Is it ok to use a NiCad charger for NiMH?

[LEDrock]

I used to have plenty of NiCad batteries and I still have a Nicad charger that charges 4AA overnight. I was satisfied with it, but my Nicads are all expired.

If I buy a package of 4AA Ni MH batteries now, can I use them in my Nicad charger? I'll be specific:

The specs on the charger are: Input AC 120V/60hz 3.0 VA Output DC 2.9V 50ma.

I'm not a techie, but I just wanted to put out that info.

 

[Marduke]

The simple answer is no, NiMH need a different charging algorithm. Your best bet is to get a pack of cells including a 4-channel smart charger. Depending on where you live, that can be quite cheap.

 

[LEDrock]

The simple answer is no, NiMH need a different charging algorithm. Your best bet is to get a pack of cells including a 4-channel smart charger. Depending on where you live, that can be quite cheap.

Thanks, Marduke! I've seen packages in Walmart and Target that have a charger with 2AA and 2AAA or just 4AA (which is probably what I'd get) and include a charger for about $10. I don't know if it's a smart charger or not. I'll have to take another look at them. But it seems like a great price for the batteries AND a charger.

 

[Mr Happy]

You know, a 50 mA charge rate is not going to harm a quality NiMH cell that much if it gets overcharged. However, consider it this way: for a 2000 mAh cell, 50 mA will take 2000 / 50 = 40 hours minimum to charge the cell. You might not want to wait that long!

Also, by way of interest, the 2.9 V spec means it charges cells in pairs and most likely cannot charge one cell individually.

 

[LEDrock]

You know, a 50 mA charge rate is not going to harm a quality NiMH cell that much if it gets overcharged. However, consider it this way: for a 2000 mAh cell, 50 mA will take 2000 / 50 = 40 hours minimum to charge the cell. You might not want to wait that long!

Also, by way of interest, the 2.9 V spec means it charges cells in pairs and most likely cannot charge one cell individually.

You're right! I don't have the instructions for it anymore, but I do remember it saying that 2 have to be charged at a time. Usually that's not a problem. But taking 50 hours to charge is something I didn't know about. I guess NiMH are much higher in capacity than Nicads were. I guess it's time to get a different charger and maybe donate this one to Goodwill (or the garbage company).

 

[Mr Happy]

...for about $10. I don't know if it's a smart charger or not...

Most likely it's not. A package of 4AA with smart charger usually starts at about $20 and up, but you might find one nearer $15 on special or clearance.

If the charger says "overnight" or "12 hours" it most likely is not a smart charger. If it says the output current is 300 mA or higher, or if it charges in less than 6 hours, then it most likely is a smart charger.

I believe there is a Kodak smart charger in Wal-Mart that comes with a set of 4AA Kodak pre-charged cells. You could look out for that, but avoid the Kodak overnight charger that will be next to it on the rack. You might even find Eneloops in Wal-Mart if you are lucky. They have sometimes had a 4AA plus charger set on clearance.

 

[LEDrock]

Most likely it's not. A package of 4AA with smart charger usually starts at about $20 and up, but you might find one nearer $15 on special or clearance.

If the charger says "overnight" or "12 hours" it most likely is not a smart charger. If it says the output current is 300 mA or higher, or if it charges in less than 6 hours, then it most likely is a smart charger.

I believe there is a Kodak smart charger in Wal-Mart that comes with a set of 4AA Kodak pre-charged cells. You could look out for that, but avoid the Kodak overnight charger that will be next to it on the rack. You might even find Eneloops in Wal-Mart if you are lucky. They have sometimes had a 4AA plus charger set on clearance.

I had written in a previous thread about overnight chargers and I think you said that they are on a "timer" and can overcharge the batteries if you charge them before they are fully discharged. Is it wise to use this type of charger if you just make sure to turn the charger off after a certain amount of time?

I'll check out those 2 that you told me about. I'll be at Walmart later today. I just hate to spend more than I must. I'm kinda cheap!

 

[Mr Happy]

It's really not wise to use a timed charger with NiMH. That's why everyone is telling you to avoid them.

"Buy cheap, buy often!"

 

[LEDninja]

Try to get a charger with 4 individual channels (They usually have 4 LEDs one over each bay). Never know if you need to charge 1 or 3 cells.

 

[LEDrock]

Most likely it's not. A package of 4AA with smart charger usually starts at about $20 and up, but you might find one nearer $15 on special or clearance.

If the charger says "overnight" or "12 hours" it most likely is not a smart charger. If it says the output current is 300 mA or higher, or if it charges in less than 6 hours, then it most likely is a smart charger.

