Solar Charge Controller

[wbwood]

Looking at solar and seeing different options for controllers. What's the difference between PWM and MPPT?

[SkiSmuggs]

I'm in a similar situation. I currently have a 100w Renogy portable with the 10a ViewStar controller mounted on it. I plan to get a second Renogy portable without the controller, remove the panel mounted controller and mount near the batteries, then use longer cables from the panel(s) to the controller. The ViewStar has an LCD display, is programmable and I set it for the Trojan T-105 specs. I have been looking for a 20a controller for when I get the second portable. The ViewStar 20a is out of stock and other 15 or 20a PWM controllers I look at, like Morningstar, are not programmable and cost about 3 times as much. I won't be getting a 2nd panel until next summer so I have time and can use the ViewStar until then, and maybe Renogy will have the ViewStar 20a by then.

[wbwood]

Thanks guys about the difference between poly and mono...I read some places that said mono was better..but if it's not much of a difference to tell, money talks. Read some other postings here on the forum that others mentioned about it. Much appreciated!

[wbwood]

Almot wrote:

wbwood wrote:
We won't use it very often with rv. And will want to use at home as I mentioned.

Do you homework, read up what was suggested on the 1st or 2nd page.

Doesn't matter where you will use it. See what Niner Bikes said about controller - it has to have the features that you need. Also, cable length and gauge. You are trying to get useful tips, but without understanding certain things you're shooting blanks.

If 100W is all that you are going to have, then cable gauge is less important (up to a certain length), but controller still needs to be a decent one. I personally wouldn't be able to do a lot with 100W panel, even with my minimalists setup. This is the problem with portables - a small one would harvest too little (almost nothing on a dark day), and a big array would be a tedious logistics of setting up and breaking down, especially if you move often.

Thanks for the posting, but I don't think you've read all my postings...I mentioned about going with 2 - 100 watt panels. AS far as not being able to do much with a portable, I think it would depend on where you are camping. If you are comparing apples to apples and have a portable panel of the same wattage as a panel mounted on the roof, it would depend on where you are camping and where your rv is set up. Unless you can move your mounted panel to follow the sun, the portable gives you the option to follow it. I would think more direct sun would be better than not having it directly. Also, it would depend on where you RV is sitting. Is it under tree coverage where the panels aren't getting much?? Is there a place that you could put a portable to get some sun? As another or two mentioned on here, they feel like they weren't get the best amount of sun with theirs mounted on top.

I also stated that I would like the portable option to be able to be used at home. Our home is total electric. Including heat. WE do have a small generator to run some things in case of emergency, but it would be nice to have a total separate battery bank at the house with an inverter. Then I could pull out the panels and use them. Wont supply power to my whole house, but sure would help some.

[Almot]

wbwood wrote:
We won't use it very often with rv. And will want to use at home as I mentioned.

Do you homework, read up what was suggested on the 1st or 2nd page.

Doesn't matter where you will use it. See what Niner Bikes said about controller - it has to have the features that you need. Also, cable length and gauge. You are trying to get useful tips, but without understanding certain things you're shooting blanks.

If 100W is all that you are going to have, then cable gauge is less important (up to a certain length), but controller still needs to be a decent one. I personally wouldn't be able to do a lot with 100W panel, even with my minimalists setup. This is the problem with portables - a small one would harvest too little (almost nothing on a dark day), and a big array would be a tedious logistics of setting up and breaking down, especially if you move often.

[NinerBikes]

smkettner wrote:

wbwood wrote:
Not mounting on top of the roof. Keeping it portable.

Same thing RJ said a year ago. Then the setup/down logistics apparently became a bore.
Not much to talk about connections with a portable... just slap it on.
I would get separate components over a kit.

Bought a portable "kit" 120 watts worth. The folding panels are the only thing from the kit that I still use. Cables too small and too much resistance after the controller, the controller is the most rudimentary and basic of controllers, and marginal at best with my T-1275 battery. Scrapped all that, kept the folding panels, bought real wire, real quick disconnect high amp male and female plugs,and read, listened and observed here, and now I have something that works to my specifications, not some fake "do it all" specification, built around the lowest common denominator.

I can not stress enough to get a good solar charge controller with adjustable bulk /absorption voltage set points, if you spend all your time dry camping or boondocking. That made all the difference in the world for me. Measure not only the voltage but the amperage at a given charge level. You'd be surprised how low the amps are that some of them put out while pulse charging, in 4 or 5 out of the 6 cycles of pulse.

