To recharge or not...

August 29, 2005 6:39 AM

Are rechargeable NiMH batteries a good idea?

Due to the recent addition of a miniature person to our family we have a need for power for ringing and singing things for him to swing in and smile at.

I can see that this will get to be expensive and not so environmentally friendly soon and have started thinking about rechargeable batteries. It turns out that they are expensive though and before I shell out $50 for a charger and some batteries I wanted to get some opinions about them.
Do they last as long as a regular battery between each charge? What is the real lifetime expectancy?
I would hate to invest in them and find that they only last 20 minutes and then stop recharging after a month.

posted by GrumpyMonkey to home & garden (27 comments total)

NIMH batteries really shine in high-drain devices, such as digital cameras. On a lower-drain device you may find that battery life is about the same or maybe even lower than an alkaline battery, which holds its charge a lot longer than NIMH.

NIMH's should be recharged with a "smart" recharger that automatically cuts the charging down to a trickle after the batteries are fully charged. They should also be periodically drained of all charge before recharging. Some high-quality chargers will do this for you. I have a charger and batteries from Powerex which are excellent. As long as you take these measures your batteries should last for some time.

Over an extended period you will probably save a fair amount of money, but you will also spend a fair amount of time charging batteries. Whether or not this is worthwhile is up to you.
posted by selfnoise at 6:45 AM on August 29, 2005

I've been using the store-bought Eveready NiMH batteries and charger for almost three years now. Same set of batteries and same charger (use them exclusively in a digital camera). I'd highly recommend them just in terms of savings and eco-friendliness. I'm not aware of any issues from an electrical standpoint.
posted by KevinSkomsvold at 6:45 AM on August 29, 2005

I've had very very good experiences with them over the last 5 years or so. Sometimes you'll run into a single battery that doesn't want to hold a charge, but that's very very rare.
posted by bshort at 6:46 AM on August 29, 2005

Sounds like a good idea to me. I used to use Energizer Rechargables (Amazon link) in my Fuji FinePix 2600 digital camera and would actually get more life out of the NiMH batteries than the standard throwaways. I used that camera for two years and never had any issues with the batteries losing life. Now, I'm not sure how green Energizers are, so that might be worth looking into if it's a concern.
posted by bwilms at 6:50 AM on August 29, 2005

NiMH batteries work best on "high-drain" devices -- like motorized toys. While each charge won't last as long as the life of an alkaline battery (lasting maybe 80% as long), they may be recharged upto 2,000 times, making their per-use cost dramagically lower than regular batteries.

Make sure you buy a "smart" charger. These have a chip in them to make sure that the batteries are charged in a way that protects their life and capacity -- due to a phenomenon called cell memory, NiCd and NiMh batteries should be charged to full capacity and then completely drained before recharging. A smart charger ensures that this happens, automatically.
posted by curtm at 6:52 AM on August 29, 2005

Unless you need the greater raw power of Li-Ions, Nickel Metal Hydride batteries offer nearly as much power, can recharge very quickly, and are generally much cheaper than Li-Ions. They claim "1000x as long" as regular Alkalines, taking recharging into consideration. $50 for charger/batteries is highway robbery, unless you're talking about a couple dozen batteries. See my link.
posted by Civil_Disobedient at 6:58 AM on August 29, 2005

Just to make this clear, NIMHs will last LONGER in high-drain devices, but probably LESS time in low-drain devices (before having to be recharged).

I've heard reports of NIMHs lasting between 500 and 1000 charges before performance degrades significantly. This is if you condition them properly, which has been described upthread.
posted by selfnoise at 7:01 AM on August 29, 2005

This is if you condition them properly, which has been described upthread.

This is slightly misleading. Unlike NiCd batteries, NiMH do not generally require "conditioning" -- that is, for typical usage. If you're constantly running them down and charging them up (for instance, if you used them in a camera flash unit) you might need to drain them down completely every once in a while. But for normal use, like in a CD player, a remote control, a clock, a toy, etc., it is not necessary.

People tend to confuse NiCd's with NiMH's in regards to the "memory" effect.
posted by Civil_Disobedient at 7:04 AM on August 29, 2005

Ah, ok. I've only used them in my battery-devouring digital camera.
posted by selfnoise at 7:11 AM on August 29, 2005

I use NiMH batteries in a CD player that I use on the way to and from work everyday. I can usually go about a month before they require recharging and then I just plug it in overnight and its done by the morning. I find the batteries are fantastic for what I need them for and recommend them to people all the time.
posted by LunaticFringe at 8:22 AM on August 29, 2005

As a parent, I have lots of ringing things, and you will be praying for those batteries to die so you don't have to hear them anymore.

Your kids will get so many toys that you may forget which ones have rechargeables. Also, a lot of the battery compartments are hard to get to and secured with screws, so you aren't really that excited to change batteries all that often.

