are there a "real" difference between Ni-MH Battery chargers?

[mason79]

I bought a MAWA supposedly they had high ratings, it "seemed" better than the cheap Casio AA charger that came with the camera, since the battery were dead with it and the MAWA revived them .It is super light(MAWA) so I don't think there is a lot of stuff inside....

I have a nice radio shack, heavy for it's size, AAA-AA Ni cad and Ni-MH combo charger and this "seems" better than the Casio.

how can you tell which one is doing damage and which one is best?

[TopCatGr58]

Hey Mason,

Take a look at this website: LaCrosse Technology, this link should put you on the POWER section of their website.

I did some research a while back wanting to find a QUALITY charger, I had bought some Panasonic rechargeable batteries and it came with a charger, but after a while, the AA's just didn't seem to hold a charge very long, for my dig camera. The batteries were NiCd. I found the BC-900 IIRC on Amazon, or Ebay, for much less than their MSRP, and it came with very high reviews.

It also came with a set of 4 AA and 4AAA rechargeable batteries, NiMh. I used it to recondition my earlier NiCd batteries, and it works great with the NiMh ones that it came with. It allows you to select charging rates, so if you want/need a QUICKIE, you can get it, but it's best to use the lower/slower rate, that way it doesn't heat up the battery so much....heat is bad!! It also shows the charging state, FULL, and works like a trickle charger to keep unused ones topped off until you need them and take them out of the charger!

From what I've read, NiCd batteries to develop a memory, and can loose their capacity if not fully discharged before recharging, and hence why reconditioning is required every so often. I think NiMh don't develop a memory condition, and they deliver the full power up to the point where they go dead, so they provide longer life in digital equipment like cameras and such!

T.C.

[mason79]

Hey TopCat,

This is what I bought and it puts out 2000 or 700 Ma depending on the battery size, some test mentioned it was the best, but it is confusing.


yours and mine came in, (as far as this article was concerned) tops...

http://www.galttech.com/research/buy...ry-charger.php

i bought mine from Thomas with some big diameter powerex2700mah AA


http://www.thomasdistributing.com/sh...8mqtmii4pvh0p6

[b.walker5]

Understand your subject..

To get the best from your batteries, first you need to understand how they work. Try this to start with, to get enough knowledge to annoy a salesman.

http://www.batteryuniversity.com/index.htm

[mason79]

To get the best from your batteries, first you need to understand how they work. Try this to start with, to get enough knowledge to annoy a salesman.

http://www.batteryuniversity.com/index.htm

all i can say is wow.

[mason79]

ultra-high capacity nickel-cadmium batteries tend to heat up more than the standard version on fast-charge. This is partly due to increased internal cell resistance. To moderate the temperature buildup and achieve short charge times, advanced chargers apply a high current at the beginning and then lower the amount to harmonize with the charge acceptance.

Interspersing discharge pulses between charge pulses improves the charge acceptance of nickel-based batteries. Commonly referred to as burp or reverse load charging, this method promotes high surface area on the electrodes to improve the recombination of gases generated during charge. The results are better performance, reduced memory and longer service life.

Full-charge detection is based on a combination of voltage drop at full charge (negative delta V), rate-of-temperature-increase (dT/dt), absolute temperature and timeout timers. The charger utilizes whatever comes first to terminate the fast-charge.

After the initial fast charge, some fast-chargers apply a timed topping charged. In an attempt to gain a few extra capacity points, some chargers apply a measured amount of overcharge. The capacity gain is about 6%. The negative is shorter cycle life. The recommended trickle charge for nickel-cadmium is between 0.05C and 0.1C. Because of memory concerns and compatibility with nickel-metal-hydride, the trickle charge is set as low as possible.

Charging nickel-metal-hydride

Nickel-metal-hydride chargers require more complex electronics than nickel-cadmium systems. To begin with, nickel-metal-hydride produces a very small voltage drop at full charge and the NDV is almost non-existent at charge rates below 0.5C and elevated temperatures. Aging and degenerating cell match diminish the already minute voltage delta further. This makes full charge detection difficult.

A nickel-metal-hydride charger must respond to a voltage drop of 8-16mV per cell. Making the charger too sensitive may terminate the fast charge halfway through the charge due to voltage fluctuations and electrical noise. Most of today's nickel-metal-hydride chargers use a combination of NDV, rate-of-temperature-increase (dT/dt), temperature sensing and timeout timers. The charger utilizes whatever comes first to terminate the fast-charge.

Nickel-metal-hydride should be rapid charged rather than slow charged. Because of poor overcharge absorption, the trickle charge must be lower than that of nickel-cadmium and is usually around 0.05C. This explains why the original nickel-cadmium charger cannot be used nickel-metal-hydride.

It is difficult, if not impossible, to slow-charge a nickel-metal-hydride. At a C?rate of 0.1-0.3C, the voltage and temperature profiles fail to exhibit defined characteristics to measure the full charge state accurately and the charger must rely on a timer. Harmful overcharge can occur if a partially or fully charged battery is charged with a fixed timer. The same occurs if the battery has aged and can only hold 50 instead of 100% charge. Overcharge could occur even though the battery feels cool to the touch.

Lower-priced chargers may not apply a fully saturated charge. Some will indicate full-charge immediately after a voltage or temperature peak is reached. These chargers are commonly sold on the merit of short charge time and moderate price.

Simple Guidelines:

* Avoid high temperature during charging. Discontinue the use of chargers that cook batteries.
* A charger for nickel-metal-hydride can also accommodate nickel-cadmium, but not the other way around. A charger designed for nickel-cadmium would overcharge the nickel-metal-hydride battery.
* nickel-based batteries prefer fast-charge. Lingering slow charges cause crystalline formation (memory).
* nickel- and lithium-based batteries require different charge algorithms. The two chemistries can normally not be interchanged in the same charger.
* If not used immediately, remove the battery from the charger and apply a topping-charge before use. Do not leave nickel-based battery in the charger for more than a few days, even if on trickle charge.

A well-designed charger is a reasonably complex device. Taking short cuts will cost the user in the long run. Choosing a well-engineered charger will return the investment in longer lasting and better performing batteries.
_________________________

[The Lorax]

I have a thing called "Re-Zap" it recharges any kind of batteries, rechargeable or not. takes AAA, AA, C, D, 9 volt, even those big square 6 volt lantern batteries. granted, the batteries don't last as long after charging as they do when they're new, but I can re charge them as many times as I want (the documentation says up to 20 times) but I put the in the charger until they don't take a charge anymore. I was skeptical at first when I got it, but it does work. my mother bought it on QVC with a toy for the 7 year old a Christmas or two ago. Good Buy! I like it. I'm sure a general internet search will yield decent results. have a nice day and ride safe