I believe there is a Kodak smart charger in Wal-Mart that comes with a set of 4AA Kodak pre-charged cells. You could look out for that, but avoid the Kodak overnight charger that will be next to it on the rack. You might even find Eneloops in Wal-Mart if you are lucky. They have sometimes had a 4AA plus charger set on clearance.

Well, I went to Walmart yesterday and found what you mentioned. It was the Kodak overnight charger with the pre-charged batteries. It was $12.97 and had 4 2100mah batteries and the charger specified 80MA output, making it an overnighter. Model number was K620-PC. I only saw this one and the one next to it with batteries that weren't pre charged. It didn't say anything about being a smart charger, and there weren't any that did. There weren't any Eneloops there etiher. I was in the electronics dept. where the cameras are. I didn't have time to look elsewhere to see if they had chargers in other parts of the store.

 

[Marduke]

WalMart hides Eneloops if they have them. They use to sell a smart charger + 4 AA's for $20 in the same part of the electronics dept that sells DVC tapes and memory cards. The past several months they have been clearing out that charger for $16, so it's worth checking if your walmart has one.


And no, almost no chargers in stores are marketed as being smart or independant channel in any way, simply because Mr. Joe Everybody doesn't have the first clue about such things. WalMart does sell Kodak Precharged, Duracell Precharged made in China and made in Japan (MIJ are Duraloops), and Rayovac Hybrids. There are two common Duracell smart charger, the travel charger which comes bundled with 4 cells (2 cells in Walgreens), and the power gage charger. The giveaway is usually if the charger has 4 seperate indicator lights, with the exception to that rule being Energizer (they only sell 2 smart chargers, but put 4 lights on most of them so they "look" smart).

 

[Bones]

Well, I went to Walmart yesterday and found what you mentioned. It was the Kodak overnight charger with the pre-charged batteries. It was $12.97 and had 4 2100mah batteries and the charger specified 80MA output, making it an overnighter. Model number was K620-PC. I only saw this one and the one next to it with batteries that weren't pre charged. It didn't say anything about being a smart charger, and there weren't any that did. There weren't any Eneloops there etiher. I was in the electronics dept. where the cameras are. I didn't have time to look elsewhere to see if they had chargers in other parts of the store.

According to its specifications (pdf document), this is the type of charger Mr Happy described in his second paragraph.

It has two rather than four channels and, although not specifically stated, is very likely a timer controlled rather than a 'smart' charger.

Its output current is actually 180mA rather than 80mA for AA cells though, but even this slightly higher rate will take quite some time to inflict significant harm to 2100mAh cells.

So, if nothing else is immediately available, it's a better charger than what you have, and it's a way better option than using alkalines.

Just keep watching for a bundle with a smart charger. Once you've tried the low self-discharge cells you'll be shopping for more anyway.

 

[LEDrock]

According to its specifications (pdf document), this is the type of charger Mr Happy described in his second paragraph.

It has two rather than four channels and, although not specifically stated, is very likely a timer controlled rather than a 'smart' charger.

Its output current is actually 180mA rather than 80mA for AA cells though, but even this slightly higher rate will take quite some time to inflict significant harm to 2100mAh cells.

So, if nothing else is immediately available, it's a better charger than what you have, and it's a way better option than using alkalines.

Just keep watching for a bundle with a smart charger. Once you've tried the low self-discharge cells you'll be shopping for more anyway.

It sounds like this might be one I could be happy with. I'm not too picky, but just don't want to regret a purchase. My flashlights aren't too fancy either, with my brightest light being a River Rock 2AA bought at Target, on sale for $10. This might give an indication about my expectations.

 

[Bones]

It sounds like this might be one I could be happy with. I'm not too picky, but just don't want to regret a purchase. My flashlights aren't too fancy either, with my brightest light being a River Rock 2AA bought at Target, on sale for $10. This might give an indication about my expectations.

I doubt you will regret the purchase, the low self-discharge cell really is a milestone advance in the NiMH world.

Insofar as the charger is concerned, I am becoming increasingly convinced that the failure of the whole generation of higher-capacity NiMH cells that preceeded the low self-discharge cells was caused more by lousy cell design and construction than lousy chargers, but a smart charger will still maximize your battery investment over the long term.

 

[Mr Happy]

Consider that the 4 x 2100 mAh AA cells that come with the charger cost $9 in a package by themselves, so you are getting the charger for an additional $4. Even if it is not the best charger in the world, you cannot really complain for that price.

 

[LEDrock]

Consider that the 4 x 2100 mAh AA cells that come with the charger cost $9 in a package by themselves, so you are getting the charger for an additional $4. Even if it is not the best charger in the world, you cannot really complain for that price.

That's true! I'd like to get a smart, or a least a "smarter" charger so these batteries will last longer, but don't do any shopping online. I might start looking in Target and Menards to see if they have any.