[Lolaeliz]

Finally I'm rewiring my solar panels from series to parallel. Does this look right?

The solar panels have 3' of wire for each +/- wire. the black wire going to the solar disconnect is going to be maybe a foot too short. Do I need to replace it, or is their a connector I can use to add a foot or so of wire? (it will be inside the van)

 

[HarryN]

It is definitely parallel as you have drawn.

If your solar charge controller is an MPPT type, then usually you are better off with them in series.

In a parallel mode, usually the correct charger controller to use is a PWM type.

 

[Lolaeliz]

It is definitely parallel as you have drawn.

If your solar charge controller is an MPPT type, then usually you are better off with them in series.

In a parallel mode, usually the correct charger controller to use is a PWM type.

The reason they need to be in Parallel is the mppt combo DC2DC only charges from the van batteries 25w on the solar. It cuts off at 25 watts. when it's a 50w MPPT. Something like that.

 

[Van vs Wild]

The reason they need to be in Parallel is the mppt combo DC2DC only charges from the van batteries 25w on the solar. It cuts off at 25 watts. when it's a 50w MPPT. Something like that.

Sounds like you’re using the Renogy DCC50S. Yes you are correct, when both the DC-to-DC and solar inputs are used, you are limited to 25A (not watts) on each input. However, that part of it isn’t your issue.

The problem is that device doesn’t handle 24v, so running panels in parallel at 12v is your only option anyways.

 

[el Jefe]

In a parallel mode, usually the correct charger controller to use is a PWM type.

Why Harry? I have heard this before but cannot find any definitive evidence. Victron does not offer a PWM, and I would consider them the crem de la crem of engineered components and systems. I there something Victron is missing?

 

[larry barello]

PWM essentially uses the PV panel as a big capacitor switching when the voltage hits some high value and dumping it into the battery. This was explained in the app notes for some Analog Devices (IIRC) solar controller chips for low power applications. MPPT switching to PWM with low light levels improves efficiency a tad.

The DCC50S cuts of at 25v. "12v" solar panels, from, Renogy or Rich Solar (and others I suspect) have a Vmp of 20 ish volts and a Vmax of 24v (again IIRC). The DCC50S starts charging the house and service batteries when the panels reach 15v which is pretty early in the day.

Check out Fun with Home Assistant and Renogy electronics for some charts.

 

[CanaDave]

Be careful with this !!! you MUST wire your panels to deliver the proper volts to the MPPT controller. And as Van vs Wild said if you are using a DC-DC / MPPT combination controller your manual will tell you - but probably 12 volt is the max. - so parallel is the answer. Any greater voltage will burn out the controller.

(I was able to over ride the 25 /25 Amp split by installing a disconnect or resettable fuse for both solar and DC-DC just before the controller)

 

[RV8R]

Why Harry? I have heard this before but cannot find any definitive evidence. Victron does not offer a PWM, and I would consider them the crem de la crem of engineered components and systems. I there something Victron is missing?

The Victron MPPT which I also love @el Jefe needs battery voltage plus 5 volts to start the charge process.

So if you run them in parallel & in crappy sunlight conditions the voltage can take forever to acquire the say 17.5 volts to start charging up a 12 volt battery.

This is not an issue with the PWM type controller/chargers.

I overcome the “plus 5 volts issue” by running my 600W panel array @ 60 volts & 10 amps.

 

[HarryN]

Why Harry? I have heard this before but cannot find any definitive evidence. Victron does not offer a PWM, and I would consider them the crem de la crem of engineered components and systems. I there something Victron is missing?

Victron actually does make both PWM and MPPT types.

@RV8R s explanation is quite good and he and I have discussed this on the forum before. I will try to find the thread(s)

I have been burned before by making the mistake of not understanding the real world effects of light spectrum, scatter, etc and it's effect on solar panel Vmp. It is a lot more significant than some research papers that only look at "intensity" would imply. I have some very good quality panels (multiple types) with a label Vmp = 18 volts that will not rise above 15 volts all day when it is overcast.

I was convinced by some of these papers and statements by others that I could use a good quality MPPT controller on some projects in the San Francisco area. The numbers and charts all seemed to align - and they were just a complete bust in real world use. The controllers just would not stay on in those coastal conditions. I sat inside of a couple vans for hours trying to figure out why it didn't work.

Finally, I swapped them out for Bogart PWM controllers (at my own expense) and the problems all went away.
__

My personal view is that Victron makes a very good 48 volt / 5 kW inverter and it is a real beast. IMHO, everything else that they do is resting on the laurels of this inverter.

Even with those, my older son bought 2 and one was DOA. He finally was able to get a replacement (after the project was completed using 1 of them) and I have the other essentially NIB sitting at my shop.

