Change the Zamp panel connection from parallel to series? Any easy way?

[John E Davies]

I am replacing my controller with an MPPT Victron unit which requires the panels to be in series (higher voltage instead of battery voltage). The Zamp panels use 2 conductor SAE connectors. Can anyone tell me an easy way to reconfigure the wires, without cutting and installing splices? Zamp:

 

Victron MPPT:

I prefer a non-invasive way so the panel wiring remains undisturbed and the warranty is not voided, but it can’t put too much current through any one port or cable. Maybe I have to change out the Triple Port Roof Cap for something different?

They make a Y splitter but I don’t think that will work. They also make an adapter cable, that could work if the roof cap has MC4 ports in it.

 

 

I emailed Zamp asking for their advice. I thought I would check here too. This is all brand new territory. Thanks.

John Davies

Spokane WA

 

 

 

Edited November 28, 2020 by John E Davies

[Overland]

I think I’d go ahead and splice them since it would give you a chance to shorten the wires to the right length at the same time. Mine are way too long. 

[John E Davies]

42 minutes ago, Overland said:

I think I’d go ahead and splice them since it would give you a chance to shorten the wires to the right length at the same time. Mine are way too long. 

Thanks, I am leaning in that direction, but with connectors not hard splices, and I would change out the roof cap for a more industry standard model with MC4 connections. I just do not trust SAE joints to stay corrosion free over a long period of time, there is no water seal. An SAE connector seems like a crappy item intended for a motorcycle battery tender...., not years-long exposure to water..

THIS:

 

 

 

Think that would do the trick? It should not be a huge job since it won’t involve stringing new wires through the roof. Thanks.

John Davies

Spokane WA

[mossemi]

11 hours ago, John E Davies said:

I am replacing my controller with an MPPT Victron unit which requires the panels to be in series (higher voltage instead of battery voltage).

 

JD,

Ok!  I found a 3rd post asking if anyone had replaced the Zamp CC with a Victron and you referenced the 150/35 which supports 12v.  So why the change to 24v?

Which Victron charge controller are referring to that requires PV panels in a series configuration?  Changing to 24v would make sense for the portable panels and your long 10 AWG extension cord runs.  You could add a small 24v charge controller under the bed or dinette using your existing Furrion port and not have to change out your roof port and connectors.

Maybe you are talking about 2 different projects, but the two topics you created have confused me, which is easily done these days.

Mossey

Edited November 29, 2020 by mossemi
Clarification 😎

[John E Davies]

I want to change to series with a MPPT controller because they perform better than a PWM controller in parallel, up to 30% better. Especially in challenging conditions such as clouds or shifting shadows. This is a different situation than the solar panel I was discussing in the other thread. Rather than spend an extra $1100 on a third 100 amp hr battery, I am choosing to go with two batteries, but to also optimize the charge from my roof panels and add amps with the portable panel that I can move to stay in the direct sun.

I can always add more batteries but I think this setup will work fine for me.

The Victron  MPPT controller is a real wizard, much more efficient than the junk Zamp unit. Why cripple it by keeping the less desirable, less efficient parallel wiring?

https://www.cleanenergyreviews.info/blog/mppt-solar-charge-controllers

John Davies

Spokane WA

 

Edited November 29, 2020 by John E Davies

[mjrendon]

Mossey, John,

I was comparing some of the Victron units for my similar project and have been running in circles.  I doubt that I would add more than one more PV on the roof.  I really like the idea of having two MMPT charge controllers with the flexibility of the other PVs being remote.

Any suggestions for which charge controllers to use SmartSolar 100/30 100/50, 150/45?

What are the real life advantages of switching to series? 

I assume the 100 and 150 charge controllers could handling either 4 or 6 12V PVs in series assuming VOP is 21V.  

 

[RnA]

3 minutes ago, mjrendon said:

What are the real life advantages of switching to series? 

