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the charge in your car’s battery. In addition, the power inverter will also draw a small current, less
than 0.1 amp, when turned off and not operating. Therefore, it should be disconnected from your
car’s battery if your vehicle will not be used for more than a day. The following chart shows typical
operation time for two typical car batteries with the engine not running for various loads. Check the
size of your battery.
Battery Life Chart
Power
Usage
Approximate
12v Current
Typical operation
time with 50 amp-
hour car battery
Typical operation
time with 100 amp-
hour car battery
100 watt
9 Amps
5.5 hours
11 hours
200 watt
19 Amps
2.6 hours
5.2 hours
500 watt
47 Amps
1 hour
2 hours
1,000 watt
94 Amps
30 minutes
1 hour
1,500 watt
140 Amps
20 minutes
40 minutes
2,500 watt
235 Amps
12 minutes
24 minutes
Actual Current Draw
Approximate 12 volt current draw is the load in watts divided by 10. Therefore, a 60 watt light
bulb plugged into the inverter will cause the inverter to draw 6 amps (60 / 10 = 6) from the
12 volt supply.
Batteries are rated in several different ways:
Peak cranking amps - This has little to do with how long an inverter can supply power, so it
is not a useful number for inverter operation.
Battery reserve capacity - This number shows how long a battery can supply a given current,
typically 25 amps, before the battery voltage reaches a low voltage. Therefore a battery
rated at 200 minutes reserve can deliver 25 amps for 200 minutes before it is discharged.
Ampere-hour capacity - This rating indicates how many amps a battery can deliver over a
period of time, typically 20 hours. Therefor a 100 amp-hour battery can deliver 5 amps
for 20 hours (5 x 20 = 100).
Actual operating time from a battery will depend upon the current draw from the battery. A
battery will deliver less total power (energy) as you draw higher amps. A 100 amp-hour
battery can deliver 5 amps for 20 hours (100 amp-hours), but it will only deliver 50 amps
for 1 ½ hours (50 x 1.5 = 75) or 75 amp-hours at the higher rate.
Also remember, battery life is decreased if the battery is discharged fully. Lead-acid
batteries have the longest life, if they are kept fully charged.
Lights and Alarms
VOLTS Meter
This 10 segment LED meter shows the actual 12 VOLT input voltage when the inverter is turned on.
Each segment represents ½ of a volt starting at 10 VOLTS up to 15 VOLTS.
