Replacing a Ni-Mh battery to AC input?

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Discussion Overview

The discussion revolves around the feasibility of replacing a Ni-MH battery in a cordless drill with an AC power source or an alternative battery solution. Participants explore DIY options, technical challenges, and the practicality of rebuilding battery packs versus purchasing new ones.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant suggests that replacing the battery with a 14.4 VDC power source is possible if it can supply sufficient current, but rebuilding the battery pack may be a more cost-effective solution.
  • Another participant mentions the specific drill model (Makita 6223d) and expresses the need for two battery packs, each costing $75.
  • Some participants discuss the high current draw of cordless drills, especially under load, and the implications of using mains power, which would negate the cordless feature.
  • A suggestion is made to create a portable battery pack using a motorcycle battery or multiple NiMH D cells, along with the need for a suitable charger.
  • Concerns are raised about the complexity of disassembling the battery pack, with one participant noting that it may be sealed and difficult to open.
  • Participants share experiences regarding the challenges of rebuilding battery packs, including the need for soldering and the potential for it being more economical to buy a new drill instead.
  • Some express frustration with the difficulty of accessing the battery pack's interior and suggest various methods for opening it, including using a hot knife or angle grinder.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best approach, with some advocating for rebuilding the battery pack while others suggest that purchasing a new drill may be more practical. The discussion includes multiple competing views on the feasibility and cost-effectiveness of DIY solutions.

Contextual Notes

Participants note the potential challenges in disassembling the battery pack, including the presence of hidden screws and the use of adhesives. There is also uncertainty regarding the current requirements of the drill and the suitability of alternative power sources.

Who May Find This Useful

This discussion may be of interest to individuals considering DIY projects related to power tools, those studying electrical engineering, or anyone looking to understand the complexities of battery replacement and power sourcing in cordless devices.

hermtm2
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Replacing a Ni-Mh battery to AC input?

Hello,

I have a cordless drill which use a 14.4v Mi-MH batter source. The battery does not work anymore. It will costs me $150. Here is my question. Is it possible to replace the power source from the battery to AC adaptor. I mean as a DIY. I have done many DIYs but not with electricity since I am in Electrical Engineering problem.

The school teach me a lot of knowledge which I don't know when I can actually apply to. I would like to have this one as the first project.

Please help me what I need...

Thanks.
 
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You could, if you can find a 14.4 VDC power source capable of sourcing however many amps the drill requires under load. You'd be better off trying to rebuild the battery pack, though. If you can get it open (some are fastened with screws, some are snap-together and others are glued or welded together) you will usually find they are constructed from standard cells, usually sub-C size. Just get new cells of the required number and type and a mAh capacity at least as large as the originals and connect them in the same configuration. If you had to cut the pack case to open it, just glue it back together with epoxy. I've rebuilt a few packs this way; the cells are MUCH cheaper than a new pack.

Also what drill is this? $150 is quite steep, even for a high-end Makita or DeWalt.
 


I have a Makita 6223d. It is a set with a work light which use the same battery pack. I need 2 of them. Each one of the battery is $75. Anyway I will try~.

Thanks.
 


There are also many places which will rebuild packs for you:

http://www.primecell.com/pctools.htm

Personally, I'm a DIY kind of guy but if don't think you can do it, the price is certainly right. Or at least better.
 


Cordless drills draw a lot of current, especially when you are working them hard.
Also, if you power them from the mains power, they are not cordless any more.

So, that would be difficult, but not impossible.

A better solution is to make up a battery pack and attach it to the drill with a short cable.
You would need to get a 12 volt battery from somewhere (like a motor cycle battery) and put it in a box that has a handle on it so you could carry it easily.
You can used the old battery holder as a connector to the drill. Just remove the old batteries and attach the cable to where the batteries used to connect.

You could also get about 10 NiMH (Nickel Metal Hydride) D cells and connect them in series to give you a 12 volt supply. You can get holders for these batteries at electronic stores, but not for 10 at a time. You might need 5 holders with 2 batteries in each.

You would have to arrange a charger, too. This should be one that detects when the battery is fully charged and stops the charging.

Before starting this, get a price on a new drill. It may be cheaper than making up a new battery pack.
 


Basically under heavy torque the current can peak above 20 amps. So unless you can find a suitable switching power supply, the simplest solution it to rebuild the battery pack.
 


huh...

Rebuild not a DIY...

Thanks.
 


I've tried that a few times and it always works out cheaper to get a new drill.

Also, they seem to put them together with strips of stainless steel joining the batteries so you have to silver solder them. Did you find that?
 


I just sas the video on Youtube.
 
  • #10


I can't even find how to disassemble the battery pack. I would like to see inside before it goes to gabage can.
 
  • #11


Probably sealed. You've got nothing to lose by carefully cutting it open along the seam, since it's dead anyway. But first, look under any labels, since manufacturers like to hide screws there.
 
  • #12


There was not the hide one. Also it seals completely.
 
  • #13


Time to break out the hot knife.
 
  • #14


Look for hot glue, too. A hot air gun will melt that OK.

If all else fails, my angle grinder will make short work of most things. Putting it back together afterwards is the hard part.

Even a bit of red-hot nichrome wire will slice neatly through plastic.
 

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