The Museum of HP Calculators

HP Forum Archive 13

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New Battery Technology Available
Message #1 Posted by Michael Meyer on 30 Oct 2003, 9:18 p.m.

Hi all! I am hoping this is of general interest to Forum members:

I just purchased Rayovac's new IC3 batteries-- 2000mah AA cells that charge in only 15 minutes! Each cell has its own charging control circuitry ("In Cell Charge Control... IC3).

Since they have to charge in the specific charger, I don't think it's going to change the way calculators charge, but I know we've talked batteries before, and the in-cell charging circuit has been mentioned here.

BTW, of all places, Walgreens has them on sale at $29 instead of $39, including the charger and 2 cells. Plus, you get a free 4 pack of batteries. The wall-wort is 14.5V at 4.5A!

Good for powering the cameras we use to photograph the calculators. (THERE. I knew there was a reason to mention them here....) Anyway, I think they're a real innovation, and a long way from NiMH technology of a decade ago!

RTN2RPN, Michael

Death of a Calculator
Message #2 Posted by Jim Chumbley on 30 Oct 2003, 10:00 p.m.,
in response to message #1 by Michael Meyer

I was using these I-C3 cells in my new HP-49g+ when it displayed its "low battery" warning. I was in the middle of formatting my 256MB SD card, so I continued, thinking I would change the cells as soon as I was finished. The display slowly began to dim, went dark, and the machine would never turn back on again. After trying every possible change of battery, including the keep-alive button cell, and every combination of key depression to turn it back on again, including the paper-clip reset hole/switch, and leaving it with no batteries for 36 hours, I gave up. So did Hewlett-Packard. The machine was exchanged for a new one, which lives only on the batteries recommended for it: disposable, Alkaline AA cells. These present 4.5 volts to the calculator, just as HP recommends. The I-C3 cells by Rayovac present only 3.6 volts. My recommendation: NEVER use rechargeable cells by any manufacturer, even the wonderful new I-C3 cells, in a voltage-sensitive application such as an HP-49g+. They are great for things like remote controls, children's toys, cameras (possibly--untested by me), and flash lights. Just please don't EVER put one into your new HP calculator. Thanks, Jim Chumbley

Re: Death of a Calculator
Message #3 Posted by Michael Meyer on 30 Oct 2003, 11:25 p.m.,
in response to message #2 by Jim Chumbley

Scary. Not good. I see that Rayovac also has the promise to "repair or replace any device damaged" by their batteries. What a hassle, though.

I know most older HP's used rechargeable cells that were lower voltage... in fact, many here on the Forum have warned the opposite: don't use disposable batteries due to their HIGHER voltage. NiCd's also have 1.2v per cell. I haven't had any trouble doing this, but it makes sense that a higher voltage could put a failing chip over the edge.

You just can't win.

I suspect your failure was a fluke, but it makes sense to use disposable cells in the newer calcs. They should last a nice long time with the lower power requirements of modern circuits and LCD displays.

The rechargeables, especially NiMH, are notorious for a sudden dropoff of voltage, which doesn't allow much warning before they go dead.

The jury is far from out on these new cells. So far, in devices like toys, they've been awesome-- taking as little as a few minutes to "top off". I'm also hoping that the internal circuits allow for longer cell life without internal pressure build-up, leading to leakage. I also wonder if they cut off before becoming completely drained. Great for cell life, but bad for a device like your calculator.

Thanks for the warning, Jim. Again, I don't see much role for these in calculators, as once built into a standard HP pack, they'd charge at the slower rate anyway.


Re: Death of a Calculator--looks like others have died also
Message #4 Posted by Michael Meyer on 30 Oct 2003, 11:28 p.m.,
in response to message #3 by Michael Meyer

Reading down further, I see other posts about dead 49G's. Nothing about your advice changes, but it may not have been just from the batteries.

Just an observation.


Re: Death of a Calculator
Message #5 Posted by James M. Prange on 31 Oct 2003, 6:01 a.m.,
in response to message #2 by Jim Chumbley

I wouldn't blame the batteries, especially as the voltage was lower than would be typical of the alkaline AAA cells.

I think you had a genuinely defective 49g+. It seems that being defective wouldn't make it a "collectors' item though. :-(

Consider the 48SX, 48GX, and 49G. With fresh cells, they get about 4.8 volts, a bit over the nominal. As the batteries are used, the voltage drops, until somewhere around 3 volts (under load), you get the low battery warning, and if you're doing I/O, or writing to flash on the 49G, that will error out. Otherwise you can keep using the calculator for quite a long time. If you keep using it for too long, it will turn itself off and refuse to stay on until the batteries are replaced. Even then, as long as you replace the batteries reasonably soon, you'll find that it kept everything in memory just fine. I think that the only cases I've ever seen of these calculators being actually damaged from low batteries were because of battery leakage.

By the way, how long did it take to get the replacement? And did they send it right away, or did they wait until they received the defective item before sending it?


Re: Death of a Calculator
Message #6 Posted by Jim Chumbley on 31 Oct 2003, 9:05 p.m.,
in response to message #5 by James M. Prange

I have been building semiconductors for 27 years. I didn't think the failure was caused by a high-voltage junction blow-out, just an internal logic lock where voltages were not high enough to signal a difference between logic 1 and logic 0. HP must have thought so too, since taking all the batteries out and letting it sit unmolested for at least 24 hours was the first thing they recommended to do.

Contacting HP was the funniest experience I've had in months. If you want to try using their telephone's expert system, call the area (800) number printed in the back of the -49g+'s manual. I was eventually able to speak with a real person who told me that, no, they couldn't swap machines with me and that I should go back to the retailer who sold it to me, as it was they who are responsible for swapping failures that occur in the first 30 days. I did, and the retailer sent out a new replacement the same day, which I received the next day.

Re: Death of a Calculator
Message #7 Posted by James M. Prange on 31 Oct 2003, 9:20 p.m.,
in response to message #6 by Jim Chumbley

Yes, I can see that a problem where something is "not 1" but "not 0" either due to low supply voltages could cause permanent damage. If that's what happened, it suggests to me that the low-battery shut-down doesn't work as well as in the previous calculators, and I suppose that the same problem may occur even with alkaline batteries.

Good to know about the replacement policy, thanks.


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