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View Full Version : AA batteries self-discharge in just hours?!



liekloo
02-02-2009, 04:06 AM
Hi all,
Thanks for reading! :)

I've been the happy owner of a Canon A510. One thing really disturbs me: my AA NiMH batteries seem to lose their functionality after just a few months and perhaps 10-20 charges (rough guess). After I bought new batteries ... the very same thing happened again! What happens is that after purchase, batteries work fine for some time (hold their charge, give many shots), until one day the camera reports them empty after they were fully charged but left unused for a few hours. I could probably take a hundred shots right after charging but leaving the batteries alone for more than an hour seems to discharge them - in other words my camera is not there when I need it. Funny detail: when put in a recharger with an LCD, the LCD shows them still half-full and charges them to full in a fraction of the normal charge time. Also, these 'empty' batteries can still drive my remote control for a year. What is wrong with my batteries, with my camera, with me?? ;)

Any help would be greatly appreciated!

liekloo
02-02-2009, 04:16 AM
Potentially relevant detail: both battery sets I bought and intensively used during a holiday, then left the camera barely used for the following months, after which the problem occured.

Visual Reality
02-02-2009, 04:43 AM
More details. What kind of AA's are these for one...are these cheap knock off types or what?

Two, buy Eneloops and you won't have that problem again. Hold their charge for 6+ months and can be recharged 1,000 times each.

liekloo
02-02-2009, 05:13 AM
Good point: they're cheap knock-offs indeed. The first set came bundled with my camera off Ebay (Bilora, apparently some German brand, 2300mAh, 1.2V). The second set were no-name batteries that came bundled with a $25 recharger I bought at Wal-Mart (2500mAh, 1.25V).

cdifoto
02-02-2009, 06:45 AM
NiMH batteries self-discharge. It's a side-effect of their chemistry. Enter Sanyo Eneloop, Rayovac Hybrid, Duracell Pre-Charged, et al. They self-discharge but at a MUCH lower rate, at the expense of capacity (number of shots per charge). Standard NiMH are better for the power user (someone who will use the batteries HARD in a short period of time), while low-discharge like the previously named are better for the casual user (someone who will let the device sit idle for long periods of time).

David Metsky
02-02-2009, 07:16 AM
The charger might be the weak link. Ultra fast charges will cook a battery. What kind of charger do you have and how fast does it charge a set of batteries?

liekloo
02-02-2009, 03:04 PM
About the charger: for the first pair of batteries I used a basic GP charger (takes 24h to charge, no fancy trickling feature though). For the second pair I used an ultra-fast 1h Wal-Mart charger (no known brand).

Thanks for the help, everyone! The first commenter's suggestion about the batteries prompted me to do some googling - and what I found goes in the same direction as your other comments: I need quality batteries and a decent charger. So I'm going to get better batteries (one of the brands mentioned) and use my slow GP charger.

I'm glad I can continue to use my camera because I honestly don't think it can be beaten in terms of image quality (among p&s). Despite its 3MP... :D

K1W1
02-02-2009, 08:49 PM
Three words,

Eneloops
Eneloops
Eneloops

On top of that buy a decent charger something like a Powerex (link here (http://servaas.com.au/maha-powerex-mhc9000-wizardone-battery-charger-analyzer-p-52.html)) and you will never look back.

ksva
02-23-2009, 12:27 PM
About the charger: for the first pair of batteries I used a basic GP charger (takes 24h to charge, no fancy trickling feature though). For the second pair I used an ultra-fast 1h Wal-Mart charger (no known brand).

Thanks for the help, everyone! The first commenter's suggestion about the batteries prompted me to do some googling - and what I found goes in the same direction as your other comments: I need quality batteries and a decent charger. So I'm going to get better batteries (one of the brands mentioned) and use my slow GP charger.

I'm glad I can continue to use my camera because I honestly don't think it can be beaten in terms of image quality (among p&s). Despite its 3MP... :D
Pretty much everything that needs to be said has already been said here by one person or another, but you still don't have a good picture of what you need to do.

