MPPT controllers.....

Michael Davis · Nov 23, 2018

I have two panels wired through one controller. Works great. I think it's the best addition we've ever put on the boat

dlochner · Nov 23, 2018

Interesting question. If you went with one controller, then it would need to be pretty beefy to handle the loads all three panels. It is also a single point of failure. If the controller craps out, then the whole system is down. With multiple controllers, if one goes down, capacity is lost, but the system will continue to work.

Just watched this video on series vs parallel wiring and the effects of shading. They used 2 panels and one controller. The effects of shading were interesting. Minor shading from rigging has very little effect, shading from a boom or taking out just one cell had a pretty big effect. It would be interesting to do the same test with 2 panels and 2 controllers feeding one load (battery).

Nigel Calder has done a lot of work in this area. Not sure if any his stuff is online. worth a search.

Stu Jackson · Nov 23, 2018

A "handy" resource:

https://handybobsolar.wordpress.com/faqs-please-read-this-first/

Ron20324 · Nov 23, 2018

+1 to dlochner. I watched the video. I installed my 2 panels with one controller, as it would handle 2 panels. I used two DPDT switches to wire the panels to either/or a/b panel, or series or parallel. I just now went to re-do the readings I had done months ago- reading the ser/par outputs. BUT, there are too many clouds passing over . I'll try it again another day.

NotCook · Nov 23, 2018

We have 4 panels installed, in parallel to a single 30amp charge controller, and are thrilled with the results. An advantage of parallel connection to the controller is that you get the combined current from whatever each the panels are putting out. One may be shaded at a give time, so it's current may be dramatically reduced, but that does not impact the current from the other panels. Our panels are 3x100 watts, and 1x123 watts for a total of 423 watts nominal. We have seen as much as 19.5 amps out of them (when looking), and love it. And, for us, usually anything more than 7-10 amps is gravy, with the SeaFrost fridge only running about 4-5 amps, when it is running (including compressor, blower, and coolant pump), and usually not much else running and drawing more than another 1-2 amps. And we aren't running an mppt controller, though that might be the next investment.

Our challenge is how do we use these same panels to run a 24V charge controller when we want to charge our 24V bow thruster and anchor windlass batteries? We don't want to dedicate panels to separate service for 12V and 24V, particularly since the 24V stuff is so rarely used and it would be a waste to have panels sitting idle dedicated to 24V duty when we are needing current for 12V side. I'm wondering if we can run two separate charge controllers in parallel to perform both functions. I'm thinking that would actually work, and that most of the current would go to the controller that was drawing it the most. Each controller might take what seems to be available, and when the 24V batteries were fully charged, that controller would not be using the current at all. Wouldn't this work? Hmmm.

Sailm8 · Nov 23, 2018

I have 4 100W flexible panels and one controller. Works great.

LeeandRick · Nov 23, 2018

NotCook said:
Our challenge is how do we use these same panels to run a 24V charge controller when we want to charge our 24V bow thruster and anchor windlass batteries? We don't want to dedicate panels to separate service for 12V and 24V, particularly since the 24V stuff is so rarely used and it would be a waste to have panels sitting idle dedicated to 24V duty when we are needing current for 12V side.

If your panels are nominal 12 volt panels in parallel you will not have high enough voltage to charge at 24 volts.

LeeandRick · Nov 23, 2018

NYSail said:
hello all...
So this winter I plan on installing solar panels on my boat. Right now it looks like I will have a minimum of 3 panels. How many mppt controllers will I need...... I hear from some 1 per panel and others that say 1 is fine.

Thanks!

Greg

There is lots of good advice on boats in this forum but you probably would not ask a question about your car here. My suggestion is to go to dedicated solar sites and educate yourself about solar and how it all works.

NotCook · Nov 23, 2018

LeeandRick said:
If your panels are nominal 12 volt panels in parallel you will not have high enough voltage to charge at 24 volts.

I had thought about going the voltage doubler route downstream of the 24V charge controller, but I don’t think they would feed back the battery voltage to the controller. Another alternative might be to charge each 12V battery in each 24V bank as individual 12V batteries, from a separate controller. Thoughts?

LeeandRick · Nov 23, 2018

NotCook said:
I had thought about going the voltage doubler route downstream of the 24V charge controller, but I don’t think they would feed back the battery voltage to the controller. Another alternative might be to charge each 12V battery in each 24V bank as individual 12V batteries, from a separate controller. Thoughts?

Series the panels, with bypass diodes between them for shade problems and buy an MPPT controller that can handle the voltage and auto since battery bank voltage. Change controller output through a switch to each bank,turning off pv supply before the switching. Most of the default settings in these controllers work well enough that you would not have to go in and change the parameters. I set my RV up like this for emergency's because I had a 24 and 12 volt system. Keep things as simple as possible.

jssailem · Nov 24, 2018

The evidence in the video suggests putting the panels in parallel will do the job.

