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Battery Amps
craigdiver - 12/7/17 at 06:13 PM

The battery out my donor BMW 523i was big, 65Ah capacity and 680A cranking power.

Do I really need 680A to crank the 2.5 6-cylinder engine or was this likely to have been rated to run the extensive BMW electrics.

Not looking for expensive lithium based battery just a smaller lead-acid, anybody up on auto electrics that can suggest capacity and power for my haynes roadster?

Cheers

Craig

britishtrident - 12/7/17 at 07:00 PM

quote:
Originally posted by craigdiver
The battery out my donor BMW 523i was big, 65Ah capacity and 680A cranking power.

Do I really need 680A to crank the 2.5 6-cylinder engine or was this likely to have been rated to run the extensive BMW electrics.

Not looking for expensive lithium based battery just a smaller lead-acid, anybody up on auto electrics that can suggest capacity and power for my haynes roadster?

Cheers

Craig



The std battery listed for your engine is short coded 110 --- which is a whacking great 80ah 800cca sae

If the car is a manual transmission and used only in summer you should get away with a good quality (ie Exide Blue or Varta/Bosch Silver) short code 063 but it will shorten the life of the battery. So treat it kindly and keep it topped up.

CCA isn't really anything to do with normal starting is is all to do with the current the battery can produce for a given time in extreme sub-zero condition before dropping below 7 volts. There are different standards for CCA and the better bsattery manufacturers are always very conservative about the ratings they publish so it is not a really useful bench mark.

Tayna Batteries Link type code 063

craigdiver - 12/7/17 at 07:05 PM

quote:
Originally posted by britishtrident
quote:
Originally posted by craigdiver
The battery out my donor BMW 523i was big, 65Ah capacity and 680A cranking power.

Do I really need 680A to crank the 2.5 6-cylinder engine or was this likely to have been rated to run the extensive BMW electrics.

Not looking for expensive lithium based battery just a smaller lead-acid, anybody up on auto electrics that can suggest capacity and power for my haynes roadster?

Cheers

Craig



The std battery listed for your engine is short coded 110 --- which is a whacking great 80ah 800cca sae

If the car is a manual transmission and used only in summer you should get away with a good quality (ie Exide Blue or Varta/Bosch Silver) short code 063 but it will shorten the life of the battery. So treat it kindly and keep it topped up.

CCA isn't really anything to do with normal starting is is all to do with the current the battery can produce for a given time in extreme sub-zero condition before dropping below 7 volts. There are different standards for CCA and the better bsattery manufacturers are always very conservative about the ratings they publish so it is not a really useful bench mark.

Tayna Batteries Link type code 063


Great answer, thank you very much AND I like the look of the prices for the 063 batteries, I'll take your advice and go for the Bosch Silver.

02GF74 - 12/7/17 at 07:33 PM

quote:
Originally posted by craigdiver

Do I really need 680A to crank the 2.5 6-cylinder engine or was this likely to have been rated to run the extensive BMW electrics.



Battery is for starting the engine, after that the alternator should generate the electricity to run the electrical gubbins.

Nickp - 12/7/17 at 08:15 PM

Job done, save weight

Xtreme Racing Dry Cell AGM Battery Motorcycle Rally XR600 alternative to PC680

craigdiver - 12/7/17 at 08:26 PM

quote:
Originally posted by Nickp
Job done, save weight

Xtreme Racing Dry Cell AGM Battery Motorcycle Rally XR600 alternative to PC680


Sold!, 6kg vs 12kg for a 063 lead acid battery.

britishtrident - 13/7/17 at 11:03 AM

There is a rough formula for guestimating the cranking time you get from a new fully charged battery in mild weather

Cranking time in minutes = (ah*30)/(actual average cranking current)

Keep in mind the AH capacity of a battery reduces with age. How much of reduction not only depends on the age of the battery but the number and depth of discharge-charge cyles it has been subject to.
A 4 year old battery may pass a voltage drop test but have only 1/4 the ah capacity it left the factory with.

A year old battery that hasn't been abused will normally have about 85 percent of its rated ah capacity.

[Edited on 13/7/17 by britishtrident]

coyoteboy - 13/7/17 at 12:43 PM

quote:
Originally posted by 02GF74
quote:
Originally posted by craigdiver

Do I really need 680A to crank the 2.5 6-cylinder engine or was this likely to have been rated to run the extensive BMW electrics.



Battery is for starting the engine, after that the alternator should generate the electricity to run the electrical gubbins.


And for carrying the load when your engine is off and the kids are sat for 20 minutes listening to the radio, or you need to leave it with the sidelights on for an hour and BMW used 400W sidelights etc etc, and then still have it start.