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Rob's Garage

How to keep your battery alive in storage Add to ...


I spend three months out of province every winter and leave my car in an underground garage that only partially protects it from outside temperatures. The car is not near an electrical outlet.

What are the pros and cons of arranging for the car to be run periodically to maintain the battery as opposed to moving the battery indoors and putting it on a so-called battery maintainer?

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John F. Brown

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Even though we are heading into summer John, what I'm about to explain applies to any time of the year.

Batteries, cars, trucks, motorcycles - pretty much anything mechanical - are like people. If you don't use it, you'll lose it. As my wife would tell you, sitting around too much will make your ass as flat as your tires if you don't get up and move.

Leaving a car to sit for long periods of time is bad, but fortunately, your situation is not too bad.

The car can be left untouched for those three months. The battery, not so much.

I am asked the vehicle storage question often and with my own experience storing my '62 Lincoln, I can say that just starting the engine to keep a battery charged is a bad idea. Others will tell you that this is good for the engine as it warms up the coolant and motor oil at the same time; but this is not a good idea. To truly be effective, a vehicle needs to be driven for at least 20 minutes - I prefer 30. If not, condensation will build up inside all the mechanical cavities of the engine, transmission and final drive. This can cause corrosion if it's not allowed to burn off. A 30-minute drive gives the vehicle time to heat up to boil off any condensate that can build up.

Batteries operate efficiently at an ideal temperature of 80F. They are also not very tolerant of "cycling" - taking the battery from a charged state to discharged, and back to a charged state.

On top of a battery's distain for discharging and recharging, it really doesn't like to remain in a low or discharged state for very long, so your observation of a battery maintainer is valid. There are many compact integrated circuit Smart chargers on the market that do a good job of keeping a battery topped up for extended periods of time. I just purchased one of these for a relative that spends six months a year out of country. Alright, my mother-in-law, so it had to be easy to use.

At the risk of sounding like a salesman, I found that this charger works very well, is small and easy to connect. It is sold under the CTEK brand name but there are others out there of varying size and capacity.

To be effective, batteries should be kept as constant to room temperature as possible if they are not being used. For you John, you may need to move the battery into a warmer area other than your car storage area.

Please be warned that during the charging of any lead-acid battery, hydrogen and oxygen gasses may be given off if the charge rate is too high. Combined, these gases are explosive if exposed to a spark.

This is another advantage to small maintenance chargers - they reduce the amount of gassing, but it's always safest to provide plenty of ventilation when charging a battery.

There are two ways to test to ensure that your battery is fully charged:

  1. Open Circuit Voltage - this is a tech term to describe the voltage across the terminals while either disconnected form the vehicle or having no electrical devices on. A fully charge battery should register 12.65 V, not 12 V as most would assume.
  2. Hydrometer - this can be difficult as most batteries nowadays are sealed and don't allow access to the sulphuric acid/water solution (electrolyte) necessary to operate a hydrometer - not to mention that this is dangerous.

And speaking of danger, working around a battery is dangerous and unless you are familiar with the safety requirements, maintenance checks are often best left to technicians.

So John, don't run your engine without going for a drive and if you can, move the battery to a warmer location and use a Smart charger to keep it fully charged. The electronics that run your car will thank you, as you will thank them when you crank the engine over for the first time in the spring - and it starts!



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