Xantrex Technology Freedom SW 2000 Battery Information, Battery Bank Sizing, Compute Amp-hours

Battery Information

Battery Bank Sizing Estimating Battery Requirements

Battery capacity Battery size or capacity is just as important as the battery type selected for use with the Freedom SW 2000. The batteries are the most important part of your system, so Xantrex recommends that you purchase as much battery capacity as possible. A large battery will extend running time and ensure that your inverter/charger delivers full rated surge.

Xantrex recommends a minimum battery size of 200 amp-hours (Ah) for moderate loads (<1000W) and greater than 400 Ah for heavy loads.

See “Estimating Battery Requirements” for information on a more detailed calculation.

About Amp-hoursA number of different standards are used to rate battery energy storage capacity. Automotive and marine starting batteries are normally rated in cranking amps. This is not a relevant rating for continuous loads like an inverter. Deep-cycle batteries use a more suitable rating system such as amp-hours (Ah).

Amp-hour capacity is the number of amps a battery can continuously deliver during a specified number of hours. It is represented by the product of the two —amps multiplied by hours.

A typical marine or RV battery rated for 100 Ah can deliver 5 amps for 20 hours (5A × 20 hours = 100 Ah). This same battery can deliver a higher or lower current for less or more time, limited approximately by the 100 Ah figure (50 A for 2 hours or 200 A for 1/2 hour), but usually the capacity figure given is only accurate for the specified duration (20 hours).

Calculating Battery Size		only.
Step 1: Compute Amp-hours		installers
For each appliance, compute the number of amp-hours that will be used
between charging cycles, as follows:
1.	Obtain the wattage. If the wattage is marked on the nameplate rating,	qualified
2.	Obtain the Watt-hours by multiplying that amount by the hours the
	use that. Otherwise, multiply the marked voltage and amperage:
	WATTS = VOLTS × AMPS.
	appliance will be used:	by
	WATT-HOURS = WATTS × HOURS.
		use
3.	Obtain the amp-hours that the appliance requires by dividing that
	amount by 10 (the factor for the Freedom SW 2000, which is a 12-voltfor
	system):	guide
	BATTERY AMP-HOURS USED = AC WATT-HOURS/10
For example, a 100 W light bulb that is used for 4 hours will use 400 watt-		This
hours (Wh) and the inverter will consume approximately 40 Ah from a 12

volt battery.

4.Enter this information on the blank calculation worksheet (page 40).

Step 2: Calculate Battery Size

5.Complete the rest of the worksheet; see Table 6, “Battery Sizing Example” on page 38 for an example.

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