Adding Solar

[paula_ke]

If you are only going to run one solar panel then don't bother with MPPT. However, if you have 2 solar panels you can run them in series. Why? because you can get a higher voltage and an MPPT controller knows how to optimize for a higher voltage. Why is a higher voltage useful? As the day progresses you will have low angle sun, full sun, partly cloudy sun and shaded sun. A single panel or a two panel parallel system with PWM will have it's voltage drop below a useful PWM voltage (say 15 volts), so you may see 'voltage' but will get NO CURRENT which is what you charge your batteries with. In a two panel series MPPT system each panel will drop voltage due to changing sun conditions but the voltages 'add' which will keep the voltage seen by the MPPT controller ABOVE the minimum charging voltage (say 15 volts) and you WILL get current flowing into you batteries.

I have a two panel system with MPPT controller on both my van and my boat and keep my fridge going off 150 amp hr battery system 24/365.

Paula

[kevinnem]

Well firstly , power is power.. so there is ultimately very you don't NEED higher voltage to use MPPT, however -- you can also get a 24 v panel, rather then 12 v. Note these are just the "class " of the panel,. a 12 v can put out 18 v open circuit.

I would say that once you are using over say 75 watts, you should use a MPPT, because below this you have a "small system" that is cost effective, but compromised. once you hit 75watts +/- you have a big enough system that MPPT makes sense.

High voltages are better for longer runs, as there is less cable loss.

[paula_ke]

Power is Voltage * amps period. PWM and MPPT controllers require a minimum voltage to run. If, due to a cloudy sky, the panel cannot achieve say the minimum 15 volts while under load then no current will flow but you will see a voltage accross the input of the controller. If you have two panels that are in parallel that cannot achieve 15 volts, again, you will see a voltage (<15) but no (or very little measured in mA) current. However, if you were to place both those panels in series and got say, 20 volts at the MPPT controller, you WILL get current, and a significant amount (not full power).

Solar panel voltages add when in series, just like batteries.

MPPT attempts to take what ever voltage is being applied to it,above the minimum operating voltage and maximize the current that can be delivered. Thus one of the major advantages of MPPT is to run series solar cells to ensure the highest possible voltage under varying sun conditions.


Paula, Ham Raido Operator NX1P, BSEE, MSCP

[Neo]

MPPT attempts to take what ever voltage is being applied to it,above the minimum operating voltage and maximize the current that can be delivered. Thus one of the major advantages of MPPT is to run series solar cells to ensure the highest possible voltage under varying sun conditions.

So effectively you're saying that the MPPT does not draw (use) current unless the voltage (from the cells) is above 15 volts?

All the best.
Neo

[whgoffrn]

I guess it depends how much $ you want to spend and how much power you think you would use..... I have a fridge and think I use a "normal amount" of lights and anchor away from marinas and 100 watts with a cheapo controller has worked fine for me so far .... most of my long vacations have been in Florida where it's pretty sunny....a week long in Seattle might require mppt

[paula_ke]

I agree, if you have lots of direct sunshine with little or no cloud or shade, a single 100 watt panel and pwm controller will keep you going pretty good. While I am here in Baja, and the days are sunny (not always) I can push 4 amps form one panel into my batteries for 6 or seven hours and easily cover my fridge and lights. When on the dry and keeping my beer cold, I use two panels and MPPT to ensure clouds/shade/low angle does not impact the temperature of my beer.

The 15 volts is a guesstimate of what the solid state component drops are in the controllers. If you want to fully charge your batteries you will need at least 14.5 to 14.75 volts at a reasonable current before the controller will go into float mode (13.5 volts or so). Since the switching transistors (FETs in this case) have a certain in-efficiency (none are 100% efficient) you need to exceed your 14.5 - 14.75 + some FET drop. The drop can vary between .7 volts and 1.3 volts and is dependent on input voltage and temperature. So !5 volts input is about where most controllers actually begin to supply 'current' to your battery. If your 'shaded or partially illuminated solar panel is putting out 10 volts you will get nothing into your battery. If you have 2 panels with the same exposure, and they are in series, then your voltage will exceed the minimum (15 volts) and you will get some current into your battery. Don't do this with your pwm controller as when you get full sun shine you will get 36 volts out of the two panels which will blow up your pwm controller.

And Neo, that goes for pwm controllers as well. They are both buck converters, I know of no charger controllers that 'boost' from a lower voltage then your battery (although it is certainly possible to design such a thing).
P

[Starscream]

Hi again,

So I'm changing my plan based on all the feedback. Now I'm planning on an MPPT controller with a battery monitor display, linked to two 50W panels wired in series. That means the controller is only hooked up to one battery, instead of two as per my previous plans.

