The "Death By [No] Battery" List

[johnb]

A friend of mine knows I'm sort of a small-time collector, and recently gifted me his HP-45 from his early college days!

It's got the nice box and the AC adapter, but no battery pack.

I'm in the process of chasing down a replacement pack (I understand the pack that fits the Spices will fit the 45?) -- but I have a question: is the 45 on the list of HP calculators that are generally intolerant of being run on the AC adapter without a good battery in place?

Since that's a VERY specific question, and hardly worth an entire thread, I'd like to broaden the question... can we collect a comprehensive list here of the models that you don't want to plug in without a battery (or with a bad battery)?


Thanks!

[brouhaha]

(06-15-2023 09:47 PM)johnb Wrote:  is the 45 on the list of HP calculators that are generally intolerant of being run on the AC adapter without a good battery in place?
...
can we collect a comprehensive list here of the models that you don't want to plug in without a battery (or with a bad battery)?

As far as I know, the never-use-without-a-good-battery-installed list includes only the Woodstock models (21, 22, 25, 25C, 27, 29C), and the 65 and 67, which power the card reader circuitry from the unregulated battery voltage.

The Topcat models (91, 92, 95C, 97) use Woodstock electronics, but a different power supply circuit. They won't work correctly without a good battery, but they supposedly won't be damaged. I have seen multiple 97s powered up without batteries over the years, and none were damaged.

I'm not sure about the 19C, which is electrically a Woodstock/Topcat machine. I wouldn't risk it.

[Edited 2023-06-16 to add 65 to the never-use-without-a-good-battery list, as pointed out by Harald.]

[teenix]

(06-15-2023 09:47 PM)johnb Wrote:  I'm in the process of chasing down a replacement pack (I understand the pack that fits the Spices will fit the 45?)

The Spice uses a 2 cell battery pack, the HP-45 (and other Classics) use a 3 cell pack, larger and higher voltage, so they aren't interchangeable.

cheers

Tony

[Harald]

The Classics (35, 45, 55, 70, 80) are fine with no battery installed. The charger has two supplies, one is voltage regulated and powers the calculator, the other is for charging the battery. While the charger is plugged in, the battery is not connected to anything but the charger, so there is no danger of damaging anything.
The 65 and 67 are a little different. The charger is the same, but the card reader circuit is connected directly to the battery. The reason for this is that the card reader motor draws too much current to be powered by the charger. I think the card reader sense amplifier might also be powered directly of the battery. And if that is the case, it might be damaged in case no battery is installed. I wouldn't risk running a 65 or 67 with just the charger plugged in.

The woodstocks did away with the second output of the charger, so all the woodstocks WILL be damaged by the charger if no battery is installed OR THE BATTERY HAS A BAD CONTACT. It is best to not use a charger at all. As long as the calculator is switched of its ok to charge the batteries in the non "C" models. The "C" models power the memory even when switched off and therefore its even more risky to charge batteries inside the calculator.
I think this inclueds the 19C, but I am not sure. I wouldn't try.

The spices seem to be a bit more resilliant and don't always die, but in theory have the same problem as the woodstocks.[/align]

[Mark Power]

If you have access to a 3d printer, you can print yourself a battery case and then add the appropriate batteries.

See https://www.thingiverse.com/thing:3125451

[johnb]

Thanks to everyone for your helpful and informative posts.

I think I must have gotten my wires crossed regarding the size of the HP-45 battery pack... it's the 35 that it uses the same size as. (Fortunately, my brain seems to be protected against trying to feed it the wrong polarity, otherwise those "crossed wires" would have been bad news!)

@Mark Power - thanks for the info, but I don't have a 3d printer and I don't know anyone who does. If someone here wants to print a battery carrier and sell it to me, though, I'm game.

Also, does anyone have any experience with "Batteries Plus" being able to build a decent carrier?

(I'm going to go with a battery "carrier" where I can swap out AAA cells, rather than a "pack" with hardwired cells. For obvious reasons.)


regards,
-- johnb

[BobVA]

I think a better option is to use a spring-loaded three cell AAA battery holder (pick one small enough to fit into the 45's battery compartment) and put contacts on the back. Modern AAA's will run the 45 for a long time, and you can choose whatever cells you like.

Mark Hoskins sells a pre-made version on eBay, discussed in this thread. (not sure if the MoHPC discount still applies, but it can't hurt to ask).

[vaklaff]

(06-17-2023 01:04 AM)BobVA Wrote:  Mark Hoskins sells a pre-made version on eBay

… and they work great for me, I have two of them

[John Garza (3665)]

And another Woodstock passes on to the Great Silicon Nirvana...

HP-25C

I get so saddened by well meaning but uninformed ebay sellers that kill perfectly good machines.
If it wasn't dead before, it certainly is now. A nice complete set too.

-J

[Steve Simpkin]

I would add the Spice models (HP-31, 32, 33, 34, 37, 38) to the list of do not use on AC power without the batteries installed. As Harold notes, they may not always be damaged by doing this but the Owner's Handbooks for these models state:
"Note: Do not attempt to operate the calculator from an ac line with the battery pack removed."