Charging AA and AAA batteries

Submitted: Saturday, Feb 27, 2010 at 00:07
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I would like to get information on how to best charge nimh or nicd batteries from either car electrics or solar. I am using a DSE 12v/240v charger but I notice that when I replace the batteries in my handheld Explorist 100 the power does not last very long. I suspect that I am not getting a full charge.Any ideas what I could do?
Thanks in advance,
Tom
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Reply By: The Explorer - Saturday, Feb 27, 2010 at 00:31

Saturday, Feb 27, 2010 at 00:31
Hi

There may be nothing wrong with your charger, it could be the batteries. I purchased an el cheapo battery tester on ebay to ensure the batteries I use are charged and as a guide to those that loose charge quickly when not in use.

Also keep in mind that rechargeables are only 1.2 V (compare to 1.5V for alkaline etc) so if they are in bad condition this will be reflected very quickly with bad performance. They work fine when in good condition though so rechargeables are the go.

Cheers
Greg
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Reply By: Member - Tom L (WA) - Saturday, Feb 27, 2010 at 00:55

Saturday, Feb 27, 2010 at 00:55
Thanks Greg, That may well be the problem. The different voltage between the two different batteries. Means I just carry a fully charged spare set to insure that we always get back to the car.
Thanks again, Tom
AnswerID: 406264

Reply By: Baz&Pud (Tassie) - Saturday, Feb 27, 2010 at 05:34

Saturday, Feb 27, 2010 at 05:34
Hi yu Tom
The recharging of batteries is an interesting subject, i don't know whether it's just me but i have found that batteries recharged through the cigarette lighter don't seem to last as long as those recharged through 240v.
This also seems to apply when recharging the mobile phone.
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Reply By: Member - Flynnie (NSW) - Saturday, Feb 27, 2010 at 09:31

Saturday, Feb 27, 2010 at 09:31
I have been using a battery charger I got from Battery World for about a year now. It works equally as well on 12 volts as 240. Across the top of the packaging is "For Lithium Ion + NiCd/NiMh AA & AAA batteries". That pretty well describes it. Cost about $80 It charges everything I use on the road and at home very well indeed. It also recharges my camera batteries. It can do 1, 2 3 or 4 AA or AAA. An older charger I used could only 2 or 4.

I find it is handy to have a single AA and single AAA torch so that you can test each battery separately if there are doubts. A multimeter and a load can do the same. The batteries only have a limited life and it is important to be able to identify failing batteries and just get rid of the bad one instead of the whole set.

Flynnie
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Reply By: Maîneÿ . . .- Saturday, Feb 27, 2010 at 10:11

Saturday, Feb 27, 2010 at 10:11
Tom,
you need to have the batteries matched to the charger that is why I have an Energiser charger and only use Energiser batteries in it.
Most of my batteries are many years old now as I rotate them in the charger when the inverter is used for any purpose at all to charge various batteries (Camera, iphone, marine radio etc - 4 products at a time) all at same time, as it saves time and uses less battery power too.

You need to have the full available 12v power connected to it too, so I would not do it via a cigarette lighter plug, connect more direct to the battery.

Maîneÿ . . .
AnswerID: 406296

Reply By: Battery Value Pty Ltd - Saturday, Feb 27, 2010 at 10:25

Saturday, Feb 27, 2010 at 10:25
Most AA/AAA cells can be fast charged (charging rate(s) are usually printed on the wrapper).
But for best cycle life, and maximum charge acceptance, it's better to slow charge them.
To recharge them to maximum capacity: slow (standard) charge at the C/10 rate for 15 hrs, e.g. 2000mAh/10h=200mA for 10hrs

If you need to fast charge them: at the C/1 rate, e.g. 2000mAh/1h=2000ma for 1.5 hours.

Fast charging requires sintered battery electrodes, which have the drawback of high self discharge rates.

Therefore it's best to have these sitting on a trickle charger, to have them at 100% when you need them.
Little solar powered chargers are most suitable for trickle charging. The disadvantage of these is that the battery temperature is high for several hours a day, which reduces battery life.

I've got a DSE and a Sony 240V powered unit, and both of them are for fast charging only, meaning the batteries get quite warm during charging (the DSE unit literally cooks the cells) - something I dislike. Annoyingly they don't offer a slow charge mode.