If cells from one panel on the starboard side are shaded the rest of the unshaded panels will still be producing energy. (i.e. when shaded the panel output dropped from 14 to 7)

dlochner · Nov 24, 2018

NYSail said:
Yes I agree..... after watching it appears that multiple controllers would keep power flow if one panel was shaded. So maybe a controller for panels on port side and one for starboard side panels....

jssailem said:
The evidence in the video suggests putting the panels in parallel will do the job.

If cells from one panel on the starboard side are shaded the rest of the unshaded panels will still be producing energy. (i.e. when shaded the panel output dropped from 14 to 7)

My suggestion for 2 controllers is simply for a fail safe approach. Wiring the panels in parallel before the controller will reduce shading issues, however, if the controller fails, then you are SOL. Wiring the panels to their own individual controllers and then parallel the controllers' output would mitigate shading effects and if one controller failed there would be another controller online.

heritage · Nov 24, 2018

NotCook said:
Our challenge is how do we use these same panels to run a 24V charge controller when we want to charge our 24V bow thruster and anchor windlass batteries? We don't want to dedicate panels to separate service for 12V and 24V

Why not wire your 4 panels 2p2s. Two pair in parallel on each side of the boat and those pairs wired in series for 24v output to a mppt controller near your 24v batteries. Then have another 24v mppt controller with 12v output located near your 12v battery bank. The second controller could be fed directly from the panels or through the 24v battery bank.

Bob J. · Nov 24, 2018

Why not just take the controller output to a manual transfer switch. One side of the switch goes to the 12 volt bank, the other to the 24 volt bank. This is what I did & have the ability to charge either the 12 volt house bank or the 48 volt propulsion bank. I have 2-100 watt 24 volt panels wired in series connected to a Midnight Kid controller. Pretty simple set up & it works pissa.

Ron20324 · Nov 24, 2018

In post 5, I have two DPDT switches to switch from ser/par. In series, IIRC, I get volts into the 40s, which you could step down to 24 for charging... IIRC. I looked at it Friday, and wrote it on a wine bottle, but left it on the boat for "emergency use".

Michael Davis · Nov 24, 2018

Ron20324 said:
"emergency use".

We had one of those as a "boat gift". Very handy in an emergency!

Tom J · Nov 24, 2018

NotCook said:
We have 4 panels installed, in parallel to a single 30amp charge controller, and are thrilled with the results. An advantage of parallel connection to the controller is that you get the combined current from whatever each the panels are putting out. One may be shaded at a give time, so it's current may be dramatically reduced, but that does not impact the current from the other panels. Our panels are 3x100 watts, and 1x123 watts for a total of 423 watts nominal. We have seen as much as 19.5 amps out of them (when looking), and love it. And, for us, usually anything more than 7-10 amps is gravy, with the SeaFrost fridge only running about 4-5 amps, when it is running (including compressor, blower, and coolant pump), and usually not much else running and drawing more than another 1-2 amps. And we aren't running an mppt controller, though that might be the next investment.

Our challenge is how do we use these same panels to run a 24V charge controller when we want to charge our 24V bow thruster and anchor windlass batteries? We don't want to dedicate panels to separate service for 12V and 24V, particularly since the 24V stuff is so rarely used and it would be a waste to have panels sitting idle dedicated to 24V duty when we are needing current for 12V side. I'm wondering if we can run two separate charge controllers in parallel to perform both functions. I'm thinking that would actually work, and that most of the current would go to the controller that was drawing it the most. Each controller might take what seems to be available, and when the 24V batteries were fully charged, that controller would not be using the current at all. Wouldn't this work? Hmmm.

You could do what Misfits did, if your controller is programmable for either 12v or 24v output. My Hamilton Ferris MPPT controller has this capability, and, with the transfer switch, could charge either system. In addition, the MPPT controller charges the batteries through the proper stages of charge, and maintains a float charge. My boat's battery charger doesn't do this, so I generally leave it off, even when hooked up to shore power.

CarlN · Nov 24, 2018

I used the relatively new Victron MPPT controllers. These are cheap enough (and very full featured) that you can pretty much use whatever is most convenient for your wiring layout. I used two controllers with four panels (port and starboard). Make sure your wire gauge is large enough to not lose a lot of the watts to wire resistance. If there is even a little shade, don't put panels in series. The Victron controller includes bluetooth to a free app on your phone to monitor what's going on and adjust settings.There are several sizes of Victron controller. This is the smallest which works fine with one or two typical panels. https://shop.pkys.com/Victron-Energ...-Charge-Controller-with-Bluetooth_p_7180.html