Check out Battery University and/or visit Candle Power Forums and their battery section.

There are two primary issues - crappy cells and crappy chargers. If you use a crappy charger with good cells, you'll eventually get crappy cells which is what you're about to do. I don't know precisely what charger you have (the 24 hour one), but it's a pretty good bet that it's a dumb charger and it's likely that it's the one that ruined your cells.

If your cells are only depleted 25% (75% left) and you charge them in that charger, it will overcharge them by 75% because it's not a smart charger. It doesn't know when they are charged - it only times the charge. Slow charging is not necessarily safe. The recommended charging rate is actually between one half (.5C) and the full capacity (1C) of the cell. An Eneloop is 2000mA, so the charging rate should be between 1000mA and 2000mA which equates to a 1-2 hour charge time for a depleted cell.

The 'fast charger' that someone referred to that cooks cells are the 10-15 minute chargers and that still isn't really a true statement. Those fast chargers do a good job with 'healthy' or good cells. They will shorten the life of your cells by a small amount, but the trade off may be worth it for serious users. Their bad rap of cooking cells is primarily because of using crappy cells in them.

I don't know which charger your 1 hour charger is, but it is likely a smart charger and therefore much better than your timed charger. You can find ratings of several chargers (Charger Shootout) on Candle Power Forums. Some chargers can overheat cells, which ruins them, or overcharge them, which ruins them, or undercharge them, which doesn't give you full use of your cells, etc.

Currently, (IMO) the best of the chargers/analyzers on the market for AA cells is the Maha Powerx WizardOne (MH-C9000) that someone referenced above. It's a bit pricey, but worth it to get the most from your investment in cells. If all you use rechargeables for are 2-4 cells for a camera, then it's probably not worth it. In that case, just get 2-3 sets of cells and a decent smart charger ($20-30) and replace the cells when they start to drop in performance.

The use of rechargeables is not just buy and use. You really need to do some research to understand them and how to use them, although Eneloops have done much to simply and idiot proof them for the masses. A good example would be someone who spends $1200 on a decent DSLR and only uses it as a point and shoot.

K1W1
02-26-2009, 03:33 AM
A good example would be someone who spends $1200 on a decent DSLR and only uses it as a point and shoot.

Or as happens here often spends $1200 on a DSLR then posts asking whether some dodgy memory cards on ebay are worth buying because they are $3 cheaper than the real thing in the stores.

liekloo
02-26-2009, 07:54 AM
Thanks for your comment, ksva!

I found that my fast charger (http://www.compsource.com/pn/CH4930/Sakar_International,_Inc._1418) is indeed a 'smart charger' (microprocessor; temperature sensors against overheating and (IMHO) overcharging); charge rate 1500mA (so that's good); trickle charge rate 60mA). The only weakness may be that batteries can get hot while (or after, not sure) charging, and Battery University says that's not good for NiMH. Anyway, I'm going to assume this charger is good enough.

(FYI, the slow charger is not a timed one, so no danger of overcharging here. The manual even suggests to permanently leave in any batteries. But thanks for warning me anyway :) )

liekloo
02-26-2009, 08:05 AM
One last question:

According to BatteryUniversity, recharging should happen while there's still 20% or so charge in the NiMH battery (except for the occasional full cycle maintenance). What I have been doing so far is recharge when the camera reports an empty battery - at that time the battery still holds some charge but not enough for the camera to use). Should I change my habit and recharge earlier? Or is the charge of the 'empty' battery sufficient?

