help with settings on series stacked inverter set up

kd7irm

guys,
i have two 4000 watt Trace sw4048 inverters wired in series stacked configuration. my question is, when changing the set up on the inverters do i need to set them the same or just input the settings into the number 1 inverter and it shares its info with the number 2? my main concern is the battery charging settings. should both inverters be set so the max current is 30amps or half that? should the generator size be set at 60 amps on each or 30 on each? (its a 62.5 amp output generator). i have the manual and it gives no information as to set points when in series stacked. thanks i advance for any info.

RCinFLA

Re: help with settings on series stacked inverter set up

The charger set voltages for float and absorb should be set the same.

Normally you would set the charger AC max input current equally between the two inverters.

The SW series have no actual DC current measurement capability. The charger bulk current rate is set by AC input level. The conversion from AC input to projected DC output is a little variable based on battery voltage. The best way to project the DC current is doing a power input/efficiency/power output calculation.

For example if you set AC max charger current to 15 amps then the input is 120vac x 15 amps = 1800 watts. The inverter efficiency at this power is about 92% so the input power is reduced by 92% efficiency to 1656 watts. If battery voltage is 49.5 vdc then the charging DC current will be 1656 watts / 49.5 v = 33.5 amps.

For series stack, figure your desired bulk current, work backwards to AC input current, then give each inverter half this number.

As the inverters get close to absorb voltage there will some thrashing of current between inverters. This is normal with the SW's.

Make sure the setting for max AC input is equal or greater then max AC charger input or the max AC input will set the charging current.

kd7irm

Re: help with settings on series stacked inverter set up

Thanks RC, but im still a little unclear on this, i have 1140AH 48volt deka unigy2 avr92-25 batts, and a 62.5amp/15kw genset, what would be your recommended settings for the 4048's (input amps ac, max charge amps ac, bulk times, bulk done amps ac, ect. each) called deka and they recommend a bulk charge of 55.2v and a float of 54.0v. genset is now set up for auto start with the inverters in control.