Power usage of calculators

[brickviking]

(07-05-2014 02:24 AM)JimP Wrote:  This presents an interesting question -- of all the calculators available on the market today (including HP and "the rest" eg TI, Sharp, Casio, Canon, etc.) -- maybe a question answerable by an expert collector -- when compared head to head for battery longevity, which brand comes out the best?

I suppose there are potentials for lots of categories -- graphing, business, scientific, dual power (ie solar/battery) so it's not an uncomplicated question. There is also the type of battery -- alkaline vs. flat Li type. Maybe a silly one, though...

I thought I'd bust this out into its own thread and start things off, as I've got both an older Casio (fx9750G+) and a slightly newer model of the same calculator (fx-9750GII). I also have a HP-50G. I chose these three because they all use four AAA batteries.

Comparing the raw "this is how much power we say we use" on the backs of each calculator, my fx-9750G+ says 0.06 W, the fx-9750GII says 0.35 W, and Eric Rechlin's thread back in 2007 describes some HP calculators in detail. From that, I can ascertain the HP-50G uses between 0.09 W and 0.56 W (idle to flash writing).

I created a grocery program on the fx9750G+ to accept input and display output. I enter in prices for items in five categories, and sum the categories as I go along. The calculator's normally running full-time waiting for input while it displays the current totals, with input taking about 0.3% of the time. It's a very specific limited use-case that most people won't have and I accept that, however it's the only thing I've had to do my testing.

As for long-term usage, I've found since 2008 that I can use my fx-9750g+ on a fortnightly basis (for about a couple of screen-on hours each time) for over a year before I need to replace a set of alkalines. I haven't had either of the others that long, neither do I use them in the supermarket, though I'd be interested to see how the GII compares for battery usage. As for the HP, I haven't written up the program I use on the Casio, that's going into another thread.

I got a Casio fx-82MS a few years before the 9750G+ which appears to use 0.0002 W, and I haven't changed the single AA battery yet. This now gets pretty minimal use though to be fair, as I normally pick up either the GII or the HP-50G now I have them. I also got a Canon F-804P back in 2008 which only uses 0.06 mW on two LR44 cells, but this gets even less use than the fx-82MS, and it spends practically all its time powered off. Still, it would appear it uses the least electricity of all the physical calculators I own.

(Post 33)

[brickviking]

Very rough comparison of TI 83+/SE, shows a description using about 30 mA while writing flash, and between 5 - 12 mA in other typical circumstances. That certainly puts the HP50G to shame, and is more comparable to the HP49G. I'm not sure how comparable that is to either of my Casios yet, I've yet to set up a testing rig to check the current draw. I also don't have the professional bench power supply that can supply a standard voltage or standard current, I've just got a digital multimeter. More info later when I have it.

(Post 39)

[Gerald H]

Interesting subject, I await your results.

My favourite calculator is the 49G, much less power hungry than the 50g although I've never measured the power consumption directly.

The saving grace for the 50g is powering via USB cable without an intervening computer.