Rick's Free Auto Repair Advice

Reserve Capacity Rating

Reserve Capacity Rating

A battery’s reserve capacity rating is the time in minutes that a new, fully charged battery will deliver 25 amperes at (80°F) while still maintaining a terminal voltage equal to, or higher than, 1.75 volts per cell.

In other words, the reserve capacity rating represents the time the battery will continue to operate essential accessories if the alternator or generator of a vehicle fails.

How much reserve capacity do you need?

Here are some typical current (amp) draw for vehicle accessories when run without the engine or charging system operating

Ignition system 2-9-amps
Radio 0.5 –5-amps
Windshield Wipers 7.5-amps
Headlamps (Low Beam, Dim) 17-18-amps
Headlamps (High Beam, Bright) 19-20-amps
Parking Lights 4-10-amps
Fog Lamps 8-amps
Brake Lights 6-11-amps
Interior Lights 2-4-amps
Hood Light 0.5-1.0-amps
Horn 4-amps
Power Window (one window) 5-amps
Trunk Light 0.5-1.0-amps
Blower motor 10-14-amps
Heated Rear Window Defogger 13-28-amps
Heated Seat 4-5-amps
Power Seat Motor 10-13-amps
Starter motor (Summer—Gas) 150-200-amps
Starter motor (Diesel) 450-550-amps
Starter motor Winter (Gas) 250-350-amps
Starter motor (Diesel) 700-800-amps

Posted on by Rick Muscoplat


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