Low Solar Power Production?

I recently installed an EMC-1 Morningstar Converter to measure how much solar power is coming into the battery. I have 510 watts of solar polar on the roof of a van. The panels are lying flat on the van (not tilt enabled). The van is often in the sunlight most of the day....
The usual max array voltage is about 20.5; the average max output watt hours varies widely but is probably around 240/250.
The average amp-hours per day received is 72.
That seems low to me ?????
The usual max array voltage is about 20.5; the average max output watt hours varies widely but is probably around 240/250.
The average amp-hours per day received is 72.
That seems low to me ?????
Comments
The EMC-1 Morningstar is just a data and communication device. So you are getting data from it...
Not sure what your array looks like, but perhaps 2 panels in series feeding an MPPT type controller?
To start, Let's talk about losses;
Here are a couple examples of STC vs NOCT provided by solar companies;
Now lets talk about angle of the panel to the sun, you can really only expect max production in the 2 hours either side of solar noon for panels angled correctly to the sun. Any off any more than 15 degrees will result in some loss to the corrected expected output.
Charging a battery, we don't know what battery chemistry you are using, but the amps across the shunt (perhaps the data collection device is shunt based?) are affected by charging/system voltage. So if charging at 14.8 volts less current will be passing the shunt than the system voltage (12 volts). This uses the basic equation amps x volts = watts.
...and of course, does your system reach fully charged? at that point the charge controller shuts down the array and you add nothing to the battery bank which is already full. Even when the battery bank reaches absorb, the batteries reduce the amount of current they will accept.
...and system loads? If this is a shunt based monitor, loads that are running while you are charging reduce the amount of current passing through the shut to the battery bank. So if you are running 100 watts of box fans and laptop, you shuld deduct that for current that coould charge a battery.
Here's some basic info on battery charging for lead acid flooded batteries;
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
I had seen estimates on the internet of a 500 watt system delivering about twice what I'm getting.
The EMC-1 attaches to the controller and measures the power coming into the battery..Does not so far as I know measure anything coming out of the battery
I noticed that when I brought another 200 watt panel along and added it (on the side of the van) that it would boost the watts and amps the battery was receiving in the morning but not when the sun was high - the battery couldn't accept more. Does that mean that with 2 battery I could make better use of the solar I'm getting?
It's a 100 amp Firefly battery by the way.
I did get a shunt-based VIctron battery monitor and am trying to figure out how to read it (and set it properly) so I can read power coming out as well.
Once the battery, is a flooded lead acid, reaches 80% full the battery will accept less current, until the charge controller 'times out' or reaches a minimal flow of current. Then the charge controller will turn off power coming into the system down to a trickle.
Off grid solar MUST have lots of losses, so the system can remain healthy. It needs to be able to come to a full charge 2-3 times a week.
I really don't know how you use your system, or where in the world you live. We use as a general rule what the battery manufacturers suggest. Being able to charge a battery bank at 10-13% of it's capacity. So a 100 amp 12 volt battery that would be 10-13 amps. Since you will be tied to poor orientation of the array "flat mounted on your van", you might bump that up a bit. "Firefly" is NOT a type of battery and I don't feel like looking it up to see what type of battery it is. With 500 watts of array, you should be able to provide roughly a max of 300 watts (derating for NOCT values and poor orientation) Or about 300/15 volts charging= 20 amps max. That should be all your battery would want in general.Cortttt said:
Indeed 72 amp hours in a day is a huge amount for a 100 amp battery. Most healthy systems are designed to use the top 20% or 20 amps and have the rest in reserve for over cast days. I can't see your loads during the day, so I don't know how much of that is consumption, but it sounds like an under sized system for the amount of charging it's doing.
- Assorted other systems, pieces and to many panels in the closet to not do more projects.
The Firefly is an unusual battery type - it's a carbon-foam battery that can be drained to low levels and returned to charge.
Firefly International Energy (fireflyenergy.com)
Firefly states that "Firefly carbon foam design resists sulfation and corrosion (two of the primary causes of failure in lead-acid batteries), while dramatically increasing the surface area within the battery, resulting in greater energy capacity, faster recharges,and deeper discharge capability."
This seems to be true as I have at times drained the battery to very low levels only to see it rebound.
I thought the battery pack might be undersized. as I see other systems with less solar and more batteries. It was what was recommended to me and tt's worked well for about six years but the battery is clearly dying now. I will go to Lithium next. I have a Victron battery monitor and am trying to figure out the load...
The system is being used constantly to power an Engel fridge (actually 2 over the past year), a computer, cell phone and sometimes a small CD player . It was at approximately 300 watts of solar power and then I added another Engel fridge and added another panel over the past year.
I've been pretty clueless, though, as to the proper sizing of this system.. As I shift to new batteries I'm finally trying to learn how much is coming in and how much is going out and get that right.