Solar Charge Controller

Yes but you don't need that big 30amper for 200w. If you get your panel(s) elsewhere, not in a kit, then at least you know what size controller you will need.

It can be cheaper now here (12v =$2/W; 24v = $1/W )to get a single 200w instead of two 100s and pay the 100 for the Eco-W. (that's what I have now -230w and an Eco-W for under $400 total) With 12v panels here now twice the price of 24s and the Eco-W price not that much more than a PWM compared with what MPPTs used to cost (other brand MPPTs still do!) it came out ok.

Eg, two 115s would be $460 here plus say $30 for an Ebay controller that is pushing $500 here. All cheaper in the States of course, so do the math for your own case. Might be cheaper to go 12v and PWM for the 200w range in some areas. Very situational.

It is easier to deal with two small 100w as a portable for storing them in the trailer between stops than one big 200w is though. I have done that both ways. I hide the big 200 behind the sofa, which is loose in our floorplan. Many sofas in rigs are nailed down though. Can lay it on the bed, but that's where we put the TV set when towing. Depends on the rig what you can do.

The ones that come with the kits are 30amp pwm.

wbwood wrote:
So the 190 and 200 watt panels mentioned are per panel or all together?

If I purchase a couple of 100 watt panels (not permanently mounting them), then a pwm will suffice?

Expected amps from a 100w panel is about 6.3a aimed at a high sun, so total for two is 12.6a. You need a 20% margin above that in controller amps rating to allow for when the panel exceeds its ratings. So another 2.6a is 15.2a.

You could go with a 15a controller or a 20a for nearly the same price. Any old eBay 15 or 20a controller will do the job for under $15. BTW don't get sucked in by claims of MPPT on those, they are actually PWM. Cheapest MPPT is about $100 by comparison (Eco-Worthy 20amper)

I was looking at This. But there are a couple of other kits a little cheaper without the brackets that I won't need. This one makes specific mention of a 20' cable, but the others don't. I will have to check further into it. Another 100 watt panel will be around $150 through them. Or I can go with a 200 watt kit for $328.

Hi,

Here is a simple flow chart.

Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT. What ever type of controller is chosen, make sure it has adjustable set points and a temperature probe that is on the battery.

In most cases MPPT may out perform PWM by about 8%. But not always.

One rule of thumb is between 60 and 150 watts of panels per 100 amp-hours of storage. The smaller the battery bank the higher the wattage needed (per 100 amp-hours). Here is a link to the rather special spreadsheet which includes an energy audit, that N8GS has created to help size solar battery charging systems!

Solar Spread Sheet N8GS

For a nice explanation of solar, try this link:

Golden rules of solar

I like the fact that I can connect my panel directly to a battery without a controller. I become the controller and disconnect when battery voltage has risen to my set point. My PWM controller direct connects (bypasses PWM) when battery voltage is below its set point logic.

Yes the panels that are typically put on houses are about 200 watts and nominal 24 volts. People also use these with MPPT to charge RV batteries.

100 watt panels are typically 12 volt nominal and will work fine with a PWM controller charging a 12v battery.

Post a link to the equipment before you click and buy for best comments on compatibility and price.

So the 190 and 200 watt panels mentioned are per panel or all together?

If I purchase a couple of 100 watt panels (not permanently mounting them), then a pwm will suffice?

I live off grid in a tiny house and have built and rebuilt my power system several times, currently on version 3.0. My current system is 200W of PV panels, Morningstar Sunsaver MPPT, 240 AH of batteries. My lifestyle is simple, but I have power for pretty much anything I want to run.

My suggestion is to skimp on panels and spend your money on MPPT charge controller instead. In fact with limited space on the roof of an RV I would say that MPPT should be the norm. You will harvest more energy per day with an MPPT charge controller than a PWM version. Yes its more money but its worth it IMO. Wait until the first cloudy day and you still are able to harvest a respectable amount of power!

There isn't an easy answer. More needs to be known about daily usage, where you will be using solar, time of year, type of panel being used, space for panels and how much you want to spend. It used to be fairly easy to do it based on cost, but MPPT controllers have come down in price and there are some inexpensive Chinese controllers that seem to perform well.

I have 505 watts of low voltage panels and a Morningstar PWM controller. My system works well, but if I were to do it again, I would probably go with high voltage panels and a MPPT controller. Both types will perform well. I average about 23 amps out in the Arizona winter with my panels mounted flat. We use our computers all day and night and have the TV on for about 15 hours per day. We have 3 group 29 batteries. We can't get 4 GC2 batteries in our tray with the starting battery, so I will be moving the starting battery and going to 4 GC2 batteries. Feel free to PM if you have any specific questions.