Solar panels

From https://www.rvweb.net/best-solar-charge-controllers-for-rv/

Maximum Power Point Tracking (MPPT)
MPPT solar charge controllers feature better technology than their PWM counterparts and work much more efficiently as a result. But it also means their operation is harder to explain as it’s a bit more complicated.
You see solar panels often generate more voltage during sunny days than your RV battery can handle, which is where an MPPT solar charge controller comes in handy. It can convert this extra voltage into more current.
It will then use this extra current at a lower voltage and does it without losing any power. With this ability, you can use your solar panel’s full power to charge your battery efficiently. And this useful quality isn’t the only one these devices offer.
MPPT solar charge controllers are also better suited for batteries and solar panels with higher voltages. Plus, you must understand that this type is the correct choice when your battery’s voltage and the solar panel’s voltage doesn’t match. In these circumstances, a PWM device will not work.
But it’s not all positives with these devices as these charge controllers are much more expensive than your standard PWM type. With this in mind, it’s essential you evaluate how frequently you’re going to rely on solar energy.
If you plan on using solar energy all the time, it’d be a wise move to spend the extra money on a high-quality MPPT model. But if you only plan on using your solar panels only during a summer trip, a PWM device would be the better option.

Caraman, I've a slight correction about the charge going into the batteries. The Votronic display is limited, it only has information about the Leisure battery, so if this battery was almost fully charged, the solar system wouldn't need to send it much current. If the Vehicle battery needed a charge I'm not sure if its charging current would be displayed on the separate LCD unit.

There is little doubt that the Epever DuoRacer has a display which provides so much more information than the Votronic Duo Dig MPPT's LCD display. Both charge controllers have bluetooth add-on boxes, and here again the Epever is better as you can see from glyne's posting about his solar setup. With the Votronics bluetooth box, the mobile phone App just has info again about the Leisure battery, unless they've improved things I'm not aware of.

Unfortunately for me the Epever controller seems such a big brick of a thing compared to the small Votronic units.

Dbvwt wrote:Caraman, I wouldn’t bother with the optional LCD display, just fit the controller to begin with and see how you get on.
I’ve been where you are now and was all set to get the - expensive- display but I’m glad I didn’t. I religiously checked the vehicle and leisure batteries every day with a meter for about 3 weeks after fitting my controller (Nov last year) and everything was fine. I’ve never needed to check things since as it just does it’s job with no fuss, it just works!
I will add that over winter my EC500 is powered down completely but not having to plug into the EHU once a week since has been a joy!

Thanks.  I agree - the optional LCD display doesn't seem worth it.  It's interesting - with the EC700 there is no need to plug into an EHU every week as all the solar charge goes to the vehicle battery when the EC700 is shutdown which seems to keep it topped up.  No charge goes to the leisure battery but the latter rarely needs charging when the EC700 is shutdown as it is largely isolated from any load.  The only load it has, which appears to be negligible, is the tracker.  The leisure battery voltage can be monitored remotely through the tracker and, if it needs a bit of a boost, all that is required is a few hours on the PX300 as the latter's charge goes to the leisure battery when the EC700 (and EC500) is shutdown.  So in my case the only justification for an improved solar charging system is for when the van is used off-grid.

Caraman wrote:I agree - the optional LCD display doesn't seem worth it.

Agreed - I fitted one and realised immediately that it was a lot less functional than the optional LCD display that you can buy for the EPIPDB.COM PWM-based controller, and it's at least 3 times the price. I hardly ever look at it anyway, so it was a waste of money - but it's hard to know that until you've tried one out yourself!

I should add that my comments above are meant not as a criticism of the Votronic MPP250, but simply a real-world view of how effective it is. In real-world use it's better than the EPIPDB.COM controller, but not 20-30% better.

Relaxez-Vous wrote:Caraman, I've a slight correction about the charge going into the batteries. The Votronic display is limited, it only has information about the Leisure battery, so if this battery was almost fully charged, the solar system wouldn't need to send it much current. If the Vehicle battery needed a charge I'm not sure if its charging current would be displayed on the separate LCD unit.

There is little doubt that the Epever DuoRacer has a display which provides so much more information than the Votronic Duo Dig MPPT's LCD display. Both charge controllers have bluetooth add-on boxes, and here again the Epever is better as you can see from glyne's posting about his solar setup. With the Votronics bluetooth box, the mobile phone App just has info again about the Leisure battery, unless they've improved things I'm not aware of.

