I have used many Solar calculators for this and everyone of them comes up with a different MPPT size. Can someone help me please. I need to order and it be CORRECT and burn something up. Thank you
I have 3—24V 200W Rich Solar mono panels going to a 24V battery bank. 600W Total.
Solar panel specs:
PMAX 200W
VMP 36.3V
IMP 5.51A
VOC 43.5V
ISC 5.93A
NOCT 113+_ 35
Temp COeff PMAX -.39F
Temp COeff VOC -29F
Temp COeff ISC .05f
MPPT 250/60 if wired 3s1p. MPPT 100/30 if wired 1s3p. Have you tried using the Victron MPPT calculators? There is one on the website and a downloadable spreadsheet version (my preferred tool).
3 panels in series. One string. Yes I have used Victrons, Exporistlife, Sun panels, etc. All seem to come up with a different size. So I need a 250/60 for 3 panels in series?
The problem with running them in series is the 150V rated MPPTs could go over voltage in cold weather. It’s on the edge so if you live somewhere warm you might get away with a 150V.
I don’t know where you live, but in NZ the 250v series are very expensive.
If i were you, i’d be putting in a 100/20
- its the only small controller that will allow you to jump to a 48v battery when you next upgrade.
- its cheap
- it has load terminals, so you can mostly get Battery Protect features without buying a Battery Protect
- it will be at about 105%, so well placed (Victron recommends up to 130%)
- the only place this doesn’t make sense is where the solar cable run is extremely long, in which case 3s (3 in series) would give you a much lower cable loss
- you would be at about 50% of max Voc, so absolutely no risk of going over-voltage
The 100/30 would be overkill - you won’t gain much with a 30A controller, and you lose load terminals and 48v capabilities.
I live in indiana but I will traveling all over the United states, so I am sure I will be in some cold areas at some point. I have a 100/50 installed now. It was 35F and cloudy the day I turned it on and got the #33 overvoltage code as soon as I did. I cleared the code and have just left it off until I can get this figured out.
Regarding going 3s (3 in series) vs 3p (3 in parallel)
You have a 24v battery, so you only need to make sure your panel array is producing your battery voltage +5 to start the mppt, and battery voltage +1 to keep it going, so if you are LiFePO4, that’s probably 32v and 28v respectively.
That’s going to be harder for a 3p array when you are somewhere hot, like 35 degrees (95 in F, or negative 8 and 3/4 fridges in american), which is why most of the advice on the forum has been to go 3s with a much higher Voc controller (the 250v controller). But … you already have a 150v …
Running your numbers; at 60C (140F) you will be getting 36v, still enough to get the mppt started with the array in 3p.
Going 3p will get you going right now, and is the safe option. Even at high temperatures, voltage goes up fairly quickly with even a small amount of sun.
What is said in my last post was not quite correct;
While this is still true, for your panels you don’t get that advantage of being able to switch to a 48v battery because with an odd number of panels you cant go 2s2p, and you won’t want to go 2s1p (losing the use of the 3rd panel), and you can’t go 2s1p plus 1s1p (voltage too low)
And … to test this out if you are short on time or want to try it before going to the work/expense of buying a 3-to-1 connector or a junction box), just plug in one panel to test.
You will get the same behaviour with respect to voltage (i.e. voltage will not change with 1 panel, or 2 in parallel, or 3 in parallel, just the amount of current will change).