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RVing message boards => Boondocking => Topic started by: Ahmetd on October 28, 2016, 10:29:38 AM

Title: Solar charge controller
Post by: Ahmetd on October 28, 2016, 10:29:38 AM
Hey guys,
Just recently bought the renogy 100 watt solar kit, comes with a pwm controller. Now I'm looking to add another panel but first is like to change the controller to a mppt, since it can increase efficiency up to 30%. Just want to see what you guys use for controllers, it'd be nice to see the kind of amps the panel is drawing in throughout the day digitally. My budget is up to 200$ for this.
Would love to see some recommendations
Thanks
Title: Re: Solar charge controller
Post by: supermanotorious on October 28, 2016, 11:05:28 AM
http://www.harborfreight.com/30-amp-solar-charge-controller-68738.html

Title: Re: Solar charge controller
Post by: Kevin Means on October 28, 2016, 11:39:36 AM
Hi Ahmetd. Do you need an MPPT controller or just want one? You didn't mention what kind of RV you have, but if your battery-bank isn't very big, or your consumption isn't very high, a PWM controller may be all you need - even with two 100 watt panels. If I'm not mistaken, the PWM controller that ships with Renogy solar kits has a readout for amps, but I may be wrong about that - that might just be with their larger kits.

In any case, ours is an Outback FM-80, and I don't think Outback sells a controller that's rated at less than 60 amps, so both of those would be overkill for your needs. Morningstar sells a 25 amp MPPT controller but I think they run about $360.00. Renogy sells a 20 amp MPPT controller, and they run about $120.00. There are others out there, but Renogy and Morningstar are pretty well regarded.

Kev
Title: Re: Solar charge controller
Post by: Gizmo on October 28, 2016, 11:51:55 AM
Totally agree with Kevin.  To tag a long with what Kevin has said, you are correct an MPPT controller can add up to 30% efficiency, but the question is do you need it?  I ask because unless you are full timing or doing a lot of boondock & travel, you can easily get by with a PWM controller and save yourself some $$.  The reason being is the occasional recreational user typically will have the time for the system to recover, in other words get the batteries up to full charge, where as a full timer or someone who boondocks and travels extensively may not and so a MPPT is of real benefit.  We right now are in the recreational category and have a Morningstar Prostar PWM 30Amp charge controller and performs quite well for our current needs.
Title: Re: Solar charge controller
Post by: Ahmetd on October 28, 2016, 11:58:26 AM
Kevin, I'm off the grid for weeks at a time right now so I do want as much efficiency as I can through my solar panel in order to not run the genny and still be able to use my furnace, (live in co high mountains gonna be in RV all winter) I just got 2 6 volt 230 amp/h batteries. I have the simpler renogy kit that does not have amp read outs. 
Thanks for the advice, there are a lot of controllers out there I wanna hear which ones are some of the better brands, so that helps
Title: Re: Solar charge controller
Post by: Gizmo on October 28, 2016, 01:37:53 PM
The two I would consider are Morninstar & Outback, both well made and very reliable
Title: Re: Solar charge controller
Post by: Kevin Means on October 28, 2016, 02:35:15 PM
With two 230 AH batteries tied together in series, you essentially have one 12 volt battery, and your amps stay the same. That means you have 115 amps to work with before your batteries are drawn down to the 50% mark. FWIW, I never draw mine down that far, but as long you recharge them relatively soon, 6 volt deep cycle batteries are capable of remaining healthy.

As you probably already know, your furnace is one of your higher consumers of propane and electricity when it's running. It probably draws about 10 amps every hour it runs. Most RVers don't camp in climates that are so cold that their furnaces run continuously, but in the Colorado mountains in the winter, you're going to be running it a lot. If it runs six hours in a 24 hour period, it's consuming basically half of your usable battery capacity by itself. You'll obviously be running other things too, but only you know what they are.

