RSS Feeds
Simple battery speeds recharging
By Rick DeMeis, Senior Technical Editor -- Design News, August 19, 2002
Madison, WI — Ever reach for that nifty digital camera after just a few shots and find the AA batteries drained? If spares aren't handy, then you may be in for an overnight wait to recharge its nickel metal hydride (NiMH) cells before you can start snapping again.
|
|
When fully charged, pressure builds inside the I-C3 battery. At a set level, the spring deflects, breaking the connection between the control plates. |
Consumer demand for digital cameras, with their need for high power delivered in a fast, battery-draining pulse, along with products such as MP3 players and hand-held communication devices, has boosted battery sales in 2001 by 29%, say A.C. Nielsen researchers.
While nickel-chemistry batteries are good for such high power applications, the charge time or charger expense has always been a drawback. While charging can be done in a couple of hours, controller chips require current and temperature sensors that drive up costs. Controllers with sensors integrated into the chips makes possible smaller, somewhat cheaper boards. But putting such intelligence in the battery increases the cost of the power cells.
Now engineers at Rayovac have come up with a battery that can charge in 15 minutes, cuts recharging cost, and provides more power for longer discharge time, thanks to optimized construction. The solution is a mechanical one, to boot: a pressure switch inside the battery. Rather than monitor battery temperature rate of change or voltage peaking during charging, a spring diaphragm inside the cell top flexes, breaking contact, when internal pressure builds to a predetermined level (150-500 psi) when the full charge is reached.
|
|
In-Cell Charging Control (I-C3) technology uses constant voltage charging, which heats the battery less than conventional constant current because the current drops during charging. |
Paul Cheeseman, senior VP for technology, says the patented pressure switch enables a charging unit with fewer expensive components, thus costing 30-50% less than today's quick chargers. He says that although the batteries should only be slightly more expensive than existing NiMH cells, they will have more power, and thus a longer time to discharge. "Before, batteries were made with 40-50% excess anode material to absorb ions in the gas generated during charging. Now we can rebalance, reducing the anode and increasing the cathode, giving greater capacity," Cheeseman explains.
For safety redundancy, the charger shuts off after 15 minutes. There is also a simple temperature cut-off and, finally, the batteries will vent to relieve pressure.
Cheeseman says the batteries will be on the market early next year. The company is working with OEMs to incorporate the technology in products available at that time.
For more information about batteries from Rayovac, www.rayovac.com: Enter 538
Talkback
DN's Resource Center Get Free Information, Made Easy
-
Making a Better Fueling Fan … for Less with Dupont Delrin
DuPont Automotive Products | White Paper
Request Item -
Present State and Futuristic of Motor Drive Technology
Yaskawa Electric America | White Paper
Request Item
