Controller for portable solar panel : Is Mppt better than Pwm? (1 Viewer)

[Captain Yoghurtpot]

Am considering a stand alone , foldable , portable solar panel around 100 to 150 W.
Have seen various types, but am currently looking at one around the £250 mark with mppt controler, but a very similar model with pwm controller is significantly cheaper.
Anyone have any recommendations on makes also?
Thanks

 

[Tombola]

MPPT can use the harvested power better and get you more into your battery.
MPPT is better than pwm all day long

 

[Captain Yoghurtpot]

MPPT can use the harvested power better and get you more into your battery.
MPPT is better than pwm all day long

Thank you Sir.
That was my understanding initially from what I had researched, but there are so many variables with questionable attributes, and at the upper level of pricing, I need to get it right.
Thanks

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[XxAnthxX]

The thing to remember with a portable panel is that it is just that....portable.

You can position and angle it to catch the sun and avoid shade and shadows much better than a fixed panel on a van roof.

My fixed panel goes through a Victron MPPT controller, but my ECO-WORTHY 120W Foldable Solar Panel has a PWM controller, but works well enough.

What Victron say......

PWM

The PWM charge controller is a good low cost solution for small systems only, when solar cell temperature is moderate to high (between 45°C and 75°C).

MPPT

To fully exploit the potential of the MPPT controller, the array voltage should be substantially higher than the battery voltage. The MPPT controller is the solution of choice for higher power systems (because of the lowest overall system cost due to smaller cable cross sectional areas). The MPPT controller will also harvest substantially more power when the solar cell temperature is low (below 45°C), or very high (above 75°C), or when irradiance is very low.

Which solar charge controller: PWM or MPPT? - Victron Energy

What follows is a summary of our white paper with the same title. For the full white paper, see: Which solar charge controller: PWM or MPPT? in the White papers section of our site. 1. What they do The PWM controller is in essence a switch that connects a solar array to a battery. The […]

www.victronenergy.com

 

[Langtoftlad]

Yes MPPT is on paper better.
I went through all this angst when my PVC converter wouldn't fit one.

The discussion here and my subsequent 4 years experience suggest in the 'real world' it doesn't make much difference.

My 120w panel & two leisure batteries seem to meet my energy needs.

 

[mitzimad]

going to mttp from pwm increases out put by 20 per cent adding another panel the same size as existing doubles your output for often a similar price

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[Lenny HB]

With a panel flat on the roof it's well worth having an MPPT regulator it will give you around 25% more output.

With a portable if you are prepared to move every hour or two to get max output you will be getting such a good output probably not worth the extra expense.

 

[Raul]

A PWM is amp in- amp out. No matter what. So if your 100w panel outputs 5 amp, the controller will output 5amp. No more, despite the extra voltage you have above battery voltage. It’s wasted.
A mppt, will track the best power point at any given irradiation, and extract everything, across all temperatures.
The mppt is : power in power out, it’s actually a full on buck converter, with added max power tracking; so a 100w panel at full output will give you more than 5amps, it will convert the rest of the voltage above battery in amps. A 100w on mppt will give you 8amp at 12,4v ; 7,25 at 13,8v or 7amp at 14,4v in absorb. The PWM with same panel will be max 5,2-5,4a no matter of circumstances; weather the battery is at 12,4v or 14,4v; still 5amps.
Don’t go for a kit, get a 100w folding from eBay triple solar 90 quid, and add a 75/10 victron mppt. Match made in heaven.

 

[Captain Yoghurtpot]

A PWM is amp in- amp out. No matter what. So if your 100w panel outputs 5 amp, the controller will output 5amp. No more, despite the extra voltage you have above battery voltage. It’s wasted.
A mppt, will track the best power point at any given irradiation, and extract everything, across all temperatures.
The mppt is : power in power out, it’s actually a full on buck converter, with added max power tracking; so a 100w panel at full output will give you more than 5amps, it will convert the rest of the voltage above battery in amps. A 100w on mppt will give you 8amp at 12,4v ; 7,25 at 13,8v or 7amp at 14,4v in absorb. The PWM with same panel will be max 5,2-5,4a no matter of circumstances; weather the battery is at 12,4v or 14,4v; still 5amps.
Don’t go for a kit, get a 100w folding from eBay triple solar 90 quid, and add a 75/10 victron mppt. Match made in heaven.