So, a new question pops up. My batteries are wired like this: http://alexiustoday.org/wp-content/uplo ... iagram.jpg to a Perko selector. From what I can tell, if the solar controller goes directly to the house battery terminals, then the controller will be charging BOTH batteries when the selector is in the BOTH position. Not that I ever really used the BOTH position, but once solar is installed could I leave the boat for short periods with the selector in BOTH and get a charge on both batteries? If the batteries are in different charge states when I go to BOTH, what happens?

Here is the new planned parts list:
https://www.amazon.ca/gp/product/B06Y6B ... YJSM&psc=1
2X https://www.amazon.ca/gp/product/B00JTM ... 37XZ&psc=1
2X https://www.amazon.ca/gp/product/B071ZB ... 2Z8F&psc=1
https://www.amazon.ca/gp/product/B07315 ... M8CJ&psc=1

I added the last one on there because I don't see any easy way to go from the MC4's on the solar panel to the battery with a quick-disconnect for trailering. I'll have to disconnect the MC4s using the tool each time I want to trailer. I plan to run the wires down through the motor cable entry. Another benefit of wiring the panels in series is no Y connector on the MC4's.

[Sumner]

If your solar array was going on a house I'd have no problem with the panels in series but on a boat I wouldn't do it if you didn't have to. It is very hard to come up with a place for panels where their won't be shading at times. Unless you do some additional wiring and use additional diodes if you have shading on one panel it will also then limit the current output from the other. Google about that....

https://www.youtube.com/watch?v=ofo1HQy ... u.be&t=561

With two in parallel you could totally shade one and still have the full output of the other. There is no way you won't have shading at times on a boat

Now saying that ...



.. the four center panels are two sets of panels wired in Series and go to the 24 volt mppt controller that charges the two 12 volt batteries in series that are there for the trolling motor. The two outer can be switched to being in series and then output to the 24 volt mppt controller for the trolling motor battery bank or switched to being in parallel where they then go to the 12 volt house bank mppt controller. For what you are trying to accomplish with a 12 volt system I'd stay with the panels in parallel.

The shorter you can keep the wires from the panels all the way to the batteries the more output you will get from the panels since you won't have as much voltage drop. On both boats I've wired from the panels to the controllers with oversized wire picked from a wiring chart...

https://www.colemanair.us/vp_asp/Script ... reSize.htm

... and kept the distance to a minimum. Those pre-made-up wires might be longer and smaller than you really want.

More on how our panels are wired...

http://1fatgmc.com/boat/mac-1/mac-outsi ... age-1.html

Sumner

============================
1300 miles to the Bahamas and back -- 2015

The MacGregor 26-S

The Endeavour 37

Trips to Utah, Wyoming, Idaho, Canada, Florida

Mac-Venture Links

[Sumner]

From what I can tell, if the solar controller goes directly to the house battery terminals, then the controller will be charging BOTH batteries when the selector is in the BOTH position. Not that I ever really used the BOTH position, but once solar is installed could I leave the boat for short periods with the selector in BOTH and get a charge on both batteries? If the batteries are in different charge states when I go to BOTH, what happens?.

I'd leave it in BOTH all the time personally,



In fact I'd tie them together as show above in parallel with the positive cable connected to one and the negative to the other. They are going to charge, discharge and last longer that way. Trying to tie them together some of the time is not going to give you the maximum life from the batteries and will also effect how useful they will be.

If you want to keep them separate then I'd spend the $80 or so on.



https://www.amazon.com/Blue-Sea-Systems ... y+combiner

an ACR that will combine them anytime there is a charging source. Still permanently tied together like the first image is best,

Sumner

============================
1300 miles to the Bahamas and back -- 2015

The MacGregor 26-S

The Endeavour 37

Trips to Utah, Wyoming, Idaho, Canada, Florida

Mac-Venture Links

[Starscream]

Thanks Sumner, good info there.

I watched the video on the parallel vs. series shading problems but I'm not sure if it tipped me off the fence on one side or the other. OK, it's better if one panel is shaded, but not a huge difference, and what about cloudy days and low solar angles? At 45N I'm not sure if my main problem is individual panel shading or just lack of direct sunlight. I'm still leaning towards series for that reason. I'm planning to mount the flexible solar panels on the bimini top, without being able to adjust their orientation, so they're going to get a lot of bad angles while sailing.

I like the idea of the Automatic charging relay on the controller. I've got to study it a bit to see how it wires up with the Perko selector. Thanks for that link.

[sailboatmike]

I've got to study it a bit to see how it wires up with the Perko selector. Thanks for that link.

