For completely off-grid SMA-powered system, why do you need both PV Inverter and Battery Inverter?

[DAM]

[USER = 18831] @DAM [/ USER] Se você definir as tensões de carga e de flutuação do seu carregador CC meio volt abaixo das configurações do carregador do Sunny Island, ele funcionará bem.

Microsoft Office Translator
Very nice So any mppt load driver, even if it's not sic50 or Midnigt (these I think they communicate by Can). Will SMA be able to add additional load data for monitoring purposes as well?

 

[DAM]

This might be worth breaking off into another thread rather than hijacking this one but the biggest issue I see here is the EMUS BMS. It's unlikely that it can talk to both the Victron and the SMA system on the same CAN bus network due to them both using the same CAN-IDs (0x351 etc) on the bus with slightly different formats of the values (as I recall). It would be worth asking EMUS about this. If they can talk to both at the same time, you are set. Just use a Venus GX and connect it to the CAN bus network with the SI and EMUS. Otherwise, your Victron MPPT will be charging without any control from the EMUS BMS. You could approximate the settings and hope for the best (they do have a lithium profile per se) but I would not advise it.

What type of lithium are you using?

I'm sorry to hijack this topic, but as you were talking about matters related to i thought it might help me in my concern.
My Litio is lifepo4

 

[toms]

Microsoft Office Translator
Very nice So any mppt load driver, even if it's not sic50 or Midnigt (these I think they communicate by Can). Will SMA be able to add additional load data for monitoring purposes as well?

No, you won’t get the additional DC coupled data via the SMA portal.

 

[DAM]

Toms, you know some installation working this way with SMA+ AC+DC +BMS (sma + Load Regulator+ BMS). Lithium or Acid? On my system I have a Data Manager sending data to the portal Wouldn't si add this DC energy generated by victron and count it as production with data transmitted by BMS? There may also be a way to get monitoring in the local Ennexos and in the portal, because there is the possibility to add spidware devices, Can and others. Can't add a meter somewhere?

 

[toms]

I have a system set up with a Sunny Island 8.0, a SunnyBoy 5kw AC coupled, and a Flexmax Fm80 DC coupled. I use a REC BMS, and this logs all current in and out of the battery. I only briefly looked at the data on the SMA portal, it only showed the input from the Sunnyboy, and the useage of the Sunny Island.

 

[Thingol]

To elaborate on Hedges point with the shunt: I have installed and calibrated shunts on SI systems and although I have not tested this, as far as I know, the SI will measure the total current entering the bank and not exceed the total maximum set in the SI. So if the max is 40A (set in the SI settings) and it's reading 30A charging from the CC, it will only add 10A. Now again, I have NOT tested this but I believe this to be the case.

In that situation, a person would need to manually set a max charge rate on the CC. Also with the Classics, as far as I remember, if you have a WhizBang Jr installed, you can set separate charge and load max amperages. Again untested but I remember a note about that from either MidNite support or perhaps someone else on their forum.

A 6KW SB + 6.0H SI will set you back around $4K before installation.

A Victron Multiplus II 5KW with a 250/100 Charge Controller would be close to ~$2,400 before accessories/installation. Now that is only a 5KW inverter with a 100A charge controller. The 250/100 is specced for a nominal input of 5800W. The output wattage will be dictated by the battery voltage x 100A - losses.

IE 48V * 100A * 0.99 = 4,752W

You do have issues here with the maximum charge current. I'm not sure if Victron has a way to compensate for loads vs charging amps. I should investigate this.

You could also consider a 5KW Victron Multiplus II with a Fronius Primo 5.0-1 5KW PV inverter. This would be overall cheaper than SMA for an AC-Coupled system. Around $2800 before installation and accessories. If I was recommending something of the above options, this would probably be it. The high voltage strings (up to 1000V) make the PV installation much cheaper.

The max PV you can AC-Couple to the Multiplus II 5KW is 5KW (1 to 1 rule). So you could install a bigger pv inverter but it wouldn't do you any good, you would have to limit its output to 5KW. With the 5KW Fronius, you could still connect 6KW of panels. It's called over-provisioning and we do it commercially all the time. It would help you in the evenings and on cloudy days.

The Multiplus II EasySolar unit does look nice. I was never very impressed with the original series like the 5K you mentioned. Just my opinion though. The Multiplus II Easysolar 3K is not a super bad price either.

For me, the biggest issue with the all-in-one units is repairability and downtime. For example if the internal charge controller fuse blows, I believe it has to be repaired by them. With a Victron multi-component installation, you'll be able to instantly replace or limp along on another part (even from another brand) while having something repaired or replaced. That is just my opinion but I'm an installer so I have a bit of a different point of view perhaps. I want to be able to get my client up and running instantly when something goes down. In my humble opinion the all-in-one units, for as tempting as they are, make that a little more difficult.

