Mod Battery Science

[urbanite]

Hey all,

reading through the GG section of this forum, I read a conversation discussing the merits of different batteries which could be used with it.

Is there already a thread about the choice of batteries for the mods? I didn't seem to find one.

Basically interested in seeing what the thinking is behind the use of mostly Li-On instead of say Ni-Mh type of rechargeables. Why the particular sizes such as CR2 or CR123, which seem to be a bit hard to find other than by ordering on the internet, etc. Why not just stick normal one charge batteries in there if there isn't a charger around or something? Which type of batteries last longer and so on.

Could someone knowledgeable about this stuff step up and write a mini guide to batteries for use in the mods?

 

[Hoosier]

Hey all,

reading through the GG section of this forum, I read a conversation discussing the merits of different batteries which could be used with it.

Is there already a thread about the choice of batteries for the mods? I didn't seem to find one.

Basically interested in seeing what the thinking is behind the use of mostly Li-On instead of say Ni-Mh type of rechargeables. Why the particular sizes such as CR2 or CR123, which seem to be a bit hard to find other than by ordering on the internet, etc. Why not just stick normal one charge batteries in there if there isn't a charger around or something? Which type of batteries last longer and so on.

Could someone knowledgeable about this stuff step up and write a mini guide to batteries for use in the mods?

Power density and charge memory.

Power density - advantage Li-Ion
Charge Memory - Li-Ion has almost none

So you are asking why folks pick the superior technology for something as important to them as their PV?

The only advantage that Ni-Mh has is quicker charge time.

Since Ni-Mh are easy to get, try an experiment. Discharge it, say 20 times, through a 3 Ohm resistor, 5 watt to be safe, and note how long it produces voltage each time. That produces quite a strain on the battery and damages it quite quickly. That amount of current even damages most Li-Ion batteries, but it will tear up a Ni-Mh even quicker.

You'd have to use a number of Ni-Mh in parallel to keep the high discharge current from damaging the batteries.

Luck for us, Li-Ion prices have been coming down and are getting more common. Hopefully Li-Film cells will follow and spur the next technology.

That is also why Li-Ions are used in all the all electric cars I am aware of, best energy density and low charge memory effect for the money.

 

[nubee]

bada bing...bada boom! Like the man said, bigger bang in smaller place for the buck.

Ni-Mh was the answer/replacement for the Ni-Cad memory problem but still in the same volatage/amp/life space. Rechargeable Alkaline was next but still at same voltage - 1.5ish (as Ni-Mh are really 1.2-1.3v)

With Li-Ion you get higher voltage with size giving you longer life (more milliamp/hour). So a 16850 last longer than a 14500 which lasts longer than a 10400 in a side by side test. Also, price for these goes up a bit as the size increases. $12 for 18650 AW's and only $3 for 10400.

The GG is one mod that allows you to grow/shrink the size of its batt holder to accomodate the different lengths of these batts. I don't know that I'd want to carry around a police night stick size mod while running around the mall on a few errands so the 10400 might be a nice choice...that kind of thing.

$0.02

 

[urbanite]

cheers for the answers guys, I'm not particularly knowledgeable about all this stuff... So thanks for clearing up a bunch of stuff...

I also finally found the ABCs of batteries thread in the Battery Mod section. Can't link to it though.

Very useful as an explanation. The only thing I deplore about these Li-On batteries is that they are near impossible to find in a physical brick and mortar store round these parts. And overseas post takes anything from 3 weeks to 2 months to get here...

 

[sailorman]

Google "battery university". Everything you wanted to know about batteries, plus some. I used to be a flashlight addict, then got into RC aircraft. So, I have just about every type of Lithium battery around. The best place for the Li-on batteries I've found is Deal Extreme. They ship out of Hong Kong (free), but pretty quick. Usually about 2 weeks to the US. No idea about Moscow though, unless it's Moscow, Idaho. LOL.