Mike Schriber
San Diego, CA
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I'm going to be installing a solar panel on my motorhome. The panel is around 125 watts (putting out 97 watts now in winter) and it's float voltage is 20vdc.
Can anyone recommend a low cost charge controller for this application? I've had some experience with Morningstar controllers and they seemed to work well but I'm not tied to any particular brand. Cost and performance are my only concerns.
Thanks!
Mike
2006 Damon Daybreak 3276 37' bunkhouse
2007 Jeep Wrangler Rubicon Unlimited
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BFL13
Victoria, BC
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This would do a good job on that. Great price.
http://boatandrvaccessories.com/2510.htm
2003 Chev 2500HD Gas, 2003 Komfort 26FS 5er
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KD4UPL
Swoope, VA
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Morningstar controllers are good. I've used many of their models and never had any problems. I would highly recommend you get a controller that is Maximum Power Point Tracking (MPPT). These are more expensive than the regular Pulse Width Modulation (PWM) controllers but they are worth it IMO.
An MPPT controller can get you up to 25% more charging amps from the same panel under the right conditions.
Blue Sky is an other good brand. Many people on this forum seem to like Rouge but I have no experience with them.
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BFL13
Victoria, BC
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I have a single 130w panel and it gets to its max rated amps of 8.2 at high noon just fine with a simple non-MPPT controller. IMO spending $400 for an MPPT for that panel would be crazy.
Say you did get 15% more from it than with the non-MPPT. 15% of 8.2 is 1.23 so you might get 9.5 amps instead of 8.2 at high noon.
If you could tilt/track etc and get 9.5a straight for a couple hours either side of high noon instead of the lower amps that you do get then without tracking, then that is an extra 1.23a for four hours.
That comes to about 5 amp hours more per day. In real life it is less than that of course. Is that worth $400 up front? Not even close IMO.
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full_mosey
Oklahoma
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SS-10 12V
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KD4UPL
Swoope, VA
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I agree that spending $400 for MPPT is crazy. Where did that number come from?
A quick google search will show you can get a Blue Sky 2512i for $162. A Morningstar SS-MPPT-15L goes for $199.
There are probably better deals out there if you look hard.
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full_mosey
Oklahoma
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KD4UPL wrote:I agree that spending $400 for MPPT is crazy. Where did that number come from?
A quick google search will show you can get a Blue Sky 2512i for $162. A Morningstar SS-MPPT-15L goes for $199.
There are probably better deals out there if you look hard.
Two 125W panels and an SS-20 would get you more watts/$.
If you are roof real estate limited, the the MPPT is indicated.
HTH;
John
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Mike Schriber
San Diego, CA
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Thanks for the replies. I think a PWM controller is fine for my application. I already have a Xantrex XBM installed so the solar controller doesn't even need to have a display. I'm just looking for something reliable that'll also cutoff and not compete with my Progressive Dynamics converter and overcharge the batteries when the rig is plugged in between trips.
Mike
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pianotuna
Regina, SK, Canada
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Hi Mike,
What ever you get make sure it does temperature compensation. Your batteries will love you longer.
Regards, Don
Kustom Koach Class C 28'5" 256 watts Unisolar, 875 amp hours in two battery banks 12 volt batteries, 2500 MSW watt inverter.
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BFL13
Victoria, BC
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Mike Schriber wrote:Thanks for the replies. I think a PWM controller is fine for my application. I already have a Xantrex XBM installed so the solar controller doesn't even need to have a display. I'm just looking for something reliable that'll also cutoff and not compete with my Progressive Dynamics converter and overcharge the batteries when the rig is plugged in between trips.
Mike
I put an on/off switch on the pos wire between panel and controller to give me control. Sometimes I want to disconnect the batteries and the way I have it wired, the solar would then go straight to the loads, which is a no-no for my model of controller (don't know about others.) So when you are on shore power Float, you could do the same to cut off the solar if required ( "depends" if that is really required or not.)
I have one of these ASC types, which works well. Mine is the 16a version with temp comp (not needed for my application) but without the load terminals (not needed either) but it does have a pot on the back where you can adjust the voltages set-points ( very useful) You can choose from such options when getting this controller.
http://www.specialtyconcepts.com/special_home.html
It has only a red light that flashes when the batteries are at high SOC, so no problem mounting it out of sight right up by the batteries, which is where the controller ought to be.
I have a Trimetric, which shows the solar input as part of the total reading. Sometimes it would be nice to see what just the solar is doing, but you get a fairly good idea of that anyway after a while.
Got it on sale at $59 here (was $89), don't know current prices.
When it was on two panels last summer for a while, and we got cloud effect that pushed amps briefly over 16a, it did allow the occasional 19 amps through with no problem, so that was good. I gather some controllers do an amps limit at their rating if that happens.
The real question is whether you will ever expand your solar. If so then the usual tip is to get more of a controller up-front than you need right away. I am dubious about that, since you don't know what controller will really match this imaginary solar set-up and if you guess wrong, that's money down the drain. You absolutely cannot have a controller with less of a Voc rating than your array's Voc at low temperature (which is higher than the array's rating taken at 25C)-so you must know that array low temp Voc before you buy, and how are you supposed to guess what that will be?
Anyway it is a fun topic with lots of different opinions on how to play it.
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