Woodstock battery holder

[PANAMATIK]

Two hints for your woodstock battery holder. Perhaps already known, but I didn't find anything about it.

I sometimes experience that a battery holder in one Woodstock calculator works and when inserting the same in another the display remains dark. This is critical, because if the batteries don't have contact you might run easier into the issue, that you try to charge the batteries and accidentally switch ON the calculator, but the battery contact is necessary to buffer the charger voltage and avoid damage.

Obviously the height of the contact pins can be different in some calculators. Todays AA batteries could have a bigger plus pole and don't fit into the case. They are 1 mm too high. To get them sit deep enough the plus pole then is recessed, in both cases there is no contact.

You can easily avoid this problem just by filing some material from the plus pole of the battery holder.

before after

Also there is an easy way to replace the batteries, when cutting only the front side of the middle peg. You just can bend it upwards to get to the batteries.

Bernhard

[larthurl]

(01-18-2018 10:25 AM)PANAMATIK Wrote:  Two hints for your woodstock battery holder. Perhaps already known, but I didn't find anything about it.

I sometimes experience that a battery holder in one Woodstock calculator works and when inserting the same in another the display remains dark. This is critical, because if the batteries don't have contact you might run easier into the issue, that you try to charge the batteries and accidentally switch ON the calculator, but the battery contact is necessary to buffer the charger voltage and avoid damage.

Obviously the height of the contact pins can be different in some calculators. Todays AA batteries could have a bigger plus pole and don't fit into the case. They are 1 mm too high. To get them sit deep enough the plus pole then is recessed, in both cases there is no contact.

You can easily avoid this problem just by filing some material from the plus pole of the battery holder.

before after

Also there is an easy way to replace the batteries, when cutting only the front side of the middle peg. You just can bend it upwards to get to the batteries.

Bernhard

Hello Bernhard:
Am I correct in thinking that your picture shows the correct orientation of cells in the hjolder?

I just received the battery holder and want to try it but want to make sure I get the cells in correctly.

Thanks

.....Art

[Bill Duncan]

Yes, that's the correct polarity.

I've modified a few of my battery holders in the same way, by cutting the crosspiece. You can then stretch the sides slightly and pull the cells out one-by-one.

I've been using aluminum foil as a "shim" to make sure the cells reach the calculator contacts. The positive end of the cells aren't as "flat" as the original unfortunately..

[larthurl]

(01-21-2018 01:25 AM)Bill Duncan Wrote:  Yes, that's the correct polarity.

I've modified a few of my battery holders in the same way, by cutting the crosspiece. You can then stretch the sides slightly and pull the cells out one-by-one.

I've been using aluminum foil as a "shim" to make sure the cells reach the calculator contacts. The positive end of the cells aren't as "flat" as the original unfortunately..

thanks, Bill
Can you share a picture of your mod?

.....Art

[Bill Duncan]

(01-21-2018 03:05 PM)larthurl Wrote:  thanks, Bill
Can you share a picture of your mod?

.....Art

It looks roughly like the photos above. I have 2 packs; on one I've taken the crosspiece out completely (although I may glue it back) and the second one, I've just cut one end similar to the photos above. If you cut one end, probably best to do so on the terminal end like the photos, so the sides will give a little while changing the cells.

[jebem]

Thank you for sharing this idea, Bernhard.
I had the same issue after replacing the original Ni-Cd batteries on one of my HP-25 machines with a new set of Chinese 900mAh Ni-Cd batteries which obviously are a little larger than the originals.

To replace the batteries, instead of breaking the plastic holder at the usual place to remove the dead batteries (cutting the middle plastic strip at the batteries side), I prefer a different approach.

The battery holder is made of two plastic pieces welded together at factory. So to open it on the original place we can use a X-acto knife and lots of patience to not destroy the plastics (or your fingers...).

After inserting a new set of batteries, the back cover can be glued to the case.

[PANAMATIK]

(01-22-2018 11:01 AM)jebem Wrote:  ... I prefer a different approach....

I prefer not to take the top and bottom side apart, because it is more laborious. And you cannot recharge the batteries externally after some weeks. But of course, it works well.

If you have to remove the original NiCd cells it is a little more difficult to remove them, when only the middle plastic strip is cut, because they are welded together by a steel band at the rear side and you cannot remove the batteries one by one. But it is possible.

Bernhard

[Sadsilence]

One more idea: There are high quality LSD AA cells with flat top around. My prefered type for HP classics, woodstock battery packs:

this one.

You can remove solder tabs with pliers for woodstock battery holder.

[BobVA]

(01-22-2018 08:52 PM)Sadsilence Wrote:  One more idea: There are high quality LSD AA cells with flat top around. My prefered type for HP classics, woodstock battery packs:

Thanks!! I'll have to see if I can find a US distributor so I won't have to bodge up packs from spot welded button-tops.

[rprosperi]

And here are some inexpensive ($3/ea, free ship) but reliable NiCD AA Flat-top cells over here (USA):

https://www.amazon.com/Exell-Rechargeable-automobiles-applications-controlled/dp/B00XWSH3L6

[Bill Duncan]

I've been wondering if I could coax a CR-V3 3v cell to work in the hp-29c. The shelf life on these is fantastic.. I had a set of duracell CR-V3 from 2003; the "best before date" is 2015. OK, so it's a little late, but they still show as 3 volts on the voltmeter..

They also have flat contacts, which might be more friendly to the calculator contacts.

https://en.wikipedia.org/wiki/CR-V3_battery

[Sadsilence]

No doubt from electrical side, provided right polarity is chosen. Cause of it's shape I fear you cannot integrate CR-V3 cell well into Woodstock battery holder. It's middle bar and the then from electrical side actual needless and cause of pressure onto CR-V3 body maybe even harmful double spring will not become your friends...