Replacing Dremel Minimite NiCd's

[JamisonM]

Last Christmas my uncle gave me one of dremel's cordless minimite rotary tools. Since then I've used it quite a bit and though, its a little underpowered and I can live with this, battery life just plain sucks. So, noticing that there were long round tubes of some kind that looked like AA batteries in the battery pack, I pried it open. Lo and behold, there were four 1.2v AA batteries inside. At first I thought they were NiMH, but after searching up the only bit of information on them, byd d-aa700p, I found out that they were in fact 700mA NiCd batteries. Now, knowing this, do you guys think I could safely replace them with 2500mA NiMH rechargables and have the same performance, but with longer work times?

 

[Gene]

Hi Jamison,
I still have three of those Dremel MiniMites. The #755 4.8V NiCD battery packs have just recently gone south on all three of them, (leaking). The original #755 packs are just about impossible to find anymore and when you do, (E-bay), they want a fortune for them.

If the NiCDs are truly AA size, I don't see why four rechargeable NiMHs wouldn't work. To save me the trouble, how did you pry them apart and when you did, can they be reassembled fairly easily?

I'm thinking replace the NiCDs with rechargeable NiMHs and make the packs to where they reassemble fairly easily so you can recharge them in regular chargers.

Nonetheless, let me know how you disassembled your pack without destroying it. Thanks.

 

[kitelights]

The packs come apart very easily - IIRC, pry the two sides that don't have the tabs on them out a bit and work the two pieces apart. I replaced mine with beefier NiCads instead of NiMH because I wanted to continue to use the standard charger.

Fitting everything back the way it was is critical or it won't work. It's a pretty tight fit in there. The ends of the cells must fit flush against the plastic or the brass spring tabs won't make contact thru the holes.

Let me know if you're interested in selling one of yours. I use mine in my work and I don't like the new ones as well as the old ones.

Two sets of two cells are connected with a welded strap (2 pairs), so it's not like you can take them out and throw them in a conventional charger. And if you were to open the pack that often, you'd stretch it to where it wouldn't stay shut on its own.

 

[Gene]

Hi kitelights,
Thanks for the reply. It was easy as pie to get the old cells out and put new ones in! These are the most user friendly packs I've ever seen. No glue and the pack even snaps back together with the flexible tabs.

I discarded the old cells and just used some thin strips of aluminum sheeting to mate the bottom + and - ends and then taped it all together with electrical tape. Worked like a charm and they run fine.

I'm using Eneloop AAs as I want there to be some charge in the packs when I go to use them. I hope the standard charger will effectively charge the Eneloops.

Oh yeah, PM sent.

 

[JamisonM]

Guys, I apologize for not responding; I thought there were no replies to this thread. I'm glade to see there were.
I eventually got my self some 2500mAh NiMH energizers to replace the original NiCD batteries in it. I got a piece of foam pipe insulation and some copper wire. I took some electrical tape and covered the top of a small square piece of pipe insulation. I laid the copper wire with ends exposed and spread out a bit. On that, I taped them down with electric tape. I even cut little piece of paper with – or + wrote on them and taped them inside to help me remember which end of the battery goes in which compartment. When I need to use the dermal, I'll either have batteries already charged or I'll have to charge some. I got a charger that can charge 4 2700mAh NiMH's in 5 hours. When their done and depending if I already have charged cells already; I just pry the empty pack open with a small philips head driver, insert cells, and snap back together. It's a bit awkward I admit, but it gets the job done and allows me to use the same batteries elsewhere's if needed.
Gene, I can't believe I didn't think about aluminum foil earlier. I tired looking all over for copper sheet metal to connect the batteries, but couldn't find any. Thanks, it works great!

 

[Gene]

Hi Jamison,
Thank you for bringing this whole thing up as I resurrected my old MiniMites because of your thread! Good job on yours. I actually used thicker aluminum than tin foil but as you found out, tin foil works fine also.

 

[JamisonM]

Hi Jamison,
Thank you for bringing this whole thing up as I resurrected my old MiniMites because of your thread! Good job on yours. I actually used thicker aluminum than tin foil but as you found out, tin foil works fine also.

I'm glade you've found this idea useful.

 

[soapy]

Not a Dremel, but I took a 3.6/7.2V PoS "Dremel-a-like" with it's 10 minute run-time from a cheap NiCd pack, and upgraded it to a parallel pair of Li 3.6V rcr18650's. Works for hours now! Sure, it's only half the rated speed but I've not done anything clever with a tap for each battery yet, since it does exactly what I need, and it keeps the recharging simple.

As and when, I'll have it set up with two taps for charging in parallel, and a way to select 3.6V or 7.2V speeds.

The joy of lithium is that the discharge curve is so much flatter that the 3.6V output from this pair of cells is genuinely more powerful than the crappy 7.2V NiCds were!

 

[MrAl]

Hi there,

I replaced the two AA NiCd cells in my little shaver a while back with two
NiMH cells and they lasted about 6 months before they died out.
I had them wired in and taped up, but after they died i got a two cell
battery holder (has two wires coming out for connections) and now i use
that. If the batteries die down i take them out of the holder and pop them
into my 15 minute charger, or use a pair that are already charged.
I usually keep it charged though, with the thing laying in the charger
24 hours a day 7 days a week. It only charges at 90ma.

