Jay Kote avatar image
Jay Kote asked

Why should I choose a Victron MPPT vs other cheaper regulators?

I want to make clear that I am not doing this to put down victron products. The reviewer makes favorable points of Victron. But it's important for Victron engineering and management to know what others are thinking.

By the way, I agree with his point on wire gauge. The biggest mistakes I see people make is using cheap wire. Event "professional" installers do it. It's way to reduce cost without customer knowing. And conventional rule is 1 - 2% loss is acceptable. But not in solar.

Think of it this way: 17% solar panels are $1/watt. 21% solar is $4/watt. It's penny wise and pound foolish to loose 1 - 2% using even "acceptable" AWG. Over gauge everything.

MPPT Controllers
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boekel avatar image boekel ♦ commented ·

You've changed your entire post, would be better if you made a separate answer, as now the answers to your first post make much less sense..

On the wire loss, did you even calculate this?

Let's say 60 volts from the panels, 20A contoller, 24V battery (most RV's have 12V I think?), full output 20A at 28V = 560W (12V system: 280W)
on the wiring from the panels this would be about 10A for a 24V system, 5A for a 12V system.

With a 5 meter cable length between controller and a 6mm2 cable, your losses are:

24V system: 0.43%
12V system: 0.22%

so your 21% panels become 20,91% not a very big deal I think...

But...(there is always a...)

as you have a fuse between panels and controller, and between controller and batteries, you can upgrade the wiring to as thick as you like.

'losing 1 or 2%' is negligible, the accusations about installers using thin wiring might have a point in some cases, but I think when you really calculate the numbers there is nothing wrong.

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Jay Kote avatar image Jay Kote boekel ♦ commented ·

You use wire gauges and distances that have losses below 1% to assert what? Nothing other than what I said. Avoid losses and keep them below 1%.

I have changed nothing other than agree with a comment that was made in the video about using over-gauge and not accept traditional view that 1 - 2% loss is okay, because for solar its penny wise and pound foolish.

But yours is the superior intellect.

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ejrossouw avatar image ejrossouw boekel ♦ commented ·

I stand to be corrected, but V loss for 24v should be less than for a 12v system and not as per your calculation.

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boekel avatar image boekel ♦ ejrossouw commented ·

an MPPT unit can only give it's maximum current, so at 12V a 20A unit has less power than at 24V, as a result, the input side also has less power = current = less losses.

that's the good thing about 48V systems, 4x the power from the same MPPT.

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ben avatar image ben ♦ commented ·

The loss is 1-2% of 17-21%, not 1-2% of 100%. That means the loss is 5 to 6 times smaller than you are suggesting it is.

It’s still important to size properly and minimize losses, but the economics of saving on copper are not such a clear slam-dunk as you make it out to be.

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Jay Kote avatar image Jay Kote ben ♦ commented ·

I agree with your math, but not your economics.

The panels will be in use for 20 years. And the few dollars people save on going cheap on wiring is bad call.

For off-griders and those with limited roof space, need to be thinking how to save power every way possible .

If it goes well, I will be upgrading someone to a 12v refrigerator. The manufacturer said 8awg was fine.

But even with short distances there is a 1 - 2 wh loss. Thats 20wh-40wh per day.

Im going to use the biggest wire I can squeeze in. Most likely 2/0 but Im hoping 4/0.

Because people who live off grid cannot afford to loose even 1w.

Am I slightly off topic, sure. But its just another case of the same store. Use fat wires.

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ben avatar image ben ♦ Jay Kote commented ·

It’s true that you can have a situation where every watt is worth its weight in gold.

But as a counterpoint, I live off grid full time and could not justify the massive cost increase for the 21% panels. I traded W for $. No big deal.

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Tom avatar image Tom commented ·

One big advantage of the Victron MPPT over the Epever MPPT is the Victron with BT is so much easier to program for custom Lithium. The Eperve MPPT functions well once programed and does allow for thicker cables. The Epever PC program software does not work. Programing the Epever with the MT-50. Is possible but has to be done in small steps or you get an error. The Victron MPPT was outside my budget at the start of my RV solar project.

