Statpower Portawattz 3000, Owner'S Manual, Page: 16 / 36

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only 4 hours, resulting in an actual capacity of 80 ampere-hours.
For this reason, it is difficult to compare rated ampere-hour
capacity with battery reserve capacity. For example a battery
with a reserve capacity of 180 minutes has the following
calculated ampere-hour capacity:
However its actual ampere-hour rating will be closer to 100
ampere-hours because it is
rated at the discharge current
required to get 20 hours of
operation (about 5 amperes).
To determine the battery
capacity you require, follow
these steps:
STEP 1 - For each piece of equipment you will be operating
from the Portawattz 3000, determine how many
watts it consumes. This can normally be found
on a label on the product. If only the current draw
is given, multiply the current draw by 115 to get
the power consumption in watts.
STEP 2 - For each piece of equipment you will be operating
from the Portawattz 3000, estimate how many
hours it will operate between battery charging
cycles.
STEP 3 - Calculate total watt-hours of energy consumption,
total hours running time, and average power
consumption as in the following example:
STEP 4 - Using Table 3, find the battery size that will give
you the required operating time at the calculated
average power consumption. For instance, from
the example below, the required operating time is
6 hours and the average power consumption is
180 min.÷ 60 = 3 hrs
Therefore...
3 hr. x 25 amps = 75 amp-hrs
Equipment
Power
Consumption
(Watts)
Operating time
Watt Hours
(
Power x Operating Time
)
TV & VCR 115 3 Hrs. 345
Sewing Machine 150 1 Hr. 150
Waterpik 90 0.25 Hrs. (15 Min.) 22.5
Blender 300 0.25 Hrs. (15 Min.) 75
Coffee Maker 750 0.3 Hrs. (18 Min.) 225
Coffee Grinder 100 0.2 Hrs. (12 Min.) 20
Microwave Oven 1500 0.5 Hrs. (30 Min.) 750
Washing Machine 1500 0.5 Hrs. (30 Min.) 750
TOTAL
6.0Hrs.
2337.5 watt-hours
Table 3