MPPT vs PWM - The Solar Controller Test!

[RAW]

A not unrelated reply to the above, so on my Van I have the following which are possible to remove prior to Sale of Sylvia:

• 285W Solar Panel (a bit awkward to remove as fixed well, but could be done)
• Victron MPPT 100/30 (NOT Bluetooth)
• Victron BMV 712 Smart Battery Monitor
• Victron Smart Battery Sense, volt and temp 12/24/48V BT
• LEOCH 160AH AGM battery
• Raspberry Pi with Venus OS and Official Victron Cable for USB to VDE

What would you do?
Leave everything as is (might improve sale value) or remove Some / All and what parts of the above list ?

TIA Robert

 

[wildebus]

A not unrelated reply to the above, so on my Van I have the following which are possible to remove prior to Sale of Sylvia:

• 285W Solar Panel (a bit awkward to remove as fixed well, but could be done)
• Victron MPPT 100/30 (NOT Bluetooth)
• Victron BMV 712 Smart Battery Monitor
• Victron Smart Battery Sense, volt and temp 12/24/48V BT
• LEOCH 160AH AGM battery
• Raspberry Pi with Venus OS and Official Victron Cable for USB to VDE

What would you do?
Leave everything as is (might improve sale value) or remove Some / All and what parts of the above list ?

TIA Robert

If it were my van I would do the following:
Solar Panel - Likely leave in place. Chances are it is not the optimum size/shape for a new vehicle; people like the idea of solar so having it in place is a definate plus point. Removing and making good any marks, holes and damage left... not worth the hassle
Battery - it is a very good battery which you got at a very good price (below cost for sure). If you are not looking at Lithium for the new van, I think I would likely remove it and get a basic 100Ah Leisure Battery to put in its place.
Raspberry Pi, Cables, BMV-712 and Smart Sense ... remove for sure. Most Motorhome buyers are not interested enough to want to pay the cost of that kind of kit and you would only end up buying the same stuff again anyway.
MPPT Controller - tricky one. For the Battery Sense to work with the MPPT, you need bluetooth. If you fit the Bluetooth dongle to the MPPT you cannot connect to the Raspberry Pi (you can only use the VE.Direct port for one OR other). I would maybe leave the MPPT installed - but probably remove with a view to sell it with the BT Dongle (a very nice combo for anyone who doesn't intend using the Victron internet portal), and instead get a SmartSolar version which will let you connect to the Pi AND use the Smart Battery Sense at the same time. (if you remove to sell on, you would need to get another Solar Controller for Sylvia of course. A 20A PWM unit is cheap and will work of course, just not get the best results. But consider that the great majority of motorhomes - even the £60K+ brand new ones - are still fitted with bargain basement PWM controllers so it is not as if you are stiffing anyone)

 

[RAW]

If it were my van I would do the following:
Solar Panel - Likely leave in place. Chances are it is not the optimum size/shape for a new vehicle; people like the idea of solar so having it in place is a definate plus point. Removing and making good any marks, holes and damage left... not worth the hassle
Battery - it is a very good battery which you got at a very good price (below cost for sure). If you are not looking at Lithium for the new van, I think I would likely remove it and get a basic 100Ah Leisure Battery to put in its place.
Raspberry Pi, Cables, BMV-712 and Smart Sense ... remove for sure. Most Motorhome buyers are not interested enough to want to pay the cost of that kind of kit and you would only end up buying the same stuff again anyway.
MPPT Controller - tricky one. For the Battery Sense to work with the MPPT, you need bluetooth. If you fit the Bluetooth dongle to the MPPT you cannot connect to the Raspberry Pi (you can only use the VE.Direct port for one OR other). I would maybe leave the MPPT installed - but probably remove with a view to sell it with the BT Dongle (a very nice combo for anyone who doesn't intend using the Victron internet portal), and instead get a SmartSolar version which will let you connect to the Pi AND use the Smart Battery Sense at the same time. (if you remove to sell on, you would need to get another Solar Controller for Sylvia of course. A 20A PWM unit is cheap and will work of course, just not get the best results. But consider that the great majority of motorhomes - even the £60K+ brand new ones - are still fitted with bargain basement PWM controllers so it is not as if you are stiffing anyone)

Silly me, not thought of replacing the LEOCH Battery and Victron for a cheaper battery and Cheaper controller - to that end if you have kit you want to sell on then drop me an email. Seeing the potential new van later so thanks for your reply.

 

[wildebus]

Silly me, not thought of replacing the LEOCH Battery and Victron for a cheaper battery and Cheaper controller - to that end if you have kit you want to sell on then drop me an email. Seeing the potential new van later so thanks for your reply.

