Is Your Car Battery Knackered?

By Henry Leung

One of the stupidest things I have ever done (and I have done many stupid things) is shock myself with a car battery. I was a teenager, and I had to change the battery in my car. The clamps were on really tight, so I thought it would be smart for me to use a metal wrench, without gloves, to take off the clamps. The second I touched the wrench on the connector, there was a burst of light as I, with my body, completed the electrical circuit. There was a small explosion and I fell back and dropped the superheated wrench. When I came to my senses several minutes later, I noticed that there were scorch marks on the wrench and that some of the metal had actually broken off. The battery was toast as well, but at least I was somewhat ok.

Batteries are probably the most low-tech of all the equipment in your car with the majority of car batteries being lead acid. However, they still require some regular maintenance. If you spend a few minutes every few months maintaining and checking your battery, it will save you hours of grief later on. Here’re some tips to help you.


You’ll find that if you haven’t maintained your battery for a long time, there will be crusty white residue on the terminals. Always disconnect the negative terminal first. Don’t ask how I know this.


Use a combination of baking soda and water with a wire brush or a toothbrush. Any dirt on the terminals attracts moisture and this will cause the battery to constant discharge even when the vehicle is turned off. To prevent this from happening in the future, coat the battery terminals with grease before reattaching the clamps.


If you have an older car, the battery may be a non-sealed type. If this is the case, you need to add distilled water to the vent caps to prevent the battery from drying out. Tap water tends to have too much mineral content and can damage the battery. Make sure to check the battery at least once during summer months because if the battery runs dry, the heat will destroy the battery cells.


Most cars will come with a tie-down strap to secure the battery. Double-check that the strap is in good condition; if there are any tears, replace it immediately. When your car is moving, your battery will become a 40lb projectile and cause some serious damage in your engine bay if it isn’t restrained.



Batteries discharge slowly, even if they aren’t being used. If you are leaving for a long trip (more than a month) or have a summer car, it’s a good idea to use a trickle charger. A trickle charger is a slow charger that maintains the charge on your battery. Just keep in mind that batteries release hydrogen gas when charged; don’t charge your car in your garage or else you might not have a garage one day.


Most batteries have a lifespan of between 3 to 6 years. If you notice that your car engine is cranking more slowly than normal, especially when it is cold outside, it might be time to replace your battery. This is also the time to borrow/steal a voltmeter. Batteries should be around 12.5V when new. If the battery voltage is below 12.0V, it’s probably time to replace your battery.

Finally, Make sure you take advantage of warranties on batteries! Costco, for example, has prorated battery warranties of 100 months (over 8 years!). While they won’t replace a battery with a new one after 3 years, they will give you a pro-rated amount of money back. My last battery from Costco lasted about 4 years and they refunded 50% of the original cost when I returned it. It’s a pretty cheap way to buy a car battery!

About Nishal Singh

Car enthusiast since before I could drive.


  1. Avatar

    Hope this helps with my car merc 320 chi 06

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    The only way one can receive a shock from a 12 volt battery is to soak one’s hands in salt water to lower skin resistance, and maybe not even then. 12 volts is not enough. What did happen, and it happened to me, is that the wrench was on the positive terminal and the other end hit something on the frame. Which is why it’s good to remove the negative lead first. In any case, lot’s of sparks were thrown, a huge current passed through the wrench, maybe burning your hands and toasting the battery. Remove the negative lead first and don’t use a wrench long enough to bridge the two terminals.

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    car batteries produce VERY high currents………a short circuit can result in quite large lumps of metal

    becoming white hot in seconds. Best to disconnect the +ve connection to the battery.

    Be especially careful with metal watch straps……the possibility of your wrist being barbequed by a red hot

    wrist band. !2 volts is rarely dangerous ……….500 amps of current is really scary

  4. Avatar

    12Volt is not enough to produce any dangerous current through the human body – dry or soaked with brinE.
    Even if a car battery is capable of sourcing 500-1000 Amps, this is only dangerous if it is connected to somthing that will allow this amount of current to flow (having low resistance, like a wrench).

  5. Avatar

    This guide is great. Thanks

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