How to buy chargers for NiMh batteries?

If I were to buy an NiMh battery kit with a charger, when the battery finally dies, can I buy a higher capacity replacement and still use the same charger for it?

My guess is it will affect the charging time since it has higher capacity but how will I know when the battery is fully charged. Are there smart chargers that can detect when the higher capacity battery is fully charged?

What is the difference between fast chargers and slow chargers? Are there advantages or disadvantages of any one over the other?

Thanks to anyone who can enlighten me on this.

If you buy a simple kit, you must use the same capacity batteries. Those chargers just have a timer. When you plug them in, they chrage for (say) 10 hours and then switch to trickle charge. When you put in a higher capacity battery, it won't get fully charged.

There are smart chargers, but expect to pay more for them. It also depends if you want to charge just AA cells, or larger batteries too. Because of the high demand for AA's, the prices for these smart chargers are a lot more reasonable than for chargers that can charge larger batteries too.
Those smart chargers usually detect if the batteries are full with a technique called "delta-V detection". If a charger mentions this, it's a good one. Another giveaway is the price. "dumb" fast-chargers can be had for $10-20. Smart ones cost 40 or more (AA chargers)

fast chargers are just that: they charge fast. They use a high current to charge (300-800mA usually for AA's), and then switch to trickle charge (50-100mA) to keep the batteries topped off and ready for use, no matter how long you keep them in the charger.

Slow chargers only charge with the 100 mA trickle current. It will take a long time to charge and the battery can be left in the charger "forever".

You see this technique employed a lot with flashlight chargers: You can put the flashlight on the charger and keep it there almost indefinately.

I was researching chargers yesterday. I discovered the ansmann brand:
http://www.ansmann.de/en/index_chargers.html
Just read the technical info on their energy 4 8 16, their accufresh and powerline chargers to get a feel for all the technical stuff /ubbthreads/images/graemlins/smile.gif

I'm thinking of buying their energy 8 model. It's a smart charger that charges pretty fast, can handle multiple sizes, can refresh batteries and does it all automatically. Read the reviews in the press section on that info page (the info in the press section with the energy 16 model is also good stuff)

Try http://www.thomas-distributing.com/

They sell the Maha line of NiMH chargers, which have received excellent reviews.

C204 review: http://www.imaging-resource.com/ACCS/C204/C204A.HTM

401FS review: http://www.imaging-resource.com/ACCS/C401FS/C401A.HTM

And of course the battery shootout: http://www.imaging-resource.com/ACCS/BATTS/BATTS.HTM

Vanson and Accupower make good chargers. The accupower charger is a quick charger that automatically detects the total capacity and charge state of each battery independantly and charges just the right time frame.. you can set it and forget it, and it still charges them fast and slows to a trickle charge when batterys are charged.

Will using either slow or fast chargers affect the battery life in any way?

Can anyone show me where I can find the Vanson and Accupower chargers?

Thanks.

Walmart has 2 very nice chargers for about $28 with some batteries: Energizer 30 minute; and Rayovac 15 minute.

The Rayovac requires special Rayovac 15 minute batteries. I have this system and it is very convenient, and the batteries seem to be very high quality. They take a charge of 1.45 volts.

The Energizer system has the advantage that it will work with any brand of batteries.

Those reviews which claim Maha is the best are very old. The Maha's aren't being compared to modern chargers. They are quite slow, and that doesn't make sense to me. Whatever you do, get a charger that can charge 1 battery or 3 batteries at a time.

Hello Billson,

Heat is the thing that destroys battery chemistry. You can charge batteries rapidly as long as they don't get too hot. Some people add fans blowing over their batteries to keep the heat down. This will help with the outside surface temperature, but I am not sure if it helps the interior cell temperature that much.

I believe there is also a problem leaving the batteries on the charger for extended periods of time. If you are not going to use the batteries for a month or more, take them out of the charger and just store them. The problem is that the batteries have a self discharge rate.

If you use the batteries up every day, this is a great use of rechargeables. If you use the batteries up only once a year, you would be better off with non rechargeable batteries. Most of us fall in between these two and just have to make a personal decision.

Here is a link to the Vanson BC-1HU charger that I use.
http://www.aspencer1.com/items.asp?db=14

Good luck with you choice and let us know how it works out.

Tom

Tom

Thanks for the explanation.

Billson

Billson,
I can say from experience that the Maha 401FS is a fine charger. It will charge at a 1 amp rate or at a 300 mAh rate. Each battery has its own charger circuitry. I have many way more expensive battery chargers, but for simplicity and ease of use, the Maha 401FS holds its own when charging AA and AAA size rechargeables.
Jerry

Does anyone have information/experience on the Ansmann Energy 8 charger?
Ansmann Energy 8 Charger @ Thomas-Distributing
I have the Maha 401FS but am now looking for a charger for 9V/C/D cells. Was all set to purchase the Accupower AccuManager 20, and then found this new charger on their site. Read some European digicamera sites reviews on the Ansmann and it sounded good but was wondering whether it is worth the extra $$ for it over the Accupower unit.

See here:
http://www.hy-line.ch/productsansmannladegeräteez.shtml

I use Energy16, I like it but I have no experiences with other chargers.

[ QUOTE ]
Billson said:
Will using either slow or fast chargers affect the battery life in any way?
Thanks.

[/ QUOTE ]
This is only my personal experience, but I tried over a long period a number of chargers, one cheap fast charger, two slow chargers without timer and a slow charger which checks the power levels on individual batteries (and is able to recharge non-rechargeables). With the slow chargers batteries seem to have an average lifetime of about ten years (mostly NiCd batteries, NiMh hasn't been available that long here) With the fast charger, battery lifetime seems to get halved. After three to five years most batteries either didn't charge anymore or produced that metal/acidic smell you get right before the start corroding. Hence I prefer to buy more batteries and slow charge them whilst keeping a charged backup set. I really like the chargers which charge individual batteries to peak power and take their time for doing it. It seems to be much kinder to their life expectancy.

Is it really worth it to spend hours, instead of minutes, waiting for your batteries to recharge, just so you don't have to buy new batteries for 10 years? I mean wouldn't it be OK if you had to replace your rechargeables every couple of years?

If you can recharge your batteries in 15 minutes or half an hour, you don't need backups, so you've already saved the money to buy a new set in a couple of years.

Besides, technology changes and improves all the time. Don't get stuck with outdated slow battery chargers when you can get really fast ones for very reasonable prices at Walmart.

I want to change mine or add to them at least every 2 years just to update the technology.

On a german forum, the accumanager is considered better, because it uses a smarter "battery full" detection system. They're both very good chargers, buy the one which fullfills your needs and is cheapest.

Thanks Raymond. Per chance, would you have a weblink to the German forum.

Michael

Beagle, search here first. Use accumanager or accucharger

to know how long a charger will take to replenish your batteries use this simple formula:

for an AA 1800ma/h battery and a 0.2A charger

(1800 x 1.2)/200 (0.2a expressed in miliamps)
total=10.8 hours

cheers