All in one unit suggestions

[NMNeil]

After running my mini split A/C on solar for the past 2 years I've decided it's time to expand my system. After watching Mr. Prowse video on the advantages of the all in one units I thought that would be the way to go, but I seem to have run into some problems, or I'm asking too much, not sure which.
I have the roof space to install two long strings of twelve 250 watt panels giving me about a 6Kw system. Southern New Mexico sunshine, 6.5 hours a day, south facing roof at almost the perfect angle and nothing anywhere near to shade them. As this will be more than enough to power my whole house I plan to give this a try later on.
The advantage that the utility company has is that if/when out power goes down I just have to call them, and they fix it within a few hours. If I am off grid I'm out of luck until I can fix it myself which, if I need parts can take days or weeks. So as a precaution I plan to run 2 independent systems each feeding into their own breaker box, so if one system quits I still have power, albeit reduced.
Looking at some of the all in one units on ebay, I found that a few will accept a PV Voc maximum of 500 volts. As the Voc of my panels is 37V, a 12 panel series string would be 440V, so this looked promising, but all the units I've looked at with a high Voc input only output 240 volts single phase.
Can any forum members point me at an all in one unit, MPPT with a Voc max input of about 450 - 500 volts, with either a 240 split phase or 120 volt single phase 3Kw output.
I'm using a 48 volt battery bank, which at the moment is SLA, but when they quit I may move over to lithium.

 

[snoobler]

You should consider not running 12 panels in series to open up your options. I have 9 panels in a 3S3P configuration with another 9 waiting to be installed for a total of 3S6P at just under 6kW. MANY folks run a xSyP configuration to optimize their panel configuration for a given SCC or AiO.

Personally, for something I truly want to count on, I'm not buying a cheap AiO MPP Solar, Growatt, etc. I'm sticking with Victron, Outback, Midnite Solar, etc., with separate charge controllers. AiO units are going to be that much heavier if they have quality components in them. IMHO, the advantages are ONLY price and possibly a smaller footprint on the panel, and both are had at the expense of reduced reliability and poor surge capacity.

 

[NMNeil]

You should consider not running 12 panels in series to open up your options. I have 9 panels in a 3S3P configuration with another 9 waiting to be installed for a total of 3S6P at just under 6kW. MANY folks run a xSyP configuration to optimize their panel configuration for a given SCC or AiO.

That was my original plan, to have 6 panels in a 3S2P configuration, to give me 4 'blocks' of 1.5Kw each. Then have a 40A MPPT controller for each block, then 2 separate 3Kw pure sine inverters from the batteries.
But the simplicity and economy of the 500V all in one units by having just 2 strings, intrigued me.

 

[snoobler]

You're sacrificing flexibility and options for perceived simplicity.

There's a potential efficiency loss. The greater the disparity between the PV input voltage and the battery voltage sacrifices efficiency. For me it's abut 200kWh per year due to 3S vs. 2S. The lower losses due to higher conductor efficiency can offset this, but if you have short runs, it doesn't matter much, and you lose 1-2% efficiency for every doubling (or so) of PV voltage.

 

[NMNeil]

You're sacrificing flexibility and options for perceived simplicity.

There's a potential efficiency loss. The greater the disparity between the PV input voltage and the battery voltage sacrifices efficiency. For me it's abut 200kWh per year due to 3S vs. 2S. The lower losses due to higher conductor efficiency can offset this, but if you have short runs, it doesn't matter much, and you lose 1-2% efficiency for every doubling (or so) of PV voltage.

Thanks for that, I had no idea that you would lose that much power by using the higher voltage. I always thought the MPPT circuitry compensated for that by boosting the current.
I'll stick with my original plan then.

 

[400bird]

The efficiency loss depends on where you are going with your output power. If your going straight from solar to AC power the high DC voltage is more efficient to go straight to 240VAC. If you can use the majority of your PV during production this is better.
If you are using a charge controller and DC coupling your solar, then yes, string voltage near battery voltage is probably better.

Higher voltage means less lost in wiring between the panel and inventer.

 

[Haugen]

Have you considered using a SolArk?
You spend a bit on the front end, but they are one of the most efficient systems round trip to the battery.

 

[dmholmes]

Personally, for something I truly want to count on, I'm not buying a cheap AiO MPP Solar, Growatt, etc. I'm sticking with Victron, Outback, Midnite Solar, etc., with separate charge controllers.

Would something like this work with the Victron MultiPlus Compact 12/2000/80-50?

PV -> SCC -> 12v LiFePO4 -> inverter/ATS -> 30A manual transfer switch (set to Gen) -> service panel

 

[Hedges]

If most of your power consumption occurs while power is produced, or for net metering, high voltage PV string to AC could be the most efficient.
That is how mine runs, 380 Vmp strings, Sunny Boy, grid tie.
During power failures the oversized PV system runs A/C and the like directly. Sunny Island usually has batteries full, so production is curtailed. Overnight batteries drain and in the morning they recharge, but batteries are small (about 1 hour's PV production.)
If planning to operate off-grid from power stored in the batteries much of the time, then round trip efficiency matters. But even then I'd try to use power when it is made (enable/disable loads according to available power.)