For RVs, I don't know of any advantage other than when using long cable runs with portable panels.  The higher voltage output lets you use a higher gage wire for the same power transmission.  With a portable panel you have the option to move the panels and keep them in the sun.  The disadvantage is that when in series, if one of the panels gets shaded your pretty much done for output.  MPPT controllers help, but they can only do so much.

When the panels are paralleled, shading of one panel will not effect the other panel and you will be down to half power, but at least something.  This may not be an issue for some that camp in sites open to the sky however much of my camping has some shade.  Sometimes one panel is shaded in the morning while the other panel gets sun and vice versa in the afternoon.  With the panels in series, I wouldn't get anything.

[BackofBeyond]

12 hours ago, mossemi said:

 Changing to 24v would make sense for the portable panels and your long 10 AWG extension cord runs.  You could add a small 24v charge controller under the bed or dinette using your existing Furrion port and not have to change out your roof port and connectors.

Mossey

Admittadly, I am a beginner in the Solar set-ups, but I do have a long standing - once professional- experience in the electrical world.  The various posts remind me of my motorcycle racing days - we were always looking for the next best set-up - power, suspension, you name it. I find it fascinating. Really enjoy the conversations. 

How far one goes towards the hot set up - really depends on your goal, or in some cases, its a continuing fascination with just making the Oliver a better solar home. But to Mossey's point - for the casual user - me-  with the original  AGM/Zamp install - wanting a little more -  would it not be a dollar wise choice to just use a good remote panel set up, with  a nice quality 10 gage cord, using the installed Zamp port - and add a charge controller as indicated? As it is tied directly to the battery bank, the rest of the system can gone on until the AGM's reach their usable  lifespan. At that point - upgrading to Lithium's, new controller - etc. - would seem a wiser choice. 

I agree, the standard SAE is not the best - but given a regular inspection, it works fine, I've been using them on the farm - out in the element's for a while now and my solar charge on tractor/battery equipment is doing fine. Not the optimum set-up but working.

NOW - if its your goal to run large loads - say - the AC - then have at it. To me the dollar value doesn't cut it:  - a  value gen set - while a little more cumbersome - just makes more sense. 

If I was starting over with my Oliver build - well - the options are certainly there.  I still think - for me - it would be a balance of performance over cost. 

Carry on - all.

I'll sit on the sidelines and learn.    -    JD , your reference site was great - thanks much. 

 

Edit here - what is a good estimate on the life span of the AGM's   - kept in good condition, never abused? 

Edited November 29, 2020 by BackofBeyond

[John E Davies]

10 hours ago, RnA said:

Sometimes one panel is shaded in the morning while the other panel gets sun and vice versa in the afternoon.  With the panels in series, I wouldn't get anything.

From the sources I have read and linked to, this is incorrect. A series panel works at the sum of the panel voltages, so shading a portion still leaves plenty of cells (voltage) to drive the system. A parallel panel when shaded “tanks” because the voltage drops too far, and the panels are already operating at battery voltage, which is well below their optimum target voltage. I am still learning like crazy, but that page link in my previous post is very adamant. PWM is a very primitive ON OF ON control. 

“MPPT or ‘maximum power point tracking’ controllers are far more advanced than PWM controllers and enable the solar panel to operate at its optimum voltage for maximum power output. Using this clever technology, MPPT solar charge controllers can be up to 30% more efficient, depending on the battery voltage and type of solar panel connected. The reasons for the increased efficiency and how to correctly size an MPPT charge controller is explained in detail below. As a general rule MPPT charge controllers should be used on all higher power system with 2 or more panels, or whenever the panel voltage is much higher than the battery voltage.”

John Davies

Spokane WA

[RnA]

Thanks John,  I was reading that on the Victron reference you provided and the Blue Sky Solar web site as well.  They have modified their MPPT controller to take higher input voltages (i.e. panels in series up to a limit) . My comment should be for a PM controller. 

[NCeagle]

26 minutes ago, John E Davies said:

From the sources I have read and linked to, this is incorrect. A series panel works at the sum of the panel voltages, so shading a portion still leaves plenty of cells (voltage) to drive the system. A parallel panel when shaded “tanks” because the voltage drops too far, and the panels are already operating at battery voltage, which is well below their optimum target voltage. I am still learning like crazy, but that page link in my previous post is very adamant. PWM is a very primitive ON OF ON control. 