With my kids (1,3,8,9) often the novelty of the toy wears off before the factory supplied batteries die, making changing them unneccessary.

We find that buying a bulk pack of cheap AA batteries and using those saves me the hassle of having my kids accidentally throw away my rechargeables.
posted by quibx at 8:27 AM on August 29, 2005

As a parent of a 1 1/2 year old, the rechargeables are a godsend. Period, end of story.

I also do a bit of photography with some Canon 420 and 550ex flashes, the rechargeables are quite nice on that front also.
posted by neilkod at 8:39 AM on August 29, 2005

Right now I am just thinking about things like swings and the like. He is only 3 weeks old so we have not gotten to the point where he can get bored of toys. It mostly just shocked me how much a pack of D batteries costs...

Thanks for all the advice though.
posted by GrumpyMonkey at 8:39 AM on August 29, 2005

NiMH are 1.2V rather than 1.5V. This means that some toys may move more sluggishly and/or some devices give "low battery" warnings for most of the life of the battery.

As has been said, their capacity (a good AA should be at least 2000mAh=2Ah) is greater than that of alkalines so they last noticeabley longer in high-drain devices (motorized toys, cameras).

However, NiMH lose their charge rapidly if left sitting on the shelf - a couple of weeks will drop their capacity by about a third and then they will degrade more slowly after the initial fortnight, but still much much faster than alkaline. Of course, a discharge/recharge cycle will bring them to full capacity again.

As a side-note, battery capacity is usually measured in Ah (amp-hours) - multiply the current you're drawing from the cell by the time you're drawing it before the voltage becomes unacceptably low. 2Ah means you can draw 2A for one hour. Or 100mA for 20 hours, or some other combination thereof. For alkaline cells, higher discharge rates (over 100mA) reduce the capacity of the cell - you might get 10 hours at 100mA but only 2 hours at 200mA.

I can get 100+ shots from my power-hungry camera on 2Ah NiMH AAs but only 10 from the ultra-expensive alkalines.

You must use a "smart" charger, specifically, a "negative delta-V" charger. Any charger that is based on a timer will be very bad for your batteries - you'll only get a handful of recharges out of them and then they will start failing to hold a charge. You should really also get a charger that has individual cell monitoring, ie it looks at the charge level on every cell independently and stops each when they're done. Cheaper chargers will charge cells in banks of two or four and will damage individual cells that start out a different charge level to the other cells in the bank.

Easy way to check this is to insert a single fully-charged cell - it should start charging and then stop shortly thereafter. If it won't charge except with a friend, the charger doesn't individually monitor. If it doesn't stop within a few minutes (10?), it's not a smart charger.

Yes, these chargers are quite expensive, but they're worth it. An inferior charger will cost you in having to keep buying replacement cells. I have the NiMH batteries I bought in 2002, have recharged each of the 3 sets about 100 times each and they're still at 90%+ capacity. 1000 times may or may not be optimistic - honestly your kid will likely grow up or you'll lose the cells before you need that many charges.
posted by polyglot at 8:40 AM on August 29, 2005

Wow, following the links from the OP's post, it looks like the price of rechargeables went up quite a bit. I bought my Maha smart charger charger from Thomas Distributing and my batteries from Batteryspace at very reasonable prices.

Again, as a parent, gadget geek, and photographer, I received a tremendous ROI on my rechargeables. Now that I think about it, just the use of rechargeables in my GPS paid for the entire system over the last two years.
posted by neilkod at 8:49 AM on August 29, 2005

Do "speed chargers" really work? I followed Civil_Disobedient's link and found 8/15 minute chargers. This seems too good to be true.
posted by autojack at 8:50 AM on August 29, 2005

autojack: yes but they can shorten the life of your batteries. Whether you care or not is up to you. Speed chargers should have temperature monitoring to prevent major damage; most don't. If you put low-capacity and/or cheap cells in one, it may lead to the rapid demise of those cells.
posted by polyglot at 8:57 AM on August 29, 2005

I've been using AAs for like a decade now, in various Walkmen (CD and cassette), portable radios, digital cameras, flashlights and LED-flashers (for night-time bike riding). I don't use any special chargers just the little black things that hold four at a time. NiCad, NiMH, to me no difference. The batteries last for many years, and hold their charge for hours. What'snot to like? How come everybody doesn't? Observing the prices for regular batteries, I just shake my head.
posted by Rash at 9:43 AM on August 29, 2005

The only NiMH batteries I ever had a problem with (and I have and use a lot of them) were Powerex batteries, which I charged with an expensive charger from Thomas. (The charger eventually failed, too.) I have had NO trouble with Energizer or Panasonic NiMH batteries charged with Panasonic or Radio Shack chargers.

I have a music-box thing in my daughter's crib that takes C-cells. I had some NiCad Cs, but they started to fail, so I now use NiMH AAs in size-adapters. They last just as long as the NiCad Cs. (The music-box manufacturer advises against using rechargeables. I have never heard a credible reason for that advice.)

