USB Charger for Woodstock

[Docj]

Hallo,

did someone have experience in this USB charging cable wich is sold on Ebay?

Ebay

With kind regards
Juergen

[teenix]

It mentions current limiting, but not voltage limiting.

You would probably have to see how much the voltage rises if the battery failed or its connection opened while on charge. If the charger voltage rises too high, then you are faced with the destroyed ACT problem.

As many have suggested on this Forum, it is always safer/wiser to charge the batteries externally.

cheers

Tony

[akpoff]

(03-28-2023 09:21 PM)teenix Wrote:  It mentions current limiting, but not voltage limiting.

You would probably have to see how much the voltage rises if the battery failed or its connection opened while on charge. If the charger voltage rises too high, then you are faced with the destroyed ACT problem.

As many have suggested on this Forum, it is always safer/wiser to charge the batteries externally.

cheers

Tony

FWIW, the page does mention both in the description, and includes a warning against applying 5V directly to the calculator. Perhaps the seller updated the description since your comment. Still, external battery charging is safest.

Cheers,

--Aaron

[John Garza (3665)]

OK, I'll mention the white elephant in the room...

Why on earth would anyone want to use a charging cable on a Woodstock, knowing their inherent weakness?

What I've done for years is terribly simple and you never have to worry about losing another Woodstock.

Remove the center plastic bar on the battery pack.
There is now enough 'play' in it to remove the cells.

Now that you have access to the individual cells you can use standard AA alkalines.
Or rechargeables, and recharge them once removed from the pack in a standard external AA recharger.

Have a couple AA's on the ready or a pre-prepped battery pack for a quick switch to preserve memory if it's a 25C or 29C.

-J

[35/45/55/80/70/65/67/97/97S/91/92/21/22/27/25C/29C/19C/10/
31E/32E/33C/34C/37E/38C/41CX/28S/19B/12C/15C/33S/35S/32S/
48GX/50G/Prime/DM42]

[striegel]

In April of last year (2022), I purchased a USB charger cable for use with my HP-45 (and later acquired an HP-55, so it has also been connected to that model).

[John Garza (3665)]

Yep, got one too.
Sits in a drawer.

I just use the classic 'reserve pack' charging cradle.

-John



[35/45/55/80/70/65/67/97/97S/91/92/21/22/27/25C/29C/19C/10/
31E/32E/33C/34C/37E/38C/41CX/28S/19B/12C/15C/33S/35S/32S/
48GX/50G/Prime/DM42]

[AndiGer]

My Woodstock reserve power pac is another toasted Woodstock

[John Garza (3665)]

Interesting...

I've wondered about the Woodstock reserve pack chargers. I have 2, one is dead and the other heats up quite a bit during charging. I stopped using it and charge the cells individually now. Most likely the same HP engineer that goofed the Woodstock internal charging circuitry did the reserve pack charger!

-John


[35/45/55/80/70/65/67/67T/97/97S/91/92/21/22/27/25C/29C/19C/10/
31E/32E/33C/34C/37E/38C/41CX/71B/28S/19B/12C/15C/33S/35S/32S/
48GX/50G/Prime/DM42]

[Docj]

Hallo,

after reading all of the answers, now i am unsettled.

I have two HP 29C and i just bought new NiCd battery packs (a little bit difficult in the EU) and i have two original chargers but now it seems to me that it is a risk to kill my calculators when i use them?

With kind regards
Juergen

[Bill Duncan]

(04-01-2023 06:14 AM)Docj Wrote:  Hallo,

after reading all of the answers, now i am unsettled.

I have two HP 29C and i just bought new NiCd battery packs (a little bit difficult in the EU) and i have two original chargers but now it seems to me that it is a risk to kill my calculators when i use them?

With kind regards
Juergen

Yes. Do NOT use the calculators with the charger plugged in. There are numerous threads on this. The design uses the battery to regulate the voltage. Even a momentary loss of contact with the battery will fry the electronics.

