Rechargeable 1.2V AA Batteries vs Alkaline 1.5V?

Question

I wonder about the power output of rechargeable batteries vs alkalkine, as there is a slight difference in voltage.

I have some heated gloves that use 3xAA batteries each. In alkaline they add up to 4.5 volts. If I go rechargeable it'll add up to just 3.6 volts.

But the alkaline (Duracell) are expensive over time and don't even last 2 hours. Whereas I'm looking to get 3800mah rechargeables that will last longer and be reusable.

But will they heat the gloves as much? These particular gloves are super cheap and the heat barely works. But they do work! At least enough to stave off my hands from freezing. I'm worried if I get the rechargeables, even if they last longer, they might not run the gloves as warm? What do you think?

I really want to get some expensive heated gloves that run a custom battery pack at 7.2 volts; I'd get them if I could but they are over $100. Whereas the rechargeable batteries and charger are less than 1/3 that price and I can use them for other things too.

As a cyclist, I'm desperate for a solution. I have Raynaud's Phenomena so no matter how effective regular gloves are, once my brain signals that it's cold, the hands will go ice cold and stay that way. Putting heat at the source is the only thing that works, and I can't use mittens with heat packs as I need full finger control.

Answer 1

If the battery pack just connects to the gloves, with a resistive heating element in the gloves, then the rechargeable batteries will work "well enough".

Note that 3800 mAh AA rechargeable batteries do not exist. Batteries of lower capacity with 3800 mAh labels may exist. Such batteries are often low quality. Reputable NimH AA are available up to 2500 mAh and PERHAPS slightly more.

An Alkaline battery is about 1.55V when new but drops rapidly to 1.3-1.4V range and then drops with use to about 1V. A NimH battery in heating use will give about 1.1V for most of the discharge period. The difference will be noticeable but probably not vast.

If you are happy to change battery packs you could use 4 x AA NimH plus an extra series resistor or (best) a current regulator.

When the batteries are discharged below half capacity Alkalines may have high internal impedance and voltage may drop more under load than expected.

3 x Alkaline: 3V to 4.6V 3 x NimH: 3V to 3.6V 4 x NimH: 4V to 4.8V (slightly more at very start).

The fresh 4 x NimH will be somewhat hotter than the new Alkalines. MAY cause trouble but probably not. The exhausted NimH will be the same as 3 x 1.33V Alkalines - still rather unused. So it will be a good solution provided that the current is not too high when the battery is fully charged.

Answer 2

Low cost heated gloves typically use resistive heating elements running off supply power without any form of regulation.

Therefore, the heat generated is a factor of supply voltage as well as battery internal resistance, i.e. current delivery capability.

Typical alkaline cells not only are rated at a higher voltage than NiCd rechargable cells, but also lower internal resistance. Presumably the ones you are considering are NiCd, based on the 1.2 Volts mentioned.

So, yes, the gloves will most likely have noticeably lower heating with the NiCd cells.