Ah... Battery Day!

[DoctorPepper]

Today was battery day... the day I break-out all of my small vintage computers (and one not so vintage) and systematically replace the 'AA' batteries. This amounts to quite a few batteries, because I have to change them in:

TRS-80 Model 100
TRS-80 Model 102
Tandy 200
Tandy WP-3
Cambridge Z88

And my not so vintage QuickPad Pro. Either way, each of these little lovelies takes 4 'AA' batteries. I buy a 24-pack of Ray-o-vac Alkaline batteriess at Wal-Mart for $8.95. I do this about every two months, to keep them running, unless I've been messing with one pretty heavily, then I replace its batteries more often.

I still remember taking a Model 100 (no, not the same one) on a Mediterranean cruise, back when I was in the Navy. I brought along an extra external power adapter cable (the transformer was defunct, but the cable was still good), and I "acquired" a 6 volt lantern battery, which I used to power that Model 100 for the entire 6 1/2 month cruise! Saved me a ton in 'AA' batteries!

 

[barythrin]

That's interesting. Do you use all of them often enough that you want to keep batteries in them? I probably need to have a battery day where I make sure I didn't leave batteries in anything.

That's something that would be interesting but overwhelming if you had a large collection. I have no idea how many systems I have anymore (maybe 80+?) but I can't imagine trying to take them all apart to do one piece of regular maintenance. Although I guess it'd be pretty cool if I was that organized lol.

- John

 

[DoctorPepper]

That's interesting. Do you use all of them often enough that you want to keep batteries in them? I probably need to have a battery day where I make sure I didn't leave batteries in anything.

No, I don't use all of them that often. I've thought of just removing the batteries, but on the M100 and M102 (at least), I would also have to turn off the back-up battery, which would mean my data and programs would be lost. I know, I could transfer them to PC, but at $4.50 US a month, it seems a small price to pay to keep them running. Besides, since I started using Linux and Unix, I've become used to "instant gratification" of computer use. In other words, I never shut my computers down. Having the batteries in these portable units means I can just pick one up and turn it on and it will work. Most times anyway ;-)

That's something that would be interesting but overwhelming if you had a large collection. I have no idea how many systems I have anymore (maybe 80+?) but I can't imagine trying to take them all apart to do one piece of regular maintenance. Although I guess it'd be pretty cool if I was that organized lol.

- John

That's why I only have six of them that require regular battery changes! ;-)

 

[tezza]

Interesting.

Two months! That seems quite a short time, unless of course you are using them regularly.

Do you replace all of them as a matter of course, or just test them to see how "good" they are, and replace only those that are starting to go?

I have a Model 100. The batteries are about 4 months old, so I guess I should check them.

 

[DoctorPepper]

I replace them as a matter of course. Having to do this six times a year isn't that bad (the total operation only takes about 30 minutes, tops), and it pretty much guarantees my data won't "evaporate".

I mainly use the M100 (I'm kind of partial to them!), and replace the batteries in it as needed. If I haven't used it within the two month window (like this last time), then it gets done on battery day as well.

The only one that needs the batteries changed more often is the M200. For some reason, it eats batteries at a prodigious rate (as compared to the M100/M102).

One other thing... I live in Florida USA. It is warm and humid (emphasis on humid!) about 10 months out of the year. If you leave the batteries in for too long, they start to corrode quite quickly. Which is also why I can't store any of my vintage computers or equipment in the garage... They corrode away very fast!

 

[nige the hippy]

I'm not absolutely sure about those particular machines, but I would have thought that alkaline batteries would last for years and years (pretty well the shelf-life of the battery) backing up CMOS RAM.

It takes pico-Amps to keep cmos ram intact, and alkaline aa batteries are rated at about 2AH - billions of hours!

I'd be inclined to just give them a christmas present!

 

[MikeS]

I'm not absolutely sure about those particular machines, but I would have thought that alkaline batteries would last for years and years (pretty well the shelf-life of the battery) backing up CMOS RAM.

It takes pico-Amps to keep cmos ram intact, and alkaline aa batteries are rated at about 2AH - billions of hours!

I'd be inclined to just give them a christmas present!

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So would I; in fact, the AAs in M100 types aren't even connected when switched off and the memory is actually maintained by an internal NiCd. They can sometimes start leaking before their shelf life expires though, especially cheap ones.