Unfortunately for me the Epever controller seems such a big brick of a thing compared to the small Votronic units.

Thanks.  Its an interesting experiment to compare parallel with series but if the only current shown on the display is that going into the leisure battery, which is demanding very little current because it is fully charged and no longer under load, I'm not sure what its going to prove.  What's needed is an indication of the current going into the depleted vehicle battery which you can't see.  The vehicle battery voltage can be seen on a multimeter which at the end of each day will indicate its SOC.  Are you going to see if the solar charge is sufficient to restore the vehicle battery's SOC, or, have you already restored it SOC with the main charger which is what I would do at this time of year.

Suppersready wrote:

Caraman wrote:

Relaxez-Vous wrote:Caraman, in my post above the charging current displayed on my Votronic's LCD display was the instantaneous current. I didn't look but I expect the total Ahs for the day would have been around zero, or possibly less then 1 Ah. From what I could see there were only 2.5hrs in the middle of the day when any charge was being delivered to the batteries sufficient to be recorded on the meter.

I rewired my two solar panels to series yesterday and I'm collecting now some readings which I will post later.

Thanks.  I'm destined to get a dual battery MPPT Votronic controller hence my interest.  The optional LCD display seems to show the voltage of the leisure battery only.  I was wondering if the current shown is also for the leisure battery only.  The Votronic trickle charges the vehicle battery up to a maximum of 1A but this appears not be shown on the display.  What is not clear is how the trickle charge is managed.  For example, if 5A of solar charge is available and both batteries are depleted, will 1A go to the vehicle battery and 4A to the leisure battery.  If 2A of charge is available, will 1A go to each of the batteries.  If 1A or less is available, will it all go to the vehicle battery or will none of it go to the vehicle battery which would account for your depleted vehicle battery.

I contacted Votronic Universe and asked them this very question, they replied they did not have the technical information to be able to answer.



Niall

I wonder if the Votronic's Batt2 charging works in the same way as the Epever if so it would explain why Relaxez-Vous's vehicle battery became depleted - see 1.4 of the Epever manual:

https://www.bimblesolar.com/docs/DuoRacer-SMS-EL-V1.0.pdf

Dbvwt wrote:Caraman, I order a lot of my electrical kit from 12v Planet. They are not the cheapest but I’ve always found them a good company to deal with (5% discount is available if you sign up to their newsletter).
I was chatting to them earlier in the week and happened to mention the Votronic supply issues. I’ve just had an email saying the 165 is now in stock if it’s any help.

https://www.12voltplanet.co.uk/votronic-mpp-165-duo-digital-solar-charge-controller-twin-output.html

Thanks.  I received an e-mail from them today and they appear now to have two in stock but I've as good as decided to go for the 250 now which is still out of stock and expensive at £134.50.  When I was deliberating over the 165 and actually had one in my 12V Planet basket, they put its price up which put me off a bit.

I've discovered another make of MPPT dual battery controller being sold by Road Pro who give a 5% discount to CAMC members:

https://www.roadpro.co.uk/product/02h05a-mppt-solar-regulators/nds-320w-sun-control-2-dual-regulator-mppt-c5701/C5701

Has anyone come across these NDS controllers before?

Parallel or Series solar panels an update, personal opinions

Not having been out in our van for several weeks, 6 days ago I found that whilst the leisure battery was fully charged the vehicle battery was only at 12.3V about 60% charged. I had left the EC700 PSU on. I concluded that my 2 solar panels in parallel could only put back into the leisure battery what the power hungry EC700 PSU was consuming, it seemed likely that there was not enough surplus power to maintain the vehicle battery.

Tests on my solar panels in Parallel
My tests showed that a threshold voltage of about 19V had to reached before any charge showed up on the Votronics LCD meter, last week this was at 11am on a dull November day. The charging current ranged from 0.0 amps or 0.1 amps, briefly 0.3 amps, By 14.30 hrs solar was down to 14V, charging was effectively over. Both batteries at the end of the day were at the same voltage they had been in the morning.

Before changing to panels in series the van had a run out last weekend. Back home afterward both batteries measured 12.52V, that's about 80% charged. My interpretation was that the split charge relay had interconnected the batteries and so equalised their charge states.

