I'm wondering this since flashlights for example won't be as bright if you use rechargable batteries rather than alkaline due to the lower voltage. Is it a technological hurdle that we can't design 1.5 volts rechargables to replace the environmentally unfriendly alkalines?
Why are rechargable AA, AAA, C, D, batteries 1.2 volts?
- Thread starter sumyungai
- Start date
Actually they're nominally 1.2 V, but it probably depends on the chemistry of the cell; I think the output of a single battery cell depends only on the chemicals used to generate the voltage. Cyclowizard would probably know... he's the chemical guy. 
The voltage in a battery is determined by the chemical reaction that creates the potential difference between the cathode and the anode. The voltage formed by the reaction is called the terminal voltage of the cell/battery. In alkaline and heavy-duty batteries which are the two types of consumer electronic non-rechargeable batteries that you can find in stores in the usual sizes, the terminal voltage is 1.5V. A battery made from a zinc-galvanized nail and a copper penny stuck into a lemon has a terminal voltage of about 1V. A lead-acid battery - such as used in cars and UPS's - has a terminal voltage of 2.1V (6 are stacked in series in a "12V" car battery).
The two most common types of rechargeable batteries that come in common consumer electronic sizes are nickel-metal-hydride and nickel-cadmium batteries. They have a terminal voltage of 1.2V. On the other hand, in applications where weight and size are important, lithium-based rechargeables are taking over - such as lithium-ion, lithium-polymer - and they have a terminal voltage of 3.6V. They aren't made in common consumer sizes because they would fry the electronics since the base voltage on them is more than twice that of a typical consumer cell.
Since the terminal voltage is a function of the materials and the chemistries involved, there's not much that can be done to change the base voltage without abandoning the battery technology completely. So, if you have a zinc-carbon battery, you are stuck with 1.5V. If you have a nickel-cadmium battery, you are stuck at 1.2V.
The two most common types of rechargeable batteries that come in common consumer electronic sizes are nickel-metal-hydride and nickel-cadmium batteries. They have a terminal voltage of 1.2V. On the other hand, in applications where weight and size are important, lithium-based rechargeables are taking over - such as lithium-ion, lithium-polymer - and they have a terminal voltage of 3.6V. They aren't made in common consumer sizes because they would fry the electronics since the base voltage on them is more than twice that of a typical consumer cell.
Since the terminal voltage is a function of the materials and the chemistries involved, there's not much that can be done to change the base voltage without abandoning the battery technology completely. So, if you have a zinc-carbon battery, you are stuck with 1.5V. If you have a nickel-cadmium battery, you are stuck at 1.2V.
I knew that batteries (with nominal current or less) will keep very near to their rated voltage for something nearing 90% of their charge (only on overcurrent their voltage drops with charge)
pm hit it on the head. The thing that dictates the voltage of a battery is the free energy resulting from the reaction going on at each electrode. The larger the difference in reaction energies (specifically, Gibbs free energy) between the two reactions, the larger the voltage. To have a 'rechargeable' battery, these reactions should be reversible such that the initial concentrations can be recovered and the process starts over again at about the same voltage. This adds additional constraints to the selection process of the reactions that may be used to generate the desired voltage, as not all reactions are simply reversed by inputting electricity.
So basically, it is a technological problem since we do not yet know what chemical properties we can use in order to attain a 1.5 volts rechargable?
But just about everything (slight exageration) has a boost or buck/boost regulator
inside so it doesn't matter (1.2 v 1.5) as long as the total energy delivered is substantial
inside so it doesn't matter (1.2 v 1.5) as long as the total energy delivered is substantial
Yeah but only one little correction, the nominal voltage of a lead acid battery is actually 2.2v per cell with only 5 cells.
No, we definitely know what the properties of these solutions are. The economics are probably the limiting factor. As with most engineering problems, it's an optimization on several variables, such as initial cost, number of charges, time to charge, output voltage, recharging rate (so it doesn't explode, but doesn't take forever), among others.
6 Cells in a Car battery x 2.2v = around 13 volts
FYI, That's why only measuring 12v across the terminals means it's discharged to some extent.
FYI, That's why only measuring 12v across the terminals means it's discharged to some extent.
2.1V, 2.2V... what's 100mV between friends?
Thanks for the correction. 6 cells @ 2.2V = "12V" car battery.
The lithium batteries that are supposed to last longer in digital cameras are 1.5V just like the alkaline batteries.
Why doesn't anyone make a charger for those?
Why doesn't anyone make a charger for those?
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