Warning about using PCB boards to rebuild old drill batteries.

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Hello and welcome to my guide on rebuilding old drill batteries.

First of all, if you want to rebuild an old battery by purchasing the correct cells for it, Ni-CD or Ni-Mh technologies with tabs, you can do but this is expensive, it is often easier just to buy a new battery from the drill makers.

This is aimed at people who may want to attempt to use Li-ion cells to replace Ni-Cd or Ni-Mh batteries.

Now on paper this should work, the voltage difference 4 Li-ion cells and 12 Ni-Cd cells is only 0.4 volts, 14.4 for the Ni-CD and 14.8 Li-ion, providing you use a suitable PCB board to control the charging and discharging of the Li-ion cells, they should be lighter, produce more torque and last longer.

Well, if you are smart enough to figure out how to bolt these cells to your drill without comprising how the drill functions then the answer is yes, they do weigh less, they are slightly more powerful but only slightly, you are talking a 4 to 5 percent gain at best, they do last longer, providing the Li-ion cells you purchase are geared towards high output levels compared to overall storage capacity.

Think of it this way, a car battery does not hold too much power but it can discharge what it has very quickly,
Compare that to a caravan battery, which can hold more overall power, but it's discharge rate is much lower.

For the record here, I attempted to convert my Makita 14.4v Ni-CD battery to a 14.8v Li-ion cell.
There is enough room inside the battery for the cells, cell holders if you are using them and the PCB controller board which is a must, otherwise your drill charger will fry the cells, Li-ion is delicate technology compared to Ni-CD.

The problem is that on paper the PCB boards needed for the job are good enough, the reality is they are nowhere close to the actual requirements, there is currently nothing available that I can find that will do the job to the required standard, nowhere close.

A cordless Drill has a discharge rate much higher than you might think, true the battery may only hold 1.3Ah worth of energy, but it can discharge that energy at a rate of 60 to 80 amps, which is actually needed for a decent drill, even under modest usage the motor will pull between 20 to 40 amps worth of power from the cells.

Tip : If you are desperate, a drill battery can jump start a small car, i know this because I've done it!

Note : in order to discover the above facts, I had to use a car battery discharger tester, a normal multimeter can not handle those kind of Amperes.

Even with the best PCB i could find, the maximum allowed discharge rate through the board was 22-25 amps, which was not good enough, it kept cutting out during mid drilling or screwing, I even used 2 board soldered together, which did improve things, but still not by enough to make the drill as functional as before with Ni-CD cells.

Also, when i connected the battery to my drill charger, it would only charge it for around 20 seconds then the PCB boards would cut out again, things did not improve with two boards either, despite the fact that the stated maximum charge rate handled by the PCB boards was 5 amps, they could not handle the 2.5 amps pumped out by my standard issue Makita drill charger.

My experience cost me some money and left me with a bitter aftertaste, this should have worked, but due to the poor performance from the PCB boards you can acquire, it did not and never will, unless they can make a PCB board with a 100 amp discharge rate.

I hope this serves as a warning to anyone who is going to attempt this, it does not work!
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