I don't know where in Colorado you'll be, but consider this - in Grand Junction, there's an average of 9 sunny days each January, and there's a little more than 5 hours of useful charging time each day, due to the sun's angle (That's better than I would have guessed.) A 100 watt Renogy panel produces 5.29 amps per hour under ideal test conditions, but solar charging conditions in the winter in Colorado will never be ideal. I think the best you'll see is 4 amps per hour (per panel) on a sunny day - probably less - and that's if the panels are tilted toward the sun.

On a clear sunny day in Grand Junction, if two 100 watt panels generated a total of 40 amps in that 5 hour charging window, that's about 2/3 of the power the furnace consumes running 6 hours a day. You might want to consider getting a catalytic propane heater. They don't produce the same amount of heat an RV furnace produces, but they really take the bite out of the cold air, which reduces the amount of time the furnace has to run. And catalytic heaters only sip propane compared to LP furnaces, they consume no battery power at all and they're indoor-safe (just leave a vent cracked).

Kev
Title: Re: Solar charge controller
Post by: John Hilley on November 10, 2016, 12:15:23 PM
With the 12 volt panel you have you won't realize the 30%, in fact with the right panels you won't see 30% except under a perfect combination of conditions. You would get 200% at about the same cost or less, by adding a second panel.
Title: Re: Solar charge controller
Post by: EriikK on May 30, 2017, 09:56:51 PM
Jumping into an old thread here, but I have recently tested some solar controllers for my day job.  A few observations:

- As an OP said, with nominal 12v panels charging a 12v battery, MPPT won't gain you much. 

- Avoid the cheap fleabay controllers.  I tested two that kinda worked, but definitely did not perform as they should.

- The Renogy PWM controllers (I tested two different models) work pretty well.  From what I have seen, this is what I would recommend on a tight budget.

Depending on which kit you got, the controller in your Renogy starter kit may well have enough capacity to add one or two more panels.  Adding a panel will definitely do you more good than upgrading the controller.

- Morningstar and Outback are quality controllers, no argument.  But for a small (under 400w?) installation is the added cost worth it?  It could be argued either way.

 
Title: Re: Solar charge controller
Post by: supermanotorious on May 31, 2017, 11:37:37 AM
I just got the HQST MPPT Solar Charge Controller from Amazon. I'm not sure how it would integrate with the battery monitor. If the controller output connects direct to the bank, and the monitor is inline with the inverter, how does the monitor "see" the controller input?

EDIT: looks like the negative output from the controller, goes to the load side of the shunt for the monitor, right?
Title: Re: Solar charge controller
Post by: Kevin Means on May 31, 2017, 11:59:37 AM
A battery monitor is installed with a shunt - a device with an alternate low resistance path for electricity to flow. Shunts are usually installed on the negative terminal of a battery-bank, and all loads are supposed to be routed through the shunt. The negative cable of the solar controller's output should be attached to the far side of the shunt (not the battery terminal side) so power from the controller flows through the shunt. That will allow the battery monitor to measure the current (amps) flowing in or out of the batteries.

Kev
Title: Re: Solar charge controller
Post by: supermanotorious on May 31, 2017, 04:00:47 PM
fair enough, but doesn't this also mean the load will pull from the panels directly?
Title: Re: Solar charge controller
Post by: Gizmo on May 31, 2017, 04:48:21 PM
fair enough, but doesn't this also mean the load will pull from the panels directly?

Yes it will, but if the shunt is wired correctly, instead of connecting the negative to the battery, it is connected to the shunt, then from the shunt to the battery.
Title: Re: Solar charge controller
Post by: Rocdad on June 02, 2017, 11:34:08 PM
I am using a Renlogy RoVER 40 amp MPPT controller with four 200 watt panels laying flat on RV and four deep cycle AGM 100 ah 12 v batteries wired in parallel into a 5000 watt pure sine inverter/transfer switch/100 amp battery charger... the set-up runs everything including roof AC, toaster, Kuerig, microwave, 36" TV, etc note my dual fuel 4800 watt generator cannot start the AC(buying hard start cap)... I'm loving it! 8)