small AA/AAA battery technology

lamplight · May 2008

recently read an article in my gaim catalog about accu batteries, and how these rechargeable batts have a self discharge of only 2% vs the 20% of standard nimh rechargables.

this lead me to find online that many brands have a line of rechargeables out lablled ACCU somewhwre in the title. (this may be old news but i found it interesting)

then I came across this interesting page:
http://users.tpg.com.au/users/p8king/news0201.htm

(scroll down, he starts talking about batteries) which discusses recharging standard alkaline batteries successfully from 10-15 times with the charger linked to on the page. this appeals to me for a number of items around the house that might stay in the device for years: thermostat: outsite temp monitor: fire alarms, etc...

Im wondering if anyone has tried one of these alkaline chargers , and/or if you can shed any light on what charging algorithm they might be using.... ie: im wondering if i could charge an alkaline in my nicad/nimh charger.

since most of of in dealing with our lead acid batteries know how important the charger quality is, im curious as to these small batts. i know that i usually use nimh AA's for my mp3 player and while they have more juice and last longer on a charge than the nicad's, the annoying thing is i have to recharge them all the time as sitting on the shelf they drop quickly .

lamplight · May 2008

Re: small AA/AAA battery technology

found another product, lower price:
http://www.allaboutbatteries.com/Alkaline-charging.html

this sounds goodf, wondering if anyones doing it. apparently just read on another page that iof you pull the batts out before they start getting low you can further extend the battery life with dozens of recharges: contrary to advice for batts used in power tools where they say let it run dry first.

lamplight · May 2008

Re: small AA/AAA battery technology

have found lots of info on this from various sources as ive been searching, just ordered the battery xtender and will report.

BB. · May 2008

Re: small AA/AAA battery technology

I am not sure that recharging Alkaline Batteries is really such a great thing...

As I understand, alkaline batteries go through a chemical change on the anode when the fully discharge/under heavy discharge--which leaves the anode stripped of an active surface for any further charging/discharging to take place...

Even from the Xtender manual (PDF file), you have to pull the batteries from service after only 20% use. Sorry, table does not format well here:

Examples of Battery Usage (battery life in sample device)
Hours of Life Recharge Every Number of Times Extra Life
Hour of Use Recharged
Light - TC Remote Control 48 / 8 / 180 / 15x
Moderate - Flash Light 20 / 4 / 26 / 6x
Severe - RC Vehicles 5 / 1 / 12 / 2x

Basically, in a remote control--you can charge 180x but the battery only lasts 15x its "normal life"--and you have to take the battery out after 8 hours of use (where it would normally last 48 hours of continuous use).

A high load device, "5 hours of use", take out after 1 hour, recharge 12x, but, in the end, the battery only lasted 2x its "normal life". I am not sure that I would care to recharge a battery set 12x rather than just replace it one times with new batteries--would be a pain for most items.

The old generation of Xtender Chargers were well known for not even being able to properly recharge a NiCAD/NiMH battery (may be 25% charge max). And they were known for having lots of batteries leaking during recharging, or the alkaline batteries leaking after being placed in service.

Don't know about the new generation of Xtender.

If you want rechargeable batteries that last longer... Look at NiMH hybrids (Sanyo Eneloops and several other manufacturers too). They support high drain devices (like digital cameras) just as well as normal NiMH batteries.

And while Eneloops (and others) AA cells are only ~2,000 mAHrs in capacity, they have very low self drain (15% over 1 year) versus the 2,500+ mAHr capacity of a standard NiMH which can loose most of its power after just sitting for several months.

In the end, Alkaline batteries have a nasty habit of leaking (more than NiMH and other rechargables), are only good for low drain devices (my experience, devices that last 10-20+ hours on a set of AA alkalines), and can only be recharged if hardly used in the first place. Even the Alkaline Batteries that were "designed for recharging" still had all of the above weaknesses (and, if I recall correctly, were pulled from the market years ago).

All of the above "Alkaline Rechargeable Advantages" have been well exceeded by the new NiMH hybrid cells (high drain, multiple discharge cycles to near zero capacity, don't leak, 85% of capacity after 1 year of storage) and they still can be recharged 500 or more times (over full capacity range).

