Xantrex Technology 815-2012, 815-3024, 815-3012, 815-2024 manual Calculations, Examples

Freedom SW 3K2K InvChg Owners Guide.book Page 40 Wednesday, October 9, 2013 1:34 PM

Configuring the Freedom SW using the SCP

Charger settings in a Dual Freedom SW con-	(Charger #1 Actual output Amps) + (Charger #2 Actual output Amps) =
	“System Total BULK output” Amps (for the stacked pair).

figuration

The Freedom SW2012 includes a 100 A charger. When using two stacked Freedom SW2012 inverter/chargers connected to the same battery bank, a total of 200 A of bulk charging is possible into that single common battery bank. For small battery banks and/or certain battery types this bulk mode current may be too high, therefore Freedom SW models include the “Battery Bank Capacity” and “Max Charge Rate” settings.

“Battery Bank Capacity” is the bank’s total Amp-hour capacity, this is best determined by a qualified RV electrical technician, while the “Max Charge Rate” is determined by the battery manufacturer/type of battery model being used, i.e. Flooded, Gel, AGM being the most popular. For “Flooded” type battery bank, the preferred charger capacity (A)/battery bank capacity (Ah) is usually 10-15%C (C = Battery Bank Amp-hour capacity), however the max charge rate allowable is often accepted as 25% C, while some AGM or Gel battery models are higher (50% C or, in rare cases, up to 100% C). Do not exceed battery manufacturers recommended max charge specifications as resultant battery temperature rise will shorten battery life.

This “Total bulk output current” flows into the battery bank. As this total bulk current is split/distributed within the bank thru each individual parallel and/or series connected battery, the current each battery “sees” must not exceed each individual battery’s max allowed charge current as specified by the battery manufacturer. Since most battery banks are/should be constructed of the same battery type, model and length of interconnecting cables, current sharing is roughly equal through each parallel branch of battery(ies), therefore the above generalizations of “Max Charge Rate %” can be made for the entire bank.

The Freedom SW’s “Max Charge Rate(%)” setting is set to “100%” by default, but is adjustable 0-100%, therefore if the charger has max possible 100 A (as in the FSW2012), when set to Max Chg Rate of 100% FSW2012 is capable of delivering its full 100 A into the battery bank. However if this is too high, the installer/operator may reduce this % setting to suit the system battery type and bank requirements/limitations, to avoid overheating the battery bank. The user/installer is responsible for configuring the charger to ensure the battery manufacturer’s recommended max charge rate Amps is not exceeded for longest battery life and best performance.

Calculations

Once installed and configured, each Freedom SW charger calculates its own actual bulk charge current limit as follows:

(User selectable “Max Charge Rate” %) x (User selectable Battery Bank Ah capacity) = Actual maximum charger #1 output Amps in bulk mode (note: Limited to the Charger’s maximum capacity) then,

Examples

Example 1: In a system composed of two stacked FSW2012’s, industry commonly accepted practice suggests a typical Flooded battery bank of capacity (C) 400 Amp-hours should not be charged at a rate in excess of 25% of “C”. i.e. 25% x 400(Ah) = 100 Amps. Therefore, when configuring the two stacked Freedom SW chargers, each charger must be limited to contributing max 50 A into the common battery bank. This is accomplished

40 Freedom SW Owner’s Guide