My 159 1.9JTDm needs a new battery...
As I see it, there are 4 aspects to a car battery - Ah, CCA, physical size and terminal layout:
- The Ah doesn't matter - that is how much charge the battery can hold. The higher the Ah, the longer the battery will run uncharged.
- The CCA is the amount of power the battery can send to the alternator when required over the sustained 30 second period.
- The battery needs to fit in the tray, so physical width is crucial as the bracket needs to secure the battery. Height is important as the strap goes over the battery and doesn't want to be loose. Length is less important - the battery could be shorter, but not longer than the tray.
- The terminal layout is important as it needs to match where the wires are in the car
Does the above seem about right?
My real question is simple, does it matter if the CCA rate of a replacement battery is higher than the original? I have read in several places that I shouldn't use a battery that is more than 10-15% higher CCA than the original. Is this true? I presume the limit is to prevent overload on the starter motor. Is this true or would the starter just draw as much power as it requires, making the CCA upper limit irrelevant?
If the CCA limit is true, then I can't find a battery to fit my car! The Exide that is in the car from new appears from its label to be only 440CCA (yet 90Ah!). This seems rather low for a diesel. The good online references (such as www.tayna.co.uk
) point to a type 027 (some say 096, but this is for the 2.4jtdm I think). Type 027 batteries have CCA rates from 540 to 640, which is much higher than the existing battery. Several people on here have recommended the Bosch S5, but that is a 680CCA battery. If I stick to the 10% rule, then 480CCA is about the limit for that car.