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HP28S battery cover - Printable Version

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HP28S battery cover - Keith Midson - 04-05-2009

Hi HP world,
Are battery covers available for the HP28S from HP, repairer, or custom made replicas (would also fit HP28C, 18C, 19B and 19Bii models).
I did send a message to HP from their website enquiry, but i've had no response yet.
I'm keen to get a new cover if they are still available.
Thanks, Keith

Re: HP28S battery cover - Walter B - 04-06-2009

Sorry, but I doubt it. That Clamshell battery cover is known to be a bad design tending to break. AFAIK nobody has started a replica production yet. Market is a bit small.

Re: HP28S battery cover - Johnny Bjoern Rasmussen - 04-06-2009

If you count in the users of Clamshell Business calculators like HP-19BII the marked might be big enough for a replica.



Re: HP28S battery cover - Raymond Del Tondo - 04-06-2009


the 19BII has a darker case than the 28S,

so it might not look too good using a 19BII batt cover on an 28S;-)

OTOH, the latest incarnation of the 19BII uses a battery door on the back side,

which is much better than the original and extremely fragile construction.

Battery doors never were a strong part of the HP hardware development department.

Ok, the doors in the HP-71B and HP-48 were designed well,

at least I didn't find broken doors on these machines so far.

Remember the batt doors on the Woodstocks, or on the Spices? Awful!

And the batt door for the HP-41 in combination with the very sensitive contact foil

was such a bad design that I still wonder how many of these doors are still around.</OT>

Re: HP28S battery cover - Mike Morrow - 04-06-2009

Remember the batt doors on the Woodstocks...

And the batt door for the HP-41...

The Woodstock battery/door assembly is IMHO one of the *best* of such HP designs. The only problem from that assembly comes when old packs are allowed to leak and corrode.

A troublesome detail of the HP-41 design is the small charger connection port cover. It is extremely flimsy, needlessly so, and easy to break or lose.

But the HP-28 cover is tops in the poor design competition.

Re: HP28S battery cover - Allen - 04-06-2009

best bet is to buy a (non) working 18c and steal the batt. cover. The color is very similar, and the cost won't put you out. I agree with earlier responses that the small market will keep both HP and replicas out.

Re: HP28S battery cover - Michael de Estrada - 04-06-2009

Yes. The Woodstock battery pack design with the integrated "door" was a great concept, especially for field use. It was very easy to swap out a spent pack with a fresh spare. No chance of losing or damaging a separate door because there was none. Also, the battery contacts were very sturdy, relying on the pack springs to provide the connection pressure and to secure the pack inside the calculator housing. Although neither HP nor the aftermarket manufactures replacement packs any more, it is very easy to re-cell them with store-bought AA NiCads.

Too bad HP also chose to make the NiCad pack part of the AC adapter circuit, which is why today there are very few remaining functional Woodstocks.

To the original poster, if you find a cheap source of clamshell battery doors, please let me know. My HP-28S is out of commission with a broken battery door.


Edited: 6 Apr 2009, 9:05 a.m.

Re: HP28S battery cover - Dan Grelinger - 04-06-2009

HP was still selling the battery covers about 10 years ago, I was able to purchase one from their parts department, along with some replacement cells for the HP-67 battery pack (82001?). I tried to get the replacement cells recently, and checked the part number at their site, and got nowhere. The same may have happened to the HP-28S battery door.


Re: HP28S battery cover - Randy - 04-06-2009

HP was out of stock years ago with no plans to change the situation. The last source I knew of was Calcpro.com but he too no longer as any stock.

Gone the way of the Dodo bird...

Re: HP28S battery cover - Nigel J Dowrick - 04-06-2009

If you are interested in functionality rather than beauty it is possible to cut a thin piece of metal sheeting to the correct shape and to slide it in in place of the battery cover. The slot around the edge of the aperture is enough to keep the metal in place; a small amount of insulating tape secures it. Sticking some thin dark plastic on top would even make it look quite nice, although I didn't bother to do this.


Re: HP28S battery cover - Michael de Estrada - 04-06-2009


About what thickness gage would you estimate is required? Should it be the same as the current metal part?

Thanks for your suggestion.


if in doubt, consult your dentist - Hans Brueggemann - 04-06-2009

because he has very fine epoxies at hand..
you might simply glue the broken pieces together with CA and ask him, whether he can do a copy of it.
textures of copied parts are just excellent and a good paint job (car paints) will do the rest.

Re: HP28S battery cover - Nigel J Dowrick - 04-06-2009

I don't have a way of measuring the thickness of the piece of metal that I used, but it looks to be about 0.2mm thick. It is thin enough for me to have been able to cut it into shape with a pair of scissors. It fits into the slots at the sides and also the slot at the "back" of the battery compartment. It is this sort of shape:

/ \
| |

I hope this helps.


Re: HP28S battery cover - Allen - 04-06-2009

I really would not recommend spending monumental effort repairing the door.. the moment you get it fixed, Murphy says the plastic around the battery door will break, leaving you something with more CA smell, and risk of breaking further at any moment.

If you're looking for something vintage, I suggest the 48SX instead, or else the 42s, or the current 35s/50g- it really depends on how you use your machine...

Re: HP28S battery cover - Michael de Estrada - 04-06-2009


I already have a HP-48SX and even a HP-50g, which I use 99% of the time. I have not used the old HP-28S for years because of the busted battery door, so I really don't have anything to lose in trying to resurrect it. Actually, the case plastic has already begun to break around the door opening, so it's on its last legs anyway. I can always hook it up directly to my bench DC power supply if I just want to play with it. But thanks anyway for your advice.


Re: if in doubt, consult your dentist - Keith Midson - 04-06-2009

Thanks everyone for your enthusiastic response! This was my first posting to the forum, and I didn't realise how active everyone would be in this forum.

By way of background I have the HP collecting bug - I now have 44 HP's (along with a bunch of pocket computers and graphing calcs from inferior brands ...).

So, I do use other vintage HP's (I have a working collection as an engineer), but my trusty 28S was the very first HP I've owned from 1990, so it's the sentimental value of keeping it alive that brings me to this thread. I actually have a "like new" 28S, as well as a 28C, 18C, 19B and 19Bii, all in excellent condition with no damage to the battery door, but I would like to bring my original back to life. I think based on all the above discussion I will try cutting some metal sheet - i'll let everyone know how it goes.


the solution - db (martinez, ca.) - 04-08-2009

you just need one of these.

Re: the solution - Walter B - 04-08-2009

Great stuff! How about casting calculators? ;-)

Re: the solution - Andrés C. Rodríguez (Argentina) - 04-08-2009


Nice to hear from you. While trying to follow the link on your message, I got an error message stating that "Veoh is no longer available in Argentina"... it seems that they (whoever they are) block the contents upon user location...

Any other way to look at your content?

Re: the solution - Marcus von Cube, Germany - 04-08-2009

It's available on YT too: http://www.youtube.com/watch?v=ggvzcGdZsTc