Newbie to solar question

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.

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.

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.

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.

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

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.

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

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.

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 !!

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.