with Li-Ion batteries! Reading the specs on the Streamlight website, they talk about using their 2 or 8 battery charger to charge these SL-B26 batteries in 5 hours. So based on the mAh, that's about 500ma. I'm sure my charger was supplying more than that (though you would think the charging circuitry would have only drawn 500ma or so...).
I went around the house looking for an older charger in a junk drawer and found an old Plantronics headset charger that put out 300ma via micro-USB. I've had that connected for hours and now the battery isn't getting hot at all. Sure it may be a slower charger, but in this case safe is definitely better than sorry!
Is this safe?
I would love to confirm (outside of the random responses I found on Google), but I believe the slight difference in voltage will not be an issue. Remember, the stock battery is 3.6V and the Streamlight is 3.7V.
From what I've been reading, it seems that the 0.1V is not a big deal and within most tolerances. Secondly, the voltage listed is a "nominal" voltage and we'll see fluctuations above and below that (though near 3.7V).
I'd hate to risk my precious, classic Sharp MD-MS200-S, so I'll probably only charge outside of the device with a slower/less-powerful charger like I mentioned before.
Hope this helps at least one MiniDisc fan out there!
So if you have one of the players mentioned, check out these Streamlight batteries. It's hard to go wrong with a 2-pack that fits perfectly and has a warranty.
With Amazon links I would be compensated - and grateful if you made a purchase!