Samlex S Series InverCharge Pure Sine Wave Inverter Chargers.

Once in a great while a line of inverter products comes along that
sends its competition back to the drawing board. The InverChargeTM
line of inverter products is that product.

We recently received our first sample shipment of the Samlex
S-2012A Pure Sine Wave Inverter Chargers. I immediately picked up
the phone and called our service center manager, asking him to stop
by the warehouse to pick up one these units and put it through his
usual field effect transistor popping, output transformer smoking, burn
in tests. When I use the word burn in I mean it in the literal sense
because very few of the new inverters that we test before they're
offered on our website survive even the first few minutes of his

I stood by in the warehouse so that I could catch the look on his face
because I knew that he would be expecting another typical 8 pound,
2,000 Watt, high frequency throwaway inverter that usually comes
from overseas. I chuckled when he tried to pick up the inverter and
immediately set it back down, opting instead for a for a dolly to wheel
the inverter over to the service center.

As I walked over, he asked me if there were two inverters packed in
the box. I said "No, we only ordered a single sample." He then said "I
take it that this this is not a  high frequency unit" I replied with a blunt

You see I had already seen the Samlex S-2012A Inverter Charger at a
recent solar energy trade show and I already knew a little about this
inverter's specifications but nothing could prepare me for how well this
inverter was to perform during our service center manager's grueling

Besides the weight of this heavy duty unit (Over 51 pounds) we were
impressed with how well this inverter was packaged. With over 11
years worth of shipping inverters all over the world, the one thing that
is lacking in most inverters is the packaging. In fact 2 out of 6
inverters that leave our warehouse usually arrive with a few dings and
dents that result in a UPS claim. Not this inverter, we probably could
have dropped this unit in its box from a height of 5 feet and it wouldn't
have been phased.

After removing the inverter from its packaging, we were still amazed at
how heavy this unit was for a 2,000 watt inverter. The fit and finish of
this inverter surprised us. The level quality represented by the
S-2012A was not what we typically see from an overseas
manufacturer. If it was simply up to the looks of this inverter, we could
see how this inverter could easily out sell many of its competitors.

Upon removing the inverter's cover, we immediately discovered why
this unit weighed so much, the output transformer and the driver heat
sink, two of the most important components in any inverter, were
simply massive. I could tell by the look on our service center
manager's face that he was impressed and so was I.

Further examination revealed a very well laid out design. There were
grommets at every potential abrasion point to protect wiring. We
found no evidence of cold solder joints, the main control and FET
board (field effect transistors) were well laid out. There were no after
thought revision jumpers or components that were soldered in a
haphazard fashion. We found two cooling fans, one for the FET board
and one for the transformer which was controlled by a heavy duty
thermistor. The inverter also included two high quality built in circuit
breakers to protect both the inverter and the charger's output as well
as 40 amp automatic AC transfer relays with an fast 16ms transfer
time which is sufficient for the prevention of data loss in most

Upon completion of our visual inspection, we both concluded that this
machine appeared to be well deigned and loaded for bear. But looks
can be deceiving in the world of high power electronics so we weren't
holding our breath. Very few inverters survive what was coming, but
to be honest, we were so impressed with our visual inspection that we
would have been disappointed if the inverter smoked like so many
inverters had in the past.

We connected the inverter to the 4/O heavy duty inverter cables that
were connected to our 810 amp hour battery pack. Next we hooked
up our oscilloscope and a true RMS multimeter and finally we hooked
up our 4kW resistive load bank and variable inductive load.

We turned on the inverter and checked for the quality of the pure sine
wave. The oscilloscope displayed a perfect sine wave with no visible
distortion. Next we began adding progressively increasing resistive
loads. 100 watts, 500 watts, 1,000 watts, 1,500 watts, 1,800, watts,
2,000 watts and virtually no distortion in the waveform. The cooling
fans gradually came on as they were designed to do and we did not
feel any unusual heat radiating from the inverter. It should be noted
that several 2,000 watt inverters that we had tested in the past started
displaying a corrupted waveform at about 1,800 watts but not the
Samlex S-2012A. We cranked up the load to 2,300 watts and still no

Next we backed the resistive load down to 1,500 watts and turned on
our variable inductive load which consists of 500 Watt Variac which is
attached to a large transformer that has had it's primary winding short
circuited. We cranked the Variac's dial back and forth from zero to
maximum voltage and nothing, this didn't even faze the inverter. It
should be noted that several inverters that have undergone the
variable inductive load test actually fried after a few seconds of this
test taking out the FETs.

Next came the Achilles Heel for most inverters, the dreaded short
circuit test. Despite the fact that many inverters advertise that they are
short circuit protected, this test has killed 2 out of 5 inverters that
we've tested in the past. I stood there with my fingers crossed as our
service center manager reached for the short circuit switch.

Before I tell you what happened next I want to describe this switch. It's
this massive 3 inch diameter 3 phase device with 3 separate contacts
that are all wired in parallel so we don't burn the thing up. There's this
big label that surrounds the switch with big bold capital letters that
read CAUTION SHORT CIRCUIT TEST ! in other words this is one of
the worst procedures that you can put any inverter through and you
had better have your safety goggles on and a fire extinguisher handy
because a short circuit can not only cause FETs (Field Effect
Transistors) to start exploding like popcorn but it can also start a small
fire in your output transformer.

Needless to say, I stood way back because I've dodged my fair share
of molten FET casings. As I closed my eyes, the service center
manager flipped the switch and...... nothing. The load bank shut down
and everything went quiet. For a few seconds I wondered if we finally
killed the inverter ?  No FETs had popped though and I didn't smell
any insulation burning so maybe the inverter shut itself down like it
was supposed to.

The service center manager reset the inverter and there it was, a
perfect sine wave on the oscilloscope. We cranked up the load to
2,000 watts and again a perfect sine wave. I left the inverter on with a
1,000 watt load for the next 8 hours and came back to the service
center that evening to test the battery charger. I set the charger to it's
maximum setting, plugged the inverter into the AC outlet on our test
bench then watched as the inverter's built in battery charger started
pumping amps into our battery pack as displayed by our test bench's
DC ammeter. At that moment I knew without a doubt that I had a
winning product on our test bench.

Since we opened our service center back in 2000 we've tested lots of
inverters that were shipped to us as samples. We have shelves that
are lined with once brand new inverters that were dead on arrival right
out of the box even before the tests began and inverters that
miserably failed our tests releasing smoke and fire. We've been
saying for years that we're going to repair them someday.

Even if an inverter survives these tests we usually find something
negative that merits a rating that is lower than the maximum 5 stars for
what we consider an ideal product but that was not the case with the
Samlex S-2012A. This is one of those rare occasions where we've
decided to undeniably give the Samlex S-2012A our highest 5 star
rating for its quality, performance, durability, warranty and value.

Here's some pictures that I took of this incredibly well built machine:

Note the massive output transformer. .

Note the huge heat sink with the row of high output Field Effect
Transistors (FETS). Also note the large Thermistor mounted on top of
the heat sink to the left and the large cooling fan.

Note the nicely designed control board. The latest in DSP (Digital
Signal Processing) technology is employed to reduce the complexity
of the control board which dramatically increases reliability due to the
reduced parts count when compared to older analog designs.

Here's another shot of the massive output transformer. Note the large
industrial grade output circuit breakers on the right.

Note the large heavy duty terminal strip for easy wiring. Above left are
the easily accessed resetable circuit breakers.