I set up two identical installs of this board and one works fine the other doesn’t. I am trying to figure out how best to diagnose what the issue is. The setup is very simple:
For both systems I am only using the 12V output on the board and this is powering some off grid sensors. On one system the total load is around 5W and the second system its 10W.
The first system works fine and is running 24/7 charging during the day and running off the battery at night. The second system works fine during daylight but fails as soon as the solar power ends each evening. At first it seemed that maybe there wasn’t sufficient power to both run the system and charge the battery so I tried swapping to a 100W panel. Now the battery charge indicator on the board indicates that the battery is fully charged but it still doesn’t power the 12V output, even for a short time.
Any tips on best way to diagnose if this is a faulty board or a faulty battery?
Some pictures may help shed some light on this one - it may seem very simple but often there are subtle details that we can see with some high-quality pictures.
For what it’s worth - what you’re doing sounds sane enough
For a split test, you could try
Swap the batteries. Does the fault follow the battery? If not;
Swap the power manager. Does the fault follow the power manager?
Hi Tim
You have the luxury of having a similar working system alongside the troublesome one.
As Michael says the way to go is to swap over modules until you can get the fault to transfer with the swapped items. like a stereo system where you can compare different bits of a faulty channel with the good one. makes life that little bit easier.
If that fails the only thing that has not been swapped is the actual interconnect wiring so check and compare that.
Cheers Bob
Thanks guys for the words of encouragement. Both these systems are at a remote location so your advice is helpful for planning how I tackle this. Should be possible to swap components as you suggest.
OK, I decided to set up another identical system to do some tests. What I have discovered is that everything seems to be working correctly except that I have vastly overestimated the efficiency of the solar panel.
So for example I have a ‘100W’ panel and 50aH 12V battery connected to a roughly 10W dc load. I though that even on a poor solar day this panel would generate at least 20W, so 10W to run the load and 10W charging the battery. In practice during winter its seems to only just generate 10W so I am getting almost no charging.
So I think the solution is just to get a bigger panel. But if anyone has tips on sizing panels it would be much appreciated so I don’t make this mistake again.
Hi Tim
One of the main factors in sizing a panel is that it will only give you the 100W when the panel is 90º to the sun which will be only a few minutes. Then there is only about 4 to 6 decent charging hours in the day unless you can track the sun.
Then the main bit. The battery will have to power everything 24hrs. Say for example 10 W which is 240Whr. This has to be replenished in say 4hr. That means that the panel has to generate 60W for 4 hrs to replenish the battery without any fudge factor.
The way to calculate this part is to determine how many watt hours the system will use then divide this by the effective sun hours. In the example above I used 240Whrs and 4 sun hours. As you have found there are many other factors involved particularly when winter rolls around and which way you point the panel is one of them. Tracking the sun would be the ultimate way.
The other important bit is measured pane efficiency. I think the panel sellers are a bit optimistic sometimes.
Cheers Bob
You probably need to add a bit to make sure the battery is charged enough
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