Batteries die before they should. A query about “battery memory” recently posted around the Internet revealed that videomakers everywhere actively suffer from this malady–or think they do.
One fellow writes that he has never seen a NiCd battery live up to the manufacturer’s promises. Another has a battery that, when fully charged, delivers just enough juice to pop the tape out before it dies. The most extreme case is a fellow who rents out camcorders. His responsibility is to keep a fleet of more than 24 NiCds fully reliable for every rental. He oversees a Byzantine system that includes an expensive voltmeter, stop watches and kitchen timers.
Some say batteries die young because of “battery memory.” They say that videomakers cause early shutdowns by charging their batteries before fully discharging them. They explain that batteries “remember” that you discharged them, say, only 15 minutes, and will thus no longer hold a charge longer than 15 minutes. They even cite NASA as expert witness. As the story runs, NASA had a satellite running on NiCds that had the same problem and for the same reason. They identify the problem; they offer a solution. They preach this news so convincingly that some manufacturers now offer “no memory” batteries to the world. But their explanation, like so many batteries is dead, and wrong.
One can create the satellite’s “battery memory” effect only by discharging a battery to precisely the same point, and recharging it, hundreds of times. No-one ever does this with a camcorder.
What happens when a doctor treats a patient with pneumonia as though he had a kidney infection instead? On one hand the pneumonia continues; on the other, the mistreatment itself could hurt the patient. Thus, the battery plot thickens.
Enter the anti-memory faction. These folks understand that the partial-discharge theory proves invalid. They even vilify those complaining of the problem. “It can’t happen,” they say, as though saying so would wake up all those sleepy batteries. In a recent trade show, representatives of two major battery makers said that battery memory is not a problem anymore. They both implied that the effect was simply an artifact of “old technology” which new technology has long since superseded. Along with others in this camp, they thus implied that “no memory” batteries could only be a solution to a non-existent problem. In other words, hype.
The anti-memory faction proclaims loudly that the patient doesn’t really have a kidney infection. It debunks the misdiagnosis as though debunking provides a cure. The patient, however, lies there coughing.
Cut to the chase. Yes, the patient really suffers, and it’s from pneumonia not kidney troubles. Also, “no memory” batteries could sometimes offer a benefit though “battery memory,” as usually understood, is not the illness.
The problem is overcharging. When you leave a battery on a charger after it’s fully charged, the charger will continue to send a slow charge through the battery. This changes the crystal structure of the Nickelic Hydroxide from its beta to its gamma form. This form discharges at a lower voltage than the beta form. The result: after the beta form has fully discharged itself at six volts, the gamma form starts discharging at, say, 5.4 volts. If your camera needs a steady six volts to keep operating, this “voltage depression” will shut it down. The camera can’t use the juice that’s left in the battery. Engineers like to call this the “lazy effect”. Let us call it that too, and leave “battery memory” to the satellites.
Well, then, what’s a “no memory” battery? In some cases, it is a battery with an additional cell. In other words, it might deliver a little more than seven volts though you use it on a six volt camcorder. The extra volt does no harm, but delivers a safeguard against “laziness.”
The treatment: don’t overcharge your batteries. Take them off their chargers as soon as they are charged. Don’t “cycle” your batteries (i.e. discharge them all the way) every time you charge them. Batteries that can take a fast charge don’t build up the gamma crystals as readily as the “trickle” chargers and batteries. Don’t store your batteries in high temperatures and don’t charge them until they feel hot. Don’t ever discharge a NiCd down to zero volts. This could cause “cell reversal” and even an explosion. Use a refresher that leaves about a volt per cell when discharging.
Thanks to all who have contributed so generously from their knowledge and experience to this exploration to date.
Stephen Muratore is Videomaker‘s Editor in Chief.