[wbwood]

We won't use it very often with rv. And will want to use at home as I mentioned.

[time2roll]

wbwood wrote:
Not mounting on top of the roof. Keeping it portable.

Same thing RJ said a year ago. Then the setup/down logistics apparently became a bore.
Not much to talk about connections with a portable... just slap it on.
I would get separate components over a kit.

[Almot]

wbwood wrote:
So the link I posted to the kit is decent?

Check Solar Blvd. Amazon rarely have decent prices on mid-size solar kits. The kit itself unlikely is "decent", and neither are low-priced kits from Solar Blvd or separately purchased cheap PWM controllers. This is all a bottom quality and features, at least as controllers go. If you care about your batteries, get a PWM with adjustable setpoints and remote temperature compensation.

Another thing to understand is that such "kits" are made for God only knows what purpose, other than unloading questionable items on a newbie that doesn't know much about solar and wants a turn-key solution. Brackets are not suitable for RV (too long to explain). Hardware, if any included, is not stainless. MC4 cables are usually too short and sometimes too thin, like gauge 12, while it should be - preferably - gauge 10, even for PWM where V-drop is less important. Cable for controller-battery is never included, and its gauge is a separate issue. Fuses, breakers, disconnects - are never included.

IMO, such a kit is OK as a quick portable setup (and even then you need a controller-battery cable), and the matter of controller quality and features remains an issue.

This topic has went far beyond the OP question about the difference btw MPPT and PWM - as noted, there are many things here that he needs to learn. Too many. The topic should've been titled like "How do I do all this solar thing", for example. Though then there would've been fewer members willing to answer. Jack Mayers is a good source. Handy Bob's blog is an easy and amusing read with few useful tips, but not a 101 on solar.

[jhilley]

Tray cable is usually THHN cable rated to used in cable trays. It is designated TC and is not usually the optimum cable for solar use. A UV resistant cable should be used in photovoltaic installations exposed to sun light. The UL standard for photovoltaic cables is UL4703.

[wbwood]

Another question.... I see "tray cable" mentioned. Looks like a cable with ring ends that go to the battery. Is that what it is?

[SkiSmuggs]

wbwood wrote:

SkiSmuggs wrote:
The 15' cable that comes with the Renogy portables is way too short so I plan to move the controller near the batteries. I really liked someone's idea of having two different length cables with quick connects. I had already replaced the alligator clips with ring/Anderson ends.

I'm debating on the portable or piecing it together. If I piece it together, I will go with some longer cable. The upside of going with the portables is that they will already be hinged together and have a built in stand. The downside is that the controller is mounted on it and thus you don't want to really have the panels too far from the batteries then.

Renogy now sells a 100w suitcase unit without controller, but I can easily remove my controller to mount in the RV. I will just need a quick connect panel to controller cable.

[NinerBikes]

ChopperBill wrote:

wbwood wrote:

SkiSmuggs wrote:
The 15' cable that comes with the Renogy portables is way too short so I plan to move the controller near the batteries. I really liked someone's idea of having two different length cables with quick connects. I had already replaced the alligator clips with ring/Anderson ends.

I'm debating on the portable or piecing it together. If I piece it together, I will go with some longer cable. The upside of going with the portables is that they will already be hinged together and have a built in stand. The downside is that the controller is mounted on it and thus you don't want to really have the panels too far from the batteries then.

My portable I mounted controller in a box and have a foot away from batteries. Use about 20 feet of cable between panel and controller.

Same idea applied here.

[FlatBroke]

wbwood wrote:

SkiSmuggs wrote:
The 15' cable that comes with the Renogy portables is way too short so I plan to move the controller near the batteries. I really liked someone's idea of having two different length cables with quick connects. I had already replaced the alligator clips with ring/Anderson ends.

I'm debating on the portable or piecing it together. If I piece it together, I will go with some longer cable. The upside of going with the portables is that they will already be hinged together and have a built in stand. The downside is that the controller is mounted on it and thus you don't want to really have the panels too far from the batteries then.

My portable I mounted controller in a box and have a foot away from batteries. Use about 20 feet of cable between panel and controller.

[MEXICOWANDERER]

MPPT re-enters the picture due to cable length.