I replace a Zamp Solar PWM so I could move to Lithium and 24-36 volts battery system.

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6 Answers
boekel avatar image
boekel answered ·

Interesting, I've used Epever's before I switched to Victron MPPT's, I've had 3 Epever's die, 1 at 24V battery, 2 at 48V. the last one luckily didn't catch fire but it smelled very bad.
I stopped using 'cheap' products since then.

the Victron terminals are big enough for the rated current btw.

He might have other video's about pwm vs mppt, but it would be good if he explains why / when mppt is better (like being able to use the cheap 'generic / household' solar panels (vs expensive '12v' / '24v' panels), higher string voltage, etc.)

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Paul B avatar image
Paul B answered ·

It still gets back to backup and Quality and backup and support, who else has these sorts of forums and gives out such open advise and help,

Also the intergration with other victron Products.

The victron units have a 5 year warranty with a 10 year option.

plus service agents all around the world.

and VICTRON will be around still in ten years so if you need to you can still get them replaced if a fault did occurs, I dought that any of the others would be claimable after 1 year (stand to be corrected here)

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ejrossouw avatar image
ejrossouw answered ·

He does some interesting testing, but can only truly achieve credibility if he is more factual. The connector types is a clear example of his lack of adequate knowledge on wire cores, heat and proper connectivity. Also, why need a stronger brace if this it a static mounted device with your wiring secured. He needs to step out of his caravan, get some real world experience and then maybe I'll be more inclined to take some of his reviews more seriously.

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Jay Kote avatar image Jay Kote commented ·

His real world experience is valid as far as I'm concerned. There are LOTs of people putting solar on their RV. It's a huge market and only getting bigger as the RV industry is moving to "high-line" coaches. "High-line" is RV industry way of saying "all electric". And customers are asking for solar.

And it's fine to go with "acceptable" gauge wiring if you are tied to the grid. But if you are relying on solar, loosing even 1 - 2% is not acceptable. As I said in my updated comment, "penny wise and pound foolish".

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ejrossouw avatar image ejrossouw Jay Kote commented ·

@rvsolartech Everyone knows they get what they pay for (can afford) so I do't understand where you are going with this. Also there are so many ways to compensate as panel efficiency / technology / price have improved greatly, energy consumers became so much more efficient too. I'd be more prone to rather look at energy storage today as e.g. lithium batteries charge faster and more efficiently etc. so there is so much more than just thicker cables. As minimum, use the manufacturer recommened. In short, if you stick to reputable manufacturer's guidelines, devices will function optimally as designed. PS - Using mono panels in series, my system fires up at sunrise and stops at sunset, so a great way to compensate for unavoidable cable loss.

Back to the original topic, VICTRON serves the sailing community well where power is even more at a premium so ... I personally like their charge controllers for being very robust, efficient, reliable, user friendly, can handle coastal climate well, are great (probably world leading in some areas) in a connected world as my system is monitored from thousands of miles away. They have a great reputation / support in the global market unlike many of the products in the reviews which are country specific. They do with price fall in the middle to top end of the market. However, one likely thing in common for all the controllers in the review ... being manufactured in Asia ;)

PS - oversized connectors as opposed to a good tight fitting ones are often more inefficient / dangerous given the poor wire to surface contact when e.g. not using the recommended multistrand AWG etc.

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Jay Kote avatar image Jay Kote ejrossouw commented ·

Unfortunately, you don't always get what you pay for. You'll see situations where people are charged a boat load, but customer ends up with inferior work and product.

But more importantly, people for some reason want to save on wiring and don't realize that "you get what you pay for" even applies. All they know is it comes on. So I wish people DID indeed know you get what you pay for when it comes to wire. Very few people do in fact because very few people think system efficiency. They are just glad it works.

As for using oversize in small connection, I would add to your point. Danger is a stray strand or two can cause a short.

If you watch the video and think about it, the only real criticism of victron was the connection size. And I think its pretty much the only one that can be made.