This may help http://www.pbo.co.uk/expert-advice/inst ... -acr-26108

[paula_ke]

Series vs Parallel and shading of one panel. All panels have bypass diodes to ensure that series panels will not be limited by one panel being shaded. Having two panels located in such a way that at least one will be likely to be in the sun ensures that you will get something from your setup and more when shading starts to decline. Ideally, we would want solar panels with multiple bypass diodes one each 12 volt cell arrays to give us benefit during partial shading. I have two panels in series and an mppt controller. One may be in partially shaded and produce only a little voltage and current and contribution to the system while the other will be producing its best.

Note: the video does not mention by pass diodes which is important when talking about series panels and shading.

In a home based fixed system you can locate your panels in such a way that there is never any shading so that particular benefit of mppt is not an issue. More likely in a home based system you would use mppt to increase the voltage and lower the power drop on your feed line.

My van has less efficient panels but has diodes across each 12 volt cell array. Partial shading still produces quite a bit of current. Having two in series keeps the voltage above the minimum for the mppt controller. Sadly, these panels are to big for my boat and I have not found any low cost 'flexible' panels with more than the one diode for the entire panel.

The cheap flexible panels that I have use a single by pass diode and no blocking diode. By pass diode is used for series connected panels in shaded conditions. Blocking diodes are used for parallel connected panels in shaded conditions.

Regarding the battery switch. When you connect the two batteries, the batteries will attempt to 'level' themselves drawing down from the higher charged battery and bringing up the lower charged battery. Sometimes this can be a lot of current (think when you jump your car battery from someone elses car). The solar charger will charge both batteries and add back amp hours.

I use the automatic switch mentioned above. I determines if the charge voltage on one or the other battery is high enough (as in being charged by something) and connects the batteries together (as long as the charge voltage on one side or the other continues to be high enough). This works well for keeping my house and engine battery separated while being able to charge both batteries from either the engine or the solar panels system or the dock connected battery charger. I don't have to think about switches.

For more info https://www.electronics-tutorials.ws/di ... iodes.html

[BOAT]

You people are driving me crazy.

I believe Paula because of that double E - but Sumner is like a friend and he has never steered me wrong. I am getting a headache trying to figure out how to do solar.

On the boat I was just going to throw one of those flexible things on top of the bimini - ? Is that okay?

On my van I wanted to put up at lease two panels.

From what I am reading hear i will be using different procedures and systems - so I need to learn different ways to do it? (my head hurts)

I guess I'll start watching all these videos.

[paula_ke]

for my van i used the unisolar panel. https://www.amazon.com/Uni-Solar-PVL-13 ... K9C728KHK8

they used to carry shorter 12 volt versions which i used two of on my van. they have bypass diodes across each cell in the panel which makes them great for partial shade, as in driving on a road with trees.

there are kind of long.. the 12 volt versions were shorter but not short enough for the boat.

Van has been running 24/365 for 3 years in cloudy, partial shade, Seattle weather and Baja weather. Similar setup on the boat. I won't run anything but mppt and series cells.

[Starscream]

Thanks for the input Paula. Sounds like you've got quite some experience with solar.

Boat, I too take Sumner's advice almost like gospel (can't argue with someone who's single-handed the Bahamas and self-manufactured an awesomely set up boat...no wait, two boats and a rocket-car or something like that). But I think our applications are different: sailing the Bahamas and being completely self-reliant is one thing, and mostly day-sailing with occasional 5-day trips in very developed areas is another. Anyway, if I'm not satisfied, going to parallel only takes a few minutes and I can run the same experiments shown on the video Sumner attached, but for my own installation. I think if partial shading is the issue, then parallel wiring is the way to go, as Sumner says. I also suspect, though, that if poor sun angles and cloudy days are the problem instead of shading, then maybe series wiring with MPPT is the way to go, as Paula suggests.

I like a semi-permanent installataion with clean lines and minimally visible wiring. My current plan is two 50W flexible marine panels on the bimini top, controlled by an MPPT controller with battery monitor. I'm playing around with the idea of an ACR, but probably won't do it right away, until I have the installation up and running and have had a chance to experiment with it. I'll just use the BOTH setting on the battery selector when I want solar (or alternator) to charge both batteries, in the short term. In the long term, though, getting an ACR in there seems the smartest solution for ease of use.

Based on the input from everyone here, I think solar can be very simple and cheap...the basic minimum is a flexible 50W panel, PWM charger, and a fuseholder. I'm making it a bit more complicated because I want a bit more power and control.

Knock knock....who's there?...control freak NOW YOU SAY CONTROL FREAK WHO