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Charging NIMH batteries with NiCad charger?

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kidthorazine

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I have a dremel that uses nicad batteries but their pretty much dead. I can replace them with some NiMH rechargable batteries but the only way to recharge them is by using the dremel nicad charger. Can I use the dremel charger to recharge the NiMH batteries?:confused:
 
Can I use the dremel charger to recharge the NiMH batteries?

It is not perfect, but it will work reasonably well.
Just be sure not to leave them on charge for extended periods once the batteries are charged.

JimB
 
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a Ni-MH battery the same size and weight of an old Ni-cad battery has about 4 times the capacity so it will take 4 times as long to chrge with the same charger.

A Ni-MH battery should never be "trickle charged" like Ni-Cad batteries were. So a Ni-MH battery must have the charging turned off when it is fully charged which is usually done with a battery charger IC. How do you know when it is fully charged? When it is still charging and begins to get very hot.
 
What about the fact that the current discharge ability of Nimh is a fraction of NiCad, and that power tools are hi demand applications? You'll get drastically less torque due to the limited current sourcing ability of NiMH over Nicad, and lifespan from the larger pack will actually be lower overall because of it's internal resistance under load and the damage the heat in the cell will cause.

Why don't you just replace them with new NiCad's? Sanyo still cells a full line of NiCad's from sites such as Digikey.

You'll find many power tools run from NiCad's and recently Lithium cells as protection/management chips have become incidental in cost. Good luck finding a NiMH based power tool! They're not used for a reason.
 
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I do not have the battery expertise but I have done and heard a few things that I can share. I was once told that they would not fully charge because they need more kick at the end that Ni-Cad chargers do not offer. They should reach about 90%.

What I have done is to swap out the Ni-Cads for NiMh in my cordless phone. I still get almost two hours of chat time which is pretty close to before. I have had them in the phone for about 6 years now with no noticeable degradation. I also use them in my wireless mouse and keyboard and they out last the alkalines I had in there but I do charge them with a proper charger.

I say try it but watch the heat that audioguru mentioned when you first try it. Worse case it doesn't work and you have to get Ni-Cads and do the surgery again.

Mike D.
 
I was once told that they would not fully charge because they need more kick at the end that Ni-Cad chargers do not offer. They should reach about 90%.
No.
Ni-MH cells have more capacity so for a full charge they should charge at the same current as a Ni-Cad for 4 times longer or charge for the same amount of time at a current that is 4 times higher. No "kick".

If your Ni-MH cell has a charge that lasts for the same duration as a Ni-Cad cell then the charger is simply a timer that charges both types of cells with the same current.

A Ni-Cad cell actually gets cooler as it charges. A Ni-MH cell warms a little as it charges. Test their temperature by charging both at the same time. Both get much hotter when over-charging.
 
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I got that tidbit from a co-worker that majored in batteries in his EE program. I can not swear to anything just passing what I heard. I suppose we could ask Eveready :)
 
Good luck finding a NiMH based power tool! They're not used for a reason.
Apparrently not so. Looks like tons of them are using NI-MH.

https://www.all-battery.com/blackco...h.aspx?zmam=55942680&zmas=1&zmac=4&zmap=60501

**broken link removed**

https://panasonic.factoryoutletstore.com/details/1446/panasonic-ey9210b.html?cid=42130&chid=400

**broken link removed**

**broken link removed**

**broken link removed**

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https://www.bizrate.com/search__keyword--nimh+in+power+tools__start--30.html
 
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I got that tidbit from a co-worker that majored in batteries in his EE program. I can not swear to anything just passing what I heard. I suppose we could ask Eveready :)
Eveready is now called Energizer. They have a Ni-MH Battery Applications Manual on Energizer's website but it is 11 years old. In those days a Ni-MH cell had a capacity that was only 40% more than a Ni-Cad cell but recently their capacity is 4 times more.
They charge almost the same except the higher capacity needs more time or more current current for a full charge as I said.

Energizer also has (had?) a Ni-Cad Applications Manual on their website.
 
Eveready is now called Energizer. They have a Ni-MH Battery Applications Manual on Energizer's website but it is 11 years old. In those days a Ni-MH cell had a capacity that was only 40% more than a Ni-Cad cell but recently their capacity is 4 times more.
I thought it was less: I know the AA NI-MH are in the 2000 - 2500 mA-Hr range and I know there are AA NI-Cads at least 1200 mA-hr because I got some of those a number of years back. I know NI-MH is better but I didn't think it was 4X (?)
 
I have been wondering about the same thing of replacing the Ni Cads cells in my cordless drills with NiMH cells.

I am aware of the lesser C rates but the way I figured it if my Ni Cads were 1800 ma/hr 10C rated and the new NiMH cells are 6000 Ma/hr rated 3C the end amp capacity is still 18 amps each.

As far as charging goes I figured I would just be replace the charge control IC in the stock chargers with ones designed for multi cell chemistry instead.

Just my theory at this point.
 
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I have some old Energizer and Dynacharge Ni-Cad AA cells in a bag in my garage waiting for disposal in the Hazzardous Waste pile at the dump. I also have many Ni-Cad AA cells from Chinese solar garden lights. They have a capacity from 350mAh to 600mAh.
I have many older Energizer Ni-MH AA cells rated at 2500mAh (the kind that hold a charge only for a few weeks.
I also have some new Energizer Ni-MH AA cells rated at 2000mAh that hold a charge for 6 months.

Here is from Energizer's datasheets:
 
I have some old Energizer and Dynacharge Ni-Cad AA cells in a bag in my garage waiting for disposal in the Hazzardous Waste pile at the dump. I also have many Ni-Cad AA cells from Chinese solar garden lights. They have a capacity from 350mAh to 600mAh.
I have many older Energizer Ni-MH AA cells rated at 2500mAh (the kind that hold a charge only for a few weeks.
I also have some new Energizer Ni-MH AA cells rated at 2000mAh that hold a charge for 6 months.

Here is from Energizer's datasheets:
But the better NI-CAD AA cells are rated about 1100 mA-hr and do a bit more than that. I have a set I used in my handheld TV device.

https://www.amazon.com/1-2V-1100MA-NiCd-Sanyo-Panasonic/dp/B000E8HKJM
 
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tcmtech, that's where things get a bit sketchy, because much of the change in modern NiMh's has come from drastic changes in internal structure and the materials it's made out of as they've gotten better over the years, the cell chemistry itself isn't much changed just how it's put together physically.

It's like a marine lead acid vs a starter battery lead acid, the chemistry is the same (more or less) the biggest change is in the plate shape and layout where marine batteries go for thicker plates with low surface area for durability and starter batteries maximize current draw my using meshed plates to provide a lot more surface area.

I'd skip NiMh altogether and jump right on the Lithium battery bandwagon if you can.
 
I would rather stay with the NiMH concept being they are exact physical drop in for the sub C size NiCads.
Lithium don't come in sub C cell size, does not work well in cold temps and needs a monitoring circuit because can not be ran flat dead without damage where as NiMH can.

Mostly I am just getting tired of these high priced name brand cordless drill battery packs that cant go 6 months without dieing. I have some old 18 volt craftsman cordless drills that had the original packs run for about 10 years of abusive treatment before they started acting like the new ones do after 6 months of regular use. :mad:
 
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