Series solar panels testing day 1
By this time I had turned off the EC700 PSU and rewired the solar panels from parallel to series. It was another dull November day during my tests. Initially I was rather disappointed with the results however, charging was higher around 0.5 amps at times. With panels in series the solar output voltage was around 39V. By the end of the first day at least the leisure battery was at 12.75V (100%), the vehicle battery was 12.36V, not as high as I was hoping.

Series solar panels testing day 2
What a difference a day makes, the day was sunny. Up to 4 amps charging rate recorded, I ended the day at 18.00hrs with both leisure and vehicle batteries at 12.86V, that's both at 100% charge. The Votronic's LCD display reports a maximum charging rate of 4 amps, 64 watt-hours of charge went in. Perhaps if the batteries had been lower in voltage / charge at the start of the day the watt-hours might have been higher. You can't put more power into an already fully charged battery.

My current observations
1. How dull or sunny it is in winter can makes a big difference to solar battery charging.
2. Our motorhome's power hungry Sargent EC700 system if left switched on can consumed a significant amount of the available solar power, in my case this can compromise the charging of the vehicle battery particularly during the winter months.
3. On a conventional vehicle a split charging relay will tend to equalise the battery voltages as you drive.
4. Two solar panels in series with a MPPT unit appear to be better than having panels in parallel.
The higher voltage (39V here) works better with a MPPT controller, making better use of the available solar power, more so with low light levels. It is important is to ensure no debris like leaves, bird dirt or green algae cover your solar panels, that's especially important with a series arrangement. With solar panels in series watch you don't exceed the voltage limit of your MPPT controller.
5. From my limited data it seems to suggest that the Votronic prioritises the charging of the leisure battery, once fully charged top-up charging of the vehicle battery commences. Having my EC700 PSU off charging of batteries is quicker.

Additional
PWM type controllers apparently works better when battery (12V) and solar voltages (20V) are close together. Having just a single solar panel I don't know of the relative performance merits of using a PWM or MTTP controller. With two solar panels connected in parallel to a PWM controller, it's likely your are not extracting all the available solar power from your system. Having panels in series with a MPPT type controller is probably much better.

So Parallel or series? It is still early days, nevertheless I am thinking the scales are balanced in favour of series. For a test I may leave the EC700 powered on for a few weeks as I had done when the panels were in parallel and see what happens to the vehicle battery's voltage.

Relaxez-Vous wrote:
1. How dull or sunny it is in winter can makes a big difference to solar battery charging.

That's exactly what I found - even in Autumn, if I get 3 dull cloudy days in a row then I'll be starting to worry about the battery voltage - it makes such a huge difference.

I know others have suggested it before, but are you not tempted to fit a switch (perhaps a centre-off switch) so that you can quickly switch between the two configurations? That would (almost) remove the effect of the light conditions changing while you alter the wiring? But I can understand any reluctance - it's a fair bit of fiddling about for something that - once you have found your preference - might seldom get changed?

The main reason I would consider it for my next 2-panel install is to cover the worry I have that one panel will fail, leaving me without any solar input if they are wired in series.

Having said that, the last panel that we had fail (on the Trooper) did not fail open-circuit, so I ~think~ there would still be some level of charging if it were in series with another fully functioning panel - but I don't know what level of charging that would provide.

Thanks Roopert, having a change over switch would make a comparison easy, I'm more looking for a fit and forget installation. I thought I had found it with the parallel connection until I measured the vehicle battery voltage at the end of last week. I was complacent, I thought with 160W of solar I was OK in winter, I hadn't reckoned on the power consumed when my EC700 PSU was left on. In our previous van a Duetto, I had none of current drain that having a Sargent ECxxx system introduces. It's so inefficient and environmentally unfriendly. Those camping with the standard A-S Sargent arrangements are being expected to use EHU even when they have an 80W solar panel.

Thanks for the warning about the possibility of failures of solar panels. I'll kept in the van the lead and Y junction I used with parallel, it would take perhaps 20 minutes of fiddling to go back to parallel. I'm sticking with series for now.

We know that identical panels in series is beneficial in low light levels when parallel doesn't generate a high enough voltage.  But a lower voltage will be generated in all light levels if one of the panels is shaded more than the other.  This might be a risk worth taking in the winter when low light levels account for a significant part of a short day but not in the summer when they don't and when parallel panels generate a high enough voltage for most of a longer day.  

