Replace/Upgrade/Repair Power Tool Batteries - SAVE 50% or more!

Picture of Replace/Upgrade/Repair Power Tool Batteries - SAVE 50% or more!
This Inscrutable will show you how to replace the internal batteries of a cordless power pack.  I will also help you determine what batteries you need.

My cordless drill has been sitting on the shelf, useless, because the batteries are dead.  Not anymore...I replaced the internal batteries with ones that were a higher quality and longer lasting!  Others have suggested zapping NiCad batteries with high current...this may work, but also runs the risk of damaging any internal circuitry the battery may have, and could cause the batteries to explode and spray hot/toxic chemicals over you!  It's also only a short term solution.  This is a safer method with a guaranteed outcome, and a great upgrade.  If you're on a very tight budget and have shorted NiCd cells, you can isolate the bad cells with a multimeter and just replace the bad individual cells.

1) Soldering equipment
2) Small heat shrink tubing (optional, if your battery pack requires splicing)
3) Large heat shrink tubing (optional, if your battery pack has a temp sensor)
4) Correct screwdriver bits for disassembling the battery case
5) New replacement batteries (see step 2 for help)

In theory this can be done to just about any item that uses rechargeable batteries, but results may vary depending on many factors.  Do not attempt this unless you are confident soldering and working with high power electrical circuitry - many of these batteries pack a mean punch, especially when assembled!  NOTE: they carry enough current to weld in some cases.  In this example I will be using the battery from a Craftsman Professional 9.6v Cordless Drill, item # 9614 or 11030.

NOTE:  This was the first time I've used a very old camera and I did not realize that the pictures were not great until after the project was over...please let me know if you need more pictures or info!
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It's very important to note that there's a lot more to swapping cell types than the number of batteries to make up a given voltage. The electrochemistry of the new cells must be compatible or the charging systems will not work, or even be dangerous. NiCd and NiMh batteries are not, necessarily, interchangeable. The latter needs a more sophisticated charging system to avoid damage. Whilst many modern chargers cope with both, this can't be guaranteed on dedicated systems. In general, the safest policy to to replace like with like.

Never, ever, put Li-ion cells in a device intended for NiMh or NiCd or vice-versa as, at best, the charging system won't work and, at worst, it can be dangerous, even if the sum total of the voltage is comparable.

Also, when replacing Li-ion cells, be very careful to ascertain if the originals have protection circuits or not. Protection circuits must be used on all Li-Ion systems or there is a considerable danger of fire (for instance, it's extremely dangerous to completely discharge a Li-Ion battery as, on, recharging it can plate electrodes with metallic lithium). Protection circuits prevent this (and other problems). Li-Ion cells come either with individual protection circuits or none. The latter are designed to be used in battery assemblies with their own protection circuit and should not be used where this doesn't exist. If, conversely, you put protected cells into a battery assembly with it's own protection circuit it will be safe, but it's quite likely to suffer from other issues, like limited current drawing capability.

On a general issue, power available is not defined by voltage alone. It's the product of voltage and current. If you try and draw too much current from a battery it will get very hot and this might not just be damaging, it can be dangerous (it's also inefficient). In general, this is something that must be considered when replacing cells on high-powered devices, like drills. These draw a lot of current and cells must be chosen which are capable of delivering the power required. It may, therefore, be necessary to pick cells capable of drawing high currents. Note that a high Ah capacity is not necessarily a guide to how much current (A) it can deliver.

This site is excellent on battery types.

You could do with a bit more discussion over voltage. For instance a lot of Li-ion cells are 3.7 v, so you need to use 1 for 3 x 1.2v NiCad, but the problem comes when you have to multiply up to say 18v should you use 5 x 3.7v = 17.7v and then double that up in parallel if you have space for 10 cells.

russ_hensel2 months ago

Just a note to let you know I have added this to the collection: Cordless-Drill-Battery-Maintenance !


Take a look at a bunch of different/similar approaches to this project.

