4.5V Battery Replacement for Early Compact Macs?

[68kPlus]

Hi everyone,

Looking to find a way to replace the expensive, hard to find 4.5v battery for the Macintosh Plus in particular. The closest replacement is the Exell PX21, which costs around $50 AUD here in Australia, and the cheapest is the Unicell A133 4.5V which is $45.
There are some German adapters that are also expensive that convert 3x LR44 to the PX21, but I can't seem to find them cheap.

Any ideas?

 

[YMK]

If it will tolerate 4.8V, I'd use a quad AAA holder and stuff it with Eneloops.

They're rechargeable, won't leak or explode and have a low self discharge rate.

There's also the 6V 476A, which is cheap and can be dropped to 4.5V with diodes if needed.

 

[VicNor]

A buddy of mine has 3D-printed a holder for three LR44 coin cells. He uses a metal strip to connect the bottom battery to the connector in the computer. Good enough, I guess? It's not like keeping the time (over time) is super important on a Plus anyway. I'll imagine that one would need to replace the LR44/SR44 at least once a year

 

[rikerjoe]

I went with the triple LR44 route for my Mystic Color Classic. I found a battery holder here.

 

[MacOfAllTrades]

I used a cr2032 cell at 3.5V in my se. I understand the old macs tolerate a wide range of voltages for this purpose and many use 2032.
I got this one

Horizontal Holder for 2025 & 2032 Coin Cell Batteries

<p>This horizontal orientation battery holder is commonly used to replace lithium ion coin cells with spot-welded solder tabs. Replacing a custom battery with this battery holder ensures simpler future battery replacement and saves money over harder

console5.com

But many exist. Some with wire leads built in (which I think makes more sense for your PLUS).
these cells don’t blow up like the originals and they still last a long time. Any leakage they have in odd occasions is much less as they simply don’t have much

 

[pfuentes69]

Another possibility, which I used in my Plus, is to use three LR50, which just make the size of the 4.5V battery.

https://www.aliexpress.com/item/1005002834311917.html

 

[misterg33]

I've used AAAs in stuff like this:

https://smile.amazon.com/gp/product/B00P2FJA2M/

If you have one of the old dead batteries, you can snip the connector end off of it and use some heatshrink to connect it. You don't have to order from Amazon either. Stuff like this is available on most electronic and hobby sites. And I think there are some pre-made ones on ebay.