Newbie to solar question

[Majja13]

I am thinking about building a some what protable solar recharge kit for my tt so I can do up to a week of boon docking. I know I need to do the total power worksheets. What I was wondeing is more or less which Charge controller to look at. I want to use 1 200 W pannel to start out with. I currently have all LED's for lights and at this time no TV or DVD's, but will be getting one in the future. Battery wise I have to GC2's. I do not have a gen set. I wanted to try and keep the cost down some what on this as to not spend as much as a generator would cost me. What are som of the brands to look for? Is a 25 or 30 amp controller also the ideal?

I willbe camping above 8000 ft most of the time and I french press my coffee.
Thanks
Matt

[time2roll]

Some of the value of MPPT is in the available programming, temperature compensation and ease of installation. Yes some PWM controllers have these feature but generally not the low cost models.
2,3,4 12v panels in parallel increases the logistic issues.

Either choice might be better depending on individual needs.

[jhilley]

I like to put the differential in cost between PWM and MPPT controllers into an additional panel. MPPT only makes a difference in bulk mode.

[HiTech]

But be sure to look at it for the actual operating temps. PWM can be a lot cheaper. For sure you won't get the same as out of it as an MPPT controller, but the thing to look at is the real world loss vs the real world cost. PWM can be a cheap way to get going with the panels you want long term, without spending the extra money on the MPPT controller right at the same time to get started. It leaves you a pretty easy upgrade path.

[hmknightnc]

jhilley wrote:


There are any number of good reasons to use PWM controllers with higher voltage panels - smaller cable, longer cable runs, lower cost, bigger panels for limited roof space, lower cost per watt panels

That is a very big misconception. A PWM controller does nothing but directly connect and disconnect the panel to the battery to control amps flow based on battery voltage (a morningstar controller does this 300 times/sec). A PWM does not do any modification to the voltage or current from the panel. So when the controller has the panel connected to the battery the panel is operating at battery voltage. If you look at the operating curve of a panel you will find you are at 50% or less of panel output (in watts) doing this. While it will work you loose at least 50% of the panel capability and are still transmitting DC current at battery voltage so not improving line loses.

Statement sounds good but PWM controllers and Solar Panel operating curves do operate such to make it true.

[jhilley]

pianotuna wrote:
Hi,

Just because the controller won't burn out doesn't mean that it is a good idea to use high voltage with pwm controllers.

jhilley wrote:


You can use PWM controllers with higher voltage panels. The TriStar works with panels up to 125 volts solar output.

There are any number of good reasons to use PWM controllers with higher voltage panels - smaller cable, longer cable runs, lower cost, bigger panels for limited roof space, lower cost per watt panels

[pianotuna]

Hi,

Just because the controller won't burn out doesn't mean that it is a good idea to use high voltage with pwm controllers.

jhilley wrote:


You can use PWM controllers with higher voltage panels. The TriStar works with panels up to 125 volts solar output.

[bka0721]

RJsfishin wrote:
Those big house panels are cheaper $ per watt, but for portable use, they are big and heavy.
I elected to go w/ 2 smaller lighter, easier to store panels And a $10 15 amp controller works fine w/ them too..

I agree here. Larger panels work well in a fixed position, except in heavy wind and snow load locations.

A smaller panel will be much better when handling them in and out of your TT and setting up. One only has to watch, once, a person wrangling a solar panel when the wind comes up, to understand what I am sharing. Imagine turning around in a wind with a large sheet of plywood in your hands as opposed to a small sheet of plywood.

b

[jhilley]

KD4UPL wrote:
A cheap (poor) charge controller can cause lots of problems. It's not the place to skimp. You want one that has programmable charging set points so you can charge your batteries to the manufacturer's specifications. A poor controller can overcharge or undercharge your batteries. Also, an MPPT controller will allow your panels full output to be better utilized than with a PWM controller. If you're going with a larger (less expensive watt/dollar) panel it will likely have a high enough Vmp that you will need a MPPT controller anyway.
RV usage, I guess because of price, is one of the last places PWM controllers are installed anymore. The home, cabin, grid tied solar industry has almost completely moved to MPPT controllers for all of their advantages.
I would highly recommend Blue Sky charge controllers.

You can use PWM controllers with higher voltage panels. The TriStar works with panels up to 125 volts solar output.

[RJsfishin]

Some of you mite like Quartzsite AZ, solar installation capitol of the world.
There ain't no cheap controllers or panels there.Name brand 130 w panel is $330
and a generic china 130 w right along side it for $299.
And you won't find a controller for less than 59 bucks, the exact same one that I paid 10 bucks for when I got back. Its really unbelievable !!

