Solar - anyone regret getting PWM charge controller?

[Cdash]

Looking to do a solar installation and have been studying up. Think I'm pretty good on most of it, however, still struggling with the charge controller. As I understand it, the PWM kind of "chops off" power above the battery charging voltage, where MPPT is covering almost all the power down to the charging voltage, thus giving as close to all the power available.

MPPT sounds great, but comes at a cost, more than double. Enough to buy almost 200 watts of panels. I read about plenty of people that share that they are fully charged by noon or 1pm, with their MPPT controller. That means that the system has quite a bit more power than is required.

To me, it seems like a WPM could still charge the batteries, but may not do it till a little later in the day.

Is my thinking flawed?

Or am I just trying to be too cheap?

[93ToyTruck]

If you've got several panels, an MPPT controller will allow you run them in a series so that a higher voltage is transmitting between the panels and your controller. Less loss, you can use smaller wire and you'll get power in lower light situations. Panels in parallel might not produce over 12 volts in low light but they probably will when they're in a series.

[scrubjaysnest]

pianotuna wrote:
Hi,

Buy a controller that has:

1. a temperature sensor on the battery bank
2. a voltage sense wire
3. adjustable voltage set points

I'd stick with pwm right up to 500 watts, beyond that and I'd go MPPT. At 1000 watts I'd switch to a 24 volt battery bank.

+1
I use 400 watts as the point at which to consider MPPT. Ours is PWM and because of a panel failure we will go from 280 watts to 360 watts.
PWM has always been fine for us but we tend to be on the conservative side. A point to keep in mind, the battery(s) determine how much current they can accept so MPPT may not be the best choice.

[mlts22]

The biggest reason why I recommend MPPT is because I want every single watt from the limited space on the roof. If I were using a larger array or something portable, a PWM might be the ticket.

PWM controller prices are easy on the budget, though. I bought a controller for $8 from eBay, and if one isn't needing every single watt, the money saved by doing that is noticable.

[CA_Traveler]

Solar Blvd 1/19/16 Comparison

Panel Watts Cost Size inch $/W W/Sq Ft

Cynergy 140 $159.00 39.5 38.3 $1.14 13.3

Ecosolar 230 $158.70 64.4 39.1 $0.69 13.2

Panels Number Watts Cost
Cynergy 5 700 $795.00

Ecosolar 3 690 $476.10

Add mounting hardware, wiring, shipping and controller

[Cdash]

So basically, what I am getting from all of this is:

If you get a PWM you are happy with it and if you get a MPPT you are happy with it!

I appreciate the information and opinions, it seems that I can't really go wrong either way. Almost seems like I am better off picking my panels, and then the charge controller.

[SkiSmuggs]

I did the research and all the conflicting data drove me crazy, but saw a few posts from knowledgeable folks that said PWM is just fine. I went with a $30 Solar30, got miffed at the single stage programming and replaced it with a $90 Viewstar 30amp PWM that is multi-stage programmable. 200w on the roof and I can easily add another 200 without giving the controller a second thought.

[CA_Traveler]

rjxj wrote:
I Don't regret it and glad I got a PWM. I went with the Bogart Engineering SC2030 paired to the Trimetric and four 130 watt panels charging four gc2. I recently helped a friend rewire his rig. He has a Blue Sky 3024 mppt with remote monitor and 470 watts and 3 agm 12 volts. I can be down 80 or 90 ah and he 50 and we are charged at about the same time. I have 50 more watts and he has mppt. As I understand it I dont believe he's getting the full benefit of mppt because his 3 panel voltages vary by almost .9 volts. They were added one at a time as his system grew.

The Trimetric is an excellent product and there are a lot of good posts on the SC2030.

For parallel panels the voltage should be very close for either controller and the amps very close for serial panels (usually MPPT).

[red31]

no regrets getting a $11 PWM controller, good for storage with little ABS time.

$50 viewstar is programmable and has coin batt to save settings when not connected. I enjoy 'viewing' the LCD. I use it to operate a few landscape lights 3hr each night.

[CA_Traveler]

RJsfishin wrote:
In partial shaded conditions, I am ahead w/ paralleled panels PWM.

And with partially shaded conditions I'm ahead with serial panels and MPPT because of their bypass diodes. I've posted several threads on this effect.

