PRAM battery voltage ranges

[wottle]

I purchased some 3x AAA battery holders to use as a replacement for the 4.5V. I also bought some Lithium batteries to use because I heard they do not leak corrosive material when at the end of their life. When I threw 3 1.5v AAA batteries in the holder, the voltage is 5.3v. I expected the voltage could be a bit over 4.5v, but I figured it would be 4.6-4.8v).

Anyone know how sensitive the PRAM is to higher voltage. I read that some people use 6v batteries, so I'm hoping a little over 5v won't be a problem. Wanted to ask before I threw it in my Mystic Color Classic and Performa 6400. Thanks for any guidance!

 

[wottle]

Bumping. I can't be the only one looking to use these 3x AAA holders for this, as I got the idea from someone on some forum. Do Lithium non-rechargeable batteries have higher voltages, or did I get a batch that simply is not within spec?

 

[madcow]

I have used 2 of the 2032 flat batteries to replace those 4.5v batteries. Unfortunately I have found that they drain really quickly for some reason. I would love to find a good replacement that would last for years and years like the original ones.

I know I have a LC 550 that used the 4.5v battery, but have seen other LC 550 machines that use the half-size battery like other macs of the era which are 3.6v I think. I am not sure if the boards are physically different, but I assume this implies some flexibility in voltage ranges.

 

[YMK]

I also bought some Lithium batteries to use because I heard they do not leak corrosive material when at the end of their life.

Where did you hear this? Lithium batteries have destroyed countless logic boards.

Alkaline batteries also leak and explode, even on the shelf.

Try a set of Eneloop cells. They don't leak, have a slow self-discharge and are rechargeable.

Three of them should produce around 4V.

 

[Fizzbinn]

Someone may prove me wrong but I think Apple didn’t change anything about their logic boards‘ battery backup voltage requirements when they switched from using 3.6v Lithium batteries to 4.5v Alkaline batteries. I believe the later just has a quicker voltage drop off, both having a voltage greater than 3v for their respective usable lifespan. (The alkaline ones just must have been cheaper though for Apple to make the switch) I found some info on this a while back that I’ll try to find again.

My understanding is modern coin cell 3v lithium battery replacements have a pretty constant >3v rating for most their usable, albeit shorter lives, and generally haven’t proven susceptible to leaking/bursting vs. old school 3.6v lithium “1/2” AA or alkaline batteries.

My take here is >3v is what’s needed and there are multiple ways of delivering that with different benefits.

 

[wottle]

Where did you hear this? Lithium batteries have destroyed countless logic boards.

Alkaline batteries also leak and explode, even on the shelf.

Try a set of Eneloop cells. They don't leak, have a slow self-discharge and are rechargeable.

Three of them should produce around 4V.

Sorry, I should have made that more clear. Yes, we've all seen our favorite Maxwell lithium batteries leak. Typically those batteries are 20-30+ years old. However, I've had 1 year old alkaline batteries leak and start corroding things. If I can get 10 years out of a battery without worrying about leakage, and said leakage is contained in a sealed plastic box, I will feel better about the safety of my machine. Most likely, I will have sold the machine or replaced the battery before the 10 years is up.

I may try some of my rechargeables. I just worry about forgetting about them.

 

[YMK]

If I can get 10 years out of a battery without worrying about leakage, and said leakage is contained in a sealed plastic box, I will feel better about the safety of my machine. Most likely, I will have sold the machine or replaced the battery before the 10 years is up.

1/2 or 2/3 AA Tadirans will easily go ten years and rarely leak or explode.

You can order them with leads, like many SEs came with.

 

[wottle]

1/2 or 2/3 AA Tadirans will easily go ten years and rarely leak or explode.

You can order them with leads, like many SEs came with.

I threw in some Eneloops in the case, added some velcro and put it in my Mystic Color Classic and it seems to be working. Was reading a bit over 4v after I charged them.

Settings are being kept between boots. I'll see how long it lasts.

 

[YMK]

Settings are being kept between boots. I'll see how long it lasts.

Nice. I've had good results with Eneloops.

These have a simple charging circuit and shouldn't need attention as long as the machine runs once in a while: