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Ni-MH Rechargeable Batteries -- Reduced Capacity and General Charging Questions
Greetings DPReview!.

I have a few questions about Ni-MH batteries in general and I decided the camera forums would be the best place to find people who use all types. Official websites always say "you should NEVER use a non (our brand) charger or battery with etc." while trickles from various forums and posts say "it really doesn't matter.." There's no current FAQ I could find, and I'm thinking chargers have gotten smarter (maybe), batteries are made better now (maybe).. ? .. So I'm asking..

1. Can different "Ni-MH" chargers be used interchangeably with differently branded Ni-MH batteries? I now have AA/AAA Ni-MH chargers by Rayovac, Panasonic, Sanyo, and Duracell...

2. If I end up with a handful of mAh 2700, 2400, 2000, 1800, etc. AA batteries can these go in the same charger at the same time? The Duracell 2700 and 2400 mAh batteries are packaged with the same model number charger, but I'm wondering if intermixing ratings is bad..

3. Is it a bad idea to put differently rated Ni-MH rechargeables in the same *device* at the same time?.

Why I got so many batteries? Unfortunately my earlier sets of Ni-MH batteries all looked too much like regular Alkalines, and family members occasionally got hold of them, discovered they were "dead", and threw them away thinking they were just regular disposables. So now I have a mix and match variety and it's getting harder to make them practical with all these different chargers and different ratings.. Thankfully they're starting to come out with much crazier looking colorful labels (I particularly like the "eneloop" white Sanyo labels for this reason)..

And finally, before I buy a new set:.

4. Is there a reason the Ni-MH battery capacities seem to be going down lately? Duracell and Sanyo both sell Ni-MH batteries in big packs at warehouse clubs, and recently I noticed the "NEW" batteries replacing the earlier sets all have reduced mAh capacities. This trend also showed up over at Best Buy where the batteries in the Duracell slot went from (approx) 2700mAh to 2400mAh and the Sanyo product is totally different now at 2000mAh, and I've seen 2700 mAh AA's there in the past. New labels on the Duracell batteries but they're in the same slot, same product description, same SKU and price.. The Sanyo website no longer even lists 2700 mAh AA batteries. They stop at 2500 in the industrial TwiCell category and the "eneloop" consumer line stops at 2000 mAh..

Best sounding answer I could get (any answer other than "uh...") when I asked at Best Buy was that the higher capacity NiMH AA batteries were getting "too hot" in some cameras and causing problems with sensitive digital equipment. So there was a general stepping-down to more manageable capacities. So is that just a whole bunch of standard retailer-honesty or is it actually true? I thought at first it was another sell less for the same price tactic.. Anybody know?.

Thanks!.

-Richie..

Comments (7)

Armed With A Banana wrote:.

Greetings DPReview!.

I have a few questions about Ni-MH batteries in general and I decidedthe camera forums would be the best place to find people who use alltypes. Official websites always say "you should NEVER use a non (ourbrand) charger or battery with etc." while trickles from variousforums and posts say "it really doesn't matter.." There's no currentFAQ I could find, and I'm thinking chargers have gotten smarter(maybe), batteries are made better now (maybe).. ? .. So I'm asking..

1. Can different "Ni-MH" chargers be used interchangeably withdifferently branded Ni-MH batteries? I now have AA/AAA Ni-MH chargersby Rayovac, Panasonic, Sanyo, and Duracell...

Nimh chemistry is mostly the same. there isn't alot of magic and the world will not end when you put a sanyo cell in a panasonic charger..

2. If I end up with a handful of mAh 2700, 2400, 2000, 1800, etc. AAbatteries can these go in the same charger at the same time? TheDuracell 2700 and 2400 mAh batteries are packaged with the same modelnumber charger, but I'm wondering if intermixing ratings is bad..

Depends on whether the charger is smart enough to monitor individual cells. there isn't much difference between the 2400 & 2700. In most cases, you want to NOT fast charge those high capacity small AAs.

3. Is it a bad idea to put differently rated Ni-MH rechargeables inthe same *device* at the same time?.

Not fatal but you're wasting electrons .

