Cobra Electronics CPI 2550 - Manual (Page 9)

13 Nothing Comes Close to a Cobra ® 12 English
Power Consumption
•
For each piece of equipment you will be operating from the
inverter, you must determine the battery’s reserve capacity
(how long the battery can deliver a specific amount of current —
in automotive batteries, usually 25 ampere)
or ampere-hour capacity (a measure of how many amperes a
battery can deliver for a specified length of time).
Example – Reserve capacity: a battery with a reserve
capacity of 180 minutes can deliver 25 ampere for
180 minutes before it is completely discharged.
Example – Ampere-hour capacity: a battery with an
ampere-hour capacity of 100 ampere-hours can deliver 5
ampere for 20 hours before it is completely discharged.
To determine the battery ampere-hour
capacity you require:
1. Determine how many watts each piece of equipment
consumes. This can normally be found on the product label.
If only the current draw is given, multiply the current draw
by 115 to get the watt consumption.
2. Estimate the time (in hours) that each piece of equipment will
be running between battery charging cycles.
3. Calculate the total watt-hours of energy consumption
(power x operating time) using the average power
consumption and the total estimated running time
(in hours). Power x Operating Time = Watt-Hours.
4. Divide the watt-hours by 10 to determine how many power
supply’s (12 volt) ampere-hours will be consumed.
Ground Wiring
•
There is a screw on the rear panel for Chassis Ground. This is
to connect the chassis of the inverter to ground.
The Chassis Ground Screw must be connected to a grounding
point, which will vary depending on where
the unit is installed. Use a #8 AWG copper wire
(preferably with green/yellow insulation) to connect
the chassis ground screw to the grounding point.
In a vehicle: Connect the Chassis Ground to the
chassis of the vehicle.
In a boat: Connect to the Boat Grounding System.
In a fixed location: Connect the Chassis Ground Screw to
earth ground by connecting to a ground rod (a metal rod
pounded into the earth) or other proper service entrance
ground.
Chassis Ground
Power Consumption Ground Wiring
Installation Installation
Laptop
50 watts x 2 hours
= 100 watt-hours
TV/VCR (up to 25")
115 watts x 3 hours
= 345 watt-hours
Blender
300 watts x 15 minutes
= 75 watt-hours