Standalone MPPT more efficient on small arrays?

[ilprepper40]

Hi All, first post here....

Currently iterating over a few solar designs which I plan to implement starting next spring.

Plan is to start small/simple with parts decision based on potential upgrade path (leaning heavily towards Victron at this point)

The question I've been pondering is: for smaller arrays, do standalone MPPT controllers (ex. Victron 150/45) generally perform better production-wise when compared to the integrated MPPTs in many AIOs?

Some color for this question: I have a multi-angled roof, and plan to start with one section which should fit roughly 1kW PV. Most of the MPPTs in AIOs I have noticed have a much higher startup voltage (120v for the EG4 IIRC) than those in standalones. This leads me to believe that, at least for a smaller array, a standalone controller will be sending power for longer in the day -- a smaller array wont reach 120v until closer to peak, where as Victron for example startup is vBat+5v...

Am I on the right track here?

 

[timselectric]

The voltage comes pretty quickly when the sun starts to rise.
Then the MPPT starts to draw current. Which pulls the voltage down. The MPPT will adjust the draw to keep the voltage and amperage at the peak wattage output.
So as long as you have enough panels to get into the voltage range. You should be producing power, most of the time.
Of course more intense sunlight, gives you more power.

 

[740GLE]

I was able to power our camps small electrical needs all summer with a 100/15 Victron SCC and 70w (50w and 20w, one east one west) worth of PV keeping 460ah LiFePo 100%.

We are weekend warriors and would draw down 10-15% over 72hrs at the camp. DC Diaphram pump was probably biggest use for water/shower needs. We have a 1500w inverter that’s isolated when we’re not there, so the only load was the BMS and the Victron unit, on good days it’d pull down 270whr with minimal standby usage.

As I add more load now the camp is wired for 120v (coffee maker, more lights, maybe a TV) I’ll need more PV to be able to meet the loads. I can’t forsee needing 120v when we’re not there so I’ll always use separates or a AIO with high standby consumption.

 

[Rednecktek]

The voltage comes pretty quickly when the sun starts to rise.

Depending on location. I haven't seen over 90v on my arrays (130v+ in sunlight) since I put them in service due to the clouds and fog burning off right about sunset.

I see the biggest advantage to multiple MPPT's when you've got smaller voltage systems (especially 12v) where 2x 40a SCC's are MUCH cheaper than a single 80a unit, or when you've got arrays facing different directions like an eastward and a westward.

 

[timselectric]

Depending on location. I haven't seen over 90v on my arrays (130v+ in sunlight) since I put them in service due to the clouds and fog burning off right about sunset.

I see the biggest advantage to multiple MPPT's when you've got smaller voltage systems (especially 12v) where 2x 40a SCC's are MUCH cheaper than a single 80a unit, or when you've got arrays facing different directions like an eastward and a westward.

I'm guessing that the 90v is after the MPPT applies the load. And adjusted for the maximum amperage available.

 

[Rednecktek]

I'm guessing that the 90v is after the MPPT applies the load. And adjusted for the maximum amperage available.

No, I've measured it a couple times at the combiner box opening the breaker and sticking the probes on to see if it was the lack of sun or the Growatt drawing down the voltage or the infamous MPPT Morning Voltage Lock issue. All 3 tests were well below the 130v+ I got when the sun was out, the highest reading was 91.6v out of the combiner box when it WASN'T connected to the Growatt.

Weather just sucks for solar unless you live in the shartiest places on earth.

 

[timselectric]

Very interesting

 

[sunsurfer]

I'm running multiple victron 100/30. On one of my systems, I notice they start up around 1 watts and 28v very early in the morning. These are small 500w strings. They ramp up from there. This is a 12v system. Max out put is around 52v from panels and 420watts per string.

Victron SCC have been very fast for me and seem good for low input capture. I also have wondered about how fast the cheap AIO mppts are.

 

[ilprepper40]

Depending on location. I haven't seen over 90v on my arrays (130v+ in sunlight) since I put them in service due to the clouds and fog burning off right about sunset.

I see the biggest advantage to multiple MPPT's when you've got smaller voltage systems (especially 12v) where 2x 40a SCC's are MUCH cheaper than a single 80a unit, or when you've got arrays facing different directions like an eastward and a westward.

I am planning to run a 24v system and yes roof angles are all different direction, so each roof plane would essentially get it's own array/SCC

I'm running multiple victron 100/30. On one of my systems, I notice they start up around 1 watts and 28v very early in the morning. These are small 500w strings. They ramp up from there. This is a 12v system. Max out put is around 52v from panels and 420watts per string.

Victron SCC have been very fast for me and seem good for low input capture. I also have wondered about how fast the cheap AIO mppts are.

'low input capture' is the phrasing I was after, thank you. I would imagine voltage comes up quickly in a large array, yes. I have a 100w/12v system running lights in my shed and noticed it will pick up 5-10 watts as early as 6am in the summer and that is with the panel facing west. Therein lies my thinking that for smaller arrays, smaller, properly sized SCC is a better choice

 

[sunsurfer]

I am planning to run a 24v system and yes roof angles are all different direction, so each roof plane would essentially get it's own array/SCC

'low input capture' is the phrasing I was after, thank you. I would imagine voltage comes up quickly in a large array, yes. I have a 100w/12v system running lights in my shed and noticed it will pick up 5-10 watts as early as 6am in the summer and that is with the panel facing west. Therein lies my thinking that for smaller arrays, smaller, properly sized SCC is a better choice

Sounds like an easy solution for your diff roof pitches. Side benefit is much more redundancy if something fails. What kind of battery are you going to be charging? I noticed slight bouncing around for a few seconds sometimes on my lead acid system with 5 victron controllers. I get zero bounce with 6 charge controllers on my lifepo4 system. The lead acid resistance to charging is the issue. I'm going add a large car stereo capacitor to see if it flattens out the voltage bounching. Just something to be aware of. Not an real big deal but it might or might not be noticeable. None of my SCC are in sync with each other. It works just fine. Works flawless with the lifepo4.

