Solar controller output destination

[booster]

I think most solar controllers are setup like the two I have used (Morningstar and Blue Sky), with the battery connection that powers the controller is also the output to the batteries for the solar charging. The panels connect separately to the controller. Marko's older shared ground unit may be the exception.

When I put in the original Morningstar a few years ago, I wired in the panels direct and put a pullable fues on the controller, so it could be turned off when not outside or plugged in, to save some parasitic draw. It seemed to work fine, but when I changed to the Blue Sky controller, the wiring directions were very specific in saying that you should not have an on/off switch in the battery lead, and if you wanted a switch on the solar to put it in the panel to controller wiring. Their explanation was that if you have output from the panels, with no battery connection, you can get a big voltage spike and fry you coach electronics.

I put a switch in the panel circuit when I put in the Blue Sky, but was undecided on which side of my battery cutoff/selector switch to connect the solar to. If I left it on the coach side, I would stand a chance of generating a spike if I had the panels on when I turned on the cutoff/selector switch. If I put it on the battery side, I would have continuous draw on the batteries from the solar controller. It was easiest just to leave it on the coach side and remember not to have the solar panels on without the battery switch on.

When I was doing my testing of the output of the third panel last week, I proved that I wasn't smart enough to remember the procedure while doing all the on/off load stuff trying to get to max output of the panels. The system had all the 12v stuff on as well as the inverter running the surround sound, to get enough load to test output, and I switched the selector switch through the off position going to connect both battery banks instead of the one I was on. Heard a small "snap" but everything 12v stayed on. The inverter had gone off and would not restart off the remote start, or the standby/on switch on the inverter. I finally got it to run by unplugging the output, cycling the GFCI outlet test, turning it on at the unit, back to standby, plug back in. It had apparently tripped out as a ground fault or overvoltage due to the spike I generated. Lesson learned. If I do the next upgrade to put the batteries in the genny spot, I will change things, someway. Probably just move the solar to the battery side of the disconnect.

What I don't know, and should probably call Blue Sky to find out, is if there is a battery in the coach circuit, panels connected to controller, and you plug the fuse back in, do you also get a big enough spike, or will the battery damp it enough? My guess is that it would damp it enough. If it does, you could put a switch to the controller only, so it was isolated by itself and couldn't power anything when off.

What is curious, is that I have not seen many solar setups that had on/off switches on the panels, so I would think all those systems would be at risk if someone removed the battery while sitting in the sun. I would think this would happen fairly often, but I haven't ever heard of anyone having a problem.

Do those of you that have solar setups have any on/off switches any place? Have you ever heard of the don't take out the battery with the solar on and in the sun potential issue?

[avanti]

I think I agree with your analysis that having a battery present is probably sufficient (and perhaps necessary) for safety--it acts like a big capacitor. For similar reasons, it is very bad to run the chassis engine with the starter battery missing.

I have the controller on the battery side of the main disconnect. I don't have any switches in the solar circuits. The solar controller is the ONLY thing still connected when the disconnect is off. I doubt that the parasitic load is enough to worry about, and I might speculate that enough power may be generated by the panels even in ambient daylight to balance it out.

If you really want to be able to disconnect the controller, I would add a switch but move the connection to the battery side of the main disconnect. Obviously, no harm can come if the disconnect is off.

[booster]

Originally Posted by avanti

I think I agree with your analysis that having a battery present is probably sufficient (and perhaps necessary) for safety--it acts like a big capacitor. For similar reasons, it is very bad to run the chassis engine with the starter battery missing.

I have the controller on the battery side of the main disconnect. I don't have any switches in the solar circuits. The solar controller is the ONLY thing still connected when the disconnect is off. I doubt that the parasitic load is enough to worry about, and I might speculate that enough power may be generated by the panels even in ambient daylight to balance it out.

If you really want to be able to disconnect the controller, I would add a switch but move the connection to the battery side of the main disconnect. Obviously, no harm can come if the disconnect is off.

So on your setup, you would need to make sure the disconnect switch was off if you removed the battery, to prevent a spike. Rare occurrence but good to know,probably. One thing that has happened to folks that had no switches in the solar was cooking batteries over outdoor storage periods, especially if plugged into shore power. It only really is a problem if you have a timer only charge controller. With a timer controller, it would go though a full absorption cycle every day, on top of the shore charger and full batteries, which is way too much high voltage on full batteries. We have the Blue Sky, which goes out of absorption on charge current and minimum time, so it wouldn't be an issue, and IIRC you have the same one.

I am leaning heavily to moving it to the battery side, may use a pullable fuse instead of switch on the battery side to help me not be so stupid, though That way at least I can disconnect the solar fairly easily if I need to do anything to the batteries.

[markopolo]

Lots of things to think about in this topic.

1. solar controller parasitic draw if parked under cover for long periods (not plugged in)
2. how to turn off voltage input from controller for battery maintenance / and also prevent # 1

also

3. overcharging batteries either with not smart solar controller or combination of charging sources.

It's very interesting seeing how things work or don't work well together.

Re: #3 I'll have to see how my new solar controller and converter/charger play together. The converter/charger in my van is timer based. Voltage is boosted to 14.4V for 15 minutes every 21 hours.

My solar controller is voltage based. I left home this morning with the van fully charged. In town, I parked in full sun and was relieved to see the solar controller in float mode: 13.8V and not in bulk charging mode. The Aopec smart battery "isolator" remained engaged so that meant all 4 batteries (2 house, 2 engine) were all being maintained.

Re: #1 I have to measure that sometime when my van is not plugged in while in the garage.

[booster]

Interesting that the timer solar controller was in float so soon. Was the van parked outside or inside before you left?

[markopolo]

Van was parked inside before I left but fully charged (always plugged in).
I checked the solar controller when parked at two different places and both times it was in float mode.

I think float mode is being triggered by the alternator voltage. My assumption is that the controller "sees" a high enough voltage for long enough to make it go to float and the batteries are charged enough to allow it to remain in float mode when I turn the motor off.

[booster]

It may be that the solar controller needs to see a low voltage to trigger a charge cycle, like maybe 12.2 volts or so. That would explain why it didn't go to absorption voltage, when you hit daylight. Good to keep from cooking batteries that way, probably not as good because it wouldn't start charging right away if you weren't down that far, but did need to charge.

The controllers that can have the problem with overcharging, that I heard of and saw on ours, were Morningstar. They initiate a charging cycle every time they see a night to daylight change, and then run the full absorption timer setting at the absorption voltage. It doesn't matter is the batteries are full, or if there is shore charger float voltage present.

I think I like the way your is working better, if it like the first way.

[markopolo]

13.2 volts at the batteries is the trigger to get this controller to go into bulk mode. The manual refers to it as the charge return voltage.

[booster]

So as long as you come out of the garage with some surface charge on the batteries, you shouldn't get a charge cycle?

[markopolo]

That seems to be how it is working. It would be easy enough to trigger bulk mode though and get the cycle started - just put a load on like the fridge.