Thanks. And is that best wired directly to the leisure battery via croc clips or an Anderson type fitting or other similar quick release?
Don’t really want to start wiring into the 12v system electronics.
Thanks.

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[Raul]

Anderson connector, or MC4 connector with the locking pins cut so you can pull it out. The MC4’s are good for 30 amps but you need to crimp it correctly to fit in. Otherwise buy a extension cable with mc4 already crimped.

 

[Captain Yoghurtpot]

Yes MPPT is on paper better.
I went through all this angst when my PVC converter wouldn't fit one.

The discussion here and my subsequent 4 years experience suggest in the 'real world' it doesn't make much difference.

My 120w panel & two leisure batteries seem to meet my energy needs.

Are the leisure batteries wet lead acid, agm or lithium please?
And could you do your set up on 1 battery alone ?
Thanks, I am still pondering.

 

[Captain Yoghurtpot]

Anderson connector, or MC4 connector with the locking pins cut so you can pull it out. The MC4’s are good for 30 amps but you need to crimp it correctly to fit in. Otherwise buy a extension cable with mc4 already crimped.

Thanks for the info, and I take it that this is a direct connection to the leisure battery or batteries?
Sorry if it’s a daft basic question, but I really don’t want to muck about with the vans 12v electrics other than to simply add a simple and portable, and transferable, scource of external charging, and a cost effective one at that , compatable with the 12v system on a 20 year old van.
Thanks.

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[Langtoftlad]

Are the leisure batteries wet lead acid, agm or lithium please?
And could you do your set up on 1 battery alone ?
Thanks, I am still pondering.

Wet lead Banner 100Ah x2
It is a basic system.
One battery? Possibly, but I think I might fret.
Lots of gadgets USB charging - phone, tablet, chromebook, mifi, speakers, fans, 12v LED lighting, TV [quite high use].
Water pump, heating fan. No inverter use [although I have one]

I was always told that an extra battery was the most cost effective power upgrade.

Truthfully, I use a lot of club sites so mainly on EHU but looking back to 2018/9, I did several rallies, 5 or so days in one place on solar/battery power alone.

 

[jongood]

Myself and funflair were side by side a few days ago and ( like a pair of anoraks) comparing the output of our relative outputs. I'm sure Martin will be along shortly to give you the actual figures but I think MPPT was outstripping PWM by about 10% , these are both roof mounted though.

 

[Captain Yoghurtpot]

Wet lead Banner 100Ah x2
It is a basic system.
One battery? Possibly, but I think I might fret.
Lots of gadgets USB charging - phone, tablet, chromebook, mifi, speakers, fans, 12v LED lighting, TV [quite high use].
Water pump, heating fan. No inverter use [although I have one]

I was always told that an extra battery was the most cost effective power upgrade.

Truthfully, I use a lot of club sites so mainly on EHU but looking back to 2018/9, I did several rallies, 5 or so days in one place on solar/battery power alone.

Thanks for this. That’s exactly the setup that I am thinking of,but my usage of 12v is only water pump, toilet flush, led lights, minimal usb usage, occasional tv and radio ,phone charge up and iPad mini.
I too would normally be on hookup, but want the flexibility for occasional THS sites and maybe a rally or two without hookup.
Shall explore further what’s available, equipment wise.

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[Ninjabob]

Interesting that the Victron advice seems to suggest wiring a MPPT array in series to create a "substantially higher voltage than the battery" is what is required. Advice from Funsters here is always wire in parallel because of shading issues when wiring in series.

 

[funflair]

Myself and funflair were side by side a few days ago and ( like a pair of anoraks) comparing the output of our relative outputs. I'm sure Martin will be along shortly to give you the actual figures but I think MPPT was outstripping PWM by about 10% , these are both roof mounted though.

