Oops sorry. Somehow I missed this question Derrel. I come from the Radio Control Car world where batteries are VERY important, so I am quite picky about chargers, as they are definitely the most important part of the battery equation. I have found this charger (lightning pack 4000N). It Costs $23 and is the size of a deck of cards (unlike the huge Maha chargers):

www.ripvan100.com

It is the best charger I have found. It has some of the same technologies that good RC Car chargers have.

#1. It is one of the few AA chargers out there to use a pulse charge. (Maha claims to also do this, but it does not seem to work in keeping temps down.. they get HOT when quick charging) This lets your batteries rest between bursts of charge so that it minimizes crystallization and keeps charge temps down (the batts never even get above room temp, which is very important for NiMH). This is usually reserved for expensive pro RC car chargers, and it is nice to find this feature in a cheap AA charger.

#2. It uses a custom charging curve and adjusts itself to the health of the battery. This is important because a battery can handle a lot of charge amps in the beginning of the charge cycle, but much less the closer it gets to full. Most chargers out there us a linear charge curve and either they overcharge (REALLY bad for NiMH) or they get the batteries warm (also really bad, but not as bad as overcharging). This curve also gets the most energy storage possible from the batts.

#3. It has many different cut off methods to prevent overcharging. It uses a delta V cutoff, a temp cutoff, and a timer cutoff to prevent overcharging, which is the worst thing for NiMH. Interesting to note, even a slight overcharge is a bad thing for NiMH, which is why trickle charging is so bad for NiMH batteries. Even one instance of overcharging can permanently reduce capacity, trickle charging is almost impossible to do without overcharging.

People are still in the NiCd mindset where they are able to absorb some overcharge, so leaving them in a trickle charge state is not too bad. NiMH batts cannot absorb any overcharge. While some chargers boast getting 100% charge... unless they are VERY sophisticated (and expensive) they are very likely to overcharge. Especially with older batteries as their charging characteristics change over time. So while a charger might get 98% charge with new batteries, that same charger will start to overcharge the batts after they have had a few cycles under their belt.

This is one of the reasons I got rid of the Maha chargers that everyone raves about. They get the batteries way too warm for one thing, second they might get good results at first ( they definitely do well in getting a very complete charge) but your batteries suffer in the long run as they are more prone to being overcharged as they age, and the heat (even 40 C is way too much in my opinion.. if they are warm at all to the touch, they are too hot) The only way I could get temps down with the Maha chargers was to run them in slow charge mode, and that risks overcharging much easier. Either way batteries had a severely shortened life, and easily noticeable if you pay attention. So bye bye Maha.

The RipVan100 on the other hand does not charge as completely as the Maha does initially, but the lifespan of the batteries is extended immensely, and if you want higher charge let them trickle for a couple more hours after the fast charge gets just as much charge and is much safer (although with a bit of risk of overcharging on older batteries). For example batteries I charged with the Maha had a lifespan of 2-3 months before there was a noticeable drop in performance! (Yes really that short!) While batteries I have charged with the Lightning pack charger have lasted over a year with no noticeable drop in capacity.

Here is a good site that shows this very clearly. Notice that the Lighting is the fastest and also the safest charger on the list. Sure some are faster, but they heat the batteries WAY too much, or they easily overcharge. Remember that fast charging is better for NiMH than slow charging because it is too easy to overcharge when slow charging. For example the Maha C401FS on slow mode actually reaches 100% capacity... but how long ago? Even when cells do not get hot (as is the case most often with slow chargers) they are still getting overcharged which is DEATH to NiMH batts. The 100% charge shown by the Maha C401FS shows me that it had reached peak charge and had been overcharging for who knows how long. Remember, NONE of these chargers have a shutoff for trickle charging, so at some point they will ALL overcharge when trickle charging.

I have owned quite a few chargers until I found the ripvan100 charger. It is the closest I could find that performs like a good RC car charger costing MANY times more. Let me know what chargers you have currently and I will tell you if I have tried them and what I thought... maybe you already have one that is pretty good. I have used some that were pretty good, but like I said, I am very picky about my chargers. :) In fact I have even thought about putting together a rig to charge my AA batts using my $150 dollar RC car charger. Then I could charge safely in 15 minutes :), why cannot charger manufactures make AA chargers as sophisticated as the hobby chargers?! :(. I know, I know... who would pay $150 for a AA charger, hehe. :)

http://www.crypto.com/chargers/

Hope I helped :)


Regards,
Sean