Well, once I am done with the testing, I have a bunch of Controllers to sell I can't match the "direct from China" prices as they don't have to pay for any shipping (It is not free shipping, it is just Royal Mail are obliged to pay for it!), but if you don't want to want 3 weeks .... You would need a 20A controller minimum
Not got any batteries - Alpha Batteries the best bet there

 

[wildebus]

While the final controller (the Victron 100/20 MPPT unit) is being tested using the same regime, I thought I would post a couple of videos that show the first two minutes of a Solar Controller starting up. Sounds as exciting as watching paint dry I know, but it is fairly interesting comparing the difference between how a PWM and a MPPT controller start up and settle into their charging routine.

The power input is the same for both units - the 27V, 2.15A Power Supply - and the battery is the same and in need in of bulk charging both times so will easily accept whatever a 60W PSU can give it so there is no limitation there.
Note: the video has no sound other than my heavy breathing so mute your speakers and sorry in advance for the movement - I am holding the phone recording this.

Video #1 - PWM Controller

VIDEO COMMENTS
Upper Monitor - INPUT into the PWM Controller
Lower Monitor - OUTPUT to the Battery
Watch the Voltage on the Upper Monitor decaying down to settle at the Battery Voltage + 0.1-0.2V.
Also note the Current out to the battery is never greater than the current into the controller.
This is indicative of how a PWM Controller operates compared to a MPPT Controller, where the Voltage stays at the initial level and the output current raises above the input current to ensure minimal solar harvesting energy losses.


Video #2 - MPPT Controller

VIDEO COMMENTS
Upper Monitor - INPUT into the MPPT Controller
Lower Monitor - OUTPUT to the Battery
Watch the Voltage on the Upper Monitor fluctuating as the MPPT Controller starts up.
Also note the Current out to the battery is always greater than the current coming into the Controller as the excess voltage is converted into a higher charge current.
This is indicative of how an MPPT Controller operates compared to a PWM Controller, where the current in is essentially just passed through and any higher incoming voltage is just chopped off so that that potential harvested power gets wasted.


It is interesting I think to actually see the way the voltage bounces up and down on the MPPT Controller as the unit is using its Power Tracking algorithm to get the best result. Because the Power Supply is providing a immediate and constant power, this happens pretty fast in this captive test environment, but you can see this behaviour just as well in the 'wild', it is just that it takes longer to settle. Below is a graph of my camper installation - you can see how in the sample day, once the controller wakes up at around 6:15 (when the incoming voltage is >5V over the battery voltage), the PV Voltage jumps up and down for around 15 minutes until it becomes fairly settled.

 

[wildebus]

Test #6 - Victron SmartSolar 100/20 MPPT 20A Controller

This is the Controller

SC - Victron_MPPT_20A by David, on Flickr

And the Test Results

SC - Victron 100-30_MPPT_20A - Test Results by David, on Flickr

Because I had the Victron connected to a Raspberry Pi runing Venus GX I could also log the data as the Controller itself recorded it ....

SC - Victron VRM Data by David, on Flickr

I think the numbers are - as they should be - very close to the battery monitors.
By cross-checking the two systems it does indicate that the battery monitors are fairly accurate and show believable and reliable information

 

[wildebus]

Summerising the results ....

Using a 27V, 2.15A Power Input

1. Test 1 - Venus M2420 MPPT 20A Controller - 51.3W/Hr
2. Test 2 - Venus PWM 30A Controller - 29.3W/Hr
3. Test 3 - CMP 2420 PWM 20A Controller - 28.2W/Hr
4. Test 4 - Generic PWM 10A Controller - 29.6W/Hr
5. Test 5 - Venus P2420 PWM 20A Controller - 28.8W/Hr
6. Test 6 - Victron 100/20 MPPT 20A Controller - 53.75W/Hr

There is a very clearly two groupings which is no great surprise.
The PWM Controllers are averaging 29W/Hr with the 27V 2.15A power input, while the MPPT Controllers are averaging 52.5W/Hr.