They are definitely better than Renogy, definitely not the best but I don't kick them to the corner like I do the renogy stuff.

Their marketing is really excellent.

 

[larry barello]

@HarryN can you divulge the name plate specs for the bay area PV panels that work well with PWM? Were there multiple panels? Series/parallel? Target system voltage? Curious minds wanna know.

 

[HarryN]

Hi Larry,

The most important things when buying a panel:

1) Will it fit?
2) Are the voltages about right?
3) Can I actually buy it?

I try to be as agnostic as possible for solar panels because it is a constantly moving target and typically my customers buy them directly with my "suggestions", but I never completely know what they will buy and sometimes it isn't what I thought.

This photo is from my test stand(s) a year or 2 ago. The blue ones are poly ~ Vmp 36 volts / 140 watt (each) and the black ones are mono Vmp ~ 18 volts / 160 watts each. Both solarland. The newer versions have slightly higher Vmp and wattage. You can buy similar ones through solar-electric.com, Unbound Solar - DIY Solar, Panels & Complete Systems and other on line retailers.

I have also had customers user renogy, grape and another brand I can't remember until I drink some more coffee.

Just before covid hit, there was a local company that was having some panels built with a Vmp of 15 volts and higher current in an attempt to work better with PWM, but they sold out almost instantly and have never been able to get another batch built since covid hit.

I also have a two of a brand (can't remember the brand right now - they used to be built locally) that has been out of business for at least 5 years now. There were mounted on my van that played bumper cars in Sept 2021. The test stand panels are a mix of these now.

With this setup, I can test customer configurations equivalent from 1 to 6 panels in series (18 volt types) with a variety of solar charge controllers (PWM, MPPT buck and boost types) and battery voltages 12, 24 and 48 volts.

This is an example of "pick a panel that fits" on this Ford explorer and the roof rail setup that I like to use. It is one of those blue mono poly ones, but the customer decided that it was too expensive of a panel so she is looking around. It is tricky because so many panels are out of stock now due to various supply chain issues.

I use the power from those test stands to test customers systems, components and power my shop.

It is interesting. In the winter sometimes having them vertical is wonderful because I can point the panels right at the sun in the morning and afternoon as it rises and falls.d

Right now, the sun angle is quite high and I am not getting much power because the sun is nearly straight up.

I need to get that panel on my explorer operating.

 

[el Jefe]

Victron actually does make both PWM and MPPT types.

@RV8R s explanation is quite good and he and I have discussed this on the forum before. I will try to find the thread(s)

I have been burned before by making the mistake of not understanding the real world effects of light spectrum, scatter, etc and it's effect on solar panel Vmp. It is a lot more significant than some research papers that only look at "intensity" would imply. I have some very good quality panels (multiple types) with a label Vmp = 18 volts that will not rise above 15 volts all day when it is overcast.

I was convinced by some of these papers and statements by others that I could use a good quality MPPT controller on some projects in the San Francisco area. The numbers and charts all seemed to align - and they were just a complete bust in real world use. The controllers just would not stay on in those coastal conditions. I sat inside of a couple vans for hours trying to figure out why it didn't work.

Finally, I swapped them out for Bogart PWM controllers (at my own expense) and the problems all went away.
__

My personal view is that Victron makes a very good 48 volt / 5 kW inverter and it is a real beast. IMHO, everything else that they do is resting on the laurels of this inverter.

Even with those, my older son bought 2 and one was DOA. He finally was able to get a replacement (after the project was completed using 1 of them) and I have the other essentially NIB sitting at my shop.

They are definitely better than Renogy, definitely not the best but I don't kick them to the corner like I do the renogy stuff.

Their marketing is really excellent.

I stand corrected on the Victron PWM controllers.

Here is some data shots that include days with mostly cloudy/overcast day performance with my MPPT controllers. Harry, do you think I could have harvested more solar with a PWM controller?

The 400w array is horizontal on the van. The 975w array is horizontal on the cargo. I get direct sun from ~7:30 am - 3:15pm due to tall pines partially blocking series connected panels. I could extend the collection after 3:15pm by simply moving the cargo 20 feet but I have plenty to fulfill my daily average use of 330ah.

 

[HarryN]

@el Jefe

Your arrays are doing pretty well IMHO.

It looks like your arrays are fairly high voltage so the wire losses will be low and they will turn on early in the morning. Moving a kW off of the roof at a lower array voltage from panels in parallel is challenging so that can be a real factor.

Once you have an array Vmp that is routinely / consistently running 15 volts higher than the max battery charge voltage, then MPPT is the way to go.

If the array Vmp label is only 5 - 6 volts higher than the max battery charge voltage, especially in an area that gets a lot of overcast, then PWM is the way to go - especially in the winter time.

In between these conditions can be a mixed bag. MPPT might be optimal for the summer, but PWM might be better for winter.

If you like playing with it, you could see if it makes sense to split the series array - if some of it remains in the sun longer?

Another path - if you were running short - would be to put some panels vertical or out somewhere where they would get sunlight later in the daytime and run a wire back to the van (with a dedicated controller)

Are you seeing times when you think that it would be a significant gain for you to have a different configuration?

Where PWM is the most helpful is

• in an area such as San Francisco with the morning overcast that does not burn off until afternoon
• Dec / Jan / Feb in this area as it is quite overcast then so solar is always running a deficit
• Fire season with the smoke
• a place like OR / WA especially along the coast

 

[larry barello]

@el Jefe : what is your load that you can measure Wh delivered each day? Don't your batteries ever fill up?

 

[Lolaeliz]

\

Sounds like you’re using the Renogy DCC50S. Yes you are correct, when both the DC-to-DC and solar inputs are used, you are limited to 25A (not watts) on each input. However, that part of it isn’t your issue.

The problem is that device doesn’t handle 24v, so running panels in parallel at 12v is your only option anyways.

I am changing them next week to parallel. Do I need to drop everything and do it now? Am I damaging the Renogy DCC50S by having them in series, or just not getting peak efficiency? I've not rushed into this change because I figured I just wasn't getting peak efficiency. The instructions didn't say not to wire in parallel.

(The panels are presently in series from when I had separate components, not the Renogy DCC50S. )

 

[larry barello]

I don't know what the DCC50S will tolerate, but two panels in series can push 48v or more in full sunlight when it is cool. The DCC50S shuts down with solar input greater than 25v so you're current arrangement is doing nothing.

Just leave the panels disconnected until you make the change.

 

[el Jefe]

@el Jefe

Your arrays are doing pretty well IMHO.

It looks like your arrays are fairly high voltage so the wire losses will be low and they will turn on early in the morning. Moving a kW off of the roof at a lower array voltage from panels in parallel is challenging so that can be a real factor.
Exactly why I run panels in series. Any gains, in my situation, are negligible running in parallel and the logistics with wiring, roof penetrations, upsized wiring and....are just not worth the effort.

Once you have an array Vmp that is routinely / consistently running 15 volts higher than the max battery charge voltage, then MPPT is the way to go.

I agree.

If the array Vmp label is only 5 - 6 volts higher than the max battery charge voltage, especially in an area that gets a lot of overcast, then PWM is the way to go - especially in the winter time.

In between these conditions can be a mixed bag. MPPT might be optimal for the summer, but PWM might be better for winter.

If you like playing with it, you could see if it makes sense to split the series array - if some of it remains in the sun longer?

Another path - if you were running short - would be to put some panels vertical or out somewhere where they would get sunlight later in the daytime and run a wire back to the van (with a dedicated controller)

Are you seeing times when you think that it would be a significant gain for you to have a different configuration?

Where PWM is the most helpful is

• in an area such as San Francisco with the morning overcast that does not burn off until afternoon
• Dec / Jan / Feb in this area as it is quite overcast then so solar is always running a deficit
• Fire season with the smoke
• a place like OR / WA especially along the coast

@el Jefe : what is your load that you can measure Wh delivered each day? Don't your batteries ever fill up?

Yes they do fill up but only if I change the charge controller settings. I have two banks of 7200 watts each but I seldom use both banks. If I allowed my reserve bank to fill up from high discharge, I would see much higher solar yield. The cargo with 975w produces much more than shows on the screenshots I provided only shows harvest when we are hooked up to it. I have a separate inverter/system for the freezer and fridge in the cargo. I just unplug the Anderson connector that goes to the van and plug it into the cargo system when we are not hauling the trailer. Although I can run a separate Cerbo/Victron 712 to combine the reporting, I just have not done it yet. I love to fiddle with stuff so eventually I would I will have that capability. Just waiting for Victron to come up with the stuff to totally integrate both systems into their VRM.

I don't flyfish anymore so I can afford to "fiddle" around with different configurations.

And to further answer if we ever fill our batteries to max capacity, we love our oven roasted veggies and meat, we run our oven for at least a couple hours every day and you know how many watts that thing uses. I also regularly heat up 10-40 gallons of water almost every day via my solar PV. When we refill our tanks, we end up with a 40-60 deltaT for 40 gallons. Dump load based on SOC or forced when shower day comes along. So, sometimes that occurs even though our battery bank SOC is far from 100%

Full overcast and cloudy here today near Flagstaff:

 

[larry barello]

Yes they do fill up but only if I change the charge controller settings. I have two banks of 7200 watts each but I seldom use both banks. If I allowed my reserve bank to fill up from high discharge, I would see much higher solar yield. The cargo with 975w produces much more than shows on the

Oh, I need to read your build thread. 2x600Ah battery banks? Electric oven? On for hours? Yikes! Do you run an air conditioner? Do you have room for a bed? Are your charts, above, when traveling? Or do you use your van and cargo to power your house?