-Bill

lamplight · May 2008

Re: small AA/AAA battery technology

the eneloops sound good, as do the accu batts i was reading about, similar low self drain and higher amp hours.

still, i figure for the longterm low power devices i mentioned originally, it can only save some money. as i was saying, if i have smoke alarms and thermostats that usually run for 6 mos or 1-2 yrs before being replaced, it wouldnt be to inconvenient to recharge the battery every 6 mos or 1 per year in these examples. each year id save the cost of the new batts, that will pay for the charger in short order as I have a number of low power devices like this. Ive read numerous positive real world reviews and also some contrary articles. one thing the bashers mention is the inability of the charger to charge nicads or nimh's, the 2 chargers on the market i found both specifically mention that you should use the appropriate charger for the appropriate battery, which is the exact same reason you'll get unsafe and unpredictable results charging a nicad/nimh in an alkaline charger. leaking is supposed to be minized with 2 factors: one review i read mentioned certain brands work much better than others for recharging (the original link), and also making sure not to charge a batteryt thats been too discharged. also it might be the inferiority of the charger, i read one reviewer who thought alkaline charging was a waste of time, who mentioned that the xtender charger had this problem the least.

i dont think this is an ideal soluition, we all know there are better , higher power, lower maint, less time wasted battery charging solutions, but fior certain applicationsit can save some $ , especially if i already have all these alkalines.

lamplight · May 2008

Re: small AA/AAA battery technology

the sanyo eneloops recommend their chargers although they say they'll work fine in other nimh chargers. the enelopp specific chargers take very long times to charge: 270mins for a aa. but they say 1000 times recharged, not 500. that is seriously impressive. Bill do you use a eneloop specific charger or not?

lamplight · May 2008

Re: small AA/AAA battery technology

i see where you got some of your numbers, the rayovac hybrids say 500 times or more, and offer an impressive 2100mah, but they say you can use any nimh charger.

i winder if there is anything to using a specialized charger to get up to 1000 charges (as sanyo proclaims re tehir hybrids) or if theres hype in there somewhere.

BB. · May 2008

Re: small AA/AAA battery technology

I bought a couple kits from Costco when they had their introduction sale (8xAA, 4xAAA, some (junk) AA-C and AA-D adapters, and a 4 channel ~6 hour charger with four independent channels). Originally price was $26 for the kit, and was even on sale for $19 per kit.

Costco is now selling a similar kit for $29--but only as 2xAAA and a 4 cell slow battery charger with only 2 channels (so you cannot charge odd number of cells or mixed AA/AAA). Really a shame that they downgraded the charger... They also sell a pack of Eneloops with 6xAA+2xAAA for ~$18 (IIRC).

Sanyo Eneloops do use a normal NiMH charger... The one that came with my kit is a slow ~6 hour, 4 channel charger which means you can charge even or odd number of cells. I have used a good quality 1 hour charger and they work fine on that too.

In theory, NiMH should be charged for 1-2 hours (faster can overheat the cells) or 10+ hour chargers... It is supposed to be difficult for the chargers to catch the voltage depression that signals the end of charge with the 2-10 hours chargers (yes, the Sanyo chargers are 6-7 hour chargers--right in the zone that is supposed to be difficult to terminate properly).

The Xtender is supposed to charge Alkaline, NiCAD, and NiMH batteries...

Recharging Alkaline 9 Volt Transistor Radio batteries (used in my smoke/CO alarms) is not supported by the Xtender. I don't think the Xtender is a good NiMH/NiMH charger.

Regarding 500 vs 1,000 times recharging--I personally believe that the batteries "will age" out in most usages long before they "cycle out" (i.e., 1,000 times once per month is 83 years)... I just don't think the batteries are going to last much more than 5-10 years at best (I don't think I have seen any lifetime tests/results/estimates for NiMH AA batteries--but I would be happy if they lasted more than 3 years)... If a $3 battery lasts 10 cycles, that is $0.30 each--so anything more is gravy ("gravy"="free" for those outside the US).

