Talk Morgan Forums Thread Like Summary - Battery Health - CCA measured value

I have just bought a Bosch 049 battery to replace the battery in my Plus 8. This is a 45AH battery rated at 330 cranking Amps.

I put a battery tester on it and go the following:

Charge 100%. 12.82V
Health 78%. CCA 292A
Internal R. 10.27 milliOhm

I've no idea how the tester works, but I would speculate it infers the state of charge from the open circuit voltage (12.82V) and it measures the internal resistance by putting the battery briefly under load (maybe 100A ?). No idea how it measures the CCA. Nor any idea of how the health number is calculated.

But anyway, 10 milliOhms seems a bit high for a brand new battery. I've seen values of 5-8 millOhms for other new batteries of similar size and technology.

Does anyone know anything about what is an acceptable. value for internal resistance of such batteries?
I don't see a date of manufacture on it, so I've no idea how long it has been sitting in store, so I'm wondering if the battery has simply degraded over time before I got it.

Typically the old style battery "testers" with the sharp prongs to interface with lead terminals take a current draw in the high hundreds or thousands of amps for a second or two, whilst indicating the current through a robust low resistance. This may prove the CCA (a laboratory figure in any case) but probably takes a lump out of a new batteries life.

Low internal resistance indicates a batteries ability to deliver high currents so is important for a starter battery but its not a figure that's often used. For longevity battery capacity measured in amp hours (Ah) is the best guide. High capacity means a) an easy starting car puts little percentage drain on it, and b) as capacity naturally reduces with age you have a usable capacity left for longer.

My Roadster is factory fitted with a generic type 075 battery with C20 rate capacity of 60Ah meaning it should provide when new 3 amps for 20 hours.

45Ah sounds a little low for such an engine but it may be you don't have space for larger capacity. As a rule I would always fit the largest capacity that can physically be accomodated. The price not being proportionate.