Personally I'm installing the Victron Multiplus II 5KW units with SMA 4KW Sunny Boy inverters. I'm also installing SI6048's but that's for larger systems. Overall I like the price of the Victron system. The SI's I can still get for under $2700 (less if refurbished) but Victron MP II units have a lower zero-load wattage (18W) which helps on small systems. Plus the monitoring solution is much cheaper (CCGX or Venus GX) than SMA's Data Manager M + COM Gateway.

Plus for $2700, I can almost install 2x Victron MP II 5KW. So 10KVA as compared to a single 5,750W SI6048.

Very good point about the system's modularity and ability to limp along when something fails.. The Easy Solar is in fact quite modular: you could literally piece it apart into the usual components. It's just neatly boxed up..

 

[evotech]

I have gotten 4 different answers to a similar question from the techs at SMA. I see no obvious reason why I can't simply use an MMPT charge controller to charge the battery bank and then feed the Inverter AKA DC Coupled. (in my case SB7000US). There has to be a simple way to prevent overcharging. Right? SMA is offering me ridiculously complicated and expensive solutions to what seems like a simple problem. I am speaking off a completely off-grid application.

 

[Hedges]

I have gotten 4 different answers to a similar question from the techs at SMA. I see no obvious reason why I can't simply use an MMPT charge controller to charge the battery bank and then feed the Inverter AKA DC Coupled. (in my case SB7000US). There has to be a simple way to prevent overcharging. Right? SMA is offering me ridiculously complicated and expensive solutions to what seems like a simple problem. I am speaking off a completely off-grid application.

SB7000US?
That's a grid-tie inverter, not meant to be fed with batteries.
Although, people have used batteries with a Sunny Island for grid support.
It does not form a grid for off-grid use, at the very least doesn't have the right firmware.
Some newer models will deliver usable AC directly off PV during grid failures.

You can improve on "expensive" with an SMA battery inverter new from eBay.

I have both configurations of Sunny Island working, both AC coupled and DC coupled.

With DC coupling, the SCC can use its own settings for battery charge modes, usually constant current of everything it can deliver bulk, followed by constant voltage absorption, then float. Or lithium settings. In most cases, it doesn't know if current actually goes into battery or is used by Sunny Island, so if available amperage is more than battery should receive it gets cooked.

Some charge controllers like Victron can use a shunt and regulate battery current. That should allow higher current from PV when consumed by inverter, but regulate battery current to target.

For DC coupling, some charge controllers (Sunny Island Charger from MSTE or Midnight Classic) can talk to Sunny Island for voltage an charge mode. But they do not regulate a particular charge current.

The other configuration, AC couping, is where you would use SB7000US. In this case, Sunny Island regulates battery charge current to target level. You can have much more PV capacity than a small battery wants, but still charge it at target current. The Sunny Boy will be told to increase and decrease its output according to AC power needs.

For a lead-acid battery, I would definitely recommend AC coupling, with Sunny Boy or another inverter supporting frequency-watts. You can add some DC coupling, but not more than maximum desired charge current.

I don't have experience with lithium. If you use it of course it may accept higher and variable current so you don't usually need a low regulated charge current. But you will have to address reduced current for some temperatures.

 

[MurphyGuy]

I have gotten 4 different answers to a similar question from the techs at SMA. I see no obvious reason why I can't simply use an MMPT charge controller to charge the battery bank and then feed the Inverter AKA DC Coupled. (in my case SB7000US). There has to be a simple way to prevent overcharging. Right? SMA is offering me ridiculously complicated and expensive solutions to what seems like a simple problem. I am speaking off a completely off-grid application.

Ya, SMA tech support is a bit finicky to work with when it comes to technical questions when you're doing something unique.

So you want to use an MPPT charge controller to charge a battery bank, then hook up an SMA Grid tied inverter to that bank? That doesn't make sense.
While solar panels will feed the grid inverter's DC inputs, that DC voltage has to be up in the >200+ volt range for it to work. Where are you going to find a DC Charge controller that operates at those voltage levels? And 200 volts is the minimum.

I think if you have a high voltage battery >200 volts and hooked it up to the MPPT inputs on the inverter, it would blow the inverter due to exceeding the inverter's maximum input current.

Grid tied inverters aren't designed to be hooked up to batteries on their MPPT inputs.. you'll let the smoke out.

Use a Sunny Island and AC Couple it.

You use both AC Coupling and DC Coupling at the same time on the same battery, but you need the correct components to do it.