g'day guys and welcome back to another 12 volt video now today i'm going to be talking
about solar regulators or solar controllers in particular the two most common types pwm
and mppt and in this video i'm going to be going through how they work
their differences and why one might be better than the other for your setup now a 12 volt solar panel
is generally putting out somewhere around 18 to 20 volts which is why it's so important that
you need a regulator if you simply plugged your solar blanket or solar panel into your battery
it would work at first but then as the charging voltage climbs it'll eventually cook your battery
that's no good back in the day there wasn't much choice when it came to solar regulators
or solar controllers you basically had an on off switch so that when the sun was out
and your battery was discharged the switch would be on and it would charge up your battery
once your battery hit that high voltage point where it didn't need any more you'd
have to turn it off or it would turn off to stop cooking the battery now that wasn't particularly
efficient and it didn't charge the battery properly these days though you've got much
better options so let's see what you need for your setup to start with let's talk about pwm
pwm stands for pulse width modulation and that's describing what this unit's
doing when it's charging your battery so to start with it pulses power into the battery
and it can actually change the amount of time or the length or width of that charge and that is
modulating so it's actually modulating the length of the pulse that might sound fairly technical so
let's take a look at a graph to make it easier to understand on the vertical axis of the graph it's
showing your voltage and on the horizontal axis is the time as you can see when the regulator
turns on it's at voltage then turns off for a short period of time before it turns on again
every time the regulator turns off it measures the voltage of the battery and adjusts for the
next pulse and you might have noticed that on this graph the charging voltage is 13 volts
that's because when you connect a pwm regulator to a solar panel and battery the large load of
the battery actually pulls the solar panel voltage down to just above the battery voltage they're not
able to actually boost that voltage any higher the voltage will simply increase as the battery
charges up then the regulator will output the higher voltage but shorten the width of each
pulse now let's talk about that in the real world so let's use this 200 watt solar blanket as an
example now i do have the exact specs but to make it easier let's assume it's putting out 20 volts
and 10 amps 20 volts times 10 amps is 200 watts once you connect this to your pwm regulator the
battery will pull that voltage down to around 13 volts and because it's not actually able to boost
the output power you're now at 13 volts times 10 amps for a total of 130 watts so your 200 watt
solar blanket is only able to put out 130 watts so as your battery is charging up and that internal
voltage does climb let's say it gets right up to 14.5 volts still getting 10 amps you're now
at 145 watts but unfortunately you're never going to get the full 200 watts out of a pwm regulator
so why would you want a pwm regulator well here's a list of pros and cons that might help you out
one massive advantage is their cost pwm regulators are fairly inexpensive which means you can get
into a solar setup without a massive entry cost secondly they're tested technology and they're
arguably more reliable and durable because they have much less complex technology inside now the
cons for a pwm regulator number one is that because they only charge at battery voltage
or just above it they're only around 70 percent efficient they can't boost the voltage or amperage
that's coming out of the unit secondly they can't use 24 volt solar panels so you can't take
advantage of a higher voltage for less voltage drop in your system these can only run with what's
called a 12 volt solar panel putting out around that 18 to 20 volt number finally they're not that
ideal for a larger solar system which doesn't matter too much if you're only talking about
camping or fall driving but you have to be mindful of it if you do ever want to grow your solar array
let's get onto mppt regulators next now mppt stands for maximum power point tracking
but that's not all it does the first difference between an mppt and a pwm is where the pwm simply
connects the circuit and brings your solar panel output right down to your battery voltage and mppt
is two separate circuits so whatever's coming in is able to go through a computer and then be
outputted at a different level this is a more technically advanced system which means it's going
to charge your batteries much better now let's use the same example as before with a 200 watt panel
and take a look at a graph of an mppt regulator hypothetically let's say we've got 200 watts
that's going into the input side of your mppt regulator or controller if your battery needs 13
volts to charge the mppt will take that 200 watts divided by the 13 volt output that's required
and then output the same amount of power minus a tiny inefficiency as what it's receiving
so it'll put out 13 volts but at around 15 amps so as well as actually taking advantage of the
entire amount of power that's coming out of your solar panel and mppt has another advantage as well
and that is in the name maximum power point tracking so as an example let's say that
the maximum power point of this solar panel sits around here on this graph as a cloud passes over
it's going to drop the output considerably but the mppt regulator is able to constantly track
scanning for that maximum power point and output it a pwm can't do that it's simply a passive
system and what this means is that as the solar panel heats up or loses efficiency clouds pass
over or you might have a tiny bit of partial shade on your panel the mppt is always able to make the
most of it and output the maximum power so let's talk the pros and cons of an mppt regulator and
why you might want one well first of all they're much more efficient than a pwm regulator
secondly they're more able to use the entire output of your solar panel because they're
not just passively dropping the voltage to your battery voltage and then using as much current
as they can these are able to actually boost up that current to use the entire panel output
thirdly because they can track that maximum power point even in low light cloudy conditions or as
the panel heats up they're able to put out more power more efficiently than a pwm and last because
they're able to actually input a larger voltage you're not restricted to using 12 volt nominal
solar panels so you could use a higher voltage solar panel for less voltage drop in your system
which equals more power getting into your batteries now the cons of an mppt regulator number
one they're generally a bit bigger and heavier than a pwm of the same capacity but it's not
usually a big deal number two because they're more advanced inside they're generally more expensive
it's all well and good to talk about the differences of these regulators on the bench
but what's much more important is to see their actual real load performance so let's take them
outside and compare them both batteries are discharged to around 12.7 volts or about 75
capacity and they've been sitting overnight we're using the same solar blanket both laying flat on
the ground which isn't ideal but it's a good comparison connecting both panels up the pwm
instantly connects the circuit while the mppt calculates that maximum power point after about
30 minutes in the sun you can see that the battery voltage is already climbing the panels are heating
up there's voltage drop in the system and it's not a perfectly bright day so we're not at full power
the pwm is putting in around 3 amps or 40 watts of charge while the mppt is taking advantage of
the extra power and charging it over 7 amps or just over 100 watts so in summary the mppt is
putting out more than double the power of the pwm the losses in the system the fact that it's not a
perfectly bright day and the heat of the panels mean that we're not getting a full 200 watts
but you can see that in the real world that's where the mppt makes such a massive difference
so if you want a simple inexpensive option that's going to work in most situations
then you can't go past a pwm however if you want to make the most of the entire amount of power
that your panel's able to put out and ensure that your battery is getting the highest charge it can
you'll need to step up to an mppt now this is a fairly shallow look at what is a very
in-depth topic so if you do have any questions make sure you throw them in the comments below
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you