Why I got so many batteries? Unfortunately my earlier sets of Ni-MHbatteries all looked too much like regular Alkalines, and familymembers occasionally got hold of them, discovered they were "dead",and threw them away thinking they were just regular disposables. Sonow I have a mix and match variety and it's getting harder to makethem practical with all these different chargers and differentratings.. Thankfully they're starting to come out with much crazierlooking colorful labels (I particularly like the "eneloop" whiteSanyo labels for this reason)..

And finally, before I buy a new set:.

4. Is there a reason the Ni-MH battery capacities seem to be goingdown lately? Duracell and Sanyo both sell Ni-MH batteries in bigpacks at warehouse clubs, and recently I noticed the "NEW" batteriesreplacing the earlier sets all have reduced mAh capacities. Thistrend also showed up over at Best Buy where the batteries in theDuracell slot went from (approx) 2700mAh to 2400mAh and the Sanyoproduct is totally different now at 2000mAh, and I've seen 2700 mAhAA's there in the past. New labels on the Duracell batteries butthey're in the same slot, same product description, same SKU andprice.. The Sanyo website no longer even lists 2700 mAh AA batteries.They stop at 2500 in the industrial TwiCell category and the"eneloop" consumer line stops at 2000 mAh..

Those very high capacity batteries were sensitive to charging profiles and it was easy to ruin them by aggressive charging. also, they tended to have high discharge resistance which heated them up which is not good. again, no free lunch, you can't continue to pack mA into a AA size shell w/o losing something in the deal. until there is a significant breakthrough in chemistry, thats how it is. the lithiums provide much higher energy density..

Best sounding answer I could get (any answer other than "uh...") whenI asked at Best Buy was that the higher capacity NiMH AA batterieswere getting "too hot" in some cameras and causing problems withsensitive digital equipment. So there was a general stepping-down tomore manageable capacities. So is that just a whole bunch of standardretailer-honesty or is it actually true? I thought at first it wasanother sell less for the same price tactic.. Anybody know?.

Thanks!.

-Richie..

Comment #1

Let me say first that I have no scientific proof, hard evidence etc. but I have been charging my new RAYOVAC Hybrids in my Energizer charger for the last 6 months and have had no problems with charging..

They hold their charge, they do not get any warmer when charging than the Energizers did etc. BTW the Hybrids are rated at 2100 and are working fine in my cameras and other electronic devices. I've even used them at times in my SB-800 when my battery pack died and I needed to finish a job..

What I have found is: Hybrids hold their charge longer. How much longer? Again no hard scientific evidence, but I can take them off charge (when finished charging) put them in my camera (Fuji S3, or Nikon D300) come back a week later and still have about a 98% charge according to the battery meter in the D300; and shoot about 450 RAW images in the S-3 before I see a drop in the battery icon. My normal NiMHs would have already lost at least 50% of their charge if not used right away. These batteries are in sets and average between 6 mos to a year old. Granted they do loose the capacity to recharge and hold a charge after a period of time, but my Hybrids are still acting like they just came from being opened from the package..

I have no knowledge as to why there is a drop in the amps by the manufactures. I also think the camera manufactures would have issued warnings, advisories etc. if there were problems with batteries and high amps and their products. It could be the typical answer you get now adays from some sales people when they don't know; instead of doing some research...

Comment #2

It is not that the capacities of the AA batteries are going down, it that there are 2 types. there used to be only the nimh, now there is the nimh lowdischarge type as well..

I use maha nimh for a lot of yrs. up the the 2500 size. but the problem was that in 10days or 2 weeks the camera would not take a shot the bateries were dead. oh, they worked fine after a charge but they would go flat in a short time. I have switched to the maha imedion lowdischarge type and am far happier. they do not go flat in 2 weeks.

The imedions are rated at 2100 against the regular 2500. yet the imedion seem stronger, I can take more pics per chage..

Maha states that any of their chargers can be used with the imedion batteries. I highly recoimmend them. I would never consider mixing a lowdischarge and regular nimh in the same camera or group of batteries. I simply bought 4 sets of imedions and put my others away. I have not gone back to the regular nimh...

Comment #3

Thanks these are good answers, you guys were fast. Lots of info...