In the past I used to wire up my own charger: resistor in series with some cells. These lasted for years as they only get a bit warm when they're fully charged.
Working out the resistor is easy: (input DC voltage - battery voltage)/(C/10) e.g. (12V-4.8V)/0.2A=36 Ohm (use a ceramic 3W or higher resistor because it'll get hot).

Best regards, Peter
AnswerID: 406299

Reply By: Member - Phil G (SA) - Saturday, Feb 27, 2010 at 10:27

Saturday, Feb 27, 2010 at 10:27
"I would like to get information on how to best charge nimh or nicd batteries from either car electrics or solar"

Tom,
My son is in the R/C airplane and car industry, and knows a heap about this rechargable batteries.
His advice is to:
#1 Buy the best rechargable batteries. The Sanyo "Eneloop" batteries are heaps better than anything else out there at the moment. They also have a very low spontaneous discharge rate.
#2 Beware of the fast chargers. He says that ideally, you should take at least 5 hours to charge these batteries, to maximise their life.
#3 The charger needs to be good quality. All the chargers these days should be "peak detection" chargers. They detect the rise in battery voltage during charging and then switch off when the voltage starts to drop ( this happens when fully charged). The cheaper rechargable batteries will "false peak", so don't get fully charged.

The second issue I raise is whether your Explorist is suitable for rechargable batteries. (rechargables are nominally 1.2V). The cutoff voltage in the GPS may be a bit high. Do the instructions say anything about this??

Your GPS takes 2 AAs so I suggest you buy the Eneloop batteries and slow charger. And see how you go.

Cheers
phil
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Follow Up By: Wok - Saturday, Feb 27, 2010 at 18:32

Saturday, Feb 27, 2010 at 18:32
#1 = Yes
#2 = Time to charge depends on both charge algorithim & battery capacity
#3 = Hobby chargers [eg Swallow...probably overkill for a few AAs] or cheapy like Soshine work directly off 12V...4AA/AAA simultaneously

NiMh come off the charger @ 1.4V...

eng hoe
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Follow Up By: Member - Phil G (SA) - Saturday, Feb 27, 2010 at 22:39

Saturday, Feb 27, 2010 at 22:39
Gday Eng hoe,
The Swallow is an amazing charger for the money. I was going to mention it, but agree with you on overkill - more likely to confuse the issue. I still run a SuperNova 250S at home for various torches and drills I have repacked with sub-C batteries. Working directly off 12V is a real bonus when out camping.

As I expect you know, NiMh have a very flat discharge curve, and are mostly discharged by the time they reach 1.25V - thats why I used the word nominally. But some GPS's don't like it - I had a Garmin 2+ that would lose its internal memory if it had NiMh, but worked perfectly with a fresh set of alkalines. I expect the new GPss should be fine with NiMh.
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Reply By: Member - Mike DID - Saturday, Feb 27, 2010 at 11:45

Saturday, Feb 27, 2010 at 11:45
If you only ever charge NiCd/NiMH batteries at C/5 or C/10 they will soon be useless due to high self-discharge from metallic whiskers growing in the cells.

Providing you have a good charger, the optimum charge rate is C/2 to burn out the whiskers.

For a 2000maH cell - C/2=1000mA, C/5=400mA, C/10=200mA.
AnswerID: 406317

Reply By: Member - Mike DID - Saturday, Feb 27, 2010 at 11:47

Saturday, Feb 27, 2010 at 11:47
For long life of NiCd/NiMH cells it's more important how you DIScharge them.

At least once every three months you need to discharge them to 1.0 volts per cell slowly.

Store them DIScharged, not charged.
AnswerID: 406318

Follow Up By: Member - Phil G (SA) - Saturday, Feb 27, 2010 at 22:46

Saturday, Feb 27, 2010 at 22:46
Mike,
Your info is true of NiCds.
NiMh are much more forgiving, and are happily stored fully charged. In fact you can buy the Sanyo Eneloop AA, off the shelf, fully charged.
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Reply By: Maîneÿ . . .- Saturday, Feb 27, 2010 at 12:13

Saturday, Feb 27, 2010 at 12:13
Energizer® * NiMH * Rechargeable AA & AAA Batteries
questions and answers from the Energizer® website

# How long can I store NiMH batteries?
Typically between 3 and 5 years if stored at room temperature.
It is recommended that NiMH batteries stored in a CHARGED state.
To attain full capacity after extended storage may require a few charge/discharge cycles to obtain maximum performance.