Visual Reality
02-26-2009, 02:29 PM
I wouldn't bother, personally. Most cameras don't even read the charge of AA's so you have no idea how much power you have left.

ksva
02-26-2009, 11:44 PM
One last question:

According to BatteryUniversity, recharging should happen while there's still 20% or so charge in the NiMH battery (except for the occasional full cycle maintenance). What I have been doing so far is recharge when the camera reports an empty battery - at that time the battery still holds some charge but not enough for the camera to use). Should I change my habit and recharge earlier? Or is the charge of the 'empty' battery sufficient?
As I understand it, the 20% is maximum discharge state before recharging. Recharging sooner with a quality charger is actually preferred.

I can't answer your question about your camera because I don't know what camera it is or what its criteria is for cutoff. Most cameras now can sense and take advantage of NiMH chemistry. Older ones (6-7 years) didn't.

Example - my first digital camera was an Olympus D-490 point and shoot and it was a power hog. So much of a power hog that it was recommended not to leave the display on when shooting. It was a 6v and set up for two CR-V3 cells which were expensive. Alkalines were almost worthless - good for maybe 30-40 shots, so now now came the search for alternative batteries. This camera used 4AA sized cells at 1.5v each, totaling 6v. The twin CR-V3s were 3v each, again totaling 6v. NiMH cell chemistry is 1.2v or 4.8v for the 4 cells. So, freshly charged cells started off at a severe disadvantage because this camera was sensing voltage based on 6v. The answer then was an external pack consisting of 5 cells (1.2 x 5 = 6) which was good for 150-250 shots. I eventually did find that I could get satisfactory results with 4AA cells in the camera if I used good cells (not crap cells) that hadn't developed a higher internal resistance. Back then, it was a battle from camera to camera how they were set up to sense voltage.

Todays cameras are set up to take advantage of NiMH which is a good thing for shooting, but possibly bad for your cells. These cells do not like to be deep discharged and can be ruined if over discharged. Having several sets of cells and recharging or topping them off after use is much preferable to running them down. To qualify, this is only true if using a quality charger that can sense when the cells are charged and will then stop charging them.

I can't state my preferences for Eneloops enough even though they have a lower capacity than traditional high capacity cells (2000mAH vs 2700mAH). Unless you are the anal obsessive type that will invest in the high quality charger/analyzer and do regular time consuming refresh and break in cycles on your higher capacity cells, you'll soon find that the lower capacity Eneloops will out perform the higher capacity cells in practical application.

That said, I would encourage everyone who uses rechargeable cells to become anal obsessive about them because it really is necessary to get the best use out your cells.

Visual Reality
02-27-2009, 05:07 AM
you'll soon find that the lower capacity Eneloops will out perform the higher capacity cells in practical application.
Which I have.

Even fully discharged in one day, my 2000mAh Eneloops give me more power than my 2500mAh Energizers, both fully charged before use. I'd say about 10% more. The mAh numbers don't tell the whole story.

Over the course of a week, or a month, obviously it's no competition, nothing will stand up to the Eneloops.

K1W1
02-27-2009, 01:28 PM
Over the course of a week, or a month, obviously it's no competition, nothing will stand up to the Eneloops.

I agree totally. It's a case of paying a bit more up front to get a huge extra benefit over the life of the cells. Over their life the Eneloops will prove to be far more economical than standard rechargeable NiHM batteries.

ksva
02-27-2009, 05:16 PM
Which I have.

Even fully discharged in one day, my 2000mAh Eneloops give me more power than my 2500mAh Energizers, both fully charged before use. I'd say about 10% more. The mAh numbers don't tell the whole story.

Over the course of a week, or a month, obviously it's no competition, nothing will stand up to the Eneloops.
In fairness to the standard higher capacity cells, the 2500mAH Energizers are known to be trash. Technically the anal retentive users of standard 2400-2700mAH cells who have good quality cells, properly care for them and charge them just prior to use, will get more mileage out of them, but it's too much work for most, even battery enthusiasts.

The 2500 Energizers are known to be so bad, that I didn't even contact Energizer to replace mine, because I didn't want them again.

For definitions sake the Eneloops and their hybrid cousins (or brothers and sisters) are known as LSD or low self discharge cells.