Regarding getting 15x the life out of the alkaline rechargeables, that is only if you change them 180x... For a smoke alarm (even if I could find a AA smoke alarm), that would be recommended once every 2 months, vs once per year--and I am not sure that I would trust a 6x recharged alkaline (at the end of one year) to be able to operate the heavy load of the siren/emergency light reliably when needed after a year's, or more, worth of recharging. Plus I am not sure a smoke alarm would last with 10x the battery changes before something would break from the flexing.

In the end, using the proper battery for the proper application is important. For high drain stuff (IMHO, things that drain a AA battery in a few hours or less), hybrid NiMH batteries are the way to go--typical digital cameras which will work for hours/100's of shots on NiMH will last minutes/10's of shots on Alkaline (or use Lithium AA non-rechargeable batteries if you are in cold/hot weather, high current, or need 10 year emergency storage--but these batteries are not cheap).

For items where the batteries last 10+ hours for a set of AA's... Then either Alkaline (non-rechargeable) or hybrid NiMH will work fine (along with Lithium AA primary cells--which are also very light weight along with long storage life and a lot more energy per cell).

-Bill

mike95490 · May 2008

Re: small AA/AAA battery technology

In my smoke alarms, I change ordinary 9V Alkalines about every 2 years. They start to chirp after 3 years (low battery alarm). this buysiness "Change Batteries EVERY DST/ST change" is BS. It's a great sound byte for the Fire Departments, but I think they are in cahoots with the battery makers.

Brock · May 2008

Re: small AA/AAA battery technology

I use a LOT of NiMH rechargeables. I really like the Enloop's, I have about 15 different brands and they are by far the most consistent overall. Some have higher "short" amps, some have a higher capacity, but they tend to be inconsistent between cells. The Enloops are almost always the same. When I get a batch of new NiMH's I go through them and sort them with a BC900, which gives your their real capacity. I typically see about 1 in 10 duds or poorly performing on no name brands and about 1 in 20 on brand names and have never seen it on Enloops.

System2 · May 2008

Re: small AA/AAA battery technology

Brock wrote: »

I use a LOT of NiMH rechargeables. I really like the Enloop's, I have about 15 different brands and they are by far the most consistent overall. Some have higher "short" amps, some have a higher capacity, but they tend to be inconsistent between cells. The Enloops are almost always the same. When I get a batch of new NiMH's I go through them and sort them with a BC900, which gives your their real capacity. I typically see about 1 in 10 duds or poorly performing on no name brands and about 1 in 20 on brand names and have never seen it on Enloops.

Very interesting. After personally experiencing repeated new "dud" NiMH batteries and others that appear to go bad sitting on the shelf for a month or so after first working fine, I've given up on them. I've gone back to using use regular Alkaline, or NiCad's. For me the reliability just wasn't there with the NiMH, and found them to be a big waste of money. I was initially very impressed with them, but that didn't last long. And yes, I did use the proper charger.
Perhaps if we could get the Enloop's here, things would have been different.
I've had NiCads in use for, in some cases, over 10 years.
Wayne

BB. · May 2008

Re: small AA/AAA battery technology

If it was not that NiMH have 2-3x the capacity of NiCads and there is no Cadmium in NiMH--NiCads would still be one of the best rechargeable cells out there (don't know now--but decades ago NiCads were used as high end aviation batteries--light, lots of current, and could recharge just as fast).

So far, the Sanyo Eneloops are working well--for me and from what I have read.

-Bill

niel · May 2008

Re: small AA/AAA battery technology

i put my aa's through the worst possible usages you could think of and i expect them to fail within a year or 2 because of it. most times they sit there not being used and no float charge to maintain them. i get a bug up my rump and then press them into service. this is for my handie talkie or ht as many hams call them and this calls for heavy transmit currents and smaller receive currents and goes on for many hours and possibly for a few days too (needing a couple full charges). after that i give a full charge to them and then they sit again until the next time with heavy usage with the possibility of a short time listening to the local police or fire if and when something happens in between.
i won't invest in these new batteries until my other ones are no good and these are fairly new 2500ma nimh in there. this new type sounds promissing for the abuses i give mine though. i usually don't have long waits between charges that they have managed to be depleted of their charges. i would float them, but the radio has a aa pack that is not meant for a recharge voltage as they call them alkaline packs and they make no provision for this charge. i must take all 6 of them out and place them into a charger.
speaking of charging alkalines, please note that standard alkalines have been known to explode when recharged with some chargers. those types of alkalines are meant to be primary batteries or in laymen's terms, throw aways. even if you manage a charge into them they won't be able to be charged many times and lose some capacity with each cycle. to me they aren't worth the time, money, or the risk to charge them up.

