What voltage should be at Yellow input to Atkinson Solar Controller?

[TMorristown]

Hi, I'm not able to charge my house batteries from my solar panels. This has been a problem since I acquired our 2016 Grand Tour. It had been modified before we bought it. Two 100w solar panels were added and the batteries were both changed to 100Ah lithium. The Atkinson PVCM20D controller wasn't changed. I know there are opinions about the Atkinson, but I don't think that's the problem in this case.

When I checked the voltage at the Yellow input lead to the Atkinson, I found -19.8V (Negative 19.8V). See attached picture. PS. Why on earth would Airstream place that Atkinson PVCM20D control box is such a $@#&%! hard-to-reach location?

The diagrams for the Atkinson all indicate the yellow wire should be attached to the Positive terminal on the Panel(s). Thanks to @Boxster1971 for posting these.

1. Is mine mis-wired? Or am I missing something?
2. Is there a "plug" on the solar panels somewhere that could be reversed?

Thanks in advance.

[Boxster1971]

19.8 volts on the yellow wire is normal when the solar panels are exposed to sunlight. That is voltage from the solar panels.

I don't think the Atkinson PVCM20D controller will work with lithium batteries. They run at a higher voltage and will likely tell the controller (falsely) that the batteries are fully charged. This controller is designed for led acid battery voltages.

I'm attaching a copy of the Atkinson PVCM20D controller manual for your information.

[Al and Missy]

Originally Posted by Boxster1971

19.8 volts on the yellow wire is normal when the solar panels are exposed to sunlight. That is voltage from the solar panels.

I don't think the Atkinson PVCM20D controller will work with lithium batteries. They run at a higher voltage and will likely tell the controller (falsely) that the batteries are fully charged. This controller is designed for led acid battery voltages.

I'm attaching a copy of the Atkinson PVCM20D controller manual for your information.

Yes, but OP said he had -19.8 volts. Unless he has the meter connected backwards, that is WRONG. Yellow wire is output from the solar panels and should be positive.

[TMorristown]

Update: Thanks gentlemen.
Abner Jenkins from Atkinson also got back to me almost immediately. He made it clear that something was mis-wired on the way to the input to their controller as the Yellow should always be positive.

He also pointed out (as Mike did) that the PVCM20D won't charge lithium batteries as the voltage output is too low (and is not adjustable in this model). Does anyone have experience with it? As it turns out, this was a small blessing. Keep reading...

I'll probably order the Atkinson PVCM25D-MPTLi that Abner recommended for the Lithium batteries.

Abner also explained that the panel mis-wiring is a hazardous situation as the big lithium batteries would have been dead-shorted through the panels if the controller had ever actually tried to charge them from the panels. Dead-short on big batteries is very bad. Note to self: Confirm all wires actually have the recommended in-line fuses.

I climbed to the top of the RV and found the SAE plug was damaged where it goes through the roof into the lounge. Obvious corrosion on the terminals and the negative was broken off. So, I've ordered a new SAE receptacle.

PS. Any recommendations on a replacement for the roof-top penetration connection? What a crummy, non-waterproofed connection for a roof-top!

[uncle_bob]

Hi

I would replace the controller with a Victron Bluetooth compatible unit. That way you can see a whole lot more about what's going on with your solar setup.

Airstream typically uses Zamp rooftop connector boxes. They are watertight and pretty durable. Since this is AS, one can *never* say "they always use this" .....

Bob

[Boxster1971]

Originally Posted by uncle_bob

Hi

I would replace the controller with a Victron Bluetooth compatible unit. That way you can see a whole lot more about what's going on with your solar setup.

Airstream typically uses Zamp rooftop connector boxes. They are watertight and pretty durable. Since this is AS, one can *never* say "they always use this" .....

Bob

I agree with Bob don't buy another Atkinson controller. Victron would be my first choice.

[TMorristown]

Thanks. Can the Victron fit in the same cabinet space? The Atkinson is small and that space is tight! In particular, is the Victron “thicker” which would prevent reclosing the cabinet. See picture.

[StogieMan]

Originally Posted by TMorristown

Thanks. Can the Victron fit in the same cabinet space? The Atkinson is small and that space is tight! In particular, is the Victron “thicker” which would prevent reclosing the cabinet. See picture.

Yes, but in front of that area under the shut off switch. Very tight but it fits. I had it there before my lithium upgrade.

Also agree with Boxster and Uncle Bob with getting a Victron and not wasting your time with another Atkinson. Did that and wasted my time and money - Abner is nice, professional and quick to respond but their product is garbage in my opinion.

[TMorristown]

Thanks Stogieman. The pictures are very helpful.
Are you no longer using the Victron with your Lithium setup? (My AI was (semi)converted to Lithium (2x100Ah) before I got it. )

[StogieMan]

Originally Posted by TMorristown

Thanks Stogieman. The pictures are very helpful.
Are you no longer using the Victron with your Lithium setup? (My AI was (semi)converted to Lithium (2x100Ah) before I got it. )

TM, Yes I'm still using the same one as you can use it on several battery types.

You might want to check that the original BIM was changed to one that can handle lithium. If the previous owners did not change out the solar charger to a lithium based one, my guess is that they also forgot to change the original BIM on your 2016. I'm assuming that it's probably the same one as my 2015.

The Lithium based BIM from Precision Circuits is literally a drop in replacement from the one that is there now. All the wires go to the same spots on the new LI-BIM 225 except for the Gen Set wire that gets capped off. Your battery switch by the driver door will function the same. Ive had no issues with it.

