MPPT or PWM? (1 Viewer)

[Langtoftlad]

Starting to think seriously about some of the factory fit accessories I'll be having on my new Wildax Aurora.

One of the 'no brainers' is the solar panel.
I talked to Duncan about upgrading to a MPPT controller but his view was that in the real world, it didn't make much of a difference and that the benefits of MPPT have been overhyped.

What are your opinions?

The Wildax option is £500 for a 120 Watt panel with PWM controller - presumably I'd also need another box of tricks to enable dual charging of both the leisure & engine batteries?

As a comparison - VanBitz has a smaller 100 Watt panel, MPPT and dual charging for about the same money after discount.

Getting the Wildax option when the van is built presumably means a 'neater' install and is convenient as it will all be done at the same time.
Getting a third party after market fitting may not be as neat [?] plus the inconvenience and costs of the 420 mile round trip to Eddies.

Is that the better option for the sake of MPPT?

 

[hilldweller]

It's only a little control box, there is no reason why you could not, at your risk, deliver an MPPT controller and tell them to fit it.

He's probably right, in the real world you'll probably never notice.

 

[jezport]

Get a system fitted locally and yes use an MPPT regulator.
Im going to be fitting a votronic duo mppt which will also keep my cab battery topped up.

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[Langtoftlad]

He's probably right, in the real world you'll probably never notice.

I'm sure he'd supply & fit whatever I asked for . They seem that sort of business.

I was mainly interested in Funsters opinions to see if they disagreed with his - your's apparently doesn't .

I've just read on the Victron page;
3. Conclusion
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.

So, in laymans terms, is a 120W panel a "small" system - and for bumbling around Britain what solar cell temperature can one expect? [45-75C sounds high].

 

[Langtoftlad]

Get a system fitted locally and yes use an MPPT regulator.
Im going to be fitting a votronic duo mppt which will also keep my cab battery topped up.

Why?
Cheaper, better in real world use?
Convenience, better install?

 

[jezport]

The price you quoted was quite expensive so you may get a better deal locally and if you buy local if there is a problem you wont have far to go.

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[Minxy]

Whichever you go for they both seem to be expensive options for a smallish single panel!

I would certainly either do it yourself of get it done locally as it's not rocket science. I fitted our solar panel and the controller which just plugged straight into our electrobloc, easy peasy and charges both hab and cab batteries! The hardest bits were working out where to drill the hole in the roof to put the cable through and then cleaning up the ruddy Sikaflex afterwards! As I needed the hole to go in a very specific spot (ours is a PVC with a ribbed roof) I had to do lots of careful measuring and fortunately it was right first time, and the Sikaflex was because I forgot just how 'sticky' it can be and a s*d to clean off, if I did it again I'd certainly do a lot more masking up of the roof first to make it much quicker and easier (and cleaner!) ... there's still a bit of it on the Heki rooflight 'glass'!

 

[hilldweller]

I'm sure he'd supply & fit whatever I asked for . They seem that sort of business..

120W is bigger then my 100W.
Just tell them to fit MPPT, it should be little ( or no more ) expensive and you not be thinking "should I, shouldn't I" forever.

I didn't spot the price. See here: Link Removed

 

[Minxy]

120W is bigger then my 100W.
Just tell them to fit MPPT, it should be little ( or no more ) expensive and you not be thinking "should I, shouldn't I" forever.

I didn't spot the price. See here: Link Removed

Unfortunately MPPT controllers can be a heck o fa lot more than a standard one ... for example for our camper's install I used a PWM LR1218 which costs around £70, to get a LRM1218 which is the MPPT one it would have been double!

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[Langtoftlad]

DIY is not an option .
My local [trusted] fitter is not significantly cheaper.
So, @Minxy Girl you also chose PWM?

 

[sallylillian]

I agree with Brian, if there is a chance that my solar output can be improved in more testing light conditions I would take it, and I did, got the factory to fit an MPPT when back for last warranty stuff. Someone on here did a live comparison, maybe @Techno, cannot remember.

 

[Minxy]

DIY is not an option .
My local [trusted] fitter is not significantly cheaper.
So, @Minxy Girl you also chose PWM?

Yes, our previous MHs/campers had always had PWM and we'd never had any problems whatsoever with insufficient charging from our solar panel which was only a 75w. Even though our new panel was only 60w I felt the improvement in electronics/design since we bought the original would make it near enough the same output and sufficient for our needs.

Our PVC has the Schaudt electrobloc in so it made sense to use a LR1218 or LRM1218 controller that connected straight into it rather than using another make which would then need modifying/an extra bit to charge both hab and cab batteries. As the PWM controller had been fine for our other use I realistically couldn't see the point in paying double for an MPPT controller as I felt that if I needed more efficiency/power, I'd be better off increasing the size of the panel, or adding another. As it turned out even with our small panel and doing 2 x 45 days trips last year without hook-up we never once came close to running out of power so the extra expense for the MPPT would, in our case, have been a waste.

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[hilldweller]

Someone on here did a live comparison, maybe @Techno, cannot remember.

He did do some testing. Trouble is to do it thoroughly is no back yard and multimeter job. You need to try almost endless combinations of available temperature and light with flat to near full batteries. Not at all trivial.

It may be out there on the www.

 

[hilldweller]

I used a PWM LR1218 which costs around £70, to get a LRM1218 which is the MPPT one it would have been double!

Yes but German pricing.

