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Looking through low-priced battery chargers, I decided to go with a brand-name charger. I narrowed the choice down to either a Duracell or Energizer charger, both around the $25-30 mark. Both included NiMH batteries, but the Energizer had batteries with a higher capacity rating, so I went with it. After a few months of usage, I have one statement that sums up my thoughts on this thing…

What a piece of junk.

First, this being a review, some basic info about the charger:

• It comes with 4 x 2500 mAH AA batteries. It can charge AA or AAA NiMH batteries.
• The tray that holds the batteries can be slid closed, or “compacted” to make it easier for travel
• It charges 2500 mAH AA cells in about 8 hours.
• It offers reverse polarity protection.
• Includes a built-in safety timer.

Now there was at least a little thought put into the charger. It’s meant to carry easily for travel, and it does. The AC-outlet prongs flip up into the charger, and the battery tray slides shut to make it one of the smallest, easiest to carry chargers around. It’s quite slim as well. You could probably put it in your pocket when not in use if you wanted to.

But there are bad points… First of all, you might have to wiggle the batteries a bit within the charger to get a good connection. It’s very easy to get the batteries in “most of the way”, but not enough to make contact. You could easily end up charging some batteries and not others.

The next problem is that you can’t charge only 1 battery. You need at least 2 in the charger for it to operate. Not a big deal, since most devices use 2 batteries anyway, but if you have a 1-battery device, plan on carrying a 2nd battery if you plan on doing any charging.

The biggest problem however, is the method of charging. NiMH batteries can not absorb overcharge. Therefore, an NiMH battery charger is supposed to detect when the battery reaches full charge, and then either cut the charge, or reduce it to a trickle charge.

Unfortunately, Energizer has apparantly decided that rather than to bother detecting when the batteries are fully charged, they would instead charge the batteries for about 8 hours, regardless of the battery charge, and then shut off the charger automatically after those 8 hours.
This is a problem. It’s a problem, because it’s not the way you’re supposed to charge NiMH batteries. It’s great if your batteries do happen to hit full charge at the 8 hour mark, but the big problem occurs when your batteries take less time to charge.

Q: What happens if your NiMH batteries are fully charged in 3 hours, but the charger applies full charge to them for 8?

A: Your batteries literally cook for the extra 5 hours.

Yes, there’s a reason that NiMH chargers are supposed to include complex detection circuitry and then cut off or reduce the charge - it’s because if they don’t, the batteries just heat up, and start to fry. This (as you might expect) reduces the life of the batteries.

As it turns out, when charging batteries, I was finding that the batteries in the Energizer charger would end up scorching hot before the end - my first indication that something wasn’t right, and what led me to investigate further.

What will make things worse for owners of this charger is when someone is in the situation where they have batteries, they can’t remember if they’re fully charged or not, so they put them in the charger overnight anyway. If the batteries are already fully charged (or almost fully charged), they’re going to be baking for the entire 8 hours. Not a good thing.
In short, I’d probably be just as comfortable with a no-name brand charger as with the Energizer. In fact I wouldn’t be surprised if most no-name NiMH chargers worked better, and of course cost less. I would have expected much more from Energizer, but seemingly they’re more concerned about cost than quality. The 8-hour timer is undoubtedly cheaper for them to use than the circuitry they’re supposed to for this kind of charger.
I’d recommend the Energizer Compact Charger only as a charger for travel and use every once in a while. It also wouldn’t be terribly bad for NiCd batteries, which don’t aren’t as susceptible to abuse. I most certainly would not recommend it as your primary NiMH battery charger for day-to-day use however.