Built A tiny home, but it has solar issues

[The_realTW]

Ok I still have a couple tests left, ill get back at this thread when finished

https://www.windynation.com/cm/Testing%20a%20Solar%20System_R1.pdf

[chrisski]

I don't know why there is no battery negative going into the battery-. You can disconnect the batteries and panels and try to do a continuity test to see which is hooked to the battery. On my PWM SCC that has Bat + and Bat -, there needs to be a connection to each before I hook up the SCC or load. Owners manual should say for sure, but that seems to be the problem.
=====
I really like Dave's idea of a PWM controller. Get the battery wired first, set the voltage, and then hook the panels up. You may have power.
======
The shunt should be the first thing on the negative battery cable. Don't know how my spell check got "moons" out of that.

[The_realTW]

I don't know why there is no battery negative going into the battery-. You can disconnect the batteries and panels and try to do a continuity test to see which is hooked to the battery. On my PWM SCC that has Bat + and Bat -, there needs to be a connection to each before I hook up the SCC or load. Owners manual should say for sure, but that seems to be the problem.
=====
I really like Dave's idea of a PWM controller. Get the battery wired first, set the voltage, and then hook the panels up. You may have power.
======
The shunt should be the first thing on the negative battery cable. Don't know how my spell check got "moons" out of that.

Yeah I am not sure, I just checked both panels from their leads, separately , and neither has any voltage coming off of it, it is cloudy but the SCC says 15 V coming in with 1 watt,

I checked both batteries with the meter, each is measuring 5.85 DC volts, however only .5 amps, it is possible the meter I bought (for 89.00!) is bad, and if that is the case all my measurements are invalid. We will pick this up tomorrow when it is sunny, and the PWM is here. Although I confess I know not how to wire it, but I will give it the ol college try!

Thanks again

BTW shunt is the first thing in the chain when the negative cable comes in from the battery

[chrisski]

Yeah I am not sure, I just checked both panels from their leads, separately , and neither has any voltage coming off of it, it is cloudy but the SCC says 15 V coming in with 1 watt,

I checked both batteries with the meter, each is measuring 5.85 DC volts, however only .5 amps, it is possible the meter I bought (for 89.00!) is bad, and if that is the case all my measurements are invalid. We will pick this up tomorrow when it is sunny, and the PWM is here. Although I confess I know not how to wire it, but I will give it the ol college try!

Thanks again

BTW shunt is the first thing in the chain when the negative cable comes in from the battery

=======

I guess you can assume the shunt is set up correct.

Is it possible the negative wire pulled out the terminal and back into the wall? I don't have a schematic, but without that battery negative attached, I don't see how the battery gets any charge at all, except perhaps it being connected to a frame ground at some point and somehow leaking through the load terminals.

========
I really think when you set the PWM Charger up, if the old SCC is out of the picture, you'll see some charging amps. Dave may have said 20-30 amps, but I think it will be around 10-15 amps of 12 volt charging at high noon.

When you get the PWM charger, take a look at the max input. This is the limit that can't be exceeded for your 12 volt system. Most PWMs are built to have a max voltage of around 20 VDC input for a 12 volt system. A lot of panels I look at are designed not to produce more than 10 amps. I think your rooftop panel is 300 watts, so my guess is that panel alone may put out 30 volts at 10 amps and may not work with the PWM. If that is the case, you can take the big panel out of the system and just use the smaller 100 watt helper panel. It will not be the amount of power you like, but if the panel puts out around 18 volts and 4 to 6 amps with direct sunshine, you've verified most of your system.

[The_realTW]

Ok everyone, I got the PWM controller, this thing is tiny. Obviously the Solar + - go into the respective slots, and the battery +, but where do i run the battery -, the other one never had one. Am I creating a new wire run back to the shunt?

I would appreciate any help.

BTW this thing says it uses less then 10MA to run when it is idle, I have a feeling that is way less power draw then the one on the wall.

Ill standby so I do not fry anything, photo of the charge controller is attached

IMG_8076.JPG



IMG_8075.JPG

[The_realTW]

=======

I guess you can assume the shunt is set up correct.

