A note about Lithium Ion Technology

Lots of of mis-information that the tool industry has perpetuated over the last several years in regard to Lithium (Li-Ion, Lipo Lipo-Poly etc, etc..) technology.

Though I am far from any authority I can offer some insight.

Regarding the new Dewalt 20V Max line:

Yes, Makita, and quite frankly all the other manufacturers entered the game years ahead of the Dewalt 20V Max line and yes, several of these manufacturers had batteries com-busting and burning houses, others merely had thousands of defective batteries that were recalled as well.

First is not necessarily best. The simple matter is Dewalt choose to make a lithium battery that could work in cordless tools that were meant for non Lithium technology. They got around that by regulating the output their lithium battery could send to the tool, so the tool would not burn out. PCB protected is a term some of you may be familiar with. It enabled them to be the only ones to make a lithium line that also retro-fitted with ANY older 18volt NiCad tool. 

The downside: the "smart" battery was loaded with "smart chip" technology that took away capacity of the battery, hence their lithium battery had shorter run-time. They grabbed a huge chunk of the market from competitors because although they had shorter run-time, they had cornered the market on a retro-fittable line of lithium that made it possible to keep all ones' older tools. Personal 2 cents: Brilliant.

Dewalt’s 20V Max platform is aimed at getting the share of the market they DID lose because of the lower run-time. So they removed the PCB technology and created a cheap 3.0 AH battery just like every other competitor that does NOT retro-fit. Whether or not someone agrees with their angle in which they attacked the market is a matter of personal opinion (although it is very hard to overlook the market share they grabbed because of their retro-fit platform, but I almost digress).

Moving on to lithium technology. I'd love to clear some air and help out any who might enjoy accurate info (I am a nut for learning). Lithium batteries are commonly comprised of a few different blends and manufacturers went about attacking the market share through designing their lithium batteries a certain way.

The (3) most common in the tool industry as far as this discussion is concerned:

1. Lithium Cobalt

2. Lithium Phosphate

3. Lithium Manganese

Each compound has its pluses and shortcomings. Generally speaking batteries comprised of Phosphate will have shorter run-time but allow more recharge cycles before the internal resistance that results from running a current through the anode and cathode (ie. re-charging ones battery on a charger) destroys the cells ability to hold a charge. Every battery has a lifespan. Manganese/Cobalt-based batteries will have longer run-times but will build up internal resistance at a higher rate until Ohm’s Law (resistance equals heat and heat equals death to a battery- hence Makita’s Fan cooled chargers which was their best attempt at solving their issues with batteries pre-maturely burning out) claims another battery. Worth mentioning is the fact that if a battery is heating up because it is charging quicker (relatively speaking) can be cooled, but the cooling is external. A fan applied to a surface area helps dissipate the heat taking place on the inside or a circuitry. Meaning, it does not prevent heat, it prevents heat build up. The limitation with this "solution" is that both heat buildup AND the heat itself generated from passing a current through a lithuim cell (or any cell for that matter) is prematurely shortening its lifespan. Heats kills. Dissipating that heats kills a little more slowly. Less heat is always better. If a battery lasted x years before it died, however long that lifespan was, it will last X minus Y with more heat. Whether one purchases a Dewalt 20V Max tool or any other manufactureres technology, one still has to contend with these issues.

On another related note: any lithium cell that is charging at higher than 1C rating (see link below) increases the internal resistance of a battery (Ohm's Law again) and decreases it’s lifespan. So any manufacturer that boasts about fast charge time is doing so withing the limitations of curent lithium limitations. Lithium cells can only hold x amount of capacity. At present that capacity is at 4.2 volts max charge (fresh off a charge cycle) per cell, which is the same as 3.0 nominal (resting) volts per cell (Dewalt 20Volt Max is the same as 18volt Nominal). So, a battery can only charge so fast, and can only hold so much capacity. Ergo, the only way to deviate from this limitation (to "cheat" the numbers, so to speak) is to manufacture battery cells at lower capacity and therefore fill up quicker than larger capacity cells, OR, use a charger that is charging at a rate higher than 1C...which bad for long term life of battery.

OK, If any of you are still reading this, I hope it offered some insight and a fresh perspective at the whole Lithium tool industry and what exactly the Dewalt 20V Max lineis doing in relation to what has already been done. I sell all the major cordless tools, own several and have followed this lithium craze for years...seen lots of industry debacles. Personally, and professionally speaking, i appreciate what Dewalt has done and think their Dewalt 20V Max line is another alternative to the contractor/homeowner who doesn’t need to retro-fit his older tools and wants longer run-time. That’s all it really is meant to be.

Cheers,

David

halfway decent link:

http://en.wikipedia.org/wiki/Lithium_ion_battery

Charging info: interesting read

http://www.rchelisite.com/lipo_batte...fety_guide.php

Ohms Law:

http://phet.colorado.edu/en/simulation/ohms-law