“MPPT or ‘maximum power point tracking’ controllers are far more advanced than PWM controllers and enable the solar panel to operate at its optimum voltage for maximum power output. Using this clever technology, MPPT solar charge controllers can be up to 30% more efficient, depending on the battery voltage and type of solar panel connected. The reasons for the increased efficiency and how to correctly size an MPPT charge controller is explained in detail below. As a general rule MPPT charge controllers should be used on all higher power system with 2 or more panels, or whenever the panel voltage is much higher than the battery voltage.”

John Davies

Spokane WA

Remember those Christmas tree lights that were hooked in series?  When one went out the whole string was dead.  Same for solar panels I thought?  What can an MPPT charge controller do when there's no current coming in at all?  I am probably missing something simple. 

[John E Davies]

2 hours ago, NCeagle said:

Remember those Christmas tree lights that were hooked in series?  When one went out the whole string was dead.  Same for solar panels I thought?  What can an MPPT charge controller do when there's no current coming in at all?  I am probably missing something simple. 

LOL, I hated those lights. But you are talking old tech vs new tech, golf cart vs Tesla.

Solar panels are made of lots of individual cells wired together in series/ parallel appropriately to get the desired voltage; a standard Zamp 170 watt panel is 18 volts maximum (operating) with 36 cells and 5 bus bars. Shading a few cells in any panel will not completely kill it. The reason the paralleled panel drops off line with a PWM controller is that the panel is only operating at battery voltage because the wires are essentially hooked directly to the battery (the controller just cycles it on and off reeeeealy fast). So your panels are operating at 12+ volts not 18 volts. Shade the panel enough for the voltage to drop too far and that panel appears to go dead. Not really, it is still producing some current but the voltage has dropped too low for the stupid controller to use it to charge a battery.

Lead acid batteries are around 12.6 volts open cell, no load, and require a slightly higher current to charge. Lithiums operate at 14.4 volts open cell. So installing a lithium battery into your Zamp system just makes this low voltage cutoff even worse because the lithiums require a higher charge current for a 100% charge. A forum member has noted this when charging his lithiums by Zamp PWM solar alone, but the shore power converter takes them all the way to 100%.

 

I enlarged and annotated their tiny power chart for clarity:

 

A MPPT controller with series panels keeps the panels in the higher MPP range and at the sum of the panel voltages, 36 volts, instead of at some artificially lower voltage, it can adjust both voltage and current for the best results. More amps to the batteries, MUCH more precise control of the system. The Victron parts are "Smart", they all talk to each other wirelessly to monitor battery voltage, individual cell voltages, temperature and charge rate, to optimize and refine the charging. It is very cool. When I add a Victron MPPT controller to my trailer, with Victron batteries and Victron Smart Bus, all I have to do is create a virtual network (click a button on the app and rename it) and join everything together so they all know what the other parts are doing. (It does require the optional $20 battery temperature probe to be installed on the Smart Bus, so the bus can transmit that number to the other components.) And I can see all that info blended together on the Victron Connect app.

It would be easy to do a "shade the panel" experiment for parallel vs series, it probably has been done but I haven't seen one yet. (I did watch a video where he did compare parallel and series but it was in full sunshine, not shaded, and the current output to the batteries was identical, which I would expect.) Just park in the direct sun and gradually shade one panel with a blanket until the output drops away. Repeat for both panels together. Record the shaded percentage of the panels. Reconfigure them to series and repeat the test. This would be very easy if all the connections on the roof were MC4 and not the standard Zamp reversed polarity double bullet connectors. You could change the Zamp roof cap to series but it would require complete removal to do that, NOT something you would want to repeat if you added another panel up top.. With exposed connectors, just unplug and rearrange as needed.

