When will batteries grow beyond sub-C?

I have implied, but should explicitly ask my question: when will the densities grow such that cell size shrinks?

You have at least two problems Internal resistance is a killer. Smaller batteries have higher internal resistance...sometimes... As do lithiums...sometimes... mike

I don't know if that's going to happen. Cell capacity (energy density) is increasing all the time. Cells are getting better all the time. If they're still putting in more cells, then the tools are getting more powerful all the time.

When it gets to the stage that the battery powered tools reach the power of mains powered tools, you'll be paying many more times for the same thing, just cordless and very much heavier.

That's when they'll start using portable generators and normal mains powered tools. Oh look, they're already doing that.

Li-ion batteries can store more energy for a given weight and volume than NiCd or NiMH, but are much more expensive and require more complex chargers and protection electronics. I suppose the the power tool manufacturers don't think their customers are prepared to pay the extra cost for a lighter and/or longer lasting battery.

Li-ion polymer batteries can store more energy for a given size and weight than Li-ion, but are more expensive. I read somewhere about some research into Lithium Sulphur batteries which could be even better, but that was only research and a long way from a finished product.

There is a lot of work being done on fuel cells aimed at replacing batteries in laptop computers, mobile phones and other portable electronic devices (though not power tools). Toshiba and NEC claim to have working prototypes which could be available in the next year or so, see:

In 2002, Toshiba announced a prototype run of 18650 lithium-ion cells that could do 6C, with a 1600mAh cell. As I can find no mention of them more recently, I can only assume that nobody expressed an interest in buying a few million, to make it worth their while setting up to make them.

The third problem is that even if you've got a smaller cell with an identical thermal resistance, it's going to get hotter, due to the lower surface area to dump the heat.

Lithium-ion is not very much better than NiMH, in terms of energy density. However, it's lots better in terms of weight per unit mass.

Try dragging that corded 1/2" drill (or sometimes sawzall) into the deepest, darkest, hottest, tightest, itchiest part of the attic with you to drill down into the wall for fishing wire. Your partner on the floor couldn't hear you screaming at him to unsnag your cord with the roar of the generator either. I'll stick to my DeWalt 18v XRP.

Whoa! Equivalence Principle violation!

Events are unfolding faster than I had anticipated.

--- Graham Cowan

Why should cell size shrink?

Do you want to make everything that uses C,D,etc. cells obsolete?

I read in sci.electronics.design that Ian Stirling wrote (in ) about 'When will batteries grow beyond sub-C?', on Sun, 18 Jul 2004:

It isn't subject to normal gravity?

I suppose I could argue that I was talking about the weight due of the extra energy storage per unit mass of battery, but of course I meant energy per unit mass, and it was a typo.

In article , vincee wrote: [...]

I have a *slightly* modified electric drill. It has a cable and connector where the battery used to be and plugs onto a battery belt. That way, you've got about 10 times as much energy and about 1/2 the weight in your hand.

Its really too bad they don't make electric tools with a standard connector you can either plug a battery or a cable into.

In article , G. R. L. Cowan wrote: [...]

I think the problem with the hydrogen fuel cell based tools is that they are so light the stores just can't keep them on the shelves.

I have, also, noticed that a battery powered drill gets heavier as you use it.

With the exception of the aforementioned Toshiba 6C cells, lithiums have much lower peak power output than NiCd. Although inferior to NiMH and Li(misc) in capacity, NiCd remains the champion of peak power output. If it weren't for that, EPA would have banned them a long time ago.

Actually the battery makers have been fighting *against* this for a couple decades now. Witness the consumer C cells and D cells that are really sub-C's or even AA-sized batteries in a hollow shell.

Tim.

That's because the weight per unit mass keeps increasing. ;-)

Ted

Then they couldn't charge the truly outrageous prices for their propritary battery packs. I have a cordless phone that uses five AA NiCds for which the manufacturer wants $85. Needless to say, I intend to rebuild it myself.

Ted

It's due to the build-up of entropy in the battery as it discharges.

Yes. An entropy weighs a lot more than a regular trophy. They even spell it differently to emphasisze the point. It's a probelm with the internal energy => mass converter which they haven't yet solved.

You gonna drive a 3/4" Greenlee through a 12" rim joist with that?