Xantrex SW5548 in series issue

Re: Xantrex SW5548 in series issue

Welcome to the Forum,

As you probably know, there are a number of settings that involve generators. There are those for qualification of the genset power, and those that involve the amount of charging current taken by each inverter, and those that govern the additional power needed for AC loads that are seen by the inverters, that must be carried when the genset is qualified and charging the batteries.

Have you tried reducing the AC Charger current setting in each inverter?

Sounds like the genset is being qualified with only inverter on-line but fails when the second connects and starts drawing additional AC current from the genset.

Disqualification COULD be either the Vin minimum spec or the Input Frequency (Hz) spec is being violated, and there disqualified.

Would first try reducing the AC Charger current settings (a bit) on each inverter.

Am using SW Plus inverters which are very similar, yet different. Little time now, but will check back.

If the inverters are trying to Bulk the batts, then there is little likelihood that the genset AC V is being dragged upward beyond the Max AC Vin spec, which can happen with smallish genserts as the inverters try to regulate to Vabsorb.

EDIT: Furthermore, that genset is really a bit small, when considering that all loads on the Inverter AC outs plus Charger AC current must be supplied by the generator. Believe that your location is around 4000 feet elevation. Generators generally need to be de-rated for altitude at 3% per 1000 feet elevation above 500 or 1000 feet, depending on the manufacturer's spec. So that could easily be a 10% reduction in the output, plus any reduction due to wear on the engine, etc. It IS true that this de-rating would have applied to your previous, somewhat larger gensets as well ... back to work ..

Good Luck, Vic

Re: Xantrex SW5548 in series issue

OK Bruce,

In the Charger menu, there should be a setting for AC Charge Amps, try cutting back on this setting on each inverter. The DC charge current will be about 2.5 times this value. You may not have too many items in the Meters menu, the SW +es have a Frequency DISPLAY, which might give you an idea of what the generator's frequency is when the generator has been qualified (if you do have that display)

Good Luck, Vic

Re: Xantrex SW5548 in series issue

OK, Bruce,

Thanks for the update. One of the issues with the SW and SW Plus inverters when Series Stacked (and perhaps in parallel), when charging, is that they do not pull current from each side AV input source in unison. So, especially on smaller gensets, this can cause voltage requlation problems on the AC input with lower current. This sensitivity will depend on how well the generator regulates voltage with asymmetrical load currents.

Your genset may not have any issue at all, may just be the nature of the way it regulates voltage with large asymmetric load currents.

It is possible that the Bulk charge stage is fine (the first hour t 25 A you mentioned (?)), as the inverters are not trying to regulate voltage. When Absorb V is reached, then there can be that situation where the inverter's charger will dump some current INTO the generator's output in order to keep the voltage near its set point. This can drag the generator's output out of regulation, causing disqualification, and dropping of that side of the AC input.

This stuff can be difficult to diagnose while using only the built-in Meters in the inverters, as they may not update quickly enough to see what is going on during the above-noted voltage regulation scenario.

Smallish gensets can be dragged around a bit with these fairly large inverters, especially when paired. Just my opinions. IMHO, these inverter/chargers are very stout indeed. Vic

Re: Xantrex SW5548 in series issue

Maybe a Balancing Transformer would help, equalizing the load on each leg ? Could be a simple step-up/down transformer with a CtrTap 240V winding.