I have to say though, that once i got the two NiMH cells in there and
charged them up that little shaver buzzed away better than it ever did,
even when it was new. Im glad i did this. It's nice to have a battery
holder too though (you could use a 4 AA cell holder if you like) so you
can pop the cells out to charge or replace in a hurry. With the holder
i can even use alkalines if i want too, you could too in a pinch.

 

[soapy]

If you want a faster shave, use the two 1.5V alkaline batteries. Or use a single Li-ion cell at 3.6V!

 

[JamisonM]

I won't be messing with my shaver anytime soon. If it suddenly decides it wants to die on me though; that's when I'll gut it. I noticed it said it 2.6v NiCad on the back of my shaver. I can only guess it has two AA's in it. I'll have to take a look at the one it replaced. It sits gathering dust on the shelf. I wouldn't mind seeing what it takes. My only problem is find some way to get batteries in and out with having to take apart it every time.

 

[jasonsmaglites]

i use dremel drills for windshield repair, and sometimes i cant drill 3 repairs with my older stock dremel batteries. i wasn't of the mindset to rebuild a pack as im getting lazy in my old age (almost 32) so i found one of the dremels that takes alkaline batteries, think golf tool or pumpkin carver, and instead of popping in alkalines i used rayovak hybrids and wa'laa, this one lasted all day and still going strong. i seriously have 8 dremel batteries in the top of my toolbox and as they die i retire them to the bottom. no longer. and also the old ones would die almost instantly when i used high. the rayovaks kick the dremel ni cads so bad it aint funny. i could hear the old batteries sagging, on low, when i had pressure on a windshield. i am so glad now. im never looking back.

so just try that, get yourself the dremels that hold alkalines but the only down side is you cant recharge them with the dremel charger, so you'll have to open it up and charge them individually. good luck.
jason

 

[JamisonM]

Honestly, I don't really mind not being able to use the factory charger. It's not something I miss. I did buy one of the AA alkaline powered beard trimmers from the local walmart, but wasn't impressed. It seemed weaker and the cutting head was little more then half of the other one. I've only replaced the battery in the other shaver, I think twice, since my last post. The LSD cells really hold a charge. I think the next thing I'll do, if anything, is work out some way that I can replace the battery without having to unscrew and take apart the whole thing.

 

[Eugene]

I put higher capacity cells in my old one but ended up being able to use it longer and burned out the contacts in the switch. I still have the motor and packs thinking someday I'd think of a way to fix it.

 

[JamisonM]

I put higher capacity cells in my old one but ended up being able to use it longer and burned out the contacts in the switch. I still have the motor and packs thinking someday I'd think of a way to fix it.

I'm sorry to hear that. I don't have the knowledge to tell you why exactly the switch burned out, but I'm surprised that just replacing the batteries with higher mAh rated cells resulted in it. Still, sounds like it might make a good weekend project.

 

[Eugene]

my guess is the motor could draw a lot more current than a nicad could source and the switch's metal was pretty thin. So when I swapped to the NiMH the motor could draw more current, it was noticeably more powerful, and it was too much for the thin contacts. I kept it thinking someday I'd use some springs from a normal battery holder to make the pack connection then put in a real switch rather than that slider that moved the battery contacts around which resulted in wear on them as well.

 

[JamisonM]

my guess is the motor could draw a lot more current than a nicad could source and the switch's metal was pretty thin. So when I swapped to the NiMH the motor could draw more current, it was noticeably more powerful, and it was too much for the thin contacts. I kept it thinking someday I'd use some springs from a normal battery holder to make the pack connection then put in a real switch rather than that slider that moved the battery contacts around which resulted in wear on them as well.

I can see that. Then again, they weren't designed for NiMH batteries.

 

[Thuddriver]

Re: Replacing Dremel Minimite 3 hour charger

Has anyone managed to replace/repair the MM 750 3 hour charger? I have 3 of these MM's and a few nights ago while I was trying to charge the battery, the charger warmed up quite a bit after only 2 hours, but no charge to the battery itself. Any idea what's going on and any "fix" for this issue ???

I hate to toss 3 MM's for the lack of a charger.

Regards/THANKS

Frank

 

[Kiss4afrog]

I know it's old but I still am using a Dremel mod.750 with a #755 4.8 volt battery pack that has now bit the dust and want to go with NiMH. I see talk of different chargers but I've also seen that people have used the nicad charger after doing a MiMH transplant and it just takes longer to charge up the higher capacity NiMH batteries. I'd rather use the stock charger, anyone have any problems using the stock original charger with NiMH batteries ??

 

[Gene]

Hi Kiss4afrog,
Wow, this thread has hung on for awhile. Yes, the stock charger will work and as you said, it will take longer to charge the cells. The original stock #755 packs called for charging 3 hours. I would double that with NiMH cells using the stock charger.

With chargers so cheap nowadays, I would look into a charger that works with NiMH cells as it will save you a lot of time and will probably charge the cells to fuller capacity than the stock charger. Also, I would use Eneloop NiMH AA's as once you charge them, they will hold their charge for months.

I'm still using the Eneloop cells I put in my Minimites in 2007 and they're still working great.