Hybrid NiMH and "Low Self Discharge" were the killer keywords to search for. I had no idea the batteries were this much improved. It seems like a pretty significant advance in rechargeables, I'm surprised I hadn't heard about it.. I'm so used to the idea that rechargeable batteries are pretty pathetic and now people are raving about the new "replacement for Alkaline"..

The vague marketing makes it kind of difficult. Rayovac calls them "Hybrids" and Duracell throws in "Exclusive Active Charge Technology", Panasonic says their new super-batteries are using "Advanced INFINIUM Technology" all making it sound like they're the only ones doing it.. Then the SANYO eneloop comes with little C and D cell adapters and mention "high output" and the ready-to-use status, but the battery is more like a concept than a battery, emphasizing fresh air and clean design rather than the change in technology. Underneath it they are apparently all using the same LSD NiMH batteries. It just comes across as all so much hype on the same old NiMH they're always saying is "better" anyway but never is. You wouldn't know this is a big improvement on the old rechargeables, you just think why are they selling lower capacity batteries now...

The missing extra few mAh was apparently mostly necessary to cover for the fact Ni-MH batteries died so much quicker and more frequently before. And the overcapacity did also make them run hotter. Now it's not necessary to compensate so 2000mAh is a comfortable safe number..

So anyway yeah now Costco has to open again so I can go get some....

Comment #4

This has been answered, but I will give my 2 cents:.

Armed With A Banana wrote:.

1. Can different "Ni-MH" chargers be used interchangeably withdifferently branded Ni-MH batteries? I now have AA/AAA Ni-MH chargersby Rayovac, Panasonic, Sanyo, and Duracell...

Of course you can but it is best to keep them matched because different brand can have differnece discharge characteristics and you can see to a lessor degree what I mention in Q3..

2. If I end up with a handful of mAh 2700, 2400, 2000, 1800, etc. AAbatteries can these go in the same charger at the same time? TheDuracell 2700 and 2400 mAh batteries are packaged with the same modelnumber charger, but I'm wondering if intermixing ratings is bad..

As stated before this depends on the charger. if the charges working in pairs make sure each pair is a match..

3. Is it a bad idea to put differently rated Ni-MH rechargeables inthe same *device* at the same time?.

YES, this can be bad. what happens is the lower rated battery will discharge quicker and the higher capacity battery(s) will continure to force the lower rated bateries to discharge further until they to the point they become unrecoverable. AFAIK this is true for any rechargable battery..

Ill give you another tip that has worked serveral times for me. may times especially with high capacity NiMH you can get what appears to be a broken battery(it wont charge). this usually happens when they have not been used for an extended time. you can take two fully charged batteries and but then together in series. connect this pair with the same polarity to the 'dead' battery. do this once or twice for no longer that one second.

I have fully recovered several batteries in this way...

Comment #5

I disagree w/ the answer in Q3..

When the lower capacity battery bottoms out, it's voltage will go low to something like 0.9-1.0v. The higher capacity battery won't 'force' anything because ultimately, the device in question looks at the aggregate voltage and that is getting pretty low assuming that the batteries are moderately close in capacity. If the batteries are wildly off incapacity, then no, that'd be a problem...

Comment #6

You dont have to agree, but I understand that this is a common occurance in all rechargable batteries. the lower capacity battery loses power before the higher one. the higher one will then push current thought the weaker battery. this current will cause a build up on the electrodes eventually causing a shorted cell and a toasted battery. this is basically simular to an electroplating process. you have two conductive plates with electolyte solution in between, when you put current though the system you get plating.

However, dont take my word for it do a google seach and find out for yourself..

Howard Moftich wrote:.

I disagree w/ the answer in Q3..

When the lower capacity battery bottoms out, it's voltage will go lowto something like 0.9-1.0v. The higher capacity battery won't'force' anything because ultimately, the device in question looks atthe aggregate voltage and that is getting pretty low assuming thatthe batteries are moderately close in capacity. If the batteries arewildly off incapacity, then no, that'd be a problem...

Comment #7

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This question was taken from a support group/message board and re-posted here so others can learn from it.

 

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