[StogieMan]

Originally Posted by StogieMan

TM, Yes I'm still using the same one as you can use it on several battery types.

You might want to check that the original BIM was changed to one that can handle lithium. If the previous owners did not change out the solar charger to a lithium based one, my guess is that they also forgot to change the original BIM on your 2016. I'm assuming that it's probably the same one as my 2015.

The Lithium based BIM from Precision Circuits is literally a drop in replacement from the one that is there now. All the wires go to the same spots on the new LI-BIM 225 except for the Gen Set wire that gets capped off. Your battery switch by the driver door will function the same. Ive had no issues with it.

Adding a PDF doc on the BIM 225

[TMorristown]

Did I get the right one? I got a SmartSolar MPPT 100| 20. It seems right for my 3 x 100W panels (one’s 6 years old so a little down)
Here’s my question. I have 2 connectors for Load on this Victron. I don’t want that. I just want the Victron to charge the Batteries until they’re full. The Magnum manages the Load.

Can I just leave the Victron’s Load connectors “disconnected? Or do I need a different Controller?

[StogieMan]

Originally Posted by TMorristown

Did I get the right one? I got a SmartSolar MPPT 100| 20. It seems right for my 3 x 100W panels (one’s 6 years old so a little down)
Here’s my question. I have 2 connectors for Load on this Victron. I don’t want that. I just want the Victron to charge the Batteries until they’re full. The Magnum manages the Load.

Can I just leave the Victron’s Load connectors “disconnected? Or do I need a different Controller?

The one that I got is the MPPT 100/30 and it does not have the loads input on it. The dimensions seem to be almost the same but slightly off so I would first check to see if it fits in that tight area that you want to install in. You should also be good with the MPPT 100/20 with three 100w panels but should consider the 100/30 if you intend on adding any more solar panels down the road.

Yes, you can use the 100/20 without using the load portion of it.

The load output is a feature available on some MPPT charge controllers to enable the user to control a load either manually or automatically using certain algorithms. The loads can be switched on and off at will, but can also be used as a safeguard to disconnect the load under low battery or overload conditions.

Did you check on the BIM situation while at it? If the old BIM wasn't changed, it won't work with lithium batteries and won't charge them with solar just like your old Atkinson Controller didn't.

[uncle_bob]

Hi

If you check the Victron manuals and app notes: The load output is there to route solar straight to a load. It does not get the battery involved. Sun goes down and load shuts off. Yes, there are a lot of strange things you can do, but that's the main thing it seems to be for. In an RV, just ignore it.

Bob

[StogieMan]

Originally Posted by StogieMan

Did you check on the BIM situation while at it? If the old BIM wasn't changed, it won't work with lithium batteries and won't charge them with solar just like your old Atkinson Controller didn't.

TM, what I meant to say is that without having some type of lithium BIM or DC charger for the lithium batteries, they won’t charge via the alternator just like the batteries didn’t charge with the old Atkinson controller via solar.

[TMorristown]

Thanks for good advice StogieMan and others. The Victron MPPT 100/20 that I installed did a nice job with Solar charging of the LiFePO4 batteries during recent trip.

You were right about needing to replace the Battery Isolation Manager (BIM) to work with Lithium batteries. The engine was only charging to (about) 12.5V or so, which is a fraction of Li battery capacity. So, I bought a Li-BIM 225 as you recommended. However it doesn't look to be a direct replacement for the current BIM. In particular, I don't know where to fit it. See photo StogieMan provided earlier in this post with my blue highlight. That's the Precision Circuits BIM that I have today. Am I looking at the right thing? Or is there a different BIM somewhere else in the Airstream Interstate 24 Grand Tour? All the wires look like they terminate at the BIM in the photo, but where I highlighted in Red, the Chassis battery cables don't seem to be connected. But the Coach battery cables do look like they are connected. I'm confused.

Where did you physically install your Li-BIM?

[StogieMan]

Originally Posted by TMorristown

Thanks for good advice StogieMan and others. The Victron MPPT 100/20 that I installed did a nice job with Solar charging of the LiFePO4 batteries during recent trip.

You were right about needing to replace the Battery Isolation Manager (BIM) to work with Lithium batteries. The engine was only charging to (about) 12.5V or so, which is a fraction of Li battery capacity. So, I bought a Li-BIM 225 as you recommended. However it doesn't look to be a direct replacement for the current BIM. In particular, I don't know where to fit it. See photo StogieMan provided earlier in this post with my blue highlight. That's the Precision Circuits BIM that I have today. Am I looking at the right thing? Or is there a different BIM somewhere else in the Airstream Interstate 24 Grand Tour? All the wires look like they terminate at the BIM in the photo, but where I highlighted in Red, the Chassis battery cables don't seem to be connected. But the Coach battery cables do look like they are connected. I'm confused.

Where did you physically install your Li-BIM?

TM,

I placed mine on the floor when I did my lithium upgrade as I had to redo everything over anyway with new cables, etc. In the pic that you reference, I was in the process of removing wires and the reason that you didn’t see a cable on the chassis side of the BIM.

It is for the most part a drop in as all the wires that went into the old BIM go into the new one for the exception of the Gen-Set wire which is just capped off and not used or needed. This has been confirmed with Precision Circuits.

Looking at some more pics, I think that once you remove the old BIM, you should be able to install the new one right there where the old one was as the wires and cables are about the same length and doable.