Battery Chargers for Vehicles That Sit a Lot
- Batteries work by transferring the power contained in an electrolyte or acid between two sets of plates. Think of this power transfer as a sort of "spark" that you can't see, and a high-voltage spark will cover distances easier than a low-voltage spark. When voltage in a battery drops below a certain point, the plates that transfer that power have to work harder to transfer energy. Over time, that excess work will eat away at the plates and permanently damage the battery.
- Most standard battery chargers, even those with a 2-amp "trickle charge" setting, aren't suited to the task of keeping a battery at its optimum voltage. The primary reason is that most batteries don't self-discharge within a tenth of the power that a trickle charger provides, so eventually the trickle charger will overcharge the battery. Modern microprocessor-controlled chargers, however, can sense battery voltage and know when to shut off to avoid overcharging. Such chargers serve the purpose for long-term storage.
- Battery tenders are essentially just small battery chargers designed specifically to keep a stored battery charged, and some computer-controlled chargers even have a "battery tender" mode that mimics what dedicated units do. Battery tenders differ from standard chargers in that they can deliver a charge measured in milliamps instead of full amps, which just offsets the battery's self-discharge rate without ever overcharging it. The only real downside to a battery tender is that it requires a power source, which may or may not be available where you parked the car.
- Solar battery tenders pick up where standard tenders leave off, and they're beginning to gain a foothold in the market as an affordable alternative to plug-in chargers. Solar chargers were, at one time, extremely cost-prohibitive to produce and sell, but the thin-film photovoltaic cells used today have brought the cost down enough that they cost nearly the same as a competitive plug-in. The solar charger's primary benefit is that it will work anywhere there's sunlight, meaning that you won't have to run a 300-foot extension cord from your house to the back yard where you've parked your project vehicle.