PLEASE, if there are any mistakes in my chart or reasoning, please comment. I am still learning this stuff, it has baffled me for a long time. If I had known this before I might have not ordered the factory solar setup and just done it myself with better parts. I personally would much rather optimize my two roof panels, than just add more of them to a dumb controller.

John Davies

Spokane WA

Edited November 29, 2020 by John E Davies

[Overland]

The series/parallel trade off is a bit tricky. Like John said, in parallel lower voltage from one panel will bring down the voltage of the entire array. In full sun, that’s never really an issue since panel voltage stays pretty consistent until a steep drop off with very little light. It’s the amperage that varies with stronger or weaker sun and in parallel, the amperage is additive.

In series, it’s the opposite, low amperage from one panel is a bottleneck to the others while the voltage of the panels is additive.  Again, not a problem in full sun even if the amperage is changing, since the amperage of each panel should track pretty closely with the others (so long as your panels are all alike - adding in a half size zamp panel like I have would cut the current of the larger ones in half!)

Also, as John points out, the panels themselves are made up of modules of grouped cells connected with bypass diodes that allow current to go around a shaded module to minimize current loss. I think the problem with running panels in series though is that you won’t have bypass diodes between the panels so if one panel has reduced amperage, the other will as well, and that can affect total power even more than the loss of voltage.

The advantage of running them in series is typically smaller wiring,  but in this case you’ve already got the heavier gauge wiring in place. I guess you’ll get less resistance nonetheless and possibly more headroom for the MPPT to do its thing?

Of course in the end you have to ask how often it is in the Ollie, with a fairly small array of two adjacent panels, that you’re going to see significant shading on one panel and not the other.  Certainly it will happen on occasion, but my personal experience is that we’re almost always either in deep shade or full sun.

I’m not sure it’s worth the trouble myself but I’m definitely curious to see the results and maybe learn something new. 

Edited November 29, 2020 by Overland

[mossemi]

Note:  I started this post this morning and then got busy with Christmas decorations, so if there are additional posts on this subject that I have not read, I apologize for being redundant.
 

It's time I add more information from my point of view to my question.  I have already acquired the following equipment for my solar replacement, which I do plan to claim for a tax credit.

3 - Battle Born BB 10012 batteries. 1 of my original lead acid batteries failed which led to the lithium upgrade.

2 - Zamp 90 Watt Long Solar Panels B Stock  These panels are considered seconds, sold by Zamp through Amazon.  A solar panel is required for the solar tax credit but these are sold in pairs.

1 - Victron SmartSolar MPPT 150/45 Tr.  Why not take advantage of the tax credit?

1 - Xantrex PROWatt 2000 Inverter.  Original failed.

Associated cable, connectors, mounts, switches and bits and pieces.

So, I have put a little thought into this project.  But I have never read anything about Victron MPPT CC's requiring 24v inputs.  I do know they support multiple voltages.  I think a 24v input would make sense if you needed to run new cable from the roof to the CC anywhere in the cabin or lower hull, but you have already indicated that you are going to use the existing Zamp cable run. The smaller cable requirements of higher voltage would certainly ease any new cable runs.

When I run my panel numbers using the method at this website Sherry posted, I would waste 128 watts of solar energy with my panels is series.  

And I don’t believe that Zamp PWM CC's are junk, they just aren’t as efficient as any quality MPPT CC.  All of my Zamp equipment has provided good service for 3 years and I can’t think of any Zamp problems mentioned on this forum, but maybe I have forgotten them.

Mossey

Edited November 30, 2020 by mossemi

[Overland]

Your Victron will do fine with 12 volt panels. It’s definitely not a requirement to do 24 volt - perhaps a recommendation?

[John E Davies]

There is not much point in changing to a MPPT control and not taking the extra step of changing to series connected panels, it is the only way to get the added benefit. It may work as well as a PWM Zamp unit but it won’t be any better. The whole point of a MPPT is to have a high system voltage. If you are not willing to switch the panels, just stay with the old one and spend that money on some other cool stuff, like a portable panel....

