My first portable tool was a very humble (cheap!) 14.4Volt portable drill made by Ryobi. It had 2 x 1200A/h (or so they say) batteries and it worked to some point it didn't have much torque or life between charges. Due to my own forgetfulness I promptly killed both packs due to overcharging from being left on the unregulated charger for too long.

Upgrade 1: I pulled the internals out all bar one cell that held the terminals in and used 12 x Ni-Mh rechargeable AA cells, they where joined end to end by being soldered with short lengths of wire. It worked reasonably ok for quite a while with a modest increase in torque and battery life. I however have some issues with the cells eventually, what was likely the stress of the high current load and being soldered caused them to deteriate.

Upgrade 2: At this point I discovered that I could very cheaply buy used laptop batteries from odd and unpopular models for very little money. I pulled 4 Lithium Ion cells out of one of these, soldered them in series and put them inside the battery housing. First up the housing was incredibly light, it felt empty. On use there was a good torque increase again and a small increase in battery life, I only used this for a short time before the next upgrade.

Upgrade 3: This was similar to the above but in an effort to make the most of what I had I chopped the housing to have 4 pairs of cells for a total of 8 (2P x 4S): this gave the same torque as above however the charge life was very long, it was about 6x the original pack. This went well but it accepted less of a charge every time. This was most likely the combination of age, over-current and me doing the poor practice of charging all the cells in series without equalising the individual cell voltages.

Upgrade 4: This leads to the final upgrade which is using the 14.5 Volt version of this below:


It's a 5A/h 14.8V Lithium Polymer/Li-Po battery pack made for large remote controlled aeroplanes and similar. I temporarily chopped the case of my battery pack to make it fit with the intention of having some metal shroud at a later date. It ended up looking as shown below, the end wrap was taken off to resolder one of the balance wires after accidently ripping it off.



With 5A/h compared to the 1.5 - 2A/h that's normal on the top end drills and my original dubiously stated 1.2A/h amount it has some serious storage. The torque increase was so massive that I literally burnt part of my hand when trying to stop it in the faster gear when before I could do so with my index finger and thumb previously. I was previously concerned about breaking the gearbox with the sheer extra torque but so far it's held up. I gave it hell and tried drilling a 10mm (3/8") hole through a thick steel plate. I came to a point where it got hot enough that a small amount of smoke came out. So it's obviously working much harder than it's designed for, this is acceptable though as I just let it cool down a bit before getting to this point, I use the heat of the handle to know. I still manage to do a large amount of high strain work with it though, I just don't do it all at once in succession.

Shown above are the various items that I use in my portable projects. Listed as numbered:


(1 + 4) Leaf Blower & Garden trimmer: This is part of Ryobi's range of portable garden tools using what they call the "ONE+" system. They give the customers the option of using a Lithium or Ni-cad battery which plugs into any of the tools in the range, great concept but not really relevant to me. What was is that they sell these tools without a charger or battery in the pack for more flexibility, this meant I was only buying what I wanted. Buying these I modified each within days of the purchase to have an external fly-lead out the back (see picture below).  For the moment I put the 18.5V lithium 5A/h battery  in my back pocket with the fly-lead attached and used as such. However I am planning on using a tool belt for which I will make and attach my own battery enclosure which will have the power socket coming out of it.



(2) Portable drill: This drill was just a very cheap and low quality unit I bought as an intermediate solution until I fixed my Ryobi battery. It's only a single speed so mainly for putting screws in. I am only converting it because it will cost me nothing due to it using the same 18V battery as my other tools and also the battery out of this also fits into my portable grinder. I am doing it mainly for my own experiments and after testing it out I may use the motor and gearbox for another project.


(3) Dewalt 3 speed drill: Bought recently to replace my Ryobi drill it is heavy, tough and very powerfull. It has a 13mm metal chuck which is something I have wanted for a long time, a metal geared three speed gearbox and a hammer function. As pictured below I made a crude yet effective extension to the battery box out of sheet metal which I then screwed into the bottom. I will have an elastic cord that holds at the front to hold the battery in. Due to it's serious weight I will use this for all my heavy duty/repedative work and the Ryobi for my lighter/more awkward work. The original 2A/h Dewalt battery packs are known to not last as long as they should are very expensive to replace, so this makes for an excellent combinaton. As a bonus I managed to get the dead battery for free and I imported the drill second hand bare for a good price.