Lots of good advice above. My very good MPPT solar was the same price as a PWM solar system. Why? Very simple as the solar panel cost per watt for 24V panels is less than 12V panels. This will continue in the future as the volume production is for homes/business and they don't use 12V panels.

The 24V panels are larger but once one begins to consider installing the panels higher off the roof that becomes a non issue.

[RJsfishin]

In partial shaded conditions, I am ahead w/ paralleled panels PWM.

[Rbertalotto]

Another +1 for the Bogart Engineering solution. You can read all about my install and the total cost structure here:

http://rvbprecision.com/diesel-stuff/dodge-cummins-diesel/solar-install-grey-wolf-19rr-toy-hauler.ht...

[Ductape]

Fred, roof space is a limitation for some of us. I need all the power I can get in a limited footprint.

[Golden_HVAC]

Back in the 90's when solar panels where super expensive, the MPPT controller alleged that it would give 20% more amperage to the battery than a PWM controller.

While they do take in 18 volts X 10 amps and can put out 13.5 volts X 12 amps (180 and 162 watts respectively) they are not worth it anymore, because you can add an additional panel of say 140 watts for $229 that might have been spent on a controller.

SunElec.com has the $229 140 watt 12 volt panel with aluminum frame that would be ideal for a RV. Many 'frameless' panels are not easy to install on a RV roof.

Yes the MPPT controller can take in 24 volts and still charge a 12 volt battery, some can take in 150 volts maximum - so you can wire all the panels in series, and then only have 10 amps or less going into the controller, so much smaller wire can be used, and savings there.

But I like my $13 PWM controller much more than my $325 SolarBoost 50 controller - that I Bought in 1999.

Back in 1999, a 120 watt panel was $429, and getting an addition 10% was well worth it to spend that kind of money on the controller.

Yes my 415 rated watts system was normally full by sunset, even if I used 120 amp hours of power overnight.

Your RV will consume 35 AH just to run the CO and propane detectors and the refrigerator for 24 hours. This is about what one of my 120 watt panels will put out in one day.

Good luck,

Fred.

[azrving]

I Don't regret it and glad I got a PWM. I went with the Bogart Engineering SC2030 paired to the Trimetric and four 130 watt panels charging four gc2. I recently helped a friend rewire his rig. He has a Blue Sky 3024 mppt with remote monitor and 470 watts and 3 agm 12 volts. I can be down 80 or 90 ah and he 50 and we are charged at about the same time. I have 50 more watts and he has mppt. As I understand it I dont believe he's getting the full benefit of mppt because his 3 panel voltages vary by almost .9 volts. They were added one at a time as his system grew.



From everything I have read mppt will do about 10 % better and that usually occurs primarily under certain conditions like very low battery and low temps at the panels.

In my friends case, he seldom goes below 12.3 volts or so and he's usually in a climate that has the panels at least warm early in the day. So he's probably not getting the best of an mppt that cost him $400. Others may explain it better???

If you do buy an mppt, buy all the panels now so you dont end up with a miss match issue. I understand PWM/parallel wiring to be more tolerant of small miss match of panels as they are not searching for a more stable voltage point??

I also like Bogarts warr. They said 4 years but if there is a problem that may be their fault they will cover it for a longer time. I would also consider a Morningstar PWM. Friends BS system goes black screen sometimes when he touches anything in the rig and discharges static electricity.

Saving $200 on a controller will put about 200 more watts on the roof. Bogarts reasons for developing PWM vs mppt was the expectation of panel prices continuing to drop and the less complex internals and power consumption of mppt. From everything I have read 30 % better from mppt isn't really going to happen but if I went to a bigger system or wanted 24 volt panels I'd go with Morningstar mppt. I stayed with 12 volt panels because their 26 inch width worked better on my rig than 24 volt panels. I can stuff 4 more panels up there where I couldn't match the wattage with 24 volt panel dimensions.

[lc0338]

If you came to this sight to get a clear decision keep trolling. I went MPPT with 2ea 270 watt panels. I wasn't sure if I would add more (watts) and didn't want to have to re-design and buy new parts. I think for the most part pwm has been around and mppt is newer technology so most of the old timers only had pwm which have served them well and don't want to spend additional money. I was putting in a NEW system and just wanted to try and install newest technology but I was not on a shoe string budget either. There again I used 4ea 6volt agm batteries which is another discussion 🙂