Multi-String High voltage MPPT with communication for large / multiple battery banks.

[ksmithaz1]

I find it interesting, that you can buy a Growatt inverter that supports 2 strings up to 7000W of PV with 550v VOC, for less money than than a couple of 500+ V mppt's by themselves. I've looked found nothing much for HV MPPT, the EG4 is a single string albeit 5KW, . I think someone should build an 4 input MPPT that possibly would communicate with inverters? that handles 500+V strings in the 15A range, to manage additional solar panels that are used for charging up larger battery banks. Most folks have a fairly finite need for AC output, after which additional inverter output is no longer desired, you just want to divert the power to storage. Was curious what others think, as it appears folks are just buying inverters when all they really want is the SCC/MPPT portion of it.

 

[AntronX]

Hybrid inverters that have 500Voc limit use simple non isolated boost DC-DC converter internally to boost PV voltage to inverter HVDC bus. Stand alone HV MPPT controllers have to use additional DC-DC stage that converts high voltage down to 48V DC. The former method uses a lot less parts and is more efficient. To replicate that with additional external MPPT you would have to tie it direct to HVDC bus which is not accessible from the outside in these 48V battery hybrid inverters. And you would need inverter's own 500 - 48V DC-DC converter to handle that extra power to step it down to 48Vdc. Makes sense to just get another hybrid inverter and disable internal inverter output to save on stand by loss. This post has nice diagram of this topology: https://diysolarforum.com/threads/t...tery-and-inverter-to-mains.74684/#post-946431

 

[Brucey]

I find it interesting, that you can buy a Growatt inverter that supports 2 strings up to 7000W of PV with 550v VOC, for less money than than a couple of 500+ V mppt's by themselves. I've looked found nothing much for HV MPPT, the EG4 is a single string albeit 5KW, . I think someone should build an 4 input MPPT that possibly would communicate with inverters? that handles 500+V strings in the 15A range, to manage additional solar panels that are used for charging up larger battery banks. Most folks have a fairly finite need for AC output, after which additional inverter output is no longer desired, you just want to divert the power to storage. Was curious what others think, as it appears folks are just buying inverters when all they really want is the SCC/MPPT portion of it.

Consider a Victron rs450/200, four mppt channels, max voltage is 8 times battery float level. Closer to 400V than 550V. Will has a great video on the 100A version (2 strings).

Ve.can daisy chaining and communication with Victron inverters via a Cerbo GX or similar.

 

[Zwy]

I find it interesting, that you can buy a Growatt inverter that supports 2 strings up to 7000W of PV with 550v VOC, for less money than than a couple of 500+ V mppt's by themselves. I've looked found nothing much for HV MPPT, the EG4 is a single string albeit 5KW, . I think someone should build an 4 input MPPT that possibly would communicate with inverters? that handles 500+V strings in the 15A range, to manage additional solar panels that are used for charging up larger battery banks. Most folks have a fairly finite need for AC output, after which additional inverter output is no longer desired, you just want to divert the power to storage. Was curious what others think, as it appears folks are just buying inverters when all they really want is the SCC/MPPT portion of it.

My experience was the EG4 6500EX's would limit PV input to 3.9Kw with a 4.24Kw string. One could split the string in 2 and half the string to one MPPT and it might do better, however the voltage drop over 420 feet one way might have hurt yield. But I did run half a string to a MPPT on the LV6548 and compared it to the EG4 100A MPPT (which is rated to 5.5Kw, not 5Kw but can only put out 100A).

This was what I found back then with testing the LV6548 MPPT to the EG4 MPPT 100-48V. https://diysolarforum.com/threads/mpp-solar-lv6548-6-x-545w-canadian-solar-panels.70621/post-895658 Results were interesting. The higher voltage 8S string would harvest more than double the 4S string at lower voltage in full sun. The 4S string would output more than half in overcast conditions. Most likely due to power loss related to string amperage.

