Rick's Free Auto Repair Advice

Cold weather car battery care

How to take care of your car battery in cold weather—cold weather car battery care

Cold weather is hard on car batteries. Here’s are the rules for cold weather car battery care to keep your car starting every time you turn the key.

Drive your car at least once a month to keep your car battery charged

Lead acid style car batteries lose about 1-2% of their charge PER DAY even when the car isn’t being run. Plus, car computers draw a small amount of power even when the car isn’t running. So if you don’t drive your car for a month, you’ll wind up with a dead battery or at least a severely discharged battery.

If you start your car, turn on the headlights, blower motor, rear window defogger and seat heaters and drive round trip to the convenience store several times in a week, without longer drives, you’re taking more power out of the battery than you’re putting back in. That kind of use can leave you with a dead battery in just a week or so. So it’s really important to driving your car for at least 20 mins at highway speeds least once a week, while running as few power items (heater, defogger, headlights, heated seats, etc.) as possible to keep your battery in peak condition. You really want to get the engine up to around 2,000 RPM so the alternator can output enough amps to fully recharge the battery. Starting it and letting it idle for 5-mins with the blower, seat heaters and rear window defogger on will actually drain the battery. It simply can’t recharge in 5-mins at idle speed.

Keep car battery terminals clean

Battery terminal corrosion creates electrical resistance and that lower the voltage available for starting and prevents the battery from getting a full charge. The pictures I show here are worst case examples of battery corrosion. If your terminals look like these, you should paste a big label on your forehead that says, “I don’t take care of my car.”

But battery corrosion doesn’t have to look this bad to create problems. I’ve seen voltage drops on battery terminals that look just fine. So next time your car is in the shop, have them clean the battery terminals and spray them with battery corrosion protectant.

Replacing a dead car battery

Most newer vehicles have electronic throttle bodies, no-pinch windows, electronic temperature blend actuators, and many other electronic devices that need to be calibrated to work properly. In the old days you could loosen the battery terminals and slap in a new battery. Not anymore. As soon as you disconnect power, the throttle body, windows, radio, and blend actuators will forget their calibration. What does that mean to you? Well, you may discover that the car won’t drive over 20-miles per hour, or the windows won’t go up or down automatically.

Professional shops plug a jumper pack into the diagnostic connector to keep power flowing to the computers before they disconnect the battery. If you don’t want to invest in a cable shown here, then leave battery replacement to a pro. Because some car makers require a scan recalibration to bring those electronic devices back into full operation. That calibration can easily cost upwards of $100, far more than the cost of professional battery installation.

If your car has a start-stop feature, you MUST reprogram the computer to tell it you’ve replaced the battery. This isn’t an option. If you don’t do it, you can damage the new battery.

How to jump start a dead car battery

Here’s a question: Would you yank your computer’s power cord out of the socket with the computer running? Well, that’s pretty much what you’re doing when you jump start a battery using cables. The second you attach the cables you create a surge that can fry your car’s computers. Pros use jumper packs and so should you. I know, you’ve jumped hundreds of cars with no problem. But when the day comes that you fry a $600 computer or heater control module, you’d wish you had invested in a $100 jumper pack.

Avoid running high-amp items at idle

Yes, this is going to sound like the first paragraph, but it’s true. Your car’s alternator can’t produce full output at idle. When you’re sitting at train tracks with your headlights, heater, heated seats, and defogger on, you’re draining your battery and you’re overheating the alternator. For maximum battery and alternator life, turn off a few accessories if you’ll be idling for a while.

Cold weather car battery care is pretty simple: keep the terminals clean, drive it long enough to charge the battery, and reduce electrical loads when idling for an extended period. And, be very careful when jump starting. Use a jumper pack and don’t volunteer to let other people use your car as the jumping vehicle—the jump can damage YOUR alternator.

For tips on how to test the condition of your battery, read this

For tips on how to buy a car battery, read this

For tips on buying a battery charger, read this

©, 2015 Rick Muscoplat

Posted on by Rick Muscoplat


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