Solar-powered calculators

[Dave Britten]

Lately I've been digging into solar-powered calculators. You know, in case the apocalypse leaves us all as hunter-gatherers with no access to batteries, and I still need to figure my tax return.

There's essentially three categories: solar only (no batteries), battery-assisted (runs fine without), and battery required. These are some of the best ones I've found in each category, and I'd be interested in hearing about any other good ones you've found.

Solar only (no batteries):

• TI-36X Solar - Full scientific, with fractions, a few unit conversions and scientific constants, base conversions and logic, two-variable stats with linear regression and x/y predictions, hyperbolics, combinatorics, polar/rectangular conversions, three memories... Probably the most complete no-battery option I've found. There were about 4 different designs, all with seemingly identical functionality.
• TI BA-35 Solar - Basic financial calculator with TVM, amortization, cost/sell/margin, percent and percent change, nominal/effective interest rate conversions, and one-variable stats.
• Casio fx-260 Solar, fx-260 Solar II - More basic scientific calculator, with only one-variable stats and no base conversions.
  

Both of the TIs will run fine in a modestly-lit room. Not sure what else Casio or Sharp offer with no battery.

Battery optional:

• Casio fx-50FH - Programmable scientific calculator. Programming features are fairly limited, but still very useful. No calculus.
• Casio fx-3650P - Similar to the fx-50FH, but with calculus functions, and less memory for programming.
  

Of those, I only have the fx-50FH and fx-115ES. The fx-50FH needs a decent amount of sunlight to run without a battery.

Battery required:

• TI-36X Pro - I couldn't get this to turn on without the battery, even outside in the sun.
  

Unsure:

• Casio fx-115ES Plus - I need to pull the battery and take this one outside to confirm it will run without. Very complete scientific calculator, with many more features than the TI-36X Solar.
• Casio fx-991EX (and similar Classwiz models) - These can supposedly run without a battery, but I don't have one to test.
• Casio fc-200V - Financial calculator with quite a lot of functionality. Hardware platform appears to be about the same as the fx-115ES Plus.
• Sharp EL-W516 family - Similar to the Casio fx-115ES, with some additional features. Haven't tried it without the battery yet.
  

[Maximilian Hohmann]

Hello!

Interesting topic, I hope for many contributions...

Just last week I received a "Ti30 SLR" in the mail, an early (1982) solar only powered calculator. According to Datamath.org it was made by Toshiba in Japan. It has fairly large solar cells and requires very very little light to operate. If I can see enough to read the display then it works.

Apart from that it is just another plain vanilla Ti30. Functionally they didn't change much from the LED to the early LCD models, the only differene being the "n!" of the LCD models which the SLR also has. But the keyboard it a lot better than those made by Ti and still works without any bouncing after almost 40 years.

Regards
Max

[Albert Chan]

(04-28-2020 07:27 PM)Dave Britten Wrote:  [*]TI BA-35 Solar - Basic financial calculator with TVM, amortization, cost/sell/margin, percent and percent change, nominal/effective interest rate conversions, and one-variable stats.

Actually, TI BA-35 Solar does 2-variables stats.
I use its interpolation a lot. Example, interpolate from 2 points (10,20), (20,100)

[MODE] // to stat mode
10 [X<>Y] 20 [Σ+]
20 [X<>Y] 100 [Σ+]
12 [Y'] → 36
36 [X'] → 12
[b/a] -60 // y-intercept
[X<>Y] 8 // slope -> Y = 8X - 60

[Dave Britten]

(04-28-2020 09:00 PM)Albert Chan Wrote:  

(04-28-2020 07:27 PM)Dave Britten Wrote:  [*]TI BA-35 Solar - Basic financial calculator with TVM, amortization, cost/sell/margin, percent and percent change, nominal/effective interest rate conversions, and one-variable stats.