In terms of Voltage and Current the averages are as follows:

1. Test 1 - Venus M2420 MPPT 20A Controller - 27.03V, 1.99A (13.34V Above Battery Voltage)
2. Test 2 - Venus PWM 30A Controller - 12.99V, 2.24A (0.16V Above Battery Voltage)
3. Test 3 - CMP 2420 PWM 20A Controller - 12.6V, 2.23A (0.33V Above Battery Voltage)
4. Test 4 - Generic PWM 10A Controller - 12.7V, 2.23A (0.23V Above Battery Voltage)
5. Test 5 - Venus P2420 PWM 20A Controller - 12.85V, 2.25A (0.16V Above Battery Voltage)
6. Test 6 - Victron 100/20 MPPT 20A Controller - 26.45V, 2.13A (13.51V Above Battery Voltage)

It is clear I think that the MPPT controller is much more adept at dealing with higher voltages and is able to convert much more energy from an input through to the battery.
Looking at the PWM numbers, basically it doesn't matter what the voltage of the power input is, anything above around 0.2V more than the Battery Voltage seems to get ignored. So a 27V input is pretty wasteful. If you had a pair of typical 12V panels (which actually run at around 18V), if they were connected in series, the 1st panel would have a fair bit of its potential wasted and the 2nd panel would be a total waste of time.
Key Conclusion: On a 12V system, never bother to connect multiple panels in series if using PWM controllers!

How close would the PWM and MPPT controllers be if using a single 12V Panel? On the info above, I would expect the MPPT to run the panel at around 18V. The same panel connected to a PWM Controller would run at between 12.2V and 14.6V (assuming a battery level of 50% going upto 100%).
This gives an average inefficiency of >25% more for the PWM over the MPPT. in other words, for every 10Ah an MPPT is harvesting, a PWM is only getting 7.5Ah from the same source.
Or put in another way, if you had a 100W (12V Panel) Solar Panel connected to an MPPT Controller, you would need a 125W Panel to get the same energy. Larger panels often run at a higher voltage then 18V and those would be even less suitable for PWM.
What is even more to the detriment of the PWM controller is the performance deficit becomes greater the more the battery is discharged, which is generally when you are most keen to get as much charge in as possible to refill your battery!


Now these are the conclusions using a steady power supply plus extrapolating the results. But what will "real world" testing tell us using solar panels?
Watch this space!

 

[SquirrellCook]

When I first connected my Victron 100/30 MPPT I had 5 100watt panels in parallel. The performance was noticeable improved.
Later I discarded 1 panel and wired them 2 pairs in series then that pair in parallel. Again the performance was increased.
The next move will be to attempt to move 2 panels to reduce shading, maybe adding another pair for good measure.

 

[wildebus]

When I first connected my Victron 100/30 MPPT I had 5 100watt panels in parallel. The performance was noticeable improved.
Later I discarded 1 panel and wired them 2 pairs in series then that pair in parallel. Again the performance was increased.
The next move will be to attempt to move 2 panels to reduce shading, maybe adding another pair for good measure.

I am not sure why removing 1 panel and changing from All Parallel to a Parallel/Series combination would improve performance?
I could understand if you went All Series to Parallel/Series and it improved if you had slight shading on a single panel it would impact the whole array. I guess maybe in lower light levels it was taking longer at the start of the day to turn on due to lower voltage levels but I would think removing 20% of the array would have more than negated that benefit?

I have 4 panels and had them in a Series/Parallel combination like you currently have. Two months ago I changed them to All Series as a test and I don't know if there was any noticable difference - and I can see all the data so if it were clear I should be able to see it.

This is the problem with evaluating Solar configurations - too much external variance (amount of solar irradiation hitting panels) that cannot be accounted for.
If there is no shading, then Series will be superior to Parallel as the higher voltage and lower current means less cable losses, but talking pretty small factors which are nigh-on impossible to measure in real-terms at the current and voltage levels involved with the small arrays that are possible on a vehicle.

 

[wildebus]

PWM vs MPPT - Direct Duel
Tomorrow is an all-day test using Solar Panels.

Change of test setup again!
Gone back to using 100W panels (my 30W ones are still brand new so don't want to get them mucky!)
I have decided to feed both controller outputs into the same battery - the amount of output I will get from a pair of 100W panels this time of year means both controllers will stay running at full available power I am sure as the battery will be down below 50%. We will see

Controllers:

SC - Testing Duel - Controllers by David, on Flickr

Quite a difference in size eh? both 20A controllers. I have plugged in the temp probe on the MPPT to enable the Temp Compensation but left it next to the controller so close to the PWM unit that also has built-in Temp Comp.

Monitors:

SC - Testing Duel by David, on Flickr
Only have two monitors so I have one of these on each Controller output which is the key information that a user is concerned of.
I do have the Victron MPPT plugged in, but just the battery connection so I can log the voltage change over time during the test.

