Be aware of battery and charger inconsistencies!

[Ether]

Originally Posted by philso

Automotive batteries rarely give an Ahr rating but they would typically be in the range of 35 to 85 Ahr

I believe the RCM (reserve capacity in minutes) rating of automotive batteries follows an industry standard of 25 amps load until voltage drops to 10.5V.

If so, you could multiply the RCM by (25/60) to get an Ahr rating (at 25 amps down to 10.5V).

For many automotive batteries, the RCM rating is available.