[JiminDenver]

Shadow Catcher wrote:
The claims for 20 to 43% increase efficiency are bogus which makes all the other claims suspect.
We have a high voltage panel that typically puts out 43V at the controller in full sun with no tilt. It is run through a Morningstar Sun Saver MPPT controller and I monitor using a Victron battery monitor. The high voltage means you get some usable current even in shaded areas. Just for fun I measured voltage from a full moon and got 12.7V.
The review in the Wind & Sun forum http://www.wind-sun.com/ForumVB/showthread.php?17511-Eco-Worthy-20a-MPPT-charge-controller-review

The RV net forum discussion http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/26464298/srt/pa/pging/1/page/2.cfm

I am the author of both threads and I am thrilled with my little el cheapo controller. The reason I didn't go even cheaper is many of those are labeled as MPPT but a look at the guts proves it isn't so. ( at least at that time) A look in the Eco-worthy shows the MPPT coil as well as the temp sensor that I can confirm at least works.

[ewarnerusa]

I jumped into solar as a newbie. I went with two 140 watt 12 V nominal panels (great price on sale) and I wanted to have the potential to upgrade without having to rewire/reinstall anything new if that happened. My tt still just has the 2 oem group 24s (140 Ah) and I know that will be a priority future upgrade. Since I would start with around 15 A max current and wanted to plan for up to double that, I started looking for 30-45 A rated PWM controllers. At the price ranges I was finding, it seemed like it was less than $50 more for a "nice" Morningstar Tristar. I've been very happy with that controller, it has the ability to be fully programmable and has many options like diversion load ability. Maybe more capabilities than I will ever use, but I feel good knowing my controller is no bottleneck to current or future use and can do so much.

[Shadow_Catcher]

The claims for 20 to 43% increase efficiency are bogus which makes all the other claims suspect.
We have a high voltage panel that typically puts out 43V at the controller in full sun with no tilt. It is run through a Morningstar Sun Saver MPPT controller and I monitor using a Victron battery monitor. The high voltage means you get some usable current even in shaded areas. Just for fun I measured voltage from a full moon and got 12.7V.
The review in the Wind & Sun forum http://www.wind-sun.com/ForumVB/showthread.php?17511-Eco-Worthy-20a-MPPT-charge-controller-review

The RV net forum discussion http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/26464298/srt/pa/pging/1/page/2.cfm

[RJsfishin]

Quote:
Also, an MPPT controller will allow your panels full output to be better utilized than with a PWM controller. If you're going with a larger (less expensive watt/dollar) panel it will likely have a high enough Vmp that you will need a MPPT controller anyway.
--------------------------------------------------------------
Again, FYI, I see MPPT controllers all the time for $59
Try one, you mite like it.

[RJsfishin]

KD4UPL wrote:
A cheap (poor) charge controller can cause lots of problems. It's not the place to skimp. You want one that has programmable charging set points so you can charge your batteries to the manufacturer's specifications. A poor controller can overcharge or undercharge your batteries. Also, an MPPT controller will allow your panels full output to be better utilized than with a PWM controller. If you're going with a larger (less expensive watt/dollar) panel it will likely have a high enough Vmp that you will need a MPPT controller anyway.
RV usage, I guess because of price, is one of the last places PWM controllers are installed anymore. The home, cabin, grid tied solar industry has almost completely moved to MPPT controllers for all of their advantages.
I would highly recommend Blue Sky charge controllers.

FYI, there are fully programmable controllers out there for as cheap as $12.50.It has so many adjustments, I don't know what 1/2 of them are for, but I know the first one (of 10) was adjustable for 5 different types of batteries. It worked perfect, but its only a 10 amper, so its now setting in my solar acumulation box.
The $10 (non prog) 15 amp ebay china controller I have now, brings my batteries into float mode at exactly the same voltage as my PD 9245, so thats good enuff for me.
Just because you spent big bucks for morningstar, doesn't mean you have to to get a controller that works just as well,
But, being a short timer, I can't speak for the longtivity of the cheap priced controllers, but I will tell you that I really couldn't care less, when I can buy 2 dozen spares for what you spent on a morningstar. And I can change it out in 3 minutes.
Now, having said that, you will notice that the purpose of my above post was to advise a nuby like myself to think about handling and storage of smaller panels verses large heavy ones,.....not to sell cheap china controllers.