Confused about Solar Input Specification

[John.DS99]

I