It's those NiCds that are the real PITAs in those machines and PCs that use them, especially some laptops; harder to replace, easier to forget, and when *they* leak they can do some serious damage, whereas tabs in battery compartments are usually easy to clean or replace.

Had to toss a half dozen terminals recently because I'd forgotten about the NiCd AAs in 'em happily spreading their destructive chemicals around inside for the last 20 years, so DON'T FORGET ABOUT THOSE NiCds, folks!

Cleared some much needed shelf space though...

m

 

[tezza]

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So would I; in fact, the AAs in M100 types aren't even connected when switched off and the memory is actually maintained by an internal NiCd. They can sometimes start leaking before their shelf life expires though, especially cheap ones.

Hmm...that last comment worries me somewhat. The internal NiCad seems to hold data well in my M100, but I haven't extracted it to look at its physical condition. As I don't know when it was last replaced, maybe I should?

Can you buy TRS-80 M100 CMOS NiCAds off the shelf, or are they some custom type particular to this machine?

 

[MikeS]

Hmm...that last comment worries me somewhat. The internal NiCad seems to hold data well in my M100, but I haven't extracted it to look at its physical condition. As I don't know when it was last replaced, maybe I should?

Can you buy TRS-80 M100 CMOS NiCAds off the shelf, or are they some custom type particular to this machine?

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Well, by the time they're leaking at least one of the cells has usually died which you'd probably have noticed, and they do seem to be the better ones and rarely leak. But considering it only takes a minute or so to open up an M100, it might be worth a look every now & then; better safe than sorry.

If you do open it up you'll probably find it's a standard shrink-wrapped 3-button-cell side-lug battery as found on many 386/486 era PC mobos, which you should be able to find in any computer shop (even down there ;-). But you would have to remove the PCB to replace it (properly).

If by chance you need one, or any other part for the M100, contact Rick at club100.org - great guy! (You _are_ a member of the club100 mailing list, aren't you? If not, you should be; lots of exciting things going on - see www.bitchin100.com !)

m

 

[Sharkonwheels]

I just got done doing that to my (2) NEC 8201a's, my (2) M102's, the (2) M100's, and also charged the (2) Epson PX-8's as well...

However, in my case, I have (2) sets per computer of NiMH rechargeables...
Duracell 2500's I think? fully charged, they last about 3-4 months in the NEC's and M10x's, and I have been doing that for about 1.5-2 years.

A full-RAM (32kb) M10x will last about 4-6 weeks on standard 4xAA, and the NiCD feeds off the AA's, so you'll still kill the AA's - the NiCD is there in case the AA's die, in which case I think the NiCD will keep the RAM alive for about 3-5 days (full 32kb).

The NEC's are both stacked with 64kb (2 x 32kb banks) so they suck up the juice a little faster.

However, with 2500/2600mah NiMH cells, they last quite a bit longer, as they have quite a bit more stored energy, so I only need to swap out the batteries about every 90 days.


T

 

[DoctorPepper]

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So would I; in fact, the AAs in M100 types aren't even connected when switched off and the memory is actually maintained by an internal NiCd. They can sometimes start leaking before their shelf life expires though, especially cheap ones.

According to the Model 100 Technical Reference guide, the internal NiCad battery can only supply power for 10 days (with 32KB of RAM installed). It further states that the NiCad battery is trickle-charged by either the A/C adapter or by the "operation batteries". Since I tend to leave my M10x systems sitting for two or more months without use, I'd have to say that the NiCad battery is either being constantly recharged by the "AA" batteries, or that the "AA" batteries are used to keep the RAM from dumping with power turned off.

 

[MikeS]

According to the Model 100 Technical Reference guide, the internal NiCad battery can only supply power for 10 days (with 32KB of RAM installed). It further states that the NiCad battery is trickle-charged by either the A/C adapter or by the "operation batteries". Since I tend to leave my M10x systems sitting for two or more months without use, I'd have to say that the NiCad battery is either being constantly recharged by the "AA" batteries, or that the "AA" batteries are used to keep the RAM from dumping with power turned off.

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Ah, s**t; you caught me! After I sent that msg it didn't make sense to me either and with another look at the schematic I realized that I'd been looking at the memory switch and not the main switch (duh!), but I was hoping no one would notice.

Of course you're right; as long as the memory switch is on, the NiCds are being trickle-charged from the main power source, if any (and also power the RAM if there's no main power).

m