Converting Cordless Tools Drills etc to Run on Lithium Batteries ~ Dons Deals

I have several Cordless Drills, that would work great. If the Darn Batteries weren't Dead. And I've been looking for Reasonably Prices Battery Replacements for them for several years now. But, the Prices have stayed pretty much the same, for quite a few years. I've wondered about using some of the newer Lithium Batteries and done some reading on that, here and there. And today I found some good info on using Batteries, that cost about $10 each (Turnigy nano-tech 1300mah 3S 25~50C Lipo Pack). That's a whole lot better than $45 and up for the Replacement Batteries, that are available for my Drills. And in my Research on Rebuilding my Battery Packs. The Price of $2 to $3 each. Just for the new Batteries needed, to build up a Pack. Quickly, adds up to be about the same Price as buying a Complete Ready to go Unit. It's really pretty easy to Convert the Drills to fit the Lithium Battery Packs into your old Battery Case. But, some caution and care needs to be taken, when Charging these Lithium Batteries. They need to be Charged with a Lithium Battery Charger. And they need to have Protection Circuits connected to them as well. To protect from Over Charging and also from being Discharged too much during use. Here's a couple of Protection Options, that I found today. Lithium Ion/Polymer USB Battery Charger IC - MAX1555 COM-00674 for $1.95 each now. "Description: This handy little IC will correctly and safely charge our Lithium Polymer batteries with power from a USB port or from a DC wall adapter. Max current is limited to 300mA using an external wall supply (3.7V to 7V). Requires almost no external components and will automatically select between a DC source and USB source if both are present. Current is automatically reduced to a trickle when charging is complete." And the MCP73831/2 Datasheet (07/08/2013) "Tiny 500mA linear charge management controller. Includes integrated pass transistor, integrated current sensing, and reverse discharge protection in 5-pin SOT-23 and thermally-efficient 8-pin 2mm x 3mm DFN packages." The list for about $0.45 (cents each). These Pre-made Circuit Boards would save some time and work over building your own. Not to mention the learning curve, for me. From all that I have read. I think, that the Main Concern in Converting Tools to Run on Lithium Batteries. Is, the Safety Factor. That's where the Research and Attention needs to be Paid, in this Project. So, You might want to read this first... http://batteryuniversity.com/learn/article/lithium_ion_safety_concerns. I'm sure there are plenty of other sources for information on Lithium Batteries. But, this site seems to put out good info. I've read other Articles on Regular Lead Acid "Car Batteries". A subject which I am much more familiar with. And the info was good and insightful (http://batteryuniversity.com/learn/article/how_to_restore_and_prolong_lead_acid_batteries). I haven't done mine yet. But, this is what I have found so far and I'm leaning towards doing this, with my Cordless Tools, that need new Batteries. It seems to be the most Cost Effective way of getting them back up and running again. And with a bit more power, to boot. Here's a bunch of links to what I have found on the subject...

Don