One aspect you are missing is many times an inverter MPPT will have a much lower output wattage than input wattage. The EG4 6500EX for example has a max 120A output for charging but that is 60A per MPPT not 120A per MPPT. https://diysolarforum.com/threads/pv-input-power-vs-charging-current.70186/post-888090 The reason is the MPPT in an AIO can output to the HV bus and thus one can pull in more watts than used for just charging.

I had considered keeping the 6500EX's and using them solely as SCC's with the ability to have backup inverters. However, the limits on charging output per MPPT made me reconsider. With a dedicated SCC, I can output the full input (minus conversion losses).

 

[ksmithaz1]

Consider a Victron rs450/200, four mppt channels, max voltage is 8 times battery float level. Closer to 400V than 550V. Will has a great video on the 100A version (2 strings).

Ve.can daisy chaining and communication with Victron inverters via a Cerbo GX or similar.

To my point It's $2000.00

 

[Zwy]

To my point It's $2000.00

One could buy 5 EG4 MPPT 100-48V for that price........

 

[rhino]

One could buy 5 EG4 MPPT 100-48V for that price........

I have to believe there are going to be differences between the two

 

[Brucey]

One could buy 5 EG4 MPPT 100-48V for that price........

Sure, the rs450 is not the optimum choice if you are looking to maximize Watt/$.

Prob something like four 250/100s for $613 each, gives you 400A of charging. For about the price of a 450/200.

Victron MPPT 150V/250V VE.Can SmartSolar Charge Controller | Current Connected

Harness the power of the sun with the Victron MPPT VE.Can Charge Controller - fast tracking, versatile settings, and effortless connectivity options.

www.currentconnected.com

 

[Brucey]

Personally I would prefer the passive/silent smart mppts versus the fan cooled rs450s.

 

[Hedges]

I'm planning to use Sunny Boy Smart Energy.
Around $2500 for 7.7kW model, which has 3 MPPT, can take in 15kW of PV, charge high-voltage battery with up to 10kW and deliver up to 7.7kW of AC. $0.17/W

Probably street price will drop 25% after a while.

With HV bus and keeping voltage high, it can be fairly economical and efficient. Output is shoehorned into 120% rule of a 200A panel. It is both grid-interactive and grid forming (requires external hardware for backup.)

Non-isolated keeps things simple and cheap. GT PV, that means PV array rides on AC voltage. With battery, I wonder if that does too? Or if they isolate that.

Sure, the rs450 is not the optimum choice if you are looking to maximize Watt/$.

Prob something like four 250/100s for $613 each, gives you 400A of charging. For about the price of a 450/200.

Victron MPPT 150V/250V VE.Can SmartSolar Charge Controller | Current Connected

Harness the power of the sun with the Victron MPPT VE.Can Charge Controller - fast tracking, versatile settings, and effortless connectivity options.

www.currentconnected.com

About $0.10/W ~ $0.12/W depending on battery voltage (SCC only, but to LV battery)

 

[Zwy]

Sure, the rs450 is not the optimum choice if you are looking to maximize Watt/$.

Prob something like four 250/100s for $613 each, gives you 400A of charging. For about the price of a 450/200.

Victron MPPT 150V/250V VE.Can SmartSolar Charge Controller | Current Connected

Harness the power of the sun with the Victron MPPT VE.Can Charge Controller - fast tracking, versatile settings, and effortless connectivity options.

www.currentconnected.com

Less PV string voltage using the 250/100. For example, I have my array 420 feet away and I wanted higher string voltage to minimize wire size/cost plus less voltage drop. If I wanted to stay under 250VOC, then I could have just used the LV6548 MPPT's.

Higher PV amps lead to higher power loss which is exponential. https://diysolarforum.com/threads/how-long-should-wire-be.41580/post-589561

 

[Zwy]

I have to believe there are going to be differences between the two

Sure is, the price.

If you just want a SCC with 500VOC rating, both will work to provide power and charge a battery.

The only thing gained with the Victron is communication with a central hub if that is important to you. I don't see it as that important, I don't use battery comms either.

 

[rhino]

Personally I would prefer the passive/silent smart mppts versus the fan cooled rs450s.

