Introduction

It's no secret digicams eat batteries, so rechargeable NiMH AA cells are a must if your camera takes that battery size. We've been playing around with batteries and chargers quite a bit lately (early Fall, 2001), and have discovered that having the right charger is at least as important as having the right batteries! Some chargers overcharge and can damage batteries, others drastically under-charge, making your high-capacity NiMH cells little better than garden-variety cheapies.

Of all the chargers we've tested, we prefer the Maha PowerEx C-204F for routine use. It's a very fast charger, but has monitoring circuitry to prevent over-charging. It delivers a full charge very quickly, yet strikes a good balance (IOHO) between charging speed and gentleness to the batteries.

In the Box

The C-204F charger comes with the usual wall-wart power adapter, but also includes a cigarette lighter adapter as standard equipment. Very handy for trips! Internet battery experts Thomas Distributing now also have a European power transformer for the C-204F, if you're going to be traveling to a country with 220v power instead of the 120v we have here in the US.

Versatility

The PowerEx C-204F handles both NiMH and NiCd batteries, automatically detecting the two different battery types and adjusting its charging profile to match.

Another nice touch is that the C-204F has two independent charging circuits in it. This is great if you have a digicam that takes only two AA cells, as you can charge pairs of batteries independently of each other. It also leads to somewhat more accurate charging of 4-cell sets, matching the charging a bit more closely to the needs of the individual batteries.

Charging

The C-204F is a "smart" charger, which means it applies a high rate of charge to the batteries when first inserted, then cuts back to a "trickle charge" when peak voltage is reached. Fast-charge current is 500 mA, about as fast as you'd want to dump charge into typical AA or AAA cells. Once maximum charge is reached, the charging current drops to 24mA, a nice, gentle level that can easily be tolerated by most any good-quality NiMH battery on the market. - It's thus save to leave batteries in the C-204F indefinitely, helping avoid the "self-discharge" of NiMH cells that would otherwise severely limit shelf life.

The "smart" charging means you can safely use the C-204F to "top off" the NiMH cells from your digicam if you're about to head out with it, without worrying about over-charging them.

Depending on the capacity of the batteries you're charging, the C-204F can bring a set of AA cells from "empty" to fully charged in about three hours. (Figure three and a half hours for the latest, high-capacity NiMH AAs.)

Conditioning

Of greatest importance for NiCd users, but still useful for NiMH cells, the C-204F includes discharge circuitry for thoroughly "conditioning" batteries to prevent the "memory" effect. Memory effect happens to NiCd cells when they've been repeatedly charged after being only partly drained, or when they've been left on trickle-charge for long periods of time. The batteries "remember" the amount of charge they've routinely received, and refuse to deliver more than that amount, even though their rated capacity may be much higher. This robs batteries of power capacity, reducing the maximum charge the batteries can deliver. Draining them fully to about 1.0 volts/cell helps restore full capacity.

There's some debate by the experts as to whether memory effect is real or not. We aren't equipped to get into that debate, but in our own experience have certainly seen NiCd cells lose capacity that was restored by a conditioning cycle or two.

Purchase/More Info

Here's a link to a page at Thomas Distributing, where they offer a C-204F with a set of PowerEx 1700 mAh batteries at a very good price. Like we said, don't even think twice. - If you have a AA-using camera, this is the kit to get.

For more info on the charger, here are some links to Maha's site: