Batteries 1.5 Volts - Require Advice Please

[Metal Head]

Hi,

The wife recently bought a battery operated "Go Duster" to help dusting the house less of a chore for me. Well I also have the vacumning, washing, d-i-y, etc to also fit in my only day off.

Well I put in 4 brand new "super heavy duty" Eveready 1.5v batteries in for it to operate. However, it didn't seem to have much grunt, so I replaced them with lithium Energizer batteries (that I use for our digital cameras) and it must have at least doubled the speed.

Why is it that these lithium batteries are so much better (last longer & give more umph) than the conventional & rechargeable batteries?

Thanking those in advance of their favourable replies.

Cheers
MH

P.S. Please find attached an image of the two sets of batteries mentioned above.

[Master Splinter]

The lithium batteries have a higher current delivery capacity/lower internal resistance as well as a voltage of 1.6 to 1.8 volts.

More current and more volts = more oooomph.

[Metal Head]

The lithium batteries have a higher current delivery capacity/lower internal resistance as well as a voltage of 1.6 to 1.8 volts.

More current and more volts = more oooomph.

Thanks for the explanation Master Splinter. However, having just checked the lithium batteries they have 1.5 volts printed on the side.

You said they have lower internal resistance - is that they have superior conductors as well as less resistant material within the battery compared to the heavy duty one?

Cheers
MH

[Master Splinter]

They'll have 1.5 volts printed on the side, but that's a nominal value, same way as 240 volt electricity can range between 220-260 volts. (actually the nominal voltage is 230 now)

You'll find that a fresh alkaline will actually read about 1.6 volts and a lithium-iron one should measure about 1.8 volts.

They are labelled as 1.5 volts as that's quite within the tolerances of the stuff they will be attached to and it means that it doesn't confuse consumers. (same way as 1.2 volt NiCd batteries are sold as replacements for 1.5 volt batteries).

Low internal resistance is a combination of both the gross physical materials making up the cell (and how well they are all joined together) as well as the chemistry of the battery (how well the chemical reaction can take place and how evenly/quickly throughout the cell it happens.). Its also influenced by charge level and temperature. (and there's even a little thermal cut out in them batteries that cuts out at 85-90 degrees to stop them going ka-plooey!)

Think of it like filling a normal soft drink bottle full of water and turning it slowly upside down; at first the water flows out smoothly, but eventually it will get to a point where it will start glugging out. That's like the battery chemistry catching up to the demand...if you change the size of the bottle neck (the battery chemistry) you'll change the way the water runs out.

Have a look here for discharge curves of LiFeS2 versus standard alkaline batteries:
http://data.energizer.com/PDFs/l91.pdf