 

[ilprepper40]

Sounds like an easy solution for your diff roof pitches. Side benefit is much more redundancy if something fails. What kind of battery are you going to be charging? I noticed slight bouncing around for a few seconds sometimes on my lead acid system with 5 victron controllers. I get zero bounce with 6 charge controllers on my lifepo4 system. The lead acid resistance to charging is the issue. I'm going add a large car stereo capacitor to see if it flattens out the voltage bounching. Just something to be aware of. Not an real big deal but it might or might not be noticeable. None of my SCC are in sync with each other. It works just fine. Works flawless with the lifepo4.

Yeah, when all complete, I'd have 3 roof arrays, and possibly a 4th on the ground as well.

I did consider lead acid, and priced out a bank of Trojan batteries, but in the end, cost is about the same as with lifepo4 when considering deeper DOD. Leaning towards EG4 or SOK rackmount

 

[Tomthumb62]

Having used a Renogy Rover MPPT (30A) for about 4 years, I recently switched to a Victron 100/30, which are the same input/output values as the Renogy.

It’s a night and day difference. My rough math suggests the Victron produces about 30% more than the Renogy. My hunch is it has to do with how much more quick and efficient the MPPT tracking is on the Victron.

The whole +5V above battery thing? I don’t notice it at all. From an end user’s practical experience, it makes not one bit of difference, at least to me. And at the end of the day, I’m producing more energy with the Victron.

I recently read one of the seasoned veterans on this forum, I think it was @sunshine_eggo , that it’s wise to spend more money on the charge controller for better production and features and quality, since it’s the brain of your whole solar system.

If you go cheap on panels, cheapish on batteries and high quality on wire, connectors and your charge controller, you’ll have made a wise investment. My only advice is that if you have a rather limited area to put panels, then don’t buy the cheapest. You can get a good deal by shopping around or buying used, but if you only have room for 2x100W panels, do some research to find the best quality for your budget.

 

[sunsurfer]

Yeah, when all complete, I'd have 3 roof arrays, and possibly a 4th on the ground as well.

I did consider lead acid, and priced out a bank of Trojan batteries, but in the end, cost is about the same as with lifepo4 when considering deeper DOD. Leaning towards EG4 or SOK rackmount

I going with SOK basic(no screen) 48v'ers on my next build. Seen to many EG4s fail. My neighbors failed.

 

[ilprepper40]

Thanks for the input all. I have a small Renogy controller in the shed (PWM no less) and now wondering how much more power it'd make on a better SCC like Victron

I have not read enough on here to know about failure rates on EG4 batteries, but would compare support and warranties among contender companies

 

[Tomthumb62]

Thanks for the input all. I have a small Renogy controller in the shed (PWM no less) and now wondering how much more power it'd make on a better SCC like Victron

I have not read enough on here to know about failure rates on EG4 batteries, but would compare support and warranties among contender companies

Well pretty much any MPPT controller will produce more power (I think the average is about 15-20%) than a PWM controller. PWM controllers can be fine and useful such as for small unimportant projects like keeping your '57 Thunderbird's battery topped off all the time. They can be had for as cheap as $9 on ebay/amz or $3-5 if you want to order from China.

But if you need to extract as much power from the panels you have, then buy the best MPPT you think you can possibly afford. Also, you can save money by buying a smaller MPPT and overpaneling it. For example, say your 30A MPPT is rated for 400W of PV input on a 12v system. Well, if you put 600-800W, you will more likely simply max out your MPPT on sunny days (extra power is just burned off as heat) and instead of only getting 260W production from your 800W PV array on a cloudy day, you'll get much more, perhaps more like 400-500W, depending upon lots of factors like temperature, panel tilt and the speed that your MPPT can keep tracking the Maximum Power Point (MMP of MMPT, the "T" means "tracking"). Better controllers like Victron are much faster/better at keeping tracked on the MPP and that alone can be worth the extra cost (I estimate 30% more production in my equally spec'd Victron compared the Renogy I used to have.) And the Victron "just works" compared the the nightmares the Renogy gave me and worse nightmares trying to deal with their customer service. I will probably never need to reach out to Victron support. Now I have joined the "victron community", which is a forum like this and staffed by some Victron employees to learn about how to use my new Victron products, but support in terms of the device doesn't work like I think it should I have not had to do. The community forum is basic but helpful. Most of my questions had already been answered and the search feature found what I needed.

 

[ilprepper40]

yeah MPPT vs PWM difference is clear for me; the Renogy was purchased before I knew the difference

 

[再生可能 エネルギー]

None of my SCC are in sync with each other. It works just fine. Works flawless with the lifepo4.

Kind of side question, does having a BMS connected and communicating with multiple SCC is critical or not ?
(for charging efficiency and battery protection)

Can you have a single SCC communicating with a BMS and the other SCC just plugged in parallel to the same battery?

 

[timselectric]

Not

 

[Rednecktek]

The BMS just balances and controls the cells in the battery, it doesn't really care how you're charging it.

 

[sunsurfer]

The question I've been pondering is: for smaller arrays, do standalone MPPT controllers (ex. Victron 150/45) generally perform better production-wise when compared to the integrated MPPTs in many AIOs?

I was hoping someone would comment on any experience of the AIOs MPPTs vs Victron (or equivelent). I keep hoping Will or someone with access to both could do some side by side test. I'm really curious how fast the AIO MPPTs are. Its all about speed.

Anyone????