(5) Dewalt 1/2" impact driver:My latest buy that was also imported used and in bare form. Being a Dewalt it shares the same battery as my drill which saves me a lot of work on my part. During testing I found this to be amazingly powerfull, it appears to have significantly more torque than my pneumatic drill.


(6) Portable Grinder: This was bought without it being expected to be usefull. It cost a grand sum of about $25 AUD and worked surprisingly well. The battery died in no time of course but sharing the same battery pack as the equally cheap 18V drill it's going to recieve a quick upgrade. During testing I have found it to be still quite usable and I will use it till I manage to finish making my own custom built portable grinder.

(7) Turnigy battery charger: This is what chargers everything, bought from Hobby City like all my other goods, it's cheap, easy and works well. It also has a built in cell equalisation mode which is a necessity for lithum cells of any type.

(8) Ryobi 14V drill: My old original drill. Originally a 14.4V Ni-cd powered unit it is the only tool I use that doesn't use the 18.5V packs and instead I have two interchangable 14.8V packs for it. It still works great despite everything I have thrown at it but really annoys me at times with its 10.5mm chuck. This drill is great for it's compact shape and light weight. As shown below I managed to slide the battery into place without chopping the bottom out like the Dewalt. While I have been using this for a while in this state I will make a protective metal shroud around the battery to protect it.

To convert the battery pack in tools the first step is to open the pack up, for Dewalt packs this is with a Torx type set of screws. Wires need to be soldered to where the original terminals connect. On all drills atleast one of the cells is in the tube that fits into the handle of the tool, in many cases the top most cell holds the terminals in. From here if the terminals can be soldered to from the underside this one cell can be glued and left in place for it to then be bypassed. Otherwise the wires can be soldered and the terminals can be held in with other means. One such means is with an epoxy type putty, shown below are two examples of this being completed.




Next up there is either the option of chopping the existing housing to fit the new battery or to glue a new enclosure on the bottom of the existing pack. If the original housing is to me modified then upon dissasembly measure the room in mm between the internal spaces available and also between the outer screw holes. Hobby city have a great battery selection chart here, the Turnigy 20C packs are the best value for money and are a proven product. All the product pages have the dimentions in them to compare with the meassurments taken earlier.

While the main plug can be kept internal the small balance plug has to be accessable externally.



Charging:

Again there are two options, to have the main power plug external as like the Ryobi as shown at the top of this page or to have an internal connection. To charge with an external connection the pack is simply unplugged and plugged into the charger. The other more elegant option is to put the main power plug and socket inside the battery enclosure and then modify the original charger to have something that lets the terminals connect directly to a Li-po charger. The charger plug will need to be able to be pulled out and plugged directly into the side of the unit.

Low voltage alarm in discharging: If Li-Po cells are discharged to a level below about 3volts per cell then permanent damage will result to the battery pack. Remote controlled vehicles solve this problem by having a programmable low voltage cut out built into the brushless motor controller. As I have no controller as such I needed a warning or a cut-off device when the cells reached a certain state of discharge. For this I used a very simple device:


This is plugged into the balance plug of the battery and for this 5 cell compatible model it will sound the buzzer when the pack reaches a combined voltage of 15V, or assuming all the cells are identical 3V. Due to the very low price ($3.50USD!!) I will stick one of these on each appliance. Time will tell if this can be heard of the sound of the tool, however some people are fitting these to R/C aeroplanes so they must make some sort of a substantial sound.  Other models for two to six cell counts are also available.



WARNING! Do not at any time use anything but a regulated Lithium Polymer charger on these cells, the Lithium cells normally available in drills are lithium Ion or Lithium Iron Oxide (LifePO4), using one of these chargers will very likely either do nothing or make the battery pack quite literally set on fire.

For the connection the packs come with a plug pre-installed, due to their bulkiness and other issues I chop these off and fit the smaller EC3 type. I can only use about 75% of the conductors at the end into the plug but for the current I use it's fine. I source these here: