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Yesterday I wrote that I was looking to replace the batteries in my newly acuired 37E. Thanks for those who responded.

At Radio Shack I purchased a cordless phone battery (23-967) with 2.4V and 1500mAh. They were the perfect size and had a soldered strap conecting the batteries in series. I let it charge overnight and tried it this morning. It worked for a few minutes but the the low voltage (litle red) light lit and soon thereafter the display went dead. The calculator works fine on the power cord.

Where did I make my mistake and what should I do now?

Thanks for your comments,

Dan

Is the charger powerful enough to charge 1500mAh in the same timeframe as it would 600 or 650?

Edited: 16 Nov 2006, 8:55 p.m.

Most likely the battery is not making good contact. You probably need to shim the strap end. I have used sticky felt like used on the bottom of pottery or Dr Scholles foot stuff..

I also forgot to mention that it is normal for a fully charged modern battery to show the "low battery" signal for a while. It is actually a "high" battery.

There is also a possibility that the calc/adapter actually didn't charge anything and that your calc "lived" on the original factory-charge of the pack.

This could be because the inner metal track of the calc is degraded or somehow doesn't make contact with the charger.

In this case, and after excluding all other possibilities, get prepared to crack open the calc(I do mean the "crack" ...horror stories ahead :-).

Etienne

Edited: 17 Nov 2006, 3:33 p.m.

Dr Scholles foot stuff...excellent tip, thanks!!

Funny, I use them as silent blocks for my Topcat printers :-)

Etienne

Thanks for all of your thoughts. The calculator works fine with the charger plugged in. I believe that the power is getting from the wall to the calculator.

The problem is that once the ac adaptor is removed then the calculator shows it low battery light after a minute. After about three minutes the display dies.

The contacts between the battery and the calculator seem solid.

Any other ideas? Does the rating of the battery have any effect?

Dan

The batteries in one of my 33C's get no charge when the plug is fully inserted in the charging slot. In this case, I stop inserting the charger's plug into the calculator just before I hear the clicking sound. This is easy to diagnose if you have a meter: measuring the voltage on the battery contacts, you should obtain 2.40 to 2.55 V, depending on the charge level. On measuring again while connecting the charger, the voltage will rise to 2.61V. If it drops to 2.50-2.55V when the plug is fully inserted, then it behaves like mine. In this case, just pull the plug a bit and check if the batteries are being charged (2.6V or more on the battery contacts).

Gerson.


Edited: 17 Nov 2006, 8:03 p.m.