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Trickle chargers vs. battery tenders: what's the difference?

We just bought a winter home in Arizona and plan to spend five months there. I will buy a new vehicle on my next trip there, probably a mid-sized sedan, and will leave it parked in the garage when we return to Canada. It will just sit there and not be restarted or run during the seven months we are away.

Is a trickle charger still the best way to prevent the battery from dying and resulting problems with the computer, alarm system, etc.? - Gerry, Cobourg, Ont.

A trickle charger never was the "best way" but thankfully new generation of "battery tenders" is on the market, which do the job nicely.

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The difference between a trickle charger and a battery tender is that a trickle charger constantly applies a charge, whether the battery is fully charged or not. A battery tender, on the other hand, has circuitry that monitors the battery and charges only when the voltage has dropped below a preset level, thus preventing overcharging and damage.

When it senses the voltage has dropped, a battery tender will resume charging. Because of this a battery tender can be left connected indefinitely. A trickle charger, on the other hand, because it keeps applying a charge, should be disconnected and reconnected occasionally, probably used for charging once or twice a month for a day.

I would be remiss if I didn't tell you there are other steps you should take before leaving a vehicle to sit that long.

Since there are no plans to give it a little exercise - a 20-mile drive, perhaps once a month - have the dealer or service shop change the oil and filter before putting it in storage regardless of mileage.

Add fuel stabilizer, fill the fuel tank and drive for 10 or 20 miles before putting it in storage.

Ideally you would put it on jack stands to prevent the tires becoming flat-spotted and, considering the summer temperatures in Arizona, make provision for air circulation in the garage.

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