Is it possible the negative wire pulled out the terminal and back into the wall? I don't have a schematic, but without that battery negative attached, I don't see how the battery gets any charge at all, except perhaps it being connected to a frame ground at some point and somehow leaking through the load terminals.

it is not in the wall, it was never placed in the chain to begin with, also as for what you said about the load terminals, if your referring to the "load terminals" on the SCC, those go nowhere but to covered wires, I set them up but nothing was ever hooked up to them. I am at a loss as to where the 12V - is going as well, which may be the entire problem in the first place.

========

I really think when you set the PWM Charger up, if the old SCC is out of the picture, you'll see some charging amps. Dave may have said 20-30 amps, but I think it will be around 10-15 amps of 12 volt charging at high noon.

The PWM charger I have is rated for 60 amp charging current, I would expect to see at least half that if not more. I show pics in the post above this one.

When you get the PWM charger, take a look at the max input. This is the limit that can't be exceeded for your 12 volt system. Most PWMs are built to have a max voltage of around 20 VDC input for a 12 volt system. A lot of panels I look at are designed not to produce more than 10 amps. I think your rooftop panel is 300 watts, so my guess is that panel alone may put out 30 volts at 10 amps and may not work with the PWM. If that is the case, you can take the big panel out of the system and just use the smaller 100 watt helper panel. It will not be the amount of power you like, but if the panel puts out around 18 volts and 4 to 6 amps with direct sunshine, you've verified most of your system.

Same as above, I think this PWM can handle the Trina and the "helper" 100 watt, but again this is only a test. Once I figure out where the - wire is run to, ill start the testing.

[chrisski]

With the load wires dummy wires to nowhere, and no negative battery wire ever attached, I can only think if it ever was charged, perhaps the current flowed through some SCC ground point. I grounded mine with the green 8 AWG grounding wire.

For wiring, are you planning on removing the MPPT for the test and installing this? If so that could make attaching the PWM easier. Still will need a way to get battery negative connected to the PWM.

[The_realTW]

With the load wires dummy wires to nowhere, and no negative battery wire ever attached, I can only think if it ever was charged, perhaps the current flowed through some SCC ground point. I grounded mine with the green 8 AWG grounding wire.

The only wires that go to the negative are the ones you saw in the video, the big black heavy gauge wire coming into the tiny home, that goes to the shunt, then the other side of the shunt goes to the inverter. Nothing ever travels outside the tiny home except on that wire (for the ground).

For wiring, are you planning on removing the MPPT for the test and installing this? If so that could make attaching the PWM easier. Still will need a way to get battery negative connected to the PWM.

I was hoping you could tell me, I do plan on attaching all the wires currently in the MPPT into the PWM, I can always swap the controllers back. I am not sure how we are getting juice to the battery via the - wire. Are you telling me you do not think the batteries were ever being used, then where has the power been coming from , I am seriously lost now. If you like I can make you another more close up video of the system, just let me know. I plan on trying to troubleshoot this tomorrow.

I need to make some forward progress on this stuff, as i am getting tired of running the car all night to charge the batteries from the isolation system.

[chrisski]

On the original post (Post #1) on this thread, looks like the MPPT has six wires going into it, but at the close up of the MPPT with the picture on the bottom of page 9, post #135, looks like there is only five. To me, it looks like there is one wire that comes out from the left side of the MPPT in post #1, that I can’t see on the bottom of Page 9 post #135.

I’m a little reluctant to say hook a new battery wire in for the PWM. Aside from the fact that I go into a great bit of effort to calculate how thick these wires should be to prevent voltage loss and wires shorting out because they’re too small, you’d need to be sure there’s not a wire floating around in the trailer wall that is hooked directly to the battery. To me there’s a lot more testing I would do than I list below to be sure I’m not going to start a fire.

================

Start by measuring VDC across the PV+ and PV- while the panels are on. There should be something above 18 if there is sunshine. If not, I would not do the rest because when I look at the labeling on your MPPT controller, the wiring is just not logical. I don’t understand why they would group the PV / Battery and load the way they did. It’s just different than the four controllers I have. Mine all have PV +/-, Battery +/-, and if applicable load +/-. That and your panel is not labeled PV+. That make me think the labeling on the MPPT could just be wrong.