When the van is out of use, the ECXXX should in my opinion always be shutdown.  Experience shows that when this happens, any decent dual battery controller will keep both batteries fully charged even in the winter with only one 80W panel.  

I would only consider the temporary use of series if I was trying to use the van off-grid in the winter which is not something I am planning to do.

Concerning the issue of shading on series connected solar panels, lets consider this in more detail.
Even with a single solar panel that we had on our previous van I noticed a drop in output if any leaves fell.onto the panel, once cleaned off the output increased back up.
Single or double the panels need to be kept clean. You should soon know with experience from observing the charging current that something has fallen onto a panel.

What is the the scenario that is envisages where shading of one panel will adversely affect charging? Is it when you have camped under a tree and the branches shade one of the panels?
I think a tree is likely to shade both panels, in which case a series connection might achieve a higher voltage than a parallel arrangement.
Anyone with a satellite dish are likely to choose a pitch away from the trees, same with those with series connected solar panels.

If my series connected panels actually demonstrate the practical disadvantages rather than just the theoretical, I can easily change to parallel, time will tell from my future experience with.series.

Caraman wrote:When the van is out of use, the ECXXX should in my opinion always be shutdown. 

Sorry to have to mention this again, but just a reminder that "ECxxx" is not a good generalisation, and it could cause some owners to be concerned when they don't need to be.

EC155, EC325 and EC328 owners should not need to worry - in my experience, none of these models cause any problems. The current drain when the panel is on seems to be significantly lower than the EC500 and EC700 based systems (and, probably the EC600 based systems, though I don't know if A/S ever installed any of those).

Caraman wrote:

Suppersready wrote:

Caraman wrote:
Thanks.  I'm destined to get a dual battery MPPT Votronic controller hence my interest.  The optional LCD display seems to show the voltage of the leisure battery only.  I was wondering if the current shown is also for the leisure battery only.  The Votronic trickle charges the vehicle battery up to a maximum of 1A but this appears not be shown on the display.  What is not clear is how the trickle charge is managed.  For example, if 5A of solar charge is available and both batteries are depleted, will 1A go to the vehicle battery and 4A to the leisure battery.  If 2A of charge is available, will 1A go to each of the batteries.  If 1A or less is available, will it all go to the vehicle battery or will none of it go to the vehicle battery which would account for your depleted vehicle battery.

I contacted Votronic Universe and asked them this very question, they replied they did not have the technical information to be able to answer.



Niall

I wonder if the Votronic's Batt2 charging works in the same way as the Epever if so it would explain why Relaxez-Vous's vehicle battery became depleted - see 1.4 of the Epever manual:

https://www.bimblesolar.com/docs/DuoRacer-SMS-EL-V1.0.pdf

At my request RoadPro obtained the following from Votronic in Germany.  I think I understand it.  What's interesting is its different from the Epever DuoRacer which is different from the NDS Sun Control 2:

The START charging output of the MPP solar controller is activated as soon as the MPP LED starts to light up continuously (solar charging is active). If the energy supplied by the solar panels is no longer sufficient to maintain solar charging, both charging outputs are deactivated again and the MPP LED goes out.
The voltage level of the charging voltage at the START charging output is always based on the voltage level of the leisure battery. If, for example, the U1 charging phase of the leisure battery is reached with 14.4V, then the START charging output delivers a charging voltage that is approx. 0.7V lower.
The START charging output supplies up to 1A charging current as long as the voltage level of the starter battery circuit is lower or equal to the voltage level provided by the START charging output (1 amp buffering at equal voltage level).

Caraman wrote:I've discovered another make of MPPT dual battery controller being sold by Road Pro who give a 5% discount to CAMC members:

https://www.roadpro.co.uk/product/02h05a-mppt-solar-regulators/nds-320w-sun-control-2-dual-regulator-mppt-c5701/C5701

Has anyone come across these NDS controllers before?