I know no one likes to be criticized, but if taken the right way can be used to make something even better.

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ejrossouw avatar image ejrossouw Jay Kote commented ·

I will now close my end on this ;), but I think your overall point is actually about people being the weak link, whether it be doing a poor installation, buyers making less optimal budget driven decisions or giving bad advice. As for feedback, Victron is one of few companies where I see their management actively being involved in listening and acting within reason. (I work in change management and continuous improvement) As for the connectors, if it ain't broke or attracted similar comments before, why change it? Given Victron has an amazing small footprint for use on e.g. boats, RV where space is at a premium, I just cannot see how the other devices can even compete ... as they say, good things come in small packages.

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Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

I haven't watched the whole video yet and may update this answer if I get the chance.

But I quickly saw a shallow price/performance comparison between PWM and MPPT charge controllers.

Victron also has a cheap PWM, and PWM is cheaper and just as efficient when matched with suitable 36 cell panels. Though I rarely recommend it.

As soon as the system is bigger than 12V and a couple of 36 cell panels, you are FAR better getting 60 cell panels (300W+ each) and using an MPPT for both total system cost, and performance.

There are many other benefits too, and this blog post and white paper go into some details. Perhaps we also need a video ;)

This is all aside from Victron vs other brands in general.

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Mark avatar image
Mark answered ·

In my opinion the terminal size on the Victron 100/20 MPPT (6mm² max cable cross section) is perfectly adequate for that particular charge controller when used in a properly designed/typical solar system.

The realistic/typical system that I have mocked up below clearly demonstrates this with <1% loss;

If you really think that your going to get some notable gain by having well under 1% loss then I think you are mistaken. There are so many other factors to consider & weigh up.

If you are knowingly designing a 12v system with with high currents and long cable lengths, then it's really a poor overall design & should be avoided wherever possible.

Copper cable is very expensive & there are also diminishing returns by spending more money on thicker cable. Costs can quickly escalate if you are going to run a ridiculously large cable size over a long length.

Also note that in many cases you will be far better off ($/W) by having a few % loss in the cables and spending the extra money on more solar panels instead - that will offer a step improvement in solar yield.

You need to design smart and use higher voltages to your advantage.

For the same power transfer, if you simply double the voltage (resulting in half the current) then you can use a cable with only 1/4 the cross sectional area to achieve the same voltage drop %.

Accordingly if you increase voltage by 4x & decrease current by 4x (12v to 48v) then you will only need a cable with 1/16 of the cross sectional area to achieve the same voltage drop % - that's a huge difference.

The same logic applies to the PV, you should also be aiming run as high voltage as practical within the MPPT max voltage limitations. In most applications domestic panels (with Voc of ~40V DC) wired in series are the most cost effective and will work much better than a heap 12v panels wired in parallel. This is also the beauty of a MPPT vs PWM charge controller.

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Jay Kote avatar image Jay Kote commented ·

You have the luxury of roof space. RVs arely have space and one has to get very creative to get more then 1 or 2 panels on a lot of units.

Even in your example you are already at almost 1%. Think about people who have to run panel 20m away (2way wire).

Remember you have 6mm going to battery, but you also have 6mm from the panel. And yes, you could add a bus bar, but bus bar junctions can add loss too.

In addition, in RV you dont always have option to co-locate. The customer doesnt want to move house batteries. They also dont want to give up limited basement storage when they do.

In your residential world who cares. In RV and off grid, I stand by what I said, use as high a grade wire you possibly can.

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iostrym avatar image
iostrym answered ·

do you have any idea if victron will do a MPPT with a 40A load output ?

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adev avatar image adev commented ·

not from what I understand reading comments on this forum. Their stance seems to be it makes more sense to run larger loads directly from the battery. I agree that a slightly larger than 20A load output would be nice but it’s not the end of the world. I have the 100/20 and at some point I plan to switch to 24v battery/loads (with a 24v->12v converter for loads that can’t run on 24v) which will double the usable power from the 20a limit.

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