You are right Jon the "anorak" bit anyway , I can't remember the numbers exactly but more like 20% more from the MPPT and that was into fairly charged gel batteries and the PWM was into LiFePO4.

Hopefully I get my MPPT back on soon

 

[Raul]

Thanks for the info, and I take it that this is a direct connection to the leisure battery or batteries?
Sorry if it’s a daft basic question, but I really don’t want to muck about with the vans 12v electrics other than to simply add a simple and portable, and transferable, scource of external charging, and a cost effective one at that , compatable with the 12v system on a 20 year old van.
Thanks.

Yes, directly to the leisure batteries.

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[XxAnthxX]

Interesting that the Victron advice seems to suggest wiring a MPPT array in series to create a "substantially higher voltage than the battery" is what is required. Advice from Funsters here is always wire in parallel because of shading issues when wiring in series.

Which could also mean that MPPT on a single panel or small array might not actually be the Holy Grail some believe it is?

 

[funflair]

Interesting that the Victron advice seems to suggest wiring a MPPT array in series to create a "substantially higher voltage than the battery" is what is required. Advice from Funsters here is always wire in parallel because of shading issues when wiring in series.

When I was installing panels on our last van I asked Votronic for their advice and it came back as "parallel" for the reason you suggest ie shading.

 

[Captain Yoghurtpot]

Thanks for the answers so far folks.
Looks like I may have inadvertently opened a can of worms.

Sorry.

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[Langtoftlad]

Thanks for this. That’s exactly the setup that I am thinking of,but my usage of 12v is only water pump, toilet flush, led lights, minimal usb usage, occasional tv and radio ,phone charge up and iPad mini.
I too would normally be on hookup, but want the flexibility for occasional THS sites and maybe a rally or two without hookup.
Shall explore further what’s available, equipment wise.

I believe there's a difference between what is theoretically best & what "will do".
You can always add another battery if you find just one isn't sufficient.
But you'll never know if you've wasted money by over specifying.

I'm sure the vast majority of motorhomers simply drive away from the dealers with one battery, maybe 100w solar and never give it a second thought.

In end of March, beginning of April 2018 I was on Chester Racecourse for the best part of six days.
I don't recall power being an issue and the weather was certainly not optimum for solar...

I've still got the same batteries 3 years on.

 

[Off da Grid]

I bought a Votronic 350 mppt controller for our 255w/ 8 amp panel because it can charge all flavours of battery and has the capability to run an aes fridge.
I’ve seen 15amps draw from our setup when I’ve pushed it hard when experimenting

 

[Tombola]

Which could also mean that MPPT on a single panel or small array might not actually be the Holy Grail some believe it is?

No but when you see x amount of power coming in from the panel but it being stepped up by the time it gets to the battery, it makes you think .

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[XxAnthxX]

No but when you see x amount of power coming in from the panel but it being stepped up by the time it gets to the battery, it makes you think .

I’m just referencing what the major solar suppliers say when comparing the two.

As I’ve already said I have both and I’m happy with both of their performances in their given situations.

 

[Minxy]

When we wanted a portable pane to supplement our existing ones over winter as we had an electric only fridge and tended to stay in one place for a while, so I bought a cheap 50w flexible solar panel off Ebay, I then added a ciggy lighter type socket under the passenger seat and wired it directly into our existing solar controller, on the panel itself I fitted a 12v ciggy plug in place of the crocodile clips so it was simply a matter of flipping the front base cover of the passenger seat down, sticking the plug in the socket and closing the flap (there was sufficient room at the top to allow the cable to pass through), the cable went under the cab door (it didn't damage it) so we could shut it without a problem.

It worked a treat and being a flexi panel it was less bulky so easy to store, lightweight too so moving it round was a doddle and we could just prop it up against a little step, we could even stick it to the windscreen with suckers!

As for our current Carthago, we have 2 x 100w panels on the roof fitted by the dealer but they come down to a less well known NDS Sun MPPT controller which has performed just as well as the one we had in our previous PVC which was a Votronic, so don't let the cheaper price put you off.