Power Supply:

SC - Solar Panel Front by David, on Flickr

Pretty standard 100W Panels, set side by side so should get the same sun. This is the spec -

SC - Solar Panel by David, on Flickr

And should be able to cross-check the performance against the level of Solar Radiation to get an idea of how much the panels could harvest, although this one could be tricky to calculate!
This is todays Solar Radiation a few metres away

SC- Solar Radiation by David, on Flickr

Off now to connect the panels now it is dark and will leave alone until tomorrow night
I really don't know for sure what the difference will be between the two but will be fun to find out!

 

[Lord Lucan]

Excellent stuff

 

[RAW]

This is a REALLY GREAT and helpful thread, thanks for all the time you are putting in @wildebus - BIG KUDOS

 

[Lord Lucan]

+1

 

[RAW]

The next move will be to attempt to move 2 panels to reduce shading, maybe adding another pair for good measure.

Shading ? Any shade falling on Solar panel from Shadows close to panel will HUGELY adversely affect the performance and ability to harvest solar power as per @Geeky Philip YT Video and my own tests that I carried out to confirm the same

 

[trevskoda]

Be interesting to see what difference you see (you could also change from Parallel to Series on the panel? that will eek out a touch more start and end of the day and give fractionally less cable loss)
The Dual Battery bit is interesting - next week I am getting in a prototype standalone starter battery trickle charger to test, which will do a similar job I expect? excepting it will be good for solar and EHU. I am assuming the starter battery trickle on the Votronic is just active with solar?

No i also have a switch in cab so i can connect all batterys up either on solar or mains charger at moment ,will still keep this when i change to new control unit to charge from numax 10ah float charger.

 

[trevskoda]

Shading ? Any shade falling on Solar panel from Shadows close to panel will HUGELY adversely affect the performance and ability to harvest solar power as per @Geeky Philip YT Video and my own tests that I carried out to confirm the same

Happens if in series.

 

[SquirrellCook]

Shading ? Any shade falling on Solar panel from Shadows close to panel will HUGELY adversely affect the performance and ability to harvest solar power as per @Geeky Philip YT Video and my own tests that I carried out to confirm the same

I run semiflexible panels, 1. due to the fact that the roof covering is not much more than a big glass fibre bag. So hard to get a rigid mounting. 2. I wanted to avoid any kind of raised structure as I often end up pushing through trees.
One of the panels I must have fitted during a dumb moment and it's too close to a sky light. Also two panels are mounted over the curvature of the roof. Not ideal.

 

[SquirrellCook]

I am not sure why removing 1 panel and changing from All Parallel to a Parallel/Series combination would improve performance?

Just crude testing, but from what I remember all in parallel I had better peak current.
Connecting in series and parallel reduced the peak current by a couple of amps, but what was notable was earlier and later in the day performance.
This was with the fifth panel disconnected,
As I've mentioned before, if your array is over seized. You probable won't notice the smaller improvement that can be made.

Now that I've been forced to park Murky at home due to fuel theft, I had the opportunity to examine the layout of the array and concluded I can do better. (upstairs windows, improved viewing)

 

[wildebus]

Just crude testing, but from what I remember all in parallel I had better peak current.
Connecting in series and parallel reduced the peak current by a couple of amps, but what was notable was earlier and later in the day performance.
This was with the fifth panel disconnected,
As I've mentioned before, if your array is over seized. You probable won't notice the smaller improvement that can be made.

Now that I've been forced to park Murky at home due to fuel theft, I had the opportunity to examine the layout of the array and concluded I can do better. (upstairs windows, improved viewing)

Ah ok. so maybe the 5th panel was suffering from regular shade and not fully effective so removing took not much away? And then the change to Series/Parallel boosted it nicely. It is tricky to really fine tune an "real" installation with the inconsistant weather we have.
Interestingly I am looking at sensible ways to add more capacity but I could only easily add 1 one - taking it to 5 in total. That knocks Series/Combo setup on the head so it would be all Parallel (not ideal as you have found yourself) and all Series is taking the total voltage over the 100V limit of the controller (I occasionally hit 84V with the 4 panels). I'll probably end up going for a pair of controllers but waiting for Victron to release the MPPT firmware update that allows the solar controllers to synchronise as a bank to get the right performance at the top end of the charge.

 

[Pugwash69]

After all the reading I've been doing, including this thread, I've decided to replace my solar charge controller. The dead cheap one I'm running may or may not be working well. It's too vague to know. It tells me I'm getting 1.7A from the battery during the day today but it was saying the same thing in the dead of night last night. I'm sure it's making up the figures.
Victron 100/20 now ordered because I downloaded their App and the demo mode convinced me it's worth the money.