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Fred Marks -> Why do RC batteries require so much care? (8/30/2003 12:53:12 AM)
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Greenboot: Your point is a good one and there is a very direct answer. When a manufacturer sells in quantity to an Original Equipment manufacturer (OEM) such as you mention, the situation is quite fixed. One pack, one charger, one use. This had largely been the case with RC systems for 30 years until different battery uses evolved. You bought a four-cell pack for the airplane and an eight - cell pack for the transmitter along with a very fixed wall wart and charged at the so-called ten hout rate. The only concern was that you charge the system overnight before you go out to fly.
However, this has all changed. People (via NASA) became aware that NI cds have memory(or voltage depression; call it what you like) and that reliability and life could be made much better by use of a "cycler". Thus, with ACE R/C, we designed and manufactured some 70,000 Digipace cyclers over some 20 years, followed by the FMA Direct EINSTEIN. I can personally attest to the fact that such a cycler in a time before Digipace would have saved me three airplanes. Fortunately, no injury resulted, but it surely destroyed three airplanes in about ten years. A good cycler will last you many years as I know some still use Digipaces that are 25 years old.
Then, users began to demand the capability to fast charge. Waiting overnight for the pack to charge was no longer acceptable. Now, fast charging brings it's own set of problems.
As long as a battery is charged at its "10 hr rate; C/10) the temperature and pressure in the cell remain in balance. As soon as you exceed the 10 hr rate, presure and temperature in the cell rise as the cell goes into overcharge. Thus, the peak detection charger came into vogue and scads of them have been sold. Cells respond differently to fast charging, particularly Ni MH. So you begin to hear terms like "false peaking"
Enter Electric flight. Now packs never dreamed of in forty different configurations, capacities from 50 mah to 10 AH, Ni cd; Ni MH, SLA, and now Li Po enter the scene. Every one of these offered something new in the way of performance, but each requires specific treatment. All are abused in ways one never dreamed of 30 years ago. As the specification and application has changed, it has become necessary to evlve with them to protect the investment in batteries.
Finally, not all is good about the OEM use. I have seen loads of batteries replaced in OEM applications when it was absolutely unnecessary. The manual for home video cams teaches you to ruin the cells with the direction: "charge the pack overnight, then charge it overnight after each use." After a short time, the pack develops memory, won't run thr cam for more than a short time, and the buyer goes off to pay $65 for a new pack. The OEM smiles all the way to the bank. he doesn't want you to know that the pack could be rejuvenated. If you just took the simple step of deep discharging the pack once a month, that pack would be in use ten years later.
Cheers,
Fred
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