I have a system with dual SW4024 inverter providing 240 volts for an off grid family. Ever since the first installing them I have been unable to get more than 60 amps out of each inverter for charging the batteries. I had an SW4024 system I installed at my home in the city and it was wired to a 35 amp breaker for (AC1)input and I was able to get almost 120 amps out of that single inverter for charging my batteries at home. Trace or Xantrex technicians have been unable to help me solve teh problem. The inverters are feed by a 22 kw generator providing more than 60 amps to the (AC2) input. With all loads in the residence disconnected each inverter can only provide a max output of 60 amps. If I increase the charge current in the program to take more than 34 amps input the 35 amp breaker on the left side of the inverters trip. I have to keep the input current for charging around 29 to 30 amps on the inverters or risk tripping the breaker on the side of the unit. Can anyone help me with this issue? My system has two 1500 amp hour 24 volt Hawker VRLA battery banks and they require a minumum of 70 amps for each bank to a maximum of 150 amps for each bank. So the only way I can really give each battery bank a good charge is to pull the battery fuse on one of the battery banks and let all the charge current go into on bank (approx 120 amps.) I am installing a third battery bank and a thrid SW4024 inverter into the system because the owner is building a 3000 sq ft home. I was looking into purchasing a Polar DC generator that can provide up to 350 amps at 24 volts but I can not find a charge controller that can handle that kind of power. arcandspark

This is a problem with stacking SW series but you probably won't find Xantrex admitting it is a significant issue. The problem is aggrevated if you do not have large enough wire size to take the peak charge current without more then 0.2 vdc or so voltage drop between inverter terminals and batteries. Running each inverter on its own battery wires and DC breaker directly back to battery terminals helps some.

It is because of the quantizing steps of the SW series. It causes 'thrashing' between the common connected inverters. One unit is faking out the other to thinking it is into second phase of charging thereby cutting down its current output.

For bulk this means you will not get anything near the expected 2X max charge rate. If you try to push up one side, the other side will suck up a portion of the charge. You will just end up popping the breaker as you have mentioned

One solution other then the DC generator you mentioned is to break the batteries into separate groups during bulk charging so one inverter serves its own group of batteries and the inverters do not see each other's charge pulses. You can manually switch the batteries back together again after charging. If you do not want to do this you have to either use external method of charging or accept the lower charge rate.

As to DC generators, the best regulator would be control directly at the generator to modulate its speed and/or field winding to regulate its voltage and current output. This is the way the old automobile DC generators worked. (pre-1962, there abouts) This is actually better for fuel efficiency then running an AC generator through the SW series since you can lower the generator RPM's as power demain for charging drops after reaching bulk voltage limit. (same principle of inverter/generator models) Secondary benefit is lower generator noise as its RPM's reduce.

I would expect a DC generator designed to charge batteries would have this capability.

Maybe look at buying an old Russian submarine. (just joking)

Two other things,

It is important the the units have the same Bulk and Float voltage settings and voltage reading calibration is close to same for both units. Check the actual battery voltage on Menu 4 to ensure they show the same voltage. If not, having the units recalibrated will help.

Second, the temp compensation is not continous verses temperature. It shifts at about 6.5 deg C increments. This means at the shift boundary temperatures, +/- 0.5 deg, one unit will shift in charge voltage (bulk or float setting) before the other. This really unbalances the charge for the small temp range where the two units are at different comp points. Look at Comp Battery voltage in menu 4 to see if the readings are same. One of the comp crossover points is at 25 deg C so at 25 deg will have comp'd voltage significantly different then 26 deg C. If you happen to be unlucky to have an ambient temp that sits near one of these comp shift points you can possibly have the two inverters on either side of the shift.

i need to ask you a question: i just looked at the specs for a sw 4024, nowhere on the spec sheet does it say you can get more than 30 amps for charging and 60 amps for ac output or input .....how did you get a 120 amp for charging