| Author | Message | ||
     Geoff Wootton Grand Master Username: dounraey Post Number: 343 Registered: 5-2012 |
I am having trouble determining which is the best replacement battery to fit on my 74 SYI. I have checked the threads on this forum and the resource file but cannot find the information I require. The battery on the car is an Everstart 27DC6. Cranking amps (32F) = 720, Cold Cranking Amps (0F) = 600. Does this look right. I assume the 27 in 27DC6 refers to the Group 27 size. I have checked out the NAPA website which lists a 1974 RR Silver Shadow but produces 17 batteries of various different capacities ranging from a CCA of 460 amps up to 850 amps. I seem to remember that the battery must match the output from the alternator. Does anyone know the correct rating for a battery on an SYI. Geoff | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 697 Registered: 6-2009 |
Geoff, First, here's the info I keep on batteries in the resources file: Group 27 batteries are used in Rolls-Royce and Bentleys from 1946 to 1980. Usually the positive post is toward the front of the car which would mean a 27F for cars with the battery on the right side [Clouds] of the car and a 27 for cars with the battery on the left side of the car [most, but not all, Shadows and Corniches]. Check the battery in your car before ordering a new one. CCA (Cold Cranking Amps) are just that - a rough measurement of the available power when it's cold outside. You can get away with a far lower value living in Las Vegas than you will in Cleveland. As far as I know, our alternators should be able to charge any Group 27 battery perfectly adequately regardless of the CCA rating. Brian | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 344 Registered: 5-2012 |
Brian Many thanks. I must have missed the entry on batteries when I checked your resource file. In view of what you have said it appears that the battery on the car at the moment is correct so I shall match it's spec. I can't recall why I have this notion that alternator/battery should match. It may be a throw back to the pre-alternator days. Geoff | ||
| Jan Forrest Grand Master Username: got_one Post Number: 528 Registered: 1-2008 |
I use the same parameters on all my cars. First I carefully measure the space to see how big a battery will fit in it. Then I trawl t'interweb for batteries of that physical size and check out the specifics of them. Living in Blighty that will usually mean one with superior cold weather ability, maximum amp hours and best Cold Cranking Amps. Then I look for the best prices on eBay and/or phoning around. The latest such battery was (surprisingly) cheapest at a local small car spares shop beating all other sources by a significant margin! I even got 3 years warranty with it, so the receipt lives inside the Shadow's battery compartment to prevent losing it. | ||
| bobuk Unregistered guest Posted From: 94.197.122.74 |
1974 shadow battery left hand side of boot Bat is 078 cold crank 455 amps 42 English pounds Fit largest capacity you can Alternator senses battery voltage and will charge it until voltage is approx just below full charge then trickle charge thereafter Any electrical loads the alternator will balance The system is automatic The size of the battery is not an issue once engine running. A motorbike battery would work but it won't start the engine The main issue is the cold crank amps and time before voltage drops below 10 volts while cranking to be kind to battery and starter do not crank more than 20 seconds with 1 minute between trys If the engine needs 400 amps to kick it over then fitting a say 600 amp Jobbie will not make the starter need 600 amps It will allow more start attempts and idiots like me to leave lights on and my grand kids to play with the Windows Calcium better because voltage is slightly higher when cranking} (Message approved by david_gore) |
