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RClifton · 09-12-2016, 07:24 PM

My wife and I recently purchased a travel trailer that came with a solar setup and inverter already installed. The system consists of a Morning Star SunSaver MPPT controller (ss-mppt-15l), a Morning Star RM-1 remote monitor, 2 Renogy RNG-235P panels mounted in parallel on the roof, 4 new Duracell SLIGC115 6v batteries (230ah ea) wired in series/parallel, and a off brand 2500w MSW inverter. The system was professionally installed about 2 years ago according to receipts and I have the documentation for it. However I am having the following issues :

1). The Renogy RNG-235P panels are rated as a 235w panel with a max power voltage of 29.8v, they have an open circuit voltage of 37v, on the RM-1 from about mid-morning till late evening I see anywhere from 30v to 33.2v registered as incoming voltage from the panels. This seems high to me, I contacted Renogy and they said so long as it's below 37v I'm fine but I could always measure directly at the panel and see what each read. Before I go tearing into the wiring up there anyone have any exp with these panels? should I be concerned?

2). The documentation I have for the RM-1 is sparse to say the least, there is a foldout that shows how the menus are laid out when stepping through them but my results don't match up and some of the info is just wrong. I see nothing in either the manual for the RM-1 or the controller on where to set or change the items either.

The documentation says the battery info menu looks like the "battery display" in the screenshot below but mine differs somewhat and has some erroneous info. Under the battery amp-hours the number for mine is constantly changing, the lowest I've seen is 1213ah and I've seen it as high as 1626ah. Clearly this is way off but how is this set in the controller and why is it changing?

Under the heading of battery maximum voltage mine currently reads 21.27v. Again pretty sure this is wrong. I also assume it is a setting changed on the controller but see no mention of how to change it in my manual.

Lastly, the last display in the battery display is a section that says "Battery Watts". What exactly is this supposed to be measuring?

Thanks, and sorry for what is probably some stupid questions, but I'd like to know exactly how this system works, and make sure everything is working properly etc.

jrusselltx · 09-13-2016, 07:03 PM

Looking at the current documentation for your controller, it has presets that are selected for battery voltage and type and that is about it. There is a PC program from the vendor that can be used to customize settings if you don't like the defaults.

The monitor doesn't change any settings in the controller, only measures and reports the data, so you need to work with the controller to change anything.

Your system appears to be wired as a 12 V system. From the maximum battery voltage you report (21.27) it seems that your controller may be set for a 24 volt system instead. Otherwise, you can reset the min max readings to make sure it isn't really getting that high.

As to the high panel voltage, if the batteries are fully charged so that the controller is in float mode and has only a very light load on the solar panels, they should read somewhat near their rated maximum of 37 volts. In that case, the load current (see the menu map) would be near 0 and the battery voltage would be at the float value of around 13.5 volts, although I have seen some chargers float at somewhat lower settings.

Hope this helps.

RClifton · 09-13-2016, 11:10 PM

Quote:

Originally Posted by jrusselltx

Looking at the current documentation for your controller, it has presets that are selected for battery voltage and type and that is about it. There is a PC program from the vendor that can be used to customize settings if you don't like the defaults.

The monitor doesn't change any settings in the controller, only measures and reports the data, so you need to work with the controller to change anything.

Your system appears to be wired as a 12 V system. From the maximum battery voltage you report (21.27) it seems that your controller may be set for a 24 volt system instead. Otherwise, you can reset the min max readings to make sure it isn't really getting that high.

As to the high panel voltage, if the batteries are fully charged so that the controller is in float mode and has only a very light load on the solar panels, they should read somewhat near their rated maximum of 37 volts. In that case, the load current (see the menu map) would be near 0 and the battery voltage would be at the float value of around 13.5 volts, although I have seen some chargers float at somewhat lower settings.

Hope this helps.

Thanks! I didn't realize if the batteries were fully charged that would affect the voltage coming in and I'm guessing that is exactly what it is. We have been on full hookups since we purchased it and I don't think I've ever seen it sending more than about 2amps to the batteries, usually it's only about 1.3 or so.

When they set the unit up they didn't attach anything to the load terminals, so the load section in the menu is pretty useless, however at 10pm now the batteries are reading 13.41v so I'm guessing they are currently at their float setting.

I had seen mention in the manual of some software but it appeared I needed another device to interface it with a laptop that I don't have. I'll have to contact Morningstar perhaps and ask them about the software etc. I was mostly concerned with the very high max voltage. I haven't seen any evidence of it ever sending that high to the batteries but want to be safe.

Thanks again for taking the time to reply and the help!

vsheetz · 09-14-2016, 12:43 AM

Since new to you and you don't know how the controller is configuted, I would suggest to reset it to defaults and then reconfigure as appropriate for your setup. Then see what the readings are. If still in question a call to MorningStar would likely bring the best answers. They have always been helpful to me.

baphenatem · 09-15-2016, 07:57 PM

Given the wattage rating of the modules and the state of charge on the batteries it sounds like things are operating normally. The kVA reading on the programming instruction sheet looks to be a misprint as the manual shows a kAh reading instead.

baphenatem · 09-15-2016, 08:01 PM

Another thing, the high voltage that you are seeing is on the module side of the charge controller, not the battery side. A MPPT controller is essentially a DC to DC converter that takes the higher voltage and lower current of the modules and changes it to a lower voltage and higher current to charge the batteries. It's not unusual for the displays on these systems to alternately display what's going on for the input side separately from the data for the output side.

RClifton · 09-16-2016, 07:33 PM

Thanks for all the replies everyone. I got caught up with a number of real life things but finally called Morningstar this morning to talk with someone and thought I would post a follow up in case anyone ever comes across this post with similar questions.

I wish now that I had looked for the manual for the remote meter as I felt pretty dumb when talking with the tech lol. First, apparently the battery maximum voltage tag, is actually the highest voltage the controller has seen on the battery side. NOT the highest voltage the unit will send to the batteries. Neither of us had any idea how the unit could have seen 21v+. As far as the AH reading goes, apparently it is the total # of AH that the controller has sent to the batteries since it was last reset.

Thanks again everyone!

LarryW21 · 12-24-2016, 07:24 PM

"When they set the unit up they didn't attach anything to the load terminals, so the load section in the menu is pretty useless"

Most RVers don't use the installed solar controller "load" feature since it only works when the sun is shining. Remember, if you do use it add a fuse. Never attach a power inverter to it.