What should be my next LED HP calculator?

[Dave Britten]

(12-07-2021 04:38 PM)BobVA Wrote:  If you're going to use it infrequently, consider making up a battery pack using low-self discharge Ni-MH batteries, like Panasonic Eneloops.
For intermittent use, three Eneloop AAA batteries in a holder would give you months of use before you have to recharge them. If you do this, use an external AAA charger. Katie's instructions here show how to build one.

I second that, grab one of these, and use your choice of AAA charger:

https://www.ebay.com/itm/323932408596

That's what I use in my 65, 45, and 80, and a similar homemade version in my TI-59. Modern AAA NiMHs will generally run the calculator longer than old NiCd AAs from the 1970s.

I'd love to get ahold of a 55, since it has built in unit conversions and linear regression - and the stopwatch is a nice addition - but the price and lack of int/frac functions has held me back thus far. Maybe one of these days when I'm not spending all of my money on ham radio stuff...

EDIT: And the lack of engineering display mode would be hard to swallow.