Upgrading solar panels on our old Dutch barge. Installing five 200w panels in two groups. One group of three panels in series on the foredeck. A second set of two panels in series on the wheelhouse roof. What’s the best way to connect the two groups to our MPPT (Victron 150/45)? Connect both pos to one buss bar and another buss for the negs and then run leads to the MPPT? Will I need a diode or anything between the connections? Thanks if you can advise!
Do you have the panel data for us … Basically, you should not build mixed series/parallel connections.
The three panels in series should always be connected in series with three panels of the same type, if necessary.
If the data allows it … all in series
or a separate MPPT … but your cable routing will probably be unfavorable here, right?
I do not have the panel stats with me, suffice to say all panels are identical. Only difference is one array has three panels and the other has two.
Not a good idea. You can kind of ‘get away with it’ when the two strings are identical in number of panels VOC
With 3 in series in parallel with 2 in series you will get between 3 and 4 panels worth of power with an odd shaped power curve.
Options.
- If there is room add a 6th panel, 2 parallel strings of 3 in series.
- Only install 4 panels in 2 parallel strings of 2, this will be better than your current plan.
- As option 2 bit buy a very small controller for the single panel. This will depend if you have 12V or 24V system and panel Voc, you need 5V above battery voltage to start charging, so 19V for a 12V system or 33V for a 24V system.
- Keep the 5 panels using current controller for the 3 series string and buy a second smaller controller for the 2 panels in series.
Option 4 is certainly viable as I already have another MPPT in storage. The other option would be to spend more money on more cable and simply run all five panels in one series…thoughts?
Without the panel specs running a series of 5 can not be confirmed. You have a 150/45, this has an absolute hard limit of 150V input from the panels before damage can occur. If the panel spec is 20V Voc then that is 520= 100V, allow 15% higher for cold days at -10degC = 115V, OK. If the panels are 30V Voc then that is 150V, allow extra for cold day = 173V, not OK, fried MPPT.
I did not really think of that option because 5 panels in series is unusual.for a 150V MPPT, but may be OK with smaller boat panels. Do check though.
Panels are rated at 20.5v. So, including a 15% overage it works out to 118v which is well under the 159v threshold, yes?
Yes, you will be OK.