My understanding is that the storage loss of charge is the same for NiMH as for NiCad: about 1% per day.
posted by Kirth Gerson at 9:52 AM on August 29, 2005

neilkod, I don't think the prices for batteries have gone up significantly, but I did notice that if you are used to pricing AA batteries for portable electronic devices, the prices of a D sized cell will come as a huge shock.
posted by Good Brain at 9:52 AM on August 29, 2005

I agree with all the above comments - but I'd recommend buying a good pack of rechargables, and have some on-hand ready to swap when old ones need recharging.
I have about 12 AA's and maybe 6 AAA's - they all can be recharged from the same unit, and it's convienient and inexpensive (in the long term) to always have a cadre of fresh batteries around.
posted by itchi23 at 10:26 AM on August 29, 2005

I'll echo the comments: Rechargeable batteries are much better for a lot of purposes, and are clearly more economical and more environmentally friendly. I have never ever had a problem using rechargables (although I've always been worried that the 1.2 V vs 1.5 V thing would cause a problem, it never has). Now, I only use rechargeables, which makes life considerably easier.

I would recommend shelling out some money in advance to get a good charger and good batteries, though. After going through a couple cheap chargers which almost always break-down and take some of your batteries with them, I finally bought the LaCrosse Technologies charger (Amazon.com link). It has the delta-V measurement system, it has tempeture detection; both you need to have on any good charger. More importantly, four features unique to this charger that I love:
1. it treats each battery individually (unlike most chargers that you can use in pairs, but no two batteries are alike so those always suboptimize one of them).
2. you can set the charge rate and thus speed (higher mA's mean shorter charge rates, but higher tempatures for batteries). So, when you have the time, you can charge your batteries gentler and slower, but if you are in a hurry, you can set it to charge your batteries in a couple hours.
3. it has an LCD readout, so you can insert a battery to see it's charge level and it will tell you how many mA's you've been able to charge on the battery. This allows you to quickly weed out faulty batteries, or identify ones that need re-conditioning.
4. It has a test charge feature (specifically to weed out defective batteries), and a conditioning feature.

I strongly recommend it.

For batteries, I would go with the brand names. I've had good experiences with Energizer, Kodak, and have heard good things about Sanyo. The ones I've had trouble with have always been JetCells and Powerex's. Powerex batteries always get good reviews in battery tests, but I think the quality just varies too much from one battery to the other, and thus it's not as reliable...
posted by tuxster at 10:47 AM on August 29, 2005 [1 favorite]

Forgot to mention: The LaCross charger looks expensive, but it comes with 4 AA and 4 AAA batteries (decent quality), a carrying case, and battery adapters to convert 4AA's to either 4C's or 4D's. Those adapters are essentially plastic casings that go around a AA battery to allow it to fit into a device that requires C or D batteries. Very useful. However, note that you cannot use both of them simultaneously (the C's have to be used to put the battery into the D casings, so you can use either C or D), and also since you only use AA capacity they will not last nearly as long as an actual D battery. But it gives you a lot of flexibility...
posted by tuxster at 10:50 AM on August 29, 2005

There exist tools to recharge non-rechargeable batteries.
posted by Araucaria at 4:27 PM on August 29, 2005

I have had great luck with NIMH batteries, especially the AAA variety. I always let them go completely dead before recharging and my biggest problem has been losing them.
posted by jben524 at 5:17 PM on August 29, 2005

You can buy rechargeable alkalines. What they don't tell you is that those are the same alkalines you always buy, it's just that the charger is a new variety that lets you recharge alkalines without overheating them and causing them to explode all over the place. So you don't have to buy special batteries, you can just recharge the ones you already have. They will wear out before NiMHs do (I seem to remember that you'll only get something like 90% of the previous capacity with each new charge) but for toys with motors and the like, they will probably last longer for the first few charges than NiMH would. So this is an interesting middle ground between throwing away your alkalines and going NiMH rechargeable. It saves you money compared to throwing them away, yet if the kids do accidentally throw out the batteries, they haven't thrown away $20 and a bunch of metals you don't really want to throw in the trash anyway.
posted by kindall at 7:49 PM on August 29, 2005

for toys with motors and the like, they will probably last longer for the first few charges than NiMH would
Apparently not. NiMH batteries actually hold more charge than new alkalines. And if the alkalines lose 10% each time you recharge them, they'd quickly become useless.

Switch over to NiMH completely, and retrain the kids to give you back the depleted batteries (or to put them in the charger, if the kids are old enough).

I no longer use AA and AAA size alkalines at all. For emergency devices where I don't want to worry that the storage loss-of-charge might mean they won't work when I need them, I use Lithium batteries.
posted by Kirth Gerson at 12:46 AM on August 30, 2005