System2 · May 2008

Re: small AA/AAA battery technology

niel wrote: »

please note that standard alkalines have been known to explode when recharged with some chargers.

Had some explode years ago, in a portable tape recorder. AC adapter was in use, but seems the battery disconnect switch in the adapter socket failed to disconnect. Around 3:00 AM, I was awakened by a gun shot beside the bed. Turned out to be the battery in the tape machine.
Wayne

icarus · May 2008

Re: small AA/AAA battery technology

The other problem that I have run into with rechargables of many types Nicd, Nimh etc., is the basic battery chemistry produces a charged voltage somewhat lower than that of conventional alkaline batteries. A typical alkaline voltage is ~1.5vdc or a bit higher, while (if memory serves) the voltage of a NiCd is ~1.25vdc. The problem I have had is that even with fully charged cells, in series the reduced voltage is considerable. It took me a long time to figure out why my Grundig radio would quit with low battery warning with "fully charged" batteries in it. 6 aa's @1.5vdc=9.vdc. 6 aa's @ 1.25=7.75vdc, below the threshold of the low battery warning.

I have had other hardware that has had similar problems. I use good rechargables for things that don't care, but still by alkalines for things that do.

Icarus

BB. · May 2008

Re: small AA/AAA battery technology

Generally though, below 1 volt (really 0.9 volts is usually the knee of the curve for both types of batteries) is considered discharged for an Alkaline--So even though a NiMH and such starts at a lower voltage, the discharge voltage is almost flat until the end. Whereas alkaline batteries tend to slope down through their entire life...

Years ago, I had seen (IIRC) a portable transmitter / walkie-talkie type device that used something like 8 cells for NiCad and 6 cells+2 blanks for Alkaline.

Here is a random link (scroll 1/2 way down the page) with representative discharge curves / characteristics of several brands/types of batteries. Also a good picture of how high load current kills alkaline batteries.

-Bill

It really sounds like your radio has the low battery warning set too high... In low drain applications, an alkaline battery with ~1.20 volts (under load) still has almost 50% of its life left.

Does the radio continue to function with the low-bat warning on--or does the audio start to fail...

From my own experience, an alkaline in very low drain application (things that run for days or longer on a set of AA cells) will last quite a bit longer than a AA NiMH (simply more power available at low drain currents).

icarus · May 2008

Re: small AA/AAA battery technology

Bill,

As usual good info,

The grundig just plain shuts off when it gets to the low voltage threshold. I solved it by wiring a 9 volt Makita drill battery to it, so it ran for months!

Tony

PS The grudig was for some reason is famous for having the batteries leak! I don't know why, but I have had three YB 400 radios and all of them have been wrecked by battery leakage! It doesn't just damage the terminals, but it corrodes all the boards causing the radio to go completely haywire. I have been able to keep 1 radio running with the parts from the three. I don't leave batteries in anything if I can help it, but this is (was) crazy! Great little radio however, aside from that problem.

Telco · May 2008

Re: small AA/AAA battery technology

Wow, that explains why my cameras will run for a hundred pics on disposables but just about half that with the rechargeable.

On the Grundig radio, sounds like there might be a little galvanic reaction going on there, accelerated by the power flow. Wonder what metal they use on the battery terminals? Might be worthwhile to change the springs and ends out with one from a different radio.

BB. · May 2008

Re: small AA/AAA battery technology

Looks like I forgot to add the random link (scroll 1/2 way down) showing discharge curves for AA alkaline and NiMH batteries... Fixed here and in the post above.

-Bill

small AA/AAA battery technology

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