Rick's Free Auto Repair Advice

What are Cold Cranking Amps

What does cold cranking amps do I need for my new car battery?

Car batteries are rating using several different tests like: cold cranking amps (CCA), cranking amps and reserve capacity. Of these ratings, CCA is probably the most important. Since a lead acid battery produces power through a chemical process, it’s sensitive to outdoor temperatures. In cold weather this chemical process slows down and produces less power.

Cold cranking amps

The official test to determine a battery’s CCA rating requires the battery to be chilled to 0°F (-17.8°C). Then the battery is put under load for 30-secs. The number of amps the battery can deliver at that temperature without dropping below 7.2-volts determines its CCA rating.

Why CCA is important?

As I mentioned, in cold weather the chemical reaction slows down and you battery can’t deliver as much power. At the same time, a cold engine requires more power to start. That’s mostly due to the fact that the engine oil is cold and thicker, cold cranking amps in cold weatherso it provides far more resistance to moving parts. Here’s a chart showing available battery power versus how much power is required to start a cold engine.

Understanding battery construction

Car Battery plate construction

Battery plates contain a grid coated with an electrically producing material. The type of metal used for the grid depends on the type of battery. For example, the grid in a maintenance free battery is often made with an alloy of lead, calcium and tin. The battery manufacturer may add antimony to stiffen the lead and increase the battery’s ability to cycle between charge car battery grid constructionand discharge operation. In older batteries that required the addition of water (not maintenance free) battery manufacturers often added 3-5% antimony to the lead grid. However, since antimony can cause the battery electrolyte to gas, antimony has been reduced to less than 2% in maintenance free batteries.

 

Paste is applied to the grids

Once the grid is formed, it’s coated with a paste. Depending on the type of car battery grid with pastebattery the paste can be made from lead oxide, sulfuric acid and water, along with fibrous additives to keep the paste bound together. An “expander” material is also added to maintain the surface area that’s required for contact with the electrolyte.

Plate separators are installed

The positive and negative plates cannot touch or they’ll form a short. So porous spacers are installed between the plates. The porous spacers allow battery acid (electrolyte) to pass between the plates but prevent the plates from touching.

exploded view of car battery

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Should you buy a battery with more CCA?

No. Automotive engineers aren’t stupid. They know how batteries are made and they know there’s always a trade-off when packing more CCA into the same size battery. To get more CCA, a battery manufacturer can use either thicker grids or more (thinner) grids. Each design has advantages and disadvantages. For example, if you buy a battery with a higher CCA rating that is recommended by the car maker and the battery achieves that higher CCA rating by using thinner grids with a higher paste density, that design is far more sensitive to high temperatures. It’s not the outside temperature per se that damages the battery, but the combination of high ambient temperatures and high under hood temperatures can literally cook the battery, dramatically decreasing its life. Thicker grids, on the other hand, allow less room for battery electrolyte. So the battery may have high initial CCA but quickly lose its ability to output high amps because of lower levels of electrolyte.

Stick with the CCA rating of the car maker

© 2016 Rick Muscoplat

 

Posted on by Rick Muscoplat

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