 

[Cal54]

Originally I had a single 100 wt panel fitted with a PWM controller. A year later I added a further 100wt panel installed, and changed the controller to an MPPT type. The later set up cost less than £300 when done at the Malvern show. My intention was only ever to tour in the uk but my van has a compressor fridge (which I love) and sufficient power to run this whilst wild camping at rallies etc was the major factor in adding an additional panel.

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[Minxy]

Yes but German pricing.

Not sure they're much, if any, cheaper than in the UK by the time you add postage:

LR1218
http://www.idealo.de/preisvergleich/OffersOfProduct/4049365_-lr1218-schaudt.html

LRM1218
<Broken link removed>

 

[stevec]

Mppt controllers work better when the panel is at low temperatures as the differential between the panel voltage and battery voltage is higher (solar panels output voltage goes down as it's temperature rises) so the advantage of an MPPT controller over a PWM is reduced. It would be more advantageous in cooler climates however. Uprating the solar panel to a larger wattage would probably be more cost effective. Having said that I fitted an MPPT (LRM1218) and 260W of panels (max my Electrobloc would handle). If fitting it yourself to a new van it will affect your habitation warranty unless you get the dealer to install the cables for you (which my dealer did at no cost).

 

[DBK]

A Victron MPPT controller for a 120W panel will cost about £80. Don't spoil your new MH by fitting something cheaper! And get them to fit a battery master as well if it isn't already in the spec.

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[andy63]

Only from what I've read.. I can't rovide any evidence but I always go for mppt. . Hoping that it will preform a bit better in the winter months in terms of getting something out of the available light..
Andy.

 

[funflair]

MPPT for me, I have two controllers fitted on different panels originally one was PWM one MPPT and over months I compared output from each, I then changed PWM to Votronic MPPT and the output jumped by 25% to 30% so it convinced me MPPT all the way.

It's only £90 for a 165w Votronic MPPT or £120 for a 240w Votronic MPPT unit with "AES out" that will run your AES fridge on spare solar power.

Link Removed

Martin

 

[TheCaller]

The Votronic (as opposed to the Victron) is already dual output, so no Battery Master needed.

To fully exploit the potential of the MPPT controller, the array voltage should be substantially higher than the battery voltage.

What this quote from Victron means in practice is that MPPT controllers really come into their own when you have multiple panels wired in series, to increase the input voltage to the controller. They continue to charge the batteries at lower light levels when a single panel, PWT controller setup would have shut down. But they don't magic up any more light, just keep using what little there is. So they are better at keeping batteries topped up over winter while the van is just sitting there with the alarm slowly draining the battery. But the difference on a UK summer day will be less marked.

So much depends on where, when & how you use the van when determining whether the extra cost of an MPPT controller will be worthwhile. If you need to extract the maximum from the available roof space, especially in the winter, then they are the way to go.

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[funflair]

The Votronic (as opposed to the Victron) is already dual output, so no Battery Master needed.

What this quote from Victron means in practice is that MPPT controllers really come into their own when you have multiple panels wired in series, to increase the input voltage to the controller. They continue to charge the batteries at lower light levels when a single panel, PWT controller setup would have shut down. But they don't magic up any more light, just keep using what little there is. So they are better at keeping batteries topped up over winter while the van is just sitting there with the alarm slowly draining the battery. But the difference on a UK summer day will be less marked.

So much depends on where, when & how you use the van when determining whether the extra cost of an MPPT controller will be worthwhile. If you need to extract the maximum from the available roof space, especially in the winter, then they are the way to go.

I asked Votronic technical man in Germany the question parallel or series? and his answer was parallel.

Martin

 

[hilldweller]

What this quote from Victron means in practice is that MPPT controllers really come into their own when you have multiple panels wired in series, to increase the input voltage to the controller.

That would surely work with any controller.

Dull - only 13V on panel, but 26V on a pair in series so can charge battery, BUT so little light it will only be milliamps.

The way MPPT works is to vary the current taken until it peaks and use that current.

 

[TheCaller]

That would surely work with any controller.

It would work with any controller that can accept the higher input voltage from multiple panels in series. In practice, that limits it to MPPT controllers.

This low light function is only one of the benefits of MPPT. It happened to be important to me because I have to rely on solar to keep the batteries charged if the van stands for a while. This applies whether I'm in it or not at the time, but I still need to get as much power as I can from the limited UK winter sun.

As you say, on a dull winter's day, it doesn't amount to much, but it's just enough to trickle charge the starter battery.

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[Lenny HB]

In low cloud on top of a mountain in April in Spain with 20yds visability, with 200watts solar and a MPPT regulator I was still getting 25 watts . With a PWM regulator it would have been zero.

 

[TheCaller]

I asked Votronic technical man in Germany the question parallel or series? and his answer was parallel.

I think a lot depends on where & when. For example, use for touring in the UK in summer & Southern Europe in winter would suggest parallel. You would almost always be above the switch-on voltage & have less losses from panel shading. If I had access to EHU for charging when not in use, I'd also go for parallel, especially if I didn't use it so much in winter. I'd still use a MPPT controller though, personally.

 

[MitchandJenny]

In low cloud on top of a mountain in April in Spain with 20yds visability, with 200watts solar and a MPPT regulator I was still getting 25 watts . With a PWM regulator it would have been zero.

Isn't that 2 amps ? ? ?
Mitch.
PS. Serious question

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