RV Solar Problems

[RobertR]

Can't charge the batteries. 

I upgraded batteries to 4 deep cycle Trogen golf cart.  Upgraded the charge controller to Morningstar MPPT 60 amp.  Upgraded the wires to welding cable #2.  Moved the panels closer to the batteries.  Got a battery monitor that registers amps in verses amp out. 

Before with the old cheep charge controller I was getting 10 amps charge out of 700 watts of panels.  After all the upgrades I am getting 5 amps charge which is not enough to recharge the batteries after a 30 amp discharge on a bright sunny day, charging all day long. 

The Morning star equipment seems to have some problems.  The remote meter has to be plugged in backwards, i.e. lead from controller to panel has to go into the meter port rather than the charger port as the directions show it should be plugged into

amp hours on meter are wrong.  It says I have 1000 amp hour batteries, but I in fact have 450 amp hours .  Can't find any directions on how to reset that.

toggle switch setting will not allow 14.7 v setting to be toggled on. when I try it, it says fault and the system shuts down. 

So far I am unable to recomend Morningstar, although every one else on the web says its the best.

any ideas?

 

[JiminDenver]

How are the panels connected, parallel or series? I ask because you should be seeing 30a-40a easily with that kind of watts. Since you saw well below that with two controllers, I think the issue is befor the controller.
I would suggest checking the connections on the roof first. do VOC and SC test on each panel to make sure they are working and then test at each connection down the line until you get to the controller.


I know nothing of Morningstar controllers except they seem to be popular. I do know that it needs to be as close to the batteries as possible with a even heavier run of wire.

 

[RobertR]

I have two 350 watt panels connected in parallel.  I checked voltage on both before hooking them up and they were both putting out 19.5v  Checked the voltage at the controller lead wires before hooking them up to the controller.  19.5v 

 

[JiminDenver]

You have voltage, that's good. Now you need to do a short circuit test in full sun. I usually use a multimeter but a 350w 12v panel by itself would fry it.

The fact that you are getting such low amps and these are 350w 12v panels leads me to my next question. Just how old are they? The last panels I saw like that were around 10 years old and being replaced due to reduced output. This may be the case here if the short circuit test confirms what you see with the controllers. 5 amp is a ridiculously low number for 700w even if it were heavily clouded.  I see 4a out of my 230w poly when I can barely see where the sun is.

 

[Tom_M]

19.5 volts open circuit seems a little low. Typical 12 volt panels put out about 21 volts open circuit. To make best use of your MPPT controller it would be better to wire your panels in series giving you 39 volts into your controller.

 

[Wavery]

What is the state of charge on the batteries? As the batteries reach capacity, the controller will cut back the output to the batteries. If it didn't, the batteries would boil. That's why you have a controller..... 

 

[CarlGeo]

Stop by Solar Mike's at Slab City.  He can run things down quickly, and his charges are very reasonable.

 

[RobertR]

You have voltage, that's good. Now you need to do a short circuit test in full sun. I usually use a multimeter but a 350w 12v panel by itself would fry it.

The fact that you are getting such low amps and these are 350w 12v panels leads me to my next question. Just how old are they? The last panels I saw like that were around 10 years old and being replaced due to reduced output. This may be the case here if the short circuit test confirms what you see with the controllers. 5 amp is a ridiculously low number for 700w even if it were heavily clouded.  I see 4a out of my 230w poly when I can barely see where the sun is.

The 19.5v was not on a full sun day .  They are about 2 years old. 

I was getting 10 amps.  Went to thicker shorter wire, and it dropped to 5 amps, same MPPT Morning Star controller, and degree of discharged on batteries. That should have increased amps not reduce them. 

I have a Fluke meter with amp port.  It says 10 amps.  I assume to do short circuit test I would put red lead in amp port, and black lead in common port, and connect to negative and positive from solar panels, at the point of entry to the controller and see what it reads? 

 

[Gary RV_Wizard]

Went to thicker shorter wire, and it dropped to 5 amps, same MPPT Morning Star controller, and degree of discharged on batteries. That should have increased amps not reduce them. 

That suggests a high-resistance connection somewhere when you changed the wire.

 

[JiminDenver]

The 19.5v was not on a full sun day .  They are about 2 years old. 

I was getting 10 amps.  Went to thicker shorter wire, and it dropped to 5 amps, same MPPT Morning Star controller, and degree of discharged on batteries. That should have increased amps not reduce them. 

I have a Fluke meter with amp port.  It says 10 amps.  I assume to do short circuit test I would put red lead in amp port, and black lead in common port, and connect to negative and positive from solar panels, at the point of entry to the controller and see what it reads?

A normal meter should be limited to 10 a, even one of the panels would blow it if working properly. At high noon they should be putting out 40-50a I would think. That's conservative considering I'm expecting 30 amps from my 450 watts. They make amp meters that can handle it.

A example of what I would expect is a 210w 12v panel has a isc of 12.2 amps. you should be getting lots more out of 700w.

I would prefer measuring it as close to the panel as possible. Do they have pigtails? I would disconnect them there and test. Then disconnect them from the controller and check it again. They may be some drop but not huge. If the panel show more like their normal out put and you don't see it at the controller, check connections and such. Is there a fuse on the run from the panels?

Disconnecting it from the controller will also give you a better view of the VOC. The working voltage is lower than the the open circuit voltage.