With battery power removed, as in cables disconnected, and solar panels off, as in circuit breakers off, so that everything in the trailer is off, including powering down the inverter, I would disconnect the PV wires and keep then reasonable far apart and then have someone turn the circuit on while the wires are at least on inch apart with the multimeter set to DC to see if I get voltage thorough the solar panels. I don’t know the short circuit voltage of your panels, but you should get at least 18. Trip the breaker so there’s no PV power and insert the wires back into the old SCC. My wires will Arc from about 1/4” and arcing is a risk in DC so you don’t want to leave those wires dangling. Voltage from the panels shows the panel wiring is good.

I don’t think you have a circuit breaker, so you could have someone cover the panels with cardboard to ensure it does not blow away and make the circuit live at a bad time. Have him take it on and off.

Provided the panels work, the next step would be figuring out where the mystery negative wire went.

With the system still completely off, and batteries still disconnected and no PV power, I’d ohm the battery cables. I had made about a 20’ test lead that is reliable enough that when I put one end on the + battery lead, +end on the wire entering the SCC Bat + and for the continuity test, the multimeter will beep. The beep is good.

Some of that can be dangerous. I tried the continuity test over a live tripped breaker before, and this is bad and there was a whole lot of sparks. THat’s how I found out a continuity test would complete a closed circuit so it should not be live. Going any further than what I’ve mentioned has a risk of doing the same if I say something wrong or incomplete or you misunderstand something.

[The_realTW]

Wow first off thanks for all the help, and yes I know this stuff carries risk, I got shocked plenty (mostly from AC) when wiring the tiny home. Ill take these one at a time in quotes so we are on the same page. I do want to point out that SOMEHOW the SCC has to be sending current to the batteries, its full darkness here, my SCC is showing the panels asleep (its a symbol of the moon) and I am still using power, both AC and DC, I simply cannot see how that would be possible otherwise. I will look back in the thread on the photos, you have a sharp eye. The rest will be detailed in the quoted blocks, thanks so much. EDIT: I looked at the photo you describe, and I can see how it looks confusing, but there was no sixth wire there, just shadows.

On the original post (Post #1) on this thread, looks like the MPPT has six wires going into it, but at the close up of the MPPT with the picture on the bottom of page 9, post #135, looks like there is only five. To me, it looks like there is one wire that comes out from the left side of the MPPT in post #1, that I can’t see on the bottom of Page 9 post #135.

I’m a little reluctant to say hook a new battery wire in for the PWM. Aside from the fact that I go into a great bit of effort to calculate how thick these wires should be to prevent voltage loss and wires shorting out because they’re too small, you’d need to be sure there’s not a wire floating around in the trailer wall that is hooked directly to the battery. To me there’s a lot more testing I would do than I list below to be sure I’m not going to start a fire.

There is a photo displaying that below, a for the wire thickness, I would just use the same stuff that we wired with in the first place, I have extra remnants.

================

Start by measuring VDC across the PV+ and PV- while the panels are on. There should be something above 18 if there is sunshine. If not, I would not do the rest because when I look at the labeling on your MPPT controller, the wiring is just not logical. I don’t understand why they would group the PV / Battery and load the way they did. It’s just different than the four controllers I have. Mine all have PV +/-, Battery +/-, and if applicable load +/-. That and your panel is not labeled PV+. That make me think the labeling on the MPPT could just be wrong.

I did that test today when I took the cover off the SCC, I measured across the PV+ - PV - and got 18.1 - 18.2 volts. As for the wiring on the MPPT I might be able to explain that , the PV + label on the inside panel was YELLOW, making it impossible to read, so Drew wrote PV + on it with black marker, but the PV+ wire is in the right spot, see a photo of the panel with cover off under this paragraph. Look closely and you will see the YELLOW writing barely.