There are 3d printed battery pack containers available if you need a spare. I've simply disassembled the original by taking out the middle post. You can then replace the nicads. If you replace them with NiMH, just make sure that you charge them outside the calculator. It will also work nicely with alkaline cells.

[Steve Simpkin]

(03-30-2023 05:19 AM)John Garza (3665) Wrote:  Interesting...
I've wondered about the Woodstock reserve pack chargers. I have 2, one is dead and the other heats up quite a bit during charging. I stopped using it and charge the cells individually now. Most likely the same HP engineer that goofed the Woodstock internal charging circuitry did the reserve pack charger!
-John
…

There is not much to the HP 82028A Reserve Power Pack. The active charging parts are a diode and a 10 Ohm, 2 Watt resistor.

https://www.keesvandersanden.nl/calculat...82028a.php

[John Garza (3665)]

I figured as much. That 2W resistor is the source of heat. Same thing inside the calculators. Some Woodstocks have a dark discoloration on the case near the resistor. Evidently from heat through many recharge cycles.

[Bill Duncan]

I wonder if the reserve battery pack charger could be 3d printed and if anyone would actually be interested. I just use alkaline batteries these days with the original holder modified. I use a piece of tin foil on the positive terminal of the cell on the left, as the cells don't have the flat terminals that the original nicads have.

The battery holder on the right was 3d printed with a lid.

While the HP-29C is arguably one of the least capable calculators in my collection, I still love using it. My girlfriend at the time had an HP-27 and I sold my TI-58 and TI-59 to become an RPN convert.. LoL..

I'm still friends with her, and RPN..

[John Garza (3665)]

Even if it doesn't look exactly like the original but works and is easy to modify - like a heat-sink for the resistor - I'd be interested.

I've seen some home-made Woodstock chargers out there and they are crude contraptions made out of wood, and USB powered for the new users that always seem to be near a USB port - unlike me. I recharge overnight from the AC line. As per spec.

And I usually use 1000mAh batteries as the old chargers have difficulty with the 3000mAh ones, and besides I don't need 8 hrs of charge. It leads to users leaving the batteries in the machine for days - which makes it more likely they will be forgotten even longer - with inevitable corrosion. The inconvenience of recharging more often is cheap insurance in my book. Besides, all my old machines are lightly used (they are 'collectibles' after all) so they are not subjected to a hard day's work.

-J

[35/45/55/80/70/65/67/67T/97/97S/91/92/21/22/27/25C/29C/19C/10/
31E/32E/33C/34C/37E/38C/41CX/71B/28S/19BII/12C/15C/33S/35S/32SII/
48GX/50G/Prime/DM42]

[desertdawg]

Thanks to this forum I learned of the danger of charging batteries in situ with Woodstock calculators. I doubt the ebay version has the necessary protections.

Here's my USB charger I made recently. I'm hoping HHC is in So Cal this year as I might present it.

----

Crap, no image upload on this site. Too bad, it's not much larger than a battery pack, which drops in just like it does on a Woodstock.

[John Garza (3665)]

You can add an image - though it's not intuitive (as in not in the editor tools). It is a little farther down the screen - look for "New Attachment"

[desertdawg]

Thanks John.

   

[rprosperi]

HHC will most likely be in Orlando, FL in early October but final decision is still about a month away.

Your charger looks excellent, small and LEDs for status. If you will be offering them for sale, I am interested to buy one, please PM me for details.. I have a vintage HP Woodstock charger, but I'd prefer to use a modern tool and put that one away for the ages.

[Docj]

(04-08-2023 12:32 PM)rprosperi Wrote:  Your charger looks excellent, small and LEDs for status. If you will be offering them for sale, I am interested to buy one, please PM me for details...

I will join the line, to save my two Bonnies.

Thanks in advance.

Juergen

[John Garza (3665)]

Oh, that looks beautiful. Put me down for one too.