I am going up on the Ollie soon to remove the Zamp roof cap, to see if there will be any hassle with changing to that Go Power able entry plate. As long as there is some cable slack it should be OK. Or hopefully I could pull out a few more inches.

John Davies

Spokane WA,

 

Edited November 30, 2020 by John E Davies

[Overland]

A higher voltage array will undoubtably give more opportunity for the MPPT to provide a charge to the batteries, but I’ve never read that there’s no advantage to using an MPPT with 12 volt panels. I think the reverse is true for sure - if you have 24 volt or higher panels then you really need to use an MPPT. I’m betting that the advantage that you’ll see is that your batteries will start charging a little earlier in the morning and will continue a bit later in the evening.  I doubt you’ll see much difference the rest of the day.

Like I said, I’m still learning as well so I’m eager to see if you find a real advantage, and there’s no downside to trying it out other than time spent rewiring. I’d be thrilled if it works well since it would mean an easy and free upgrade for me. 

[NCeagle]

4 hours ago, John E Davies said:

There is not much point in changing to a MPPT control and not taking the extra step of changing to series connected panels, it is the only way to get the added benefit. It may work as well as a PWM Zamp unit but it won’t be any better. The whole point of a MPPT is to have a high system voltage. If you are not willing to switch the panels, just stay with the old one and spend that money on some other cool stuff, like a portable panel....

I am going up on the Ollie soon to remove the Zamp roof cap, to see if there will be any hassle with changing to that Go Power able entry plate. As long as there is some cable slack it should be OK. Or hopefully I could pull out a few more inches.

John Davies

Spokane WA,

 

John, I'm no expert on solar either - still learning - but I have a totally different understanding of MPPT vs PWM than you have arrived at.  If hooking solar panels in series was the only way to take advantage of MPPT controllers, then very few would be using them.  I am seriously considering a MPPT controller WITH my parallel solar panels to get 10-30% more energy out of each panel.  They are especially good in the winter, when solar panels produce even more voltage (due to efficiency at cooler temps).

Here's my interpretation of what I've read/learned... 

Single/Parallel panel example:  The bottom line is that all solar panels put out 16 - 20 volts BY THEMSELVES - they have to be higher than 14-16 volts required to charge 12V batteries of all sorts.  A PWM controller will not be able to take full advantage of the higher voltage being produced and loses up to 50% of the wattage.  On the other hand, a MPPT controller can utilize the extra voltage and increase efficiently over a PWM controller by ~10% - 30%.  So as an example, given a single, parallel 175 Watt panel during a full sun day, a PWM controller would put about 90 Watts of charge into the battery while a MPPT controller would put anywhere from 105 - 140 watts of charge into the battery.  

Multi/Series panel example:  This one is easy - a PWM controller will fry with voltages higher than 20 or so.  A MPPT controller will take higher voltages from series connected panels and efficiently charge a battery bank the same as it does for a single panel at 20 volts. 

Conclusion:  Since MPPT controllers optimize any panel or set of panels producing more than 16 volts, there are compelling reasons to convert a system to MPPT (even with a small number of panels in parallel in my humble opinion).   Compelling reasons to go with series over parallel?  Not sure in a system with only a few panels, but obvious reasons would be to use smaller gauge wires and/or have significantly longer wire runs to the panels.

I personally will start with just an MPPT controller and see what the gains are in my current setup.  If there is a true advantage to series, I'm all in but I need proof before I rip things off the roof and rewire my panels.  🙂 

[mjrendon]

Before you change your roof cap, an easy way to test the series vs parallel setup with would be to use three connectors like these

To convert to series simply unplug both PV panels from the Furion roof connector and convert them to them both to MC4. Next connect the panels  in series and use the third connector to convert the series chained panels from MC4 back to Furion. Plug this into the roof down link using a single port.  Make sure you double check polarity before plugging into your new MMPT charge controller.  Simple to test both modes...

 

[John E Davies]

Thanks for the replies, this is all very complicated, isn’t it? I hate being the pioneer in stuff like this, certainly somebody has already done these rooftop tests.... but I haven’t found one yet. As I mentioned before, the only one was for series vs parallel with a MPPT controller in full 100% sunlight, and there was zero difference in the current output to the batteries.