IMG_8078.JPG

With battery power removed, as in cables disconnected, and solar panels off, as in circuit breakers off, so that everything in the trailer is off, including powering down the inverter, I would disconnect the PV wires and keep then reasonable far apart and then have someone turn the circuit on while the wires are at least on inch apart with the multimeter set to DC to see if I get voltage thorough the solar panels. I don’t know the short circuit voltage of your panels, but you should get at least 18. Trip the breaker so there’s no PV power and insert the wires back into the old SCC. My wires will Arc from about 1/4” and arcing is a risk in DC so you don’t want to leave those wires dangling. Voltage from the panels shows the panel wiring is good.

I am currently solo and have no one to help me but I will say this I have already tested those wires in and OUT of the SCC Bare wires read about 18V or so , short circuit I believe is 36.6 V on the trina, I saw a slight bit of arcing when i put the wires back in yesterday.

I don’t think you have a circuit breaker, so you could have someone cover the panels with cardboard to ensure it does not blow away and make the circuit live at a bad time. Have him take it on and off.

I have the converter box , all the breakers are inside there. While I cannot have someone help me at the moment, I an do some testing myself.

[QUOTE=chrisski;n425393Provided the panels work, the next step would be figuring out where the mystery negative wire went. [/QUOTE]

IF you look in this photo (taken the day after the solar was installed , you can see there never was a - to the battery from the SCC

pvwall-closeup.jpg

With the system still completely off, and batteries still disconnected and no PV power, I’d ohm the battery cables. I had made about a 20’ test lead that is reliable enough that when I put one end on the + battery lead, +end on the wire entering the SCC Bat + and for the continuity test, the multimeter will beep. The beep is good.

I will perform that test

Some of that can be dangerous. I tried the continuity test over a live tripped breaker before, and this is bad and there was a whole lot of sparks. THat’s how I found out a continuity test would complete a closed circuit so it should not be live. Going any further than what I’ve mentioned has a risk of doing the same if I say something wrong or incomplete or you misunderstand something.

I do understand about 95% of what your telling me I assure you, also something that came to mind tonight, could the negative and positive current be flowing BOTH ways on the battery? if so could I not just run a wire from BAT - on the PWM to the shunt, would that not send electricity into the battery along the wire, the Positive side goes that route???

Ill be making a video, just so you know exactly what is going on

I await your reply, that negative wire is going to have to go somewhere, otherwise I cannot install the new PWM

[The_realTW]

Chrisski, and anyone else, here is an in depth trace of the wiring

https://youtu.be/M_Fl4il-WCc

[chrisski]

Looks like you found the problem. A black wire from the shunt to the bat neg of the charge controller will give SCC what it needs to charge.

Whether that’s the MPPT or PWM, should not matter. Without that bat - attached, it should have never worked.

I don’t like the idea of multiple lugs to the shunt. I connect each lug to its own stud on a busbar to split at a busbar. The only thing that would change that for me would be if the documentation on the shunt said four lugs connected there is fine.

Really sounds as if you know your system.

[The_realTW]

Looks like you found the problem. A black wire from the shunt to the bat neg of the charge controller will give SCC what it needs to charge.

Whether that’s the MPPT or PWM, should not matter. Without that bat - attached, it should have never worked.

I don’t like the idea of multiple lugs to the shunt. I connect each lug to its own stud on a busbar to split at a busbar. The only thing that would change that for me would be if the documentation on the shunt said four lugs connected there is fine.

Really sounds as if you know your system.

im flattered but I only know it as setup, I do not understand how it ever charged in the first place. I will run a black wire from the existing controller today, and to the shunt to start. What I’m curious is why the MPPT never sent the current out, did it “sense” the black wire missing and therefore scale it back? Also if I have 33-36 volts of solar coming in, why am I only seeing 18V at .2 amp, I really think there is more to the issue. I’ll report back once the black wire has been rigged to the shunt.

[oregon_phil]

chrisski , I looked at your RV build on another site and I think you have the negative PV lead going straight to the Victron MPPT controller right? Not to a common 12VDC ground bus bar like The_realTW setup. I have a mechanical background, not electrical but I'm thinking that can't be good either.

[The_realTW]

I have news ill be back soon with an update!