Basic rechargeable batteries question

chemistry

Phlogiston

martin

Because you touch yourself at night.

The voltage of any battery (rechargeable or disposable) depends on the chemical reactions that occur within the battery.

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Rechargeable batteries generate electricity by a different chemical reaction than that used in alkaline batteries

and that is why the nominal voltages are different. If you searched on chemical thermodynamics and Gibbs free energy you might find a more detailed explanation - I studied it in my second year at university (1961) and retain very little of it.

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Bill Sloman, Nijmegen

"Ninad Tipnis"

** Because that is what the chemical reaction inside generates.

Batteries are products of chemical engineering - not the efforts of electronics designers - they can only do what the laws of chemistry allow. A good performing, rechargeable cell that generated a steady 1.5 volts would be sensation in the battery market place.

Luckily, the 1.2 volt NiMH ones we have now are very useable in most devices originally intended to use non rechargeables. This is because that

1.2 volts of output is quite steady during discharge - unlike alkalines etc that constantly lose output voltage as they go - right down to 0.8 volts before they are exhausted.

....... Phil

Oops. The second URL should have been

here's another

The battery chemistry determines the voltage. Change plate material and you change the voltage out for a given electrolyte.

1.2 volts will almost always work in place of 1.5 volt primary cells - the battery keeps putting out 1.2 volts for most/all of its life - unlike 1.5 volt alkaline or zinc carbon batteries which droop from the time you start drawing power.

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It's because of a plot by the Great Satan.

This is not a design question. It belongs on news:sci.electronics.basics

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Michael A. Terrell
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Hi,

I would like to why AAA/AA/C/D rechargeable batteries have 1.2V nominal voltage? and not 1.5V as the case for alkaline batteries.

Thanks,

Ninad Tipnis .

----------------- Wish I really knew.. I'm still stuck on why a nail and a penny stuck in a lemon produces electricity. Apparently 4 lemon batteries lights an LED! As an hobbyist/designer I just see 1.5V and 1.2V and other specs...I try to stay in the electronics domain and avoid chemistry. Besides, I didn't do so well in chemistry and it's messed up my electronics work sometimes. So I recommend learning chemistry ..And physics,..and math and ...Damn it! It's endless!! I'm warning you...Do you really want an answer to that battery question because once you're down that rabbit hole.... there's no getting out. :) D Sorry...after seeing some of the funny replies to this thread I had to add.

different chemicals => different voltage

the word for today is "electronegativity"

Bye. Jasen