Low Battery Warning Sign After Replacement?



#8

I've recently (3-4 days ago) replaced my batteries when the low battery warning sign went on with Duracell rechargeable batteries (fully recharged when I put them in).

However, now the low battery sign is on again. Are the batteries out already or is it signaling the coin battery? How do I know which one it is talking about? Should I recharge my batteries again (mabye because they are new and this is the first time using them?)? Thanks.


#9

I've just woken up and to my surprise the low battery sign is
gone! ...however, it came back after about 10 minutes. Does anyone
know what is happening here? Should I download the batstatus 1.3 from
http://www.hpcalc.org/search.php?query=batstatus ? Is this program
compatible with the 50g and where can I read a tutorial on how to
download programs into my calculator from my computer? Does it show
the battery status of both the 4 AAA and the coin battery? Thanks.


#10

I posted some information on this subject:
http://www.hpmuseum.org/cgi-sys/cgiwrap/hpmuseum/archv017.cgi?read=112318#112318

As a Physics Nerd, you should have access to a digital voltmeter. Open up the back of your HP50G and touch the voltmeter probes to the ends of each cell to check its voltage. Do this with the calculator turned on. See if any one of the cells is substantially lower in voltage than the others. You may have a bad cell.

If you have access to a variable power supply as well, you can do the test I did. Connect the supply in place of the battery. Slowly adjust the supply from 4.5 volts to lower voltage. Make a note of the voltage when the low battery indicator comes on. Divide this number by 4 and that will be the per cell voltage that just causes the low battery indicator to come on. You can compare that number to the result I got.

As I mention in my post referenced above, on the HP50G that I have, the low battery indicator comes on when the NiMH cells are about 70% discharged. This has the obvious disadvantage that if you replace (and charge) them at that time, you will only be getting about 70% of the use per charge. But, it has the advantage that you have ample warning to replace (charge) them. This is good because normally NiMH and NiCAD cells have a very rapid drop in voltage when they are about dead, and you could only have a few minutes left when the low battery indicator comes on if it was set to come on when the cells were 99% discharged.

Have you been giving your HP50G expecially heavy use since you switched to rechargeable cells?

Edited: 1 Aug 2007, 11:11 a.m.

#11

You didnt mention which handheld your using nor what sort of rechargable cells your using. If your machine has a backup cell then I'm guessing its a 48/48/50 series. If your using NiCd (nicad) then a low battery status is to be expected as they have a significantly lower voltage to start with (1.2-1.25V). You may fare better with NiMH (Nickle Metel Hydride cells) which start at 1.5V. If you insist upon using rechargables do make sure you have a good backup cell in place as the discharge characteristics of most rechargables means the backup cell will be needed.


#12

Quote:
You didnt mention which handheld your using nor what sort of rechargable cells your using. If your machine has a backup cell then I'm guessing its a 48/48/50 series. If your using NiCd (nicad) then a low battery status is to be expected as they have a significantly lower voltage to start with (1.2-1.25V). You may fare better with NiMH (Nickle Metel Hydride cells) which start at 1.5V. If you insist upon using rechargables do make sure you have a good backup cell in place as the discharge characteristics of most rechargables means the backup cell will be needed.

I have a hp 50g and I'm using Duracell AAA Rechargeable batteries NiMH, 1.2 V each, 1000 mAh.

I charged them before I put them in my calculator. After I wait a few hours and then turn on my calc, the low battery warning sign disappears. I turn it off and then on again, still no sign. However, if I use it for a while, turn it off and on, it appears! The process starts over...

#13

What are all of these codes for the Batstatus? I want to learn about how to download these program and more able calculators. Where can I go to seek the information?

http://groups.google.com/group/comp.sys.hp48/browse_thread/thread/453d77ac9ecbf7e1/ebe420474f36c151?lnk=st&q=BatStatus+group%3Acomp.sys.hp48&rnum=8#ebe420474f36c151


#14

This is post from the website link you gave me:

Quote:
In powering our data collection system (www.pssllc.com) we've learned lots about batteries.

Most interesting is that certain units respond differently to the same sets of batteries. Some calculators appear to respond with a low voltage message much earlier than others.

One in particular, will give 8 full hours of use after the first low voltage warning. That is powering two long range (up to 1700' working range!) Bluetooth adapters and an external communication circuit board. The same set of batteries, charged in the same manner, will only last 3 hours past the warning on other units.

Some units will run for 3 days consistently moving in and out of the "low voltage" warning level, and then moving above the threshold.

In short, I've learned never to replace the batteries until the calculator refuses to turn on. I often get several more days out of my rechargeables on my "non" data collector units.

TW


Does that mean the low battery warning on my calc is not really an indicator that my batteries need to be changed? Will it gradually disappear?


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