My Car's Battery Goes Dead

Q: Our 1999 Ford Taurus, which resides under a cover, almost always has a dead battery after it sits for a month. I have had to replace it three times in the past seven years. I tried one of those solar panels plugged into the cigarette lighter by having a clear plastic window installed in the cover. The plastic housing on the charger actually melted when the heat outside got to 118 F and shorted, further draining the battery. Who knows what the temperature got to inside the car? Sure, I can disconnect and reconnect the battery, but for what that takes I can jump-start it with a portable jump-start battery device easier. Any advice to keep the battery from dying? The car’s parked in a lot across the street from the house, so running an extension cord to a trickle charger isn’t an option.

A: Melted the solar charger? Man, I bet you could bake cookies in there on a sunny day.

Letting any battery discharge that deeply will damage it immediately, which explains your high failure rate. And the heat will make the battery self-discharge even faster than normal.

My best suggestion: Get a battery disconnect switch, wired into the ground cable. This won’t prevent normal self-discharging, but it will eliminate any parasitic drains (like the radio presets and computer memory) that are killing the battery between uses. Then whenever you need the car, all you have to do is open the hood, turn the switch on, and start it up and drive away with clean hands. A decent battery should have enough juice left after a month to light the fires. In case the idle period is a little longer, keep an auxiliary starter box in the house on a charger. You can probably get enough charge into the nearly dead battery by plugging one of these gadgets into the cigarette lighter, also leaving you with clean hands.

A second suggestion would be to hard-mount the solar charger on the front license-plate bracket and leave it uncovered by your car cover. Park the car pointing southwest toward the afternoon sun to catch the most rays.

Would The Prius Get Better Gas Mileage If It Weighed Less? Part 2

Q: I read your answer concerning "Would The Prius Get Better Gas Mileage If It Weighed Less?". It was very interesting and I agree with your discussion but I'd like you to go a step further. The thing that is confusing about hybrids has to do with their efficiency. It seems to me that using an internal combustion engine to charge the batteries which power the electric motors that move the car would be less efficient that moving the same car with the internal combustion engine. I recall someone's theory having to do with "Conservation of Energy". Applying the same technologies that maximizes the efficiency of the gas engine as a "charger" could also make it a better "mover". Right?

A: You are correct, charging the batteries onboard with an IC engine and then powering the wheels with an electric motor is inherently less efficient than just gearing the IC engine to the wheels. That’s why most hybrids have some way of doing either or both.

Two compelling reasons to use batteries:

In a conventional hybrid, the batteries are on board to capture energy during regenerative braking, using this energy (normally wasted as heat in the brakes) to accelerate the car later.

In a plug-in hybrid, the batteries are recharged by the grid. A PHEV, if driven for short enough distances to not drain the batteries, may never consume gasoline.