Morningstar RD-1 put back to work

[ChrisOlson]

After a couple days it's got the battery at full charge now.  I checked the battery at noon with the panel unplugged and the voltage of it was 12.83 volts after I let it set about 30 minutes with the panel unplugged.

It must have some sort of regulator in that cigarette lighter plug.  It had the battery up to 13.25 volts before I unplugged it.  I would think that with the battery fully charged now that it would drive the voltage higher than that if it didn't have some sort of regulator in there.  It was in bright sunshine too, and not very hot here today, so the panel was putting out full power.

I didn't take the plug apart.  But Tom told me there's a little circuit board inside that plug.  I assume that circuit board does the regulating when it's plugged into a 12 volt power source.

I took those suction cups off it when I got it,  Then I took the four screws out and sealed the wires.  I made an aluminum bracket to mount it to the genset housing and then I put some clear silicon in the holes where the suction cups were.

It's not sealed between the plastic housing and the glass.  So to be safe I drill two 5/32" drain holes in the bottom of the plastic housing so the water can drain out if some gets in there.  I think I got it pretty well weather-proofed.  In the winter I'll unplug it and bring it inside because it's not needed then.
--
Chris

[ghurd]

"It must have some sort of regulator in that cigarette lighter plug"
Not many VW PVs have the regulator built in, but that one does for sure.
They tend to regulate to about 13.7V or so, and have a pretty large hysteresis (0.3V?), but perfect for maintaining a FLA or SLA.

I think there are 2 types of regulators I have seen.  They function the same.
But like I said, most VW PVs do not have them.

Inside the plug, it looks something like this...

[ChrisOlson]

That looks like the unit I got.  That's pretty cool how they stuck that little circuit board in there.   

We have a very heavy overcast today.  So heavy that 2.7 kW of installed solar capacity on MPPT is only putting out 320 watts.  So the little genset battery maintainer is not putting out much power.  The genset battery has "sagged" to 12.55 volts.  Which is not discharged by any means.  But the little solar panel will not make the one amp-hour today that is required to offset the usage of the electronics in the generator.

But it has proven that it can "catch up" on the next sunny day.

I'm pretty sure the battery in the generator is 12 amp-hours.  So I would assume that if it gets 6 amp-hours pulled out of it that it's down below 12 volts.  The generator will still start with the battery discharged that low, but it's not good for the battery.

Generac recommends exercising the generator every seven days.  The only reason to exercise it at that 7 day interval is to maintain the battery.  It's got a brushless generator in it so it depends on residual magnetism in the core to excite the field.  It could sit all summer without running and the field would still excite without having to flash it.  Exercising a generator once a week JUST to maintain the starting battery is bad design, to my way of thinking.  And Generac does this on both their off-grid, and grid-standby units.

It would seem to me that Generac, claiming to build the "ultimate" off-grid standby generator, would think of putting a solar battery maintainer on the thing - built right into it.  VW could've hired somebody to run around and start all the cars up once a week but they came up with this very simple solution that worked.

I'd tell Generac Customer Service about this, but talking to anybody at Generac is about as fruitful as talking to a dead stump in the middle of the woods.  And you'd probably get better understanding from the dead stump.  Generac has an excellent dealer network, and if you carefully select your dealer you can get good service on your generator installation.  Their factory customer service sucks real bad.
--
Chris

[ChrisOlson]

Inside the plug, it looks something like this...

(Attachment Link)

Whatever it is that little circuit board does in there, it works really well.  That VW solar panel floats the genset starting battery all day at 13.25 volts - it never goes over that.  I have checked it now and then to make sure this is going to work long-term.  I now have no doubts it is working fine, and will not harm the battery by over-charging it or anything.

It is unlikely from this point on that the generator will be run at all thru the summer months, except for its monthly exercise for 30 minutes.  It's pretty amazing that the generator electronics draw about the same amount of power as the little panel is rated at for output, but it still puts out enough "extra" to keep the battery right up to 100% SOC.

What's kind of funny is that my wife didn't notice the solar panel on the generator until three days ago.  She went out to our camper to get a cast iron skillet out of it.  As she was walking back to the house she suddenly stopped staring at the generator.

I was working around there and after a few seconds she says matter-of-factly, "We got a solar panel on the generator."

"Yep"

I don't think she knew what to ask but finally she asked the question that was obviously plaguing her: "So........what does it do?"

"It keeps the battery in the generator charged up."

<a few seconds while she absorbs this tidbit of information> "Oh.  It's cute.  We have solar panels on the house and the shop and the generator."  And she disappeared into the house.

LOL!
--
Chris

[ghurd]

Inside the plug, it looks something like this...

(Attachment Link)

Whatever it is that little circuit board does in there, it works really well.  That VW solar panel floats the genset starting battery all day at 13.25 volts - it never goes over that.  I have checked it now and then to make sure this is going to work long-term.  I now have no doubts it is working fine, and will not harm the battery by over-charging it or anything.

It is unlikely from this point on that the generator will be run at all thru the summer months, except for its monthly exercise for 30 minutes.  It's pretty amazing that the generator electronics draw about the same amount of power as the little panel is rated at for output, but it still puts out enough "extra" to keep the battery right up to 100% SOC.

The circuit in the VW PVs (the ones that have the circuit in there) usually regulate to about 13.7V average, maybe 13.5 to 13.9V.
The hysteresis is about 0.3V to 0.4V, with serious slop from one to the next.
Meaning (in good sun) it can cycle on a full charged 7AH 12V SLA (in decent condition) maybe 3 to 20 times a minute?  Cycling also depends on the actual SoC of the battery, not just the terminal voltage.


What you are seeing now is very similar to what you saw earlier.....

The battery was at 12.44 volts when I plugged it in.  It took about 30 minutes and it had already come up to 12.92 but it wouldn't go over that.

Now, the power it is putting into the battery is basically balancing out to keep the battery at 13.25V.
Earlier, it was balancing out at 12.92V.
Later, mid summer, it will be higher, and may even start to show the hysteresis if it cycles from 13.8 to 13.5 to 13.8 to 13.5....
If the battery or drain is too large, it may never make it up to the point of shutting off.

The controller in it is not overly fancy, and the PV is small enough to hve a low risk of overcharging a car battery with any drain at all.

VW must have figured that out at some point, or some of their PV maufactures did, and thats why most do not have the built-in controller.
Most VW PVs only have a blocking diode.

All that pertains to the old crystaline PVs.  I don't know about the newer amorphous type, or the newer newer amorphous type with the computer OBD plug end.
G-

[ChrisOlson]

Later, mid summer, it will be higher, and may even start to show the hysteresis if it cycles from 13.8 to 13.5 to 13.8 to 13.5....

I'm happy to report that this little 3 watt solar panel is doing an exceptional job of keeping the battery up in our genset.  I checked it 2 or 3 days ago and it had the battery up to 14.0 in the beautiful sunshine.

I looked at the inverter and it says 3 days to gen exercise.



If the generator fails to make its appointment at the gym this time, it won't be because of a dead battery   
--
Chris