I am fascinated by the PWM vs. MPPT debate, and I have been doing a bit of research. Here is a tasty morsel:

Technical-Information-Which-solar-charge-controller-PWM-or-MPPT.pdf (victronenergy.com)

NB. Victron used a relatively small panel with a Vmp of 18v for their analysis. There seems to be no mention of a +5v difference needed before MPPT performs better than PWM.

 

[el Jefe]

@el Jefe

Your arrays are doing pretty well IMHO.

It looks like your arrays are fairly high voltage so the wire losses will be low and they will turn on early in the morning. Moving a kW off of the roof at a lower array voltage from panels in parallel is challenging so that can be a real factor.

Once you have an array Vmp that is routinely / consistently running 15 volts higher than the max battery charge voltage, then MPPT is the way to go.

If the array Vmp label is only 5 - 6 volts higher than the max battery charge voltage, especially in an area that gets a lot of overcast, then PWM is the way to go - especially in the winter time.

In between these conditions can be a mixed bag. MPPT might be optimal for the summer, but PWM might be better for winter.

If you like playing with it, you could see if it makes sense to split the series array - if some of it remains in the sun longer?

Another path - if you were running short - would be to put some panels vertical or out somewhere where they would get sunlight later in the daytime and run a wire back to the van (with a dedicated controller)

Are you seeing times when you think that it would be a significant gain for you to have a different configuration?

Where PWM is the most helpful is

• in an area such as San Francisco with the morning overcast that does not burn off until afternoon
• Dec / Jan / Feb in this area as it is quite overcast then so solar is always running a deficit
• Fire season with the smoke
• a place like OR / WA especially along the coast

Thanks Harry. Don't think I am ignoring your post but you probably already know how I have "fiddled around" with solar systems since the early 80's. All off grid and primarily marine blue water cruisers. However, I have never designed or installed a system that primarily or permanently resides in Northern Cal, Oregon or Washington.

My introduction to MPPT controllers in the mid 80's, I believe.

There was a guy in Austrailia who had developed one of the first MPPT controllers. I met him at a solar conference here in the states. At the time, I had an off grid property near Wilson, Wy. He(Stu IFIAK) was gracious enough to send me one of his beta controllers to retrofit into my existing system.

That was the last time I designed a system for or used a PWM controller.

I totally understand the challenges you have in those coastal areas. However, I don't believe that this particular sc

Oh, I need to read your build thread. 2x600Ah battery banks? Electric oven? On for hours? Yikes! Do you run an air conditioner? Do you have room for a bed? Are your charts, above, when traveling? Or do you use your van and cargo to power your house?

I am fascinated by the PWM vs. MPPT debate, and I have been doing a bit of research. Here is a tasty morsel:

Technical-Information-Which-solar-charge-controller-PWM-or-MPPT.pdf (victronenergy.com)

NB. Victron used a relatively small panel with a Vmp of 18v for their analysis. There seems to be no mention of a +5v difference needed before MPPT performs better than PWM.

enario translates relevantly to van lifers who are not limited to your local atmospheric conditions, day in and day out.

 

[el Jefe]

Oh, I need to read your build thread. 2x600Ah battery banks? Electric oven? On for hours? Yikes! Do you run an air conditioner? Do you have room for a bed? Are your charts, above, when traveling? Or do you use your van and cargo to power your house?

I am fascinated by the PWM vs. MPPT debate, and I have been doing a bit of research. Here is a tasty morsel:

Technical-Information-Which-solar-charge-controller-PWM-or-MPPT.pdf (victronenergy.com)

NB. Victron used a relatively small panel with a Vmp of 18v for their analysis. There seems to be no mention of a +5v difference needed before MPPT performs better than PWM.

Yes, two battery banks
Yes, we use the oven a lot.
Yes, sometimes we use the Penguin2 air conditioner. Depending on the weather, we mostly use a 1300CFM portable evap cooler.

Yes, we occasionally do hook up to our off grid yurt when we are there.

Yes, we have room for a bed(Queen chopped in half, N to South). We have a 159 extended and are close to max weight depending how much water we carry.

No, we do not have a build thread. I am sure if you do a search, you will find some pix.

We would love to get rid of the Penguin to get more real estate on top of the van for solar panels when we are not towing the cargo.