Statpower Portawattz 3000, Owner'S Manual, Page: 15 / 36

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the charge. Battery isolators can be obtained at marine and RV
dealers and most auto parts stores.
If your application involves relatively low power loads (i.e. power
consumption of 300 watts or less) and relatively short operating
times before recharging (one hour or less), you may connect
the Portawattz 3000 directly to the vehicle starting battery.
5.2.2. Battery Sizing
There are a number of different standards for rating battery
energy storage capacity. Automotive starting batteries are
normally rated by cranking amps. This is not a relevant rating,
for continuous use. Deep-cycle batteries are rated either by
reserve capacity in minutes or by ampere-hour capacity.
Battery reserve capacity is a measure of how long a battery
can deliver a certain amount of current - usually 25 amperes.
For instance, a battery with a reserve capacity of 180 minutes
can deliver 25 amperes for 180 minutes before it is completely
discharged.
Ampere-hour capacity is a measure of how many amperes a
battery can deliver for a specified length of time - usually 20
hours. For example, a typical marine or RV battery rated for
100 ampere-hours can deliver 5 amperes for 20 hours (5
amperes x 20 hours = 100 amp-hrs).
Actual battery capacity decreases as discharge current
increases. A battery rated at 100 ampere-hours which can
deliver 5 amperes for 20 hours, may deliver 20 amperes for
Figure 6. Connection for Light-Duty Applications
CAUTION!
The Portawattz 3000 must be connected only to batteries with a nominal output
voltage of 12 volts. The Portawattz 3000 will not operate from a 6 volt battery,
and will be damaged if it is connected to a 24 volt battery.