Charging AA and AAA batteries

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

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

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.
Cheers
Baz

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

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 . . .

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

"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

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.

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.

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 . . .

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

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.

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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.