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I drive a 2004 VW Passat B5. Recently, my insurance company came round to fit a black box to my car as part of the terms and conditions of my car insurance policy. Whilst they were doing this they had to visually check the condition of the car, as well as check the state of the battery.

A concern that they had to raise on the report was that the battery was in poor condition and that I should consider getting it replaced. If I don't, they said the car may not start reliably in cold weather.

I saw the following reading:

REPLACE BATTERY
Battery State 52%
12.3V
226 CCA

What does this mean? Does my battery really need to be replaced?

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A battery for your car might be a Varta 545 412 040 which has 45Ah and a cold crank current (CCA) of 400A. Your value is about 56% of this.

From Wikipedia's "Automotive battery" article:

Cold cranking amperes (CCA) is the amount of current a battery can provide at 0 °F (−18 °C). The rating is defined as the current a lead-acid battery at that temperature can deliver for 30 seconds and maintain at least 1.2 volts per cell (7.2 volts for a 12-volt battery). It is a more demanding test than those at higher temperatures. This is the most widely used cranking measurement for comparison purposes.

It is a measure of the power of your battery, which slowly gets lower over time. And yes, if your battery is too old, the CCA may be so low, that the battery can't start the motor when it's cold. And about 50% isn't that much any more...

However, I wonder how they got this value, as the test conditions are hard to achieve with this little box.

Typically, you will notice your battery is old when starting isn't that easy any more or if lights become really dim when you start it.

  • "I wonder how they got this value, as the test conditions are hard to achieve by this little box" The mechanic took the reading when he fitted the box, it was not done remotely using the information transmitted by the box. "Will this affect your insurance rates as you don't care about your car?" - I do care about my car! Otherwise great answer. – Max Goodridge Jan 12 '16 at 15:57
  • And since you asked, the only things that effect my premiums are driving behaviour and car mileage (this applies to most UK black box policies). – Max Goodridge Jan 12 '16 at 15:58

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