How many amperage of battery is the right specification for my M45 2003 please? Can a 75A or a100A battery provide the necessary crank?

Do you mean CCA? Cold Cranking Amp? If so, 75 or 100 is VERY low. Most are 600-700.

Dunno the answer, but the OP probably means aH and not CCA. I don't think Nissan specifies aH, I believe their specs are in CCA only.

For an 18 year old car, I'd grab an inexpensive battery in size 24F. I've had good luck with WalMart batteries in my vehicles.

I meant AH. Eg., 75AH, or 100AH. Kinda like the capacity here.

I never even looked at AH before of a car battery. I figured they would be all around the same fort a specific size battery. I suppose that isnt really tue if the CCA can be different in the same size, means different material construction and so different capacity too.


I just looked up the battery I have which has been the best battery I have used so far. These are the specs on it:
Pulse (5 second) Hot Cranking Amps (PHCA) 1500
Cold Cranking Amps (CCA) 850
HCA 1250
MCA 1050
20Hr Nominal Capacity (Ah) 68
10Hr Nominal Capacity (Ah) 62
Reserve Capacity Minutes 135


So just based on the AH capacity of mine, I would think a 75AH battery should be plenty fine for your car? I cant imagine a 2003 has more electronics than a 2006 that I have.

I have gone thru several batteries in my 2006 M35 trying to figure out the best CCA. They would last a month or so then I would have to charge them. I finally went with a group 34 battery with at least 750 CCA and I didn't have any more problems after this.