The only piece of equipment I know of that takes high voltage PV array and has no fans is a Morningstar TriStar MPPT 600V which is about $1100 and only takes a single string.

 

[rhino]

Sure is, the price.

and noise

There's a lot of differences people glance over.. Self consumption of the EG4 is 25W compared to 15mA on the Victron. That's quite a bit of heat/inefficiency difference. Victron is also fully isolated.. along with other differences.. so you do in fact get a higher quality product so it isn't exactly a 1 to 1 comparison solely on price... whether those differences matter to you is up to you.

 

[Hedges]

There is a thread discussing SCC that killed BMS and over-voltaged batteries.
A non-isolated SCC, if FETs short, can do that.
One that isolated (at least positive lead transformer isolated, negative lead can be common between battery and PV), if it isn't switching, no power delivered.

 

[rhino]

There is a thread discussing SCC that killed BMS and over-voltaged batteries.
A non-isolated SCC, if FETs short, can do that.
One that isolated (at least positive lead transformer isolated, negative lead can be common between battery and PV), if it isn't switching, no power delivered.

This got me thinking.. relating to high voltage SCC failing or even other surge events that may damage your BMSs.. what if you had a Midnite 115V SPD on your battery cabling? That would seem like a good safety addition that could mitigate that?

 

[Hedges]

SPD can snub thousands of amps and thousands of volts, but only for microseconds. Can't protect against PV over voltage or anything else with power behind it. The IV curve of MOV is too sloppy as well, so can't use it to flip a switch. Need accurate voltage measurement against a reference circuit.

Something like BMS that detects over-voltage and sends a signal could turn off a remote-trip breaker.
I have a non-isolated charger SIC-40, with "overvoltage" signal. I plan to use it that way.
Easiest is to buy an isolated charger. Midnight Classic reportedly is (and survives PV Voc up to max voltage rating plus battery voltage.)

 

[Zwy]

and noise

Victron has fans too.

There's a lot of differences people glance over.. Self consumption of the EG4 is 25W compared to 15mA on the Victron.

EG4 consumes nothing when it isn't running. I'll wager the Victron does not shut down when PV input drops to 0 as it runs communication which will draw power. The EG4 does shut down.

If you're concerned about it taking 25W when running with 5000W PV input, you have some serious issues.

That's quite a bit of heat/inefficiency difference.

With the fans running on the Victron, what is the self consumption? I can assure you it isn't 15mA.

Victron is also fully isolated..

The 2 Victron MPPTS are isolated from each other, the EG4 only has one MPPT. You're kinda stretching things there.

Maybe you need to read this concerning Victron MPPT's. https://community.victronenergy.com/questions/25541/isolation-of-mppt-solar-chargers.html

along with other differences.. so you do in fact get a higher quality product so it isn't exactly a 1 to 1 comparison solely on price... whether those differences matter to you is up to you.

The idea behind a stand alone SCC for the intended purpose of this thread is to simply charge batteries and provide power on the DC bus of the system.

We don't know if the Victron is higher quality or not. You are assuming it is. It might be the same quality, after all, the Victron mentioned is built in India.

Time will be the judge on whether the quality of either unit is superior to the other.

 

[Zwy]

There is a thread discussing SCC that killed BMS and over-voltaged batteries.
A non-isolated SCC, if FETs short, can do that.
One that isolated (at least positive lead transformer isolated, negative lead can be common between battery and PV), if it isn't switching, no power delivered.

Prove the EG4 unit isn't isolated.......

at least on the positive lead. Most likely it copies Victron which is common on negative.

 

[Hedges]

The 2 Victron MPPTS are isolated from each other, the EG4 only has one MPPT. You're kinda stretching things there.

Maybe you need to read this concerning Victron MPPT's. https://community.victronenergy.com/questions/25541/isolation-of-mppt-solar-chargers.html

"Accepted answer" i.e. not authoritative.

It doesn't address at all the issue of whether the MPPT charger will "fail safe" or "fail deadly".