# What is the difference between nickel cadmium and nickel metal hydride batteries?
Both types of batteries are rechargeable but NiMH batteries have a higher energy density (ratio of energy to volume).
NiMH batteries are also considered more environmentally friendly than NiCd batteries.


# How long will a nickel metal hydride battery hold its charge?
When not in use, nickel metal hydride batteries will lose 20% to 50% of their charge within six months due to self-discharge.
Several factors such as cell size, construction and storage temperature can impact the self discharge rate.
NiMH batteries that have not been used for an extended period of time should be recharged before being put into use to obtain maximum performance.

Maîneÿ . . .



AnswerID: 406321

Reply By: dbish - Saturday, Feb 27, 2010 at 15:48

Saturday, Feb 27, 2010 at 15:48
Best bit of advice you will get is from Phil. Sanyo Eneloop is the only way to go they dont self dis charge as quick, in 12Mnths they only loose 20% charge. I use them in a hand held VHF marine 2way & in a HH GPS. Daryl
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Follow Up By: Maîneÿ . . .- Saturday, Feb 27, 2010 at 17:05

Saturday, Feb 27, 2010 at 17:05
Daryl,
if you gauge the efficiency of any battery by it's "discharge time" when NOT in use, then yes, your correct.

However if you buy an "AA" battery and it has a higher capacity than another "AA" battery, then the higher mAh rated battery ( Energizer® ) has to be a more efficient battery in heavy use.

AA Energizer® = 2,450 mAh
AA Eneloop battery = 2000 mAh

AA Energizer® = 1.2v
AA Eneloop battery = 1.2v

As can be easily seen the AA Energizer® has 450 mAh extra, which is ~23% more available power than the Sanyo AA Eneloop.

Maîneÿ . . .
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Follow Up By: dbish - Saturday, Feb 27, 2010 at 18:01

Saturday, Feb 27, 2010 at 18:01
Mainey I based my use in comparison with expensive alkaline cells. the Sanyo Eneloop gave me double the usage hours in the portable GPS went from 16Hrs To 33Hrs. Since the GPS does sit around not used for a while I found ordinary rechargable batterys self discharged to quick, so the extra capacity wasnt mutch help. The normal larger capacity cells are ok if your using them regularly. Cheers Daryl
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Follow Up By: Member - Kingsley N (SA) - Saturday, Feb 27, 2010 at 22:08

Saturday, Feb 27, 2010 at 22:08
My vote goes to Sanyo Eneloop. These batteries are very popular in the RC aircraft business. I use them in planes and cameras. The dedicated charger that is usually purchased at the same time can automatically discharge then recharge 4 AA cells from 12 or 240V. The cells will hold a charge for a very long time and I have complete faith in them with my expensive equipment. I think I paid about $60.00 for the charger and 4 AA cells. You can get them at RC Hobby stores and sometimes DSE.

I just found this review which is quite interesting.

Eneloop

Kingo
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Follow Up By: Maîneÿ . . .- Saturday, Feb 27, 2010 at 22:12

Saturday, Feb 27, 2010 at 22:12
dbish,
so from your information the AA Energiser should last even longer then, as you were comparing your Sanyo eneloop battery with an "ordinary" rechargable battery and not the larger mAh capacity of an Energiser AA battery ?

Maîneÿ . . .
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Follow Up By: Member - Phil G (SA) - Saturday, Feb 27, 2010 at 23:05

Saturday, Feb 27, 2010 at 23:05
Mainey,
Don't believe whats on the label or a website.
The R/C people often measure the capacity and discharge voltage of every cell they use. They know what's best. They only use the best because those batteries prevent a $5-10,000 model aircraft from falling out of the sky.
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Follow Up By: Maîneÿ . . .- Saturday, Feb 27, 2010 at 23:16

Saturday, Feb 27, 2010 at 23:16
Phil,
It's a wonder they have never been sued for printing what your eluding to as misleading information on their battery packets by some of the guys with expencive planes, the oposition battery companies or even consumer affairs don't you think?

