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CR2032 as a Rayovac 840 Replacement?


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I've heard that the circuitry is tolerant of a 3V power source vs the 4.5V from the 840.  I know that there are 3xAA boxes that work but they are just ... big.  Much bigger than I want to deal with.  If I could use a CR2032 holder and wire it up that would be great, and easy, and considerably less to leak.

 

Has anyone done tried this?

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You can go for 3xAAA instead of 3xAA if you want to save some space. I tried using a CR2032 in my Performa and it didn't like it - super buggy performance and frequent NVRAM corruption. A "triple-triple-A" box is small enough to tuck away nicely inside most chassis.

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I've had good luck using a CR2032 in my Performa 636, Mac IIfx, Mac IIcx, Mac IIsi, Mac SE, etc. I've not had any real issues with such a setup, plus they're a bit more leak resistant (but not impossible to leak!).

 

636_Battery.thumb.jpg.b6ad06f18ec1835ec6dc93b29fae93a2.jpg

 

 

 

IIfxbatteryholders.thumb.jpg.631de50ae1e52c67e2d0162617701334.jpg

 

 

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This is relevant to my interests... as the batteries age and drop below factory voltage, have you seen any issues with PRAM loss?

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38 minutes ago, defor said:

as the batteries age and drop below factory voltage, have you seen any issues with PRAM loss?

 

This is the issue I had when I tried a CR2032 in my Performa 5400. It "worked" but a month later the PRAM was corrupt after every hard reboot despite the battery still measuring at 3V. I hypothesised that the voltage was frequently dropping just below the threshold voltage when the cell was actually under load, causing the corruption. I measured the cell while it was actually under load and saw exactly that - constant drops from 3V to 2.6V. This was a Panasonic cell. I really just don't see how a 3V button cell can ever be expected to properly do the job of a 4.5V battery.

 

 

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2 hours ago, PowerMac_G4 said:

I measured the cell while it was actually under load and saw exactly that - constant drops from 3V to 2.6V. This was a Panasonic cell. I really just don't see how a 3V button cell can ever be expected to properly do the job of a 4.5V battery.

What about running two in parallel?

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26 minutes ago, History_SE30_Dude said:

What about running two in parallel?

Putting non-rechargable batteries in parallel is generally not a good idea if you don't know that they will be in the exact same charge state, because otherwise they might try to charge each other at fairly high current.  If you used a pair of diodes that would help, but you'd be dropping too much voltage in this situation.

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Some Macs (G4 era things in particular) have problems where the PRAM/SMC will just kind of run away if you hit certain buttons on the motherboard the wrong number of times. The service manual for machines of the era are quick to point out, like, hit the reset button but don't hit it the wrong number of times or you'll drain the battery!

 

So, anyway, I wonder if something like that is happening with your 5400? I get the impression Compgeke's done this a couple different times and mostly had success.

 

I'll be honest, my strategy at this point is to only put PRAM batteries in machines that don't work or work poorly without them, like the LC family and the 6100 needing the PowerToggle (th alternative there is to do the PowerToggle but just leave the machines running most of the time so as to reduce the risk of causing problems.)

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