Hi, this is Amy from the Alte Store.
I just did a video showing you the difference between using a 60 cell 20 volt solar panel
and a 70 cell 24 volt solar panel to charge a 24 volt battery with a PWM charge controller.
So I'm going to do the same thing but with an MPPT charge controller.
So now I'm using the midnight kid.
And this is a MPPT charge controller.
So I've got my cheat sheet.
I've got a Canadian solar 280 watt panel that 72 cells so it's 24 volts.
And I've got a SolarWorld 275 watt panel 60 cell.
So it is very hot out so the voltage of these solar panels has dropped dramatically and
you can check out that other video I will show you some of the voltages there because
of the heat.
But what I want you to remember is that battery manufacturers recommend about 28.8 volts to
charge a sealed battery.
So let's see what we get with these solar panels.
And I do apologize about the wind, it's picked up.
So we're starting with a 24 volt solar panel.
I've got it connected to the midnight kid and it is charging the batteries.
I can look and see coming out of that solar panel I've got 30.6 volts now that's just
a little bit higher than what the recommended 28.8 volts was for charging my charge controller.
It's getting a little later in the day so the sun isn't as intense as it was earlier.
But I think this is still really good to see.
So we've got 30.5 volts going into the charge controller 27.79 volts coming out
and 7.1 amps.
Now when I was doing this earlier when it was actually mid-day I was actually seeing
about 6 amps coming out.
So the MPPT charge controller is certainly boosting the output of this and getting my
maximum output.
So now lets switch this around and see what outputs we get using the 60 cell 20 volt solar panel.
Okay?
Okay so I've got the 20 volt solar panel.
And again this is a 275 watt solar panel vs the 280 watts so very similar.
But the big difference is it's putting out a lower voltage because it only has 60 cells.
So if we take a look, it's putting out about 30.5 volts into the charge controller
26.3 volts into the battery 5 amps.
So I'm getting a full amp less from this 20 volt solar panel than from the 24 volt solar
panel.
And that's significantly more of a change than you would see just because of that 5
watt difference in their ratings.
So I am absolutely not getting as good power out of my 20 volt solar panel into a 24 volt
battery they really do prefer to matched up nicely even with an MPPT charge controller.
An MPPT charge controller can take a higher voltage and drop it down to a lower voltage
battery.
But most MPPT charge controller with a couple of specialty ones that are exceptions.
They need to have a higher voltage going into the batteries.
So it's ever so slightly higher.
Like I'm dropped down to 29.8 volts so it's a little bit higher than where the battery
bank wants to be charging at.
Again AGM wants to be charging up around 28.8 volts so I barely have the voltage and this
is really full sun.
If a cloud were to go by I would not have higher voltage, I would probably have higher
voltage in the battery than my solar panel.
So it really does make a difference of having a 24 volt 72 cell or 2 12 volt 36 cell panels
wired in series to make your 24 volts.
If this was winter time it would probably not be as bad because when it is cold, the
silicon voltage goes up in solar panel.
So it would probably work better in the winter but in the summer when it's hot.
It's probably well in the eighties right now.
The voltage of these solar panels really drops down and just doesn't efficiently charge these
batteries.
If this was a flooded battery it wants to be up around 30, 31 volts.
I'm really not going to be able to give it a good full charge, with a 20 volt solar panel.
So while it looks like yeah everything is cool, it's charging, it's not going to give
it that really big top off.
It's going to be at risk of being in a partial state of charge which most batteries do not
like to be.
So while it will appear that it's working okay, you're going to shorten the life of
your batteries.
So just important note to keep in mind 72 cells for a 24 volt battery.
This is Amy from the AltE Store, I hope this was helpful, if so give us a like and a share,
and be sure to subscribe to our AltE Store Channel so we'll send you notifications when
we've got new videos.
And make sure to go to our website at altestore.com where we've been making renewable do-able
since 1999.