welcome back to steve rob reviews today we're going to have a lot of fun i'm not going to
make anybody do any math i'm going to do all the math myself and it's all about power inverters
and this is the power inverter that i'm going to be using today just a 300 watt power inverter and
this is the specs right there okay today we are going to delve into what is the efficiency of a
power inverter and how do you actually check it and you're going to witness voltage drop which
is exactly what it sounds like when voltage drops amperage goes up why does that make a difference
when you have a power inverter well today i'm going to show you in this little 300 watt power
inverter how all these relationships actually make a huge difference for anybody who's considering to
buy a power inverter and what they can actually plug into it and what they can expect to have
for cables to plug into their particular battery that they have now this is a 12-volt system today
and this particular experiment well it's not really an experiment this particular
values recording is going to be used with ohm's law to show you that you can test what goes in
to your power inverter from your dc supply and you can test what comes out of your inverter in
ac voltage and ac amperage and we're going to check both at both ends compare the difference
and record the efficiency of whatever inverter you have because if you're looking at getting
a particular appliance that runs off of wattage how does that relate to your power inverter
well a lot of people think you can just do ohm's law and your honky-dory and everything's
fine right no no it doesn't quite work like that because you've got all the losses that go through
your power inverter as well you've got losses going through your cables all your connections
there's all kinds of different losses that actually cause a voltage drop and as i said
in the beginning as your voltage drops your amperage increases when your amperage increases
well you really have to know how many amps your particular conductor cable from the back of your
power inverter going to your battery bank how large does it have to be depending on
the amount of space between the two distances either it's in feet yards meters
it all makes a difference so let's get to the experiment right here
well the value recording and let's take a look and see what we got
well let's start off at the battery end so you can see i've got a fully charged battery 12.7
down here i've got my amp clamp set up so i am going to get a reading from the battery connection
going to the inverter coming out of the inverter i have my ac amp clamp
and that is going to take a reading coming out these two probes here are for my voltage coming
out that's just ghost voltage don't worry about that for now and down here i've got my watt meter
so what i'm going to do here is i have a 100 watt bulb and i'm going to turn the 100 watt
bulb on and then we're going to look at the values so let's just turn the power inverter on
if i can do that now the first thing you notice is nothing happened to the battery voltage
if we take a look down here yes and that is the proper spec it's about 300
milliamps just to turn this unit on and have it run now there's no amperage going through the
ac side and the voltage is 127. now you'll see in a lot of these smaller inverters that they
will have a high startup voltage but you're gonna see how they drop when you turn the uh
when you turn any load on okay so down here is i got the watt meter plugged in so you can actually
verify this is a 100 watt bulb and it is going to register 94 watts now let's come over to our
volts here and we're already down to a voltage drop of 12.1 take a look at our amperage reading
eight point
four what you have to really look for is the stabilization of your voltage so we got in
between 12 and 12.1 and 8.4 8.5 as the voltage drops the amperage will go up but we got 8.5
yeah on the 120 volt side it's 8 2.82 so it's almost 1 amp and what are we we're still at 94
watts so we got eight and i'll just turn it this way here so we could actually verify that
yeah it's point eight two at a hundred and
not twenty hundred and fifteen point four four so numbers do matter right it's not 120 volt
point eight two we're going to go with 0.82 it's almost an amp and we're down to here yeah we're
gonna call that eight four and it hasn't budged really here so 12.1 we started at 12.7 i believe
so what does all this actually mean so i'm gonna get a piece of paper and pencil and we're gonna
do some math well here we go i did the math and if we just take a look at the dc side of the circuit
the voltage was 12.1 we had a recording of 8.4 amps now if you do ohm's law you take your load
which is 94 watts you divide it by your voltage 12.1 and we get 7.7 amps now on the ac side you
had 115.45 volts the amperage was 0.82 so if we do ohm's law we got 94 watts you divide it by your
voltage and we have 0.81 and that's very close to the 0.82 you know because the amp clamp you know
is not exactly the highest resolution but you could see that there's a a correlation
here you know 0.82 and 0.81 compared to the 8.4 amps and ohm's law which is 7.7 so if we take a
look at the efficiency or the inefficiency so if we do ohm's law you take 7.7 amps
compared to the actual reading which is 8.4 the differential is 0.07 now 7.7 amps you just take
a factor of 10 and that's 0.77 so yes this actual inverter when you load it to 94 watts
you are losing 10 in efficiency and that's also 10 loss between the dc side of the circuit and the ac
side of the circuit when you're trying to figure out wattage so yes there's a 10 loss between
these cables that attach to the battery and what you got out the front here in ac voltage or your
amperage draw or your wattage there was 10 percent difference between here and out of here and that
makes a huge difference now if you're taking a look at this particular inverter here it's a 300
you know watt inverter and that's 150 watt aside so we loaded it up pretty good on the one side
because it was 94 watts right now i predict that you would not get as much of a loss
at a lower wattage amount so what i've noticed with inverters is as you load them up more
yeah you'll get more of a voltage drop and you'll get more of a loss so depending on your inverter
you buy like a 25 inverter you could expect to get 25 dollars worth of efficiency right
so you know really that's what it comes down to now this is a great a great relationship between
the dc side and the ac side when you're thinking about wattage because a lot of people just look at
their particular appliance and say okay i've got you know a specific size inverter and i can take a
look at the specs on the back of my appliance here i go by the wattage and i just plug it in right
well no there's a huge difference there as you can see here there's a 10 difference so when you're
thinking about just your cables how do you size your cables well the best thing to do is measure
because as you can see here today there is a 10 loss in efficiency between the battery side to
the output side and ac and that's something that a lot of people have to consider about because
you know there's a lot of different reasons why you have voltage drop and power losses
and a lot of it has to do with using like alligator clips insufficient cabling there's
all kinds of different reasonings matching your battery up specifically there's all
kinds of different reasons and that's the fun part about solar and using off-grid appliances
now the one thing i i will say is a lot of people decided to go to strictly dc appliances and of
course you would not get these losses because you're not going through an inverter right
but just think about if you wanted to go to a dc appliance you know i mentioned before i've got a
regular 4.5 cubic foot fridge up at my cabin and it cost me 160 bucks if i tried to buy
the same size fridge you know in a really nice unit you're about a thousand dollars so i mean
it depends how you want to build your system and remember when you're talking about dc loads
you have to attach the proper cabling to match the amperage of your load and in my experience if your
appliances are close to your batteries the dc may be a good choice but if they're a distance apart
like in mine you know i've got quite a large distance in between where my fridge is and
where my battery bank is i would have to run like huge cables to run that different distance
and for me it's it's not really feasible i like going the inverter away and i find it's the most
economical as well but you just have to know the losses and in this particular situation yeah it's
a 10 percent loss on this so thanks for joining me here today i hope you found this interesting
of some sort because you can actually do the exact same thing to your inverter and test the ohm's law
relationship of amperage wattage and voltage check the back side the dc side then compare it to the
ac side using the same amount of wattage and you can check your efficiency so thanks for joining
me here today if you haven't seen this channel before you're welcome to subscribe come back
again and have some more fascinating ideas that i come up with on testing different things cheers
you