I've had a good look at this relatively new Italian NDS Sun Controller 2 and it seems to me to compare favourably with the German Votronic Duo Dig and Chinese Epever Duo Racer.  It's a little bigger than the Votronic but a lot smaller than the Epever.  It is unsuitable for solar panels in series but it has two separate solar panel inputs which could be useful.  The NDS website refers to the MPPT's 30% potential improvement over a PWM but in the detail it only claims 25%.  I don't know if this is significant.  Unlike the Votronic, a reasonable explanation is given in the manual on how the vehicle battery is charged which seems superior to both the Votronic and Epever.  The 360 model seems to be the same as the 320 except is has a temperature regulated cooling fan which allows it to be rated higher.  360 watts is way beyond my requirements but the fan could be beneficial if the unit is mounted in the EC700 enclosure next to the Truma Combi where cooling may not be that good.  The LED display is basic but for an out of sight fit & forget its fine.  Desulphation might have to be turned off so it doesn't spook the EC700 or trigger an alert on AS Monitor.  What do others reckon about this new controller?

Caraman wrote:
It is unsuitable for solar panels in series but it has two separate solar panel inputs which could be useful. 

That's interesting, but it will depend on the internal implementation. At one extreme, it could simply parallel the two inputs together inside the box, and at the other it could have a 2-channel MPPT controller which could simultaneously adapt to two different panels. The latter would be a very strong selling point, because that's where MPPT really comes into its own, with two separate optimisation processes going on, one for each panel.

Here are just my quick impressions.
Well it's another dual battery solar charge controller in the market alongside the Votronics Duo Dig and the Epever DuoRace.

The maximum voltage Voc this controller can accept is 29.5V. Our PV logic's 80W panel A-S fitted to our van has a Voc of 22V, so only parallel connected solar panels can be connected to this controller.
Incidentally if anyone wants a second 80W panel they supplied one to me last year, a special because it's not listed on their website. It was rather expensive and came in a box from PV Logic with Auto-Sleeper printed on the cardboard.

All the references to de-sulphating etc about battery recovery suggests it is designed to appeal to as many customers as possible. With a properly installed solar system you don't need de-sulphating. If I had a flat battery I'd know that it was nearly at the end of its usable life. I'd use a CETEK charger to try a final resurrection, I would not rely on my solar charge controller to do it.

It doesn't have Bluetooth but does have some display unit which I haven't checked out. I'd be half expecting to read that it been made out of recycled plastic and no whales were harmed in its manufacture.

My opinion is that you are far better buying a Votronic or Epever solar controller.

Roopert wrote:

Caraman wrote:When the van is out of use, the ECXXX should in my opinion always be shutdown. 

Sorry to have to mention this again, but just a reminder that "ECxxx" is not a good generalisation, and it could cause some owners to be concerned when they don't need to be.

EC155, EC325 and EC328 owners should not need to worry - in my experience, none of these models cause any problems. The current drain when the panel is on seems to be significantly lower than the EC500 and EC700 based systems (and, probably the EC600 based systems, though I don't know if A/S ever installed any of those).

Helpful clarification Roopert. We have a EC155 system with an after-market 100W Truma PV panel and dual battery controller added. I'm thankful that the system is as simple and problem-free as it is.  Very much a case of fit and forget, which works for me!

Tim

Kemerton-bath wrote:

Roopert wrote:

Caraman wrote:When the van is out of use, the ECXXX should in my opinion always be shutdown. 

Sorry to have to mention this again, but just a reminder that "ECxxx" is not a good generalisation, and it could cause some owners to be concerned when they don't need to be.

EC155, EC325 and EC328 owners should not need to worry - in my experience, none of these models cause any problems. The current drain when the panel is on seems to be significantly lower than the EC500 and EC700 based systems (and, probably the EC600 based systems, though I don't know if A/S ever installed any of those).

Helpful clarification Roopert. We have a EC155 system with an after-market 100W Truma PV panel and dual battery controller added. I'm thankful that the system is as simple and problem-free as it is.  Very much a case of fit and forget, which works for me!

Tim

As a point of principle if there is no tangible benefit in leaving something switched on, I switch it off even if there is sufficient solar or mains power for it.  If my Nuevo had enough solar panels and a good enough solar controller to power the EC700 throughout the winter, I would still turn it off when out of use just as I do in the summer.

I confess that, having thought about it, my point is a bit pointless, really - because on the EC155, EC325 and EC328 there is no "system shutdown" function! You can turn off the power to the leisure systems but the display stays on, whatever. The only way to "shutdown" one of those would be to pull out the supply fuses for both the leisure and vehicle batteries.