MPPT or PWM

I have a basic PWM connecting my 100w panel to 2x 90amp batteries and wondered whether it was worth upgrading to an MPPT May have already been posted but in doing a bit of market research, I found this which others might find of interest...

www.motorhomefun.co.uk

 

[TheCaller]

Looks like I may have inadvertently opened a can of worms.

That's true!

As Victron says, the MPPT controller really comes into its own in terms of extracting the maximum amount of power from the available sunlight when it is connected to multiple panels wired in series. The improvement is still there with a single panel, but it's less significant.

In terms of power output, you will get more power for your money by having an additional panel than spending the cash on an MPPT controller, but do you really want to mess around with a bigger panel or two panels when the system is supposed to be portable?

There is no doubt that an MPPT controller is 'better'. Whether it is better enough to be cost effective depends on individual circumstances.

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[Captain Yoghurtpot]

Hello Folks, it’s me again, the Portable Solar Panel pest.
After much researching and mathematical calculus on the back of a fag packet, I am , I think, at a conclusion.
However, if anyone wants to cast an eye at my figures and comment, I am all eyes.
I have deduced the following based on my actual 12v usage within the van and the actual wattage consumption against actual time used as follows:
6 LED strip lights at 1w for 6 hours per day
1 water pump at 40 w for 12 mins per day
LCD 12 v TV at 45w for 2 hours per day
12v Radio at 24w for 2 hours per day.
This gives:
Total Wattage is 115w per day
Total Current draw at 12v in Amps at 9.58Amps per day
Total Hours of use collectively = 10.2 hours per day
Total Actual Amphours required = 13.67 Ah per day.
By my reckoning I think I would need a minimum of 1 and a half hours per day charging on solar to keep a single 100 ah 12 volt leisure battery topped up to deliver my needs if all the above appliances are used accordingly.
I am now considering whether a 50w panel is too small and 100w too big.
All comments gratefully received.

 

[XxAnthxX]

Hello Folks, it’s me again, the Portable Solar Panel pest.
After much researching and mathematical calculus on the back of a fag packet, I am , I think, at a conclusion.
However, if anyone wants to cast an eye at my figures and comment, I am all eyes.
I have deduced the following based on my actual 12v usage within the van and the actual wattage consumption against actual time used as follows:
6 LED strip lights at 1w for 6 hours per day
1 water pump at 40 w for 12 mins per day
LCD 12 v TV at 45w for 2 hours per day
12v Radio at 24w for 2 hours per day.
This gives:
Total Wattage is 115w per day
Total Current draw at 12v in Amps at 9.58Amps per day
Total Hours of use collectively = 10.2 hours per day
Total Actual Amphours required = 13.67 Ah per day.
By my reckoning I think I would need a minimum of 1 and a half hours per day charging on solar to keep a single 100 ah 12 volt leisure battery topped up to deliver my needs if all the above appliances are used accordingly.
I am now considering whether a 50w panel is too small and 100w too big.
All comments gratefully received.

Well......go budget, on a larger panel with a cheaper controller.

Dokio 100W 18V PORTABLE FOLDABLE Solar Panel Kit (54 * 73cm, 2.7kg) Monocrystalline(HIGH Efficiency) with CONTROLLER 2 USB Output to Charge 12V Batteries (All Types: Vented AGM Gel) RV Camper Boat Amazon product ASIN B078W4HY9T

Or


ECO-WORTHY 120W Foldable Solar Panel for Portable Power Station & RV Battery, DC Output for Solar Generator, with 20A Controller for SLA/AGM/Lithium Deep Cycle Battery RV Motorhome Camping Amazon product ASIN B08K2Y7NVQ



It won’t matter if you don’t ‘need’ all of the power (it’s free) and you won’t have to worry about how inefficient the controller is either

 

[Minxy]

Hello Folks, it’s me again, the Portable Solar Panel pest.
After much researching and mathematical calculus on the back of a fag packet, I am , I think, at a conclusion.
However, if anyone wants to cast an eye at my figures and comment, I am all eyes.

All comments gratefully received.

Stop smoking and buy yourself a writing pad ...