I will hold off on this part of my winter projects until next camping season when I can do some realistic solar gain tests using two of those reverse adapter kits;  thanks so much mjrendon for the tip, I had not seen those before. I would need the MC4 connectors and tools anyway, to complete the roof cap change if the series turns out to be better in “challenging” solar conditions like the typical partial shifting shade in a USFS campground. But I really hate those SAE connectors for this type of application.

My gut feeling is that with identical panels, series will be better. For those of you who have added extra smaller panels on the roof in parallel, the system will choke on those if changed to series. In that case for series, it would be best to move all small (matching output) ones to their own dedicated MPPT controller, with the main Zamp panels going to the main controller. That will involve more expense and running roof wires, and not worth the effort unless you are truly anal...

John Davies

Spokane WA

Edited November 30, 2020 by John E Davies

[Overland]

Well you’ve definitely gotten me interested and thinking about this again. I would definitely like to get more out of my solar panels, especially in the winter. This past trip was a bit painful being in full sun and seeing at most about half of the rated capacity. I know that the most effective modification would be to make my panels tiltable, but I always seem to plant the trailer on a north south axis for some reason. 

[SeaDawg]

John, I  knew that I had read some info on shading and series vs parallel when we were trying to determine best setup for our 6 x 100 watt panels on the boat.

This set of tests is 4 years old, but probably still relevant. 

https://www.altestore.com/blog/2016/08/wiring-shaded-solar-panels/#.X8UsyWlOkwA

 

[mossemi]

11 minutes ago, Overland said:

Well you’ve definitely gotten me interested and thinking about this again. I would definitely like to get more out of my solar panels, especially in the winter. This past trip was a bit painful being in full sun and seeing at most about half of the rated capacity. I know that the most effective modification would be to make my panels tiltable, but I always seem to plant the trailer on a north south axis for some reason. 

Did you use your suitcase panels on this trip?  Didn’t you have plans to wire the portables in series?  Wasn’t it your intention to add another MPPT CC for the suitcase panels?  Am I making you feel lazy by reminding you of all the projects you are neglecting while you mess around with duct work?

Mossey

[Overland]

Still on the list.  You should see the list I have for the house. 

[John E Davies]

47 minutes ago, SeaDawg said:

John, I  knew that I had read some info on shading and series vs parallel when we were trying to determine best setup for our 6 x 100 watt panels on the boat.

This set of tests is 4 years old, but probably still relevant. 

https://www.altestore.com/blog/2016/08/wiring-shaded-solar-panels/#.X8UsyWlOkwA

Wow, that is really interesting, it refutes all the many claims I have read that series is better for shade, she shows clearly that parallel in shade is better. Very informative, everybody should watch it! OTH she says that for shady conditions EACH panel should have its OWN controller, to maximize current. I can’t see that happening in most RVs.

“So, this kind of shows you, that if you do have some partial shading, and it’s on only one of the panels at a time, so say you’ve got a chimney that you really have no control over, or if it’s on a sailboat, and you’ve got the mast that is kind of important, if you’ve got partial shading that’s going to be changing, it’s better to wire them in parallel to give the parallel path for the non-shaded panel. Ideally, and I know I say this a lot, ideally each panel should have its own charge controller, that way you will get absolute maximum performance, but if it’s not an option, wiring in parallel with partial shading is your better solution.”

This video convinced me to keep the roof array “as delivered”. IMHO, folks who want a more reliable supply of amps when camped under trees need to get a portable panel and park it at an angle facing unobstructed direct sunlight (and rotate it and/ or reposition it a few times each day). I have one coming for Christmas. I may mount a more efficient MPPT controller for it inside the trailer, I will see how the suitcase unit does first. I am still going to replace the Zamp controller with a Victron MPPT, locating it under the street side bed, for a variety of reasons.

Thanks so much!

John Davies

Spokane WA

Edited November 30, 2020 by John E Davies