Leared6 months ago

A nice
help-oriented tutorial! Thanks a lot! I regret that I did not see it when my
old electric beard trimmer went dead. To be more precise, its lithium ion
battery went dead. That time, I followed the selection tips that a professional
barber gave here and bought a new beard trimmer with stronger
and more reliable batteries. But now I know how to deal with such battery

tashammer2 years ago
There are little sets of pry bars that are readily available e.g.

That last url is nice and short?
Akbhar3 years ago
Very informative (and handy) tutorial.

It helped me fix a defective power drill battery pack - when I disassembled to change the batteries I noticed that a soldering point was broken. Fixed that and now works like new.

Thank you!
ömustafa3 years ago
This may be obvious to others but can I replace the NiCd originals with the same spec NiMH ones? will the power tools charger be able to recharge the new battery type I wonder? Could you even go for Li-ion?
drcustom (author)  ömustafa3 years ago
It's definitely not so obvious...I have to go back and reference info from time to time.  I think there's also some misinformation out there. If you do not have a strong understanding of the positive/negative aspects of each battery type then I would strongly recommend replicating the exact specifications of the batteries you are replacing.  In most (but not all) situations, if the same type and all specs are the same just with a higher capacity (ie, greater mAh) then you can sleep at night and will have the added benefit of longer run times.   For example, if your drill lasts for an hour using 1200mAh batteries, the same spec'd batteries with 2400mAh will last 2 hours...they will also take 2x as long to charge.  Here's a VERY short list of my thoughts on battery types:

NiCd - Really ideal for power tools.  They take a beating and keep on going, and they're cheap.  If I used the drill more or for heavy duty use I'd have went with these, but I didn't want to loose another good battery pack to dendrite crystals.  I was willing to give up a little 'ooomph' for longer runtimes.

NiMH - Not ideal for most power tools.  Still, I made an educated decision and selected these because I wanted a lighter duty drill that will last longer with a full charge.  With that said, your application may differ and if I used this drill more I would have went with NiCd.  Probably the biggest thing to watch out for is your charger...compared to NiCd these batteries NEED a slow charge.  I have a trickle charger so it wasn't an issue, but not all NiCd chargers will work!  (Although I infrequently miss the extra punch in the NiCd's had, the NiMh's still get my small jobs done. For example, I sometimes think that it might get bogged down when doing something like drilling a 3/8" hole through a 2x4, but it manages to get through, just slower than it would with NiCd batteries).

LiIon -I would not use these as a power tool battery.  The deal-breaker is that they're just not safe in a high-discharge and/or rugged environment.  Great for low voltage and long term a watch battery.  With that said, there are exceptions (ie, LiFePO4) which are more ideal for power tools, but for the price they just don't hold much juice.  I'm not sure offhand how much of a punch they pack but my hunch is that they're less than NiMh...though you'd want to look it up to be sure.

Having said all that, I'm sure that most power tools are built/designed with a certain battery type in mind.  It's an "experiment at your own risk" situation unless you are fairly certain about the details.  As always, Google can tell you more than you ever dreamed possible (it's the ultimate rabbit hole).
hoosierray3 years ago
Ok, sorry for my last comment...I hadn't read on! Bravo writer, my foot is in my mouth!
hoosierray3 years ago
Very important to know that you should NEVER solder a connector directly to a cell, they should only be SPOT-WELDED. Too much heat directly on the cell will certainly limit capacity, and stands a minimal (but not negligible) chance to actually explode.

This is an adequate step-by-step for using the "with Tabs" cells the writer referred to. If you just have the cells sans tabs, here are a couple tips:

1. Use the lowest possible setting for your soldering iron...just barely melt the solder and use FLUX!

2. Try using non-braided wire (around 16ga) instead of tabs to connect each cell to one another.

3. Use a rotary tool to lightly scuff the surface of the cells and also the surface of your connecting material.

4. Don't mix old cells with new cells; your battery is only as good as its weakest cell!

Source: Built and repaired batteries(especially drill packs) for over 4 years for major retail company.
GEOD9983 years ago
great info-I have a remmington beard trimmer that I'm gonna do this procedure to-Its not the price of the replacement trimmer,its just hard to find one I really like.Now that I'm accusomed to this beauty-I aint letting her go-lol
zipperboy4 years ago
NIce job
GoodRubbish4 years ago