Actually, TI BA-35 Solar does 2-variables stats.
I use its interpolation a lot. Example, interpolate from 2 points (10,20), (20,100)

[MODE] // to stat mode
10 [X<>Y] 20 [Σ+]
20 [X<>Y] 100 [Σ+]
12 [Y'] → 36
36 [X'] → 12
[b/a] -60 // y-intercept
[X<>Y] 8 // slope -> Y = 8X - 60

Yup, you're right, I missed the x' and y' functions on the left. It looks like it only has a subset of 2-variable stat functions, though, unless there's some non-obvious way to get the actual summation register values.

[EugeneNine]

I have an HP6s laying around somewhere

[ijabbott]

I'd add Casio fx-411, fx-450 and fx-451 to the "solar only" list.

There is also the fx-451M variant for the "battery optional" list with battery backup for settings and memory. The battery is not meant to be replaceable, but I have done it.

[twdeckard]

Has anyone ever ginned up a solar powered HP41? I know there isn’t enough real estate on the calculator so it would mean dangling a solar cell off of it? However given it only draws a few hundredths of a milliamp when off and 10mA when running would make a fun project? Wasn’t there a power from USB module hack?

[Dave Britten]

(04-29-2020 01:03 PM)twdeckard Wrote:  Has anyone ever ginned up a solar powered HP41? I know there isn’t enough real estate on the calculator so it would mean dangling a solar cell off of it? However given it only draws a few hundredths of a milliamp when off and 10mA when running would make a fun project? Wasn’t there a power from USB module hack?

I was kind of wondering if anybody had attempted this with the Voyagers, since they apparently draw only 70 micro Amps when on and idle:

https://www.hpmuseum.org/forum/thread-14886.html

Could make a little solar panel assembly with the contacts on a small barrel that's sized to match 3 LR44s.

[rprosperi]

I like the Casio fx-995 (photo below). This is a [Solar-Only machine].

It is a decent algebraic scientific machine with the usual Base, Stats and Unit conversion functions you would expect in a machine from the mid 80s.

What is unique about is it's size, or rather, lack of size.

It's dimensions are 70mm x 124mm but only 3mm thin.

I have wanted one of these since I first saw one in the early 90's but could never find them anywhere. At an HHC about 5-6 years ago, someone put one on the prize table, and it was #1 on my list when I got to pick, however as luck would have it, Felix Gross got to visit the table exactly one spot ahead of me, and he liked it too! So of course, the hunt was on at that point, but it took several more years to finally locate one. Now, of the many (many!) machines I am happy to own but hardly ever use, this one makes me almost the happiest.

Being so thin, there is obviously no key 'travel' when pressing them, not even a little flex of a soft key-top. Yet I found to my surprise it registers keystrokes rather well and reliably. Having had "HP finger" disease for so long, I found I need to watch the display to ensure I am entering right, but I rarely ever miss a keystroke, and don't recall ever seeing double-entries.

The back side includes unlabeled mm/cm on one side and inches/sixteenths on the other side and some Metric conversion factors listed in the middle.

I'd be curious to know what these cost when new if anyone knows that.

Thanks Dave for this interesting topic; easy to see folks have lots of different favorites here, well away from the normal suspects.

[Dave Britten]

That fx-995 looks pretty neat! Though based on my experience with the membrane keyboards on the fx-7500g, fc-1000, and SF-3500, it's probably not an optimal typing experience.

I also forgot about the Casio CM-100 - it's kind of like a poor-man's HP 16C. Not programmable, and limited to 32 bits, but a pretty decent computer science calculator overall. It's actually a bit easier to scroll through long binary values than on the 16C. No batteries in this one, as far as I can tell.

https://casio.ledudu.com/pockets.asp?type=1300&lg=eng

[johanw]

My second calculator in Highschool, the first one I bought myself, was a Casio FX-98: a solar only scientific calculator in credit card format so I could carry it easily in my shirt pocket instead of my bag. I still have it and it still works, although I switched to Free42 on Android as my main calculator now.

