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Power Department
 Application Notes:
Solar Panels for Battery Charging
This note is provided as a guide to those who want to charge batteries for their GPS unit, digital camera, PDA, or other small electronics while outdoors & away from household power.
For small electronics that use a special battery such as cell phones, PDA's and some digital cameras, refer to our note on direct charging systems. This is an important distinction to make as not all devices use the same voltage or battery types.
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Battery Charging : for devices that use 'AA' or 'AAA' batteries
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Many devices that use standard 'AA' or 'AAA' batteries can be made portable for outdoor use by using a solar panel to recharge the batteries. If your device uses a special type of rechargable battery pack such as Sony's InfoLithium for cameras & camcorders, please refer to our application note covering direct power, or the note covering small portable power solutions.
The most basic solar charging system will be able to charge batteries directly via an on-board compartment (see: PowerFilm USB+AA, e-Power). Brunton produces the popular Solaris USB panel, which works exceptionally well with USB Mini AA chargers like the Impact model.
For demanding applications, we recommend using a battery charger designed with control features for properly caring for your batteries. In this way, the charger can properly adjust the voltage & current being applied to your batteries, thus providing better battery performance and longer battery life. At the top of the heap is the amazing PowerEx C9000 Wizard, followed by the BC-700 Alpha from La Crosse.
To connect a battery charger to most solar panels requires a standard 12V DC plug like those used in automobiles. We carry several models of charger that provide power adaptors for both household AC and 12V DC power sources (see: Delta-V, PowerEx C9000 Wizard, PowerEx C401fs). Simply choose a solar panel large enough to provide a charging current that will charge your batteries at an acceptable rate (3-12 Watts is the range to consider), and connect the two - plug & play. Most of the panels we carry between 2 & 25 Watts offer a DC outlet either built-in or as an optional accessory.
A few words about battery technologies...
There are three main types of rechargeable battery on the market today for small electronics: NiCd (Nickel Cadmium), NiMh (Nickel Metal Hydride), & Li-Ion (Lithium-Ion). NiCd is the oldest of the three, and is the cheapest & most widely available. The problem with NiCd is its nature of developing a 'memory' if not cycled completely (ie fully charged & discharged). Over time a NiCd battery will lose its capacity & will require more frequent charging. If you own a cordless phone you are probably familiar with this effect - when the battery was new you could talk for hours, and a year later you're lucky to get 30 minutes.
It is for this reason that we recommend NiMh or Li-Ion batteries for use with solar or dynamo charging systems where it is not always possible to know whether the batteries have been completely recharged.
Both NiMh & Li-Ion technologies are becoming more readily available, & do not exhibit the 'memory' effect. Not only will they maintain their performance over their lifetime, but they also happen to be more tolerant of low temperatures. Most battery chargers are able to charge either NiCd or NiMh. Li-Ion chargers tend to be unique, so check with the manual for your charger to determine if it is safe to charge Li-Ion batteries with it.
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PowerFilm USB+AA
