BATTERIES - PART 4
BOOT YOUR BATTERY OR GIVE IT THE BOOT?
A market survey of batteries in common stores will reveal the banning of lead acid batteries and the proliferation of alkaline batteries. Reading up on the care and feeding (recharging) of a variety of finicky batteries is complicated and sometimes confusing.
THE FINICKY BATTERY
How many times did a trusty rechargeable battery go dead in your lifetime? A battery is not a simple thing to maintain. It needs levels of charge, specific voltages, specific currents, and specific charging times. It requires a charging cycle involved with timing variants that cannot be too much or too little, too frequent or too infrequent. Plus, to add to the confusion, no two batteries are exactly alike.
UNENDING MISERY HAS COMPANY
It doesn't end there. Nickel metal hydride and nicad batteries have memory, so trying to trickle charge these is either impossible with simple charging or it becomes a complicated set of rules to follow with a smart programmed charger that can not only recharge batteries but sense their condition as well. Even more complicated is that devices drain batteries at different rates and different batteries may drain at different rates even with the same machine.
MAINTAINING BATTERIES
Batteries must also be maintained. Overcharge, undercharge, and the frequency of charging all effect the battery life. Charging may never reach the full capacity of the battery, depending on its age life cycle. Environment is also a factor as batteries can give up the ship when the temperature drops to freezing temps in winter.
NEW TECHNOLOGY SUPER CAP
The dream is to perhaps toss the battery altogether and use another technology like a super super capacitor that can hold a large enough amount of energy so that it can be drained over several days. However, these are often quoted as having the ability to last only minutes or seconds!
SUPER CAP LONGEVITY
We determined the longevity (time in which it can deliver useable power) of a massive super capacitor using calculus dv/dt = i/c. At .03 amps and rounding to 3 volts for the Propeller chip, a 100 F super capacitor can provide only 2.7 hours of drain, while a 500 F super capacitor is more practical at 13 hours. Two of these capacitors in tandem could indeed help the Cortex make it through the night without solar power, providing the caps are fully charged during the day and the batteries have full reserves.
CORTEX REQUIREMENTS
Our requirements are to supply some charging energy from a solar panel that may have periods of lessened energy during the day (as if the sun went behind clouds, or more realistically, a light was turned off inside a room.
During the night, the machine will draw energy and the solar panel will automatically disengage. The battery, or super super capacitor must have enough energy to survive the night. In this situation, we set the bar at 2 days reserve.
TRI LEVEL ENERGY SYSTEM
Now considered is a tri level energy system. The TRI POWER includes the solar cells, super super capacitor, and batteries. Room lighting will activate the solar panel and trickle charge the super capacitor which helps maintain the battery during the night.
CHARGING COMMON ALKALINE
A number of sources describe charging common alkaline batteries, but this is complicated too, as its important to sense the heat level of the battery to ascertain when the charge cycle should be completed. This does not fit into a simple charging scheme.
CONCLUSION
It's still up in the air as to which battery type will work the best with a simple charging system. Alkaline is most common, yet the availability of Nickel Metal Hydride is still a consideration. Lithium Ion has charging requirements that are not met by the solar panel. Lead acid batteries are not available in the size required. Yet, energy supplied to the Cortex must be constant, reliable, or the brain will die and cease to function. This is why the consideration is now from three electric sources - solar, capacitive, and battery. Solar is renewable energy and the capacitor can store it and release it over time. The challenge is now finding a suitable battery.
Brain Cortex Index Part 16