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We gave my father-in-law an 28S some years ago. He is now asking that we bring batteries with us when we go to England for Christmas. He is unable to tell us what the battery looks like (he's pretty old), and I can't find reference to it anywhere. Could someone help by letting me know what batteries to get? Thanks.

Dear Jeannine, You need 3 size-"N" batteries. They are available at Radio Shack store in packages or 2.

If the "N" size you're referring to is the one that's about the size of a AA cell, Radio Shack is now packaging them as a pre-assembled 3-pack also (same per-cell price). I just got a couple, and they're a good fit in an HP 35.

N cells are about a half AA in size.

You need 3 alkaline cells, N size (similar to a AA or AAA cell, but about half the height). N size is a good manner to ask for them. In Duracell family, they are known as MN 9100.

A good way to ask for them?

I've tried "do you have any N cells?" answer "No we don't carry those." I then found them on the battery rack as I walked past it on my way out.

Smarter attempt at a different place (or so I thought). "I need four of these type of batteries (show sales person an example of an N cell)". "Oh yes, we have several types of those" (I secretly congratulate myself for smart thinking). The sales person produces a blister pack with a 12V battery of approximately the same proportions "It was four that you wanted?" AAAAAAAAAAAAAAAGH!

Steve: Calling them N size (or MN 9100)worked most times when looking for batteries for my HP41 and my laser pointer, but I indeed agree, sometimes the best thing is to have a sample on hand... At least, be sure that the cells are 1.5 volt, alkaline (non rechargeable)! - - - - - - BTW, (I had discussed this before in this forum), the way to refer to batteries is country dependent; here in Argentina there are no Radio Shack stores, but plenty of electronic products stores that understand N cell denomination.

Andrés: Help me I have a HP 28c and the later model 28s. The scan funktion in catalog and units does not work in my 28s. The calculator is ok (no fail) when i run test. Is it possible that there is no scan funktion in a HP28s??

Stefan: I do not have any HP 28x, I just had one loaned for some days (years ago), so I remembered the batteries being N-size, as in my dear HP 41C. In fact, I asked for that loaned machine, trying to decide if I should buy (in 1988) a -28 to so replace the aging -41. The symbolic math, graphics and overall features of the -28 pleased me, but the "extreme" use of reverse notation was very uncomfortable (RPL) for me. As I was very accustomed to the "classic" RPN, 4-level stack, etc., I decided to get an HP-42S and not to take the -28, and later -48 path. I hope someone here may be more helpful. Andrés