[Dave Britten]

(05-01-2020 01:11 PM)johanw Wrote:  My second calculator in Highschool, the first one I bought myself, was a Casio FX-98: a solar only scientific calculator in credit card format so I could carry it easily in my shirt pocket instead of my bag. I still have it and it still works, although I switched to Free42 on Android as my main calculator now.

That's a nice little tiny one.

I got a Casio fc-200V in the mail today, which is one of only a very small number of solar-powered (battery-assisted) financial calculators. It's got a lot of features, but the interface is a little clumsy, with a lot of using the up and down arrow keys to scroll through the different solvers and menus. So not as elegant to use as the original fc-200 (which has almost nothing in common apart from being another financial model), nor is it programmable like the fc-200, but it's certainly got a lot of functionality crammed into it. The two Shortcut keys are particularly handy: you can open up the various solver applications and store a shortcut to that application along with all the variable values. So pressing Shortcut 1 could take you directly to the compound interest (TVM) mode and recall a set of saved values of all the TVM variables.

[Eddie W. Shore]

Happy that the fx-50FH can run sans battery, however, I doubt any programs can be retained after the calculator is turned off. Same for the fx-3650P. I am also getting the Radio Shack Equivalent of the fx-10f/50f this month.

I am also on the (semi) hunt for a fx-995, it just looks cool.

The TI-30SLR+/TI-31 is solar light only.

[Dave Britten]

(05-02-2020 01:43 PM)Eddie W. Shore Wrote:  Happy that the fx-50FH can run sans battery, however, I doubt any programs can be retained after the calculator is turned off. Same for the fx-3650P.

It seemed like you can get away with turning it off without losing anything, but if it's left without sufficient light, it will no doubt lose the contents of memory.

[John Galt]

http://www.hp.com/hpinfo/newsroom/press_...-hires.pdf

It says "Solar power, battery backup" which implies the battery is optional.

[mfleming]

The Casio fx-450 & fx-451 are solar only scientific calculators with keyboards on two halves like the 28s. Fairly unique, with a Radio Shack branded version of the 451.



Small, hex/octal/bin operations, DMS and fractional representation, polar/rectangular, one variable stats all in a small form factor. Big fun!

[ijabbott]

(05-10-2020 01:31 AM)mfleming Wrote:  The Casio fx-450 & fx-451 are solar only scientific calculators with keyboards on two halves like the 28s. Fairly unique, with a Radio Shack branded version of the 451.



Small, hex/octal/bin operations, DMS and fractional representation, polar/rectangular, one variable stats all in a small form factor. Big fun!

Yes, although the fx-451M in your picture has a backup battery to save settings and memory, although all the original batteries in these calculators will be dead by now, making most of them effectively solar only. I was mad enough to take mine apart and replace the battery. The calculator part can be unclipped from its frame using a spudger. When putting it back together, rub down the connector to the membrane keyboard, because it is likely to have become partially unstuck during the dismantling and battery replacement. Use a GR927, SR57, 395/399 or equivalent replacement battery, preferably silver oxide.

[mfleming]

Well, that's quite interesting to know! I had considered messing around with one that has the intermittent hinge connector problem, but would never have guessed that a battery might be found there. Reminds me of too many other calculators that have to be disassembled to get at the battery

[cdmackay]

I used one of these when it was current (along with most other UK Casio scientifics), and found it a pleasure to use. I worried about the hinge, but it never gave any problem.

Sadly I don't have one in my "current" collection — they don't come up on eB often — but my original must be somewhere

[BillBee]

(05-10-2020 01:31 AM)mfleming Wrote:  The Casio fx-450 & fx-451 are solar only scientific calculators with keyboards on two halves like the 28s. Fairly unique, with a Radio Shack branded version of the 451.



Small, hex/octal/bin operations, DMS and fractional representation, polar/rectangular, one variable stats all in a small form factor. Big fun!

That was a great calc. Prior to my discovery of HPs I used this one in HS - the ole red led Ti died. I hope your post doesn't have me digging through boxes as I should still have it somewhere.

I usually keep an old Casio solar scientific in the car for "needs be".

-Bill

-B