Maîneÿ . . .
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Follow Up By: Member - Phil G (SA) - Sunday, Feb 28, 2010 at 00:53

Sunday, Feb 28, 2010 at 00:53
Mainey,
I don't believe there is a industry standard method for measuring battery capacity. Probably the same with lead acid batteries - get different methods used by different manufacturers.

What's written on a label might be termed "nominal" capacity or rated capacity or minimum capacity or whatever - usually not "actual capacity"!!

But how well a battery holds its voltage during discharge is usually more important than capacity.
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Follow Up By: Maîneÿ . . .- Sunday, Feb 28, 2010 at 01:06

Sunday, Feb 28, 2010 at 01:06
Phil,
do you believe Sanyo would put only 2000 mAh as their AA battery capacity when they are aware that Energiser is 2450 mAh, which is ~23% extra capacity ?

Usually batteries are rated at their highest attainable capacity, not average

Maîneÿ . . .
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Reply By: Gone Bush (WA) - Saturday, Feb 27, 2010 at 16:35

Saturday, Feb 27, 2010 at 16:35
If the volts in your rechargeable NiCd or NiMh batteries ever fall really really low you can bring them back up to a level where they will take a charge with this gadget.

Image Could Not Be Found

I made it up from a 12v cigarette lighter plug and the leads from a defunct multi-meter.

Just plug it into a 12v DC supply and put the black lead on the -ve pole of the battery and quickly (very quickly) touch the +ve pole with the red lead, but only 2 or 3 times depending on how low the volts were to start with.

Once the volts in the battery are up it will resume charging as if nothing was ever wrong.

Mainly applicable to AA and AAA batteries and ONLY NiCd and NiMh.

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Follow Up By: Member - Kingsley N (SA) - Saturday, Feb 27, 2010 at 21:53

Saturday, Feb 27, 2010 at 21:53
To all who read this - be careful because you are playing with fire here!

I have seen it demonstrated and it can shock a cell out of a low state or even reversed polarity state. But I have also seen a cell smoke and melt using the same technique. Think of all those amps flowing through that little AA or AAA cell made of thin bits of metal and plastic.

A new set of rechargeable cells doesn't cost much. I use the Sanyo AA Eneloops for cameras and my RC aircraft. They are the best!

Kingo
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Follow Up By: Maîneÿ . . .- Saturday, Feb 27, 2010 at 22:05

Saturday, Feb 27, 2010 at 22:05
Kingsley,
I'm just asking a simple question :)

How can "Sanyo AA Eneloops" be the 'best' when in actual fact they are actually ~23% less powerful than the AA Energiser batteries ??

Yes, this is only a question and not a statement of fact, as you are making the claim, I'm only asking you how you quantify your statement ??

Maîneÿ . . .
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Follow Up By: Gone Bush (WA) - Saturday, Feb 27, 2010 at 22:21

Saturday, Feb 27, 2010 at 22:21
Kingsley, you nervous Nellie.

I DID say, touch the +ve pole VERY quickly, ONLY 2 or 3 times.

Of course, if you hold the red lead on for too long you risk blowing up the battery.

Boy, I bet you'd advocate banning Cracker Night if we still had it.



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Follow Up By: Member - Kingsley N (SA) - Saturday, Feb 27, 2010 at 23:01

Saturday, Feb 27, 2010 at 23:01
Maîneÿ

As you are probably aware there are many different brands of rechargeable NiMh batteries. For years in the RC game Sanyo NiCads were the only ones to use. When NiMh became more readily available many RCers changed over only to find that the advertised lack of memory effect was not always evident. I have used several different brands of NiMh from the camera shops for my various Canon cameras over the last five years or so. Inevitably the useable time from a full charge tapers off after a few months of use. I tried the Sanyo Eneloops for the first time in cameras about a year ago and I have been impressed with their ability to hold a charge. I also like the slow discharge and recharge method used by the supplied charging device. I have been using them in my RC gear for about six months with equal satisfaction.

Yes, the capacity of the Eneloops is less than that of many Camera store NiMh, but the fact is I have had to discard several sets of them over the years.

Eneloop gets my vote.

Kingo
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