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NiCd AAA on 49G+ or 48GII - Printable Version

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NiCd AAA on 49G+ or 48GII - Leucas - 06-02-2004

Good afternoon...

I have both calculators, and I use too much both.

Can I use NiCd AAA rechargeable normaly? I haven't found nothing in internet about it... Can these calculators work with a 1,2V baterry or they will get "low batt" error??

ps: here, in Brazil, AAA alcaline are much expensive for an eletrical engeneering student... so I designed a AAA/AA NiCd charger, it works well with my discman's baterry...


Leonardo Leucas

Re: NiCd AAA on 49G+ or 48GII - Dave - 06-02-2004

I am sure you will be fine, but... NiCads voltages drop rapidly so you will not have much warning as they lose charge. Of course I think there are backup batteries in the newer designs and you can always make sure you keep a charged set handy...

Re: NiCd AAA on 49G+ or 48GII - David Smith - 06-02-2004

Actually nicad voltage starts off at around 1.4V, drops rapidly to its nominal 1.2V where it stays until just before they die when it drops to 1.0V

Why not recharge alkalines? - Tom (UK) - 06-02-2004

You CAN recharge alkaline batteries but only with a special charger designed for this. The manufacturers don't like this as they then sell less batteries. In the UK stern warnings are given not to recharge alkalines at all - I'm not sure if other countries have these warnings - Germany is more 'green' and may have a different warning. I think the chargers use a charge/dicharge cycle to build up energy in the battery.

There are some 'rules' you must try to follow, one of them is to not alow the batteries to fall below 30% charge as they won't recharge very well if you allow them to fall below this. Estimating this is difficult so I usually recharge them after every few weeks. You could look at the battery voltage to estimate the remaining charge, however the battery indicator in the HP calcs is far too late to use for this.

Perhaps a small program could be written for the HP48/49 to estimate the running time and give an output of charge left (assuming fully charges batteries were inserted) an alarm could be made whe 70% discharge was reached.

Recharging only works 10 to 20 times (but thats 5 to 10 times more use than if you threw them away after one complete discharge).

Just like NiCads, you will need to keep a spare set of batteries to use while the others are charging.


Re: Why not recharge alkalines? - Gordon Dyer - 06-02-2004

I have an Alkaline re-charger and it works well on good quality alkalines (e.g. standard Duracell). Some cheap alkalines like Rayovac have a habit of leaking easily so be careful! Special high power alkalines like Duracell Ultra do not seem to re-charge so well.

Usually standard Duracell alkalines will re-charge 3 or 4 times, although the charge retained reduces a lot with each re-charge. I think I reduce my battery cost by 50% to 70% using the re-charger.

Re: NiCd AAA on 49G+ or 48GII - Vieira, Luiz C. (Brazil) - 06-02-2004

Olá, Leo Leucas; tudo bem? (is it everythign fine?)

Just to let you know that I found some interesting NiMH AAA cells that were no so cheap, but also not too expensive (if we consider that they will last longer than a regualr Alkaline pack...) It's the SONY® Cyber-shot (DI HR 11/45, 1.2V 750mAh). It works pretty fine with the HP49G, I guess it will do also well with the HP49G+.

If you want to go for BR/PO and further contacts, feel free: lcvieira@quantica.com.br (e vamos papear...)

Good luck and success.

Luiz Cláudio