Little Morningstar - boat solar controller

Surfpath

Well, here's a slightly different solar set-up....

I worked a little on the boat today to try to get the solar panel up and running again. I have a 5 watt flexible panel connected to a Morningstar Sunguard 4.5A 12v controller. I use this system to keep the marine battery charged at dock, as well as to limit downdraw on the battery when I am parked up and playing tunes.

Both panel and controller worked great, until one of the wires very near the panel got accidentally severed by a guest on the boat. At the time, it was a challenge to reconnect it so I stowed it away.

Fast forward to today: With some spare wire I did a quick cleanup and started reattaching everything. When the panel leads were reconnected I took a direct reading from them and saw 19 to 20volts (great), and reattached the controller.

However, when I next took a test reading from the leads that go from the controller to the battery I also got a reading of 19-20 volts (see photo). I brought the panel home. I thought the high voltage may damage the battery.
Attachment not found.

Surely the controller should be reducing the voltage to a more acceptable 12-13v?

Sob sob....did my little 'bulletproof' controller just got shot???
-SP

Surfpath

Re: Little Morningstar - boat solar controller

I have cut and pasted some text from the morningstar manual below in case it's helpful.

6.0 TROUBLESHOOTINGThe SunGuard can be tested with a power supply used in
place of either the solar array or the battery. Observe the
following cautions:
• Current limit the power supply to 2 amps.
• Set the power supply to 15 volts DC.
• Connect only one power supply to the controller.

IF THE BATTERY IS NOT CHARGING:
If the SunGuard is regulating (in PWM), then the controller is
charging and operating correctly. If the battery voltage is low
(under 12.5V - this test will not work if the SunGuard is regulating
in PWM), then measure the solar voltage and battery
voltage close to the SunGuard. If the voltages are within a few
tenths of volts, the array is charging the battery. If the solar
voltage is close to 20 volts and the battery voltage is low, the
controller is not charging the battery and may be damaged.

IF THE BATTERY VOLTAGE IS TOO HIGH:
First account for the temperature compensation (for example:
0°C = 14.8 charging volts). Next, disconnect the solar
array and measure the voltage at the SunGuard solar yellow
and black leads. If battery voltage is measured at the solar
leads, the controller may be damaged.

BB.

Re: Little Morningstar - boat solar controller

In general, the battery is what sets the "voltage" for the system... If the battery was between 12.7 and 14.5 volts or so, (sun down, sun up, no other loads), then probably everything is OK.

The solar panel itself will read ~19-20 volts or so with no load. If the charge controller is not "turning on" when the battery needs charging, then the solar panel voltage will remain high and the battery will not receive any charging current.

If the battery voltage is between ~12.7 and 14.3 volts (or so), the controller will be turning on and off during that time (the more "on time", the more average current). Easy to see with a scope, but sometimes hard to measure with a standard volt meter. (some controller have very slow on/off cycles, others have have higher frequencies--don't know about this guy).

-Bill

Surfpath

Re: Little Morningstar - boat solar controller

Hi Bill,
Thanks for the reply. Maybe this info will be of help:

The charge controller and panel have not been connected to the battery in many months - I didnt connect them yesterday when I went to fix the panel. I just measured the voltage coming out of a) the panel and then b) the controller. Then when I saw 20v I did not make the connection.

Basically, I have been keeping the battery charged during this time by periodically turning on the engine and running it for about half an hour (the meter read the battery at 12.5v yesterday).

You said: "The solar panel itself will read ~19-20 volts or so with no load. If the charge controller is not "turning on" when the battery needs charging, then the solar panel voltage will remain high and the battery will not receive any charging current"

OK, I didn't know that. But the problem, I think, is the opposite. 20v is coming out of the charge controller, even though it is not connected to the battery. It's basically the same as what is coming directly out of the panel.

My gut tells me that's too high, and the most that should be coming out of this little 12v CC whether it is connected or not is ~14v.

Is my gut off. Do you think I should connect it to the battery and let it do its thing? Ie. to let the controller sense a 'load' and then it'll adjust from 20v to the correct charging voltage?
-SP

BB.

Re: Little Morningstar - boat solar controller

It will not be a problem. Your panel is 5 watts or less than 1/2 amp. Your typical 12 volt boat battery can take 5 watts of charging current for 4-6 hours a day without needing a charge controller at all (battery may consume more water, and bubbling a battery with excessive charging voltage, long term, is not the best thing for long life).

Many charge controllers when not connected to a battery bank/load may have unexpected voltages, especially when using a digital meter (which pulls almost no current--so any "leakage" current in the charge controller will float up to the solar panel input voltage).

Solar panels are, more or less, current sources... That panel will output ~0.5 amps in full sun whether the battery voltage is 14.5 volts, 12.5, or even near zero volts... (more or less constant current output below Vmp rating of panel).

Batteries are "voltage sources"--And will absorb or output large amounts of current to stay around 12 to 14 volts dc.

The only time a solar panel could "over voltage" a battery is if the current output of the solar array is very large (over ~1,200 watts for a typical boat/automotive battery), or if a solar array is left connected to the battery for hours/days/weeks on end and the battery is "boiled dry" from over charging.

The one warning, when dealing with electricity and batteries (and boats) is to watch for electrical sparks that could ignite hydrogen gas or gasoline fumes when making/breaking connections (the usual warnings that we don't want to see anyone hurt while working on their power systems, take off jewelery, etc.).

-Bill

Windsun

Re: Little Morningstar - boat solar controller

You cannot test a charge controller unless it is hooked up to some kind of battery. Most will not even turn on unless there is at least 9+ volts or so at the battery. Without a battery to "look" at, the controller just gets confused and basically does nothing. Reading the voltage on the output terminals with no battery, you are going to read either zero or the panel voltage (depending on the controller).

Surfpath

Re: Little Morningstar - boat solar controller

Windsun wrote: »

You cannot test a charge controller unless it is hooked up to some kind of battery. Most will not even turn on unless there is at least 9+ volts or so at the battery. Without a battery to "look" at, the controller just gets confused and basically does nothing. Reading the voltage on the output terminals with no battery, you are going to read either zero or the panel voltage (depending on the controller).

Thanks Windsun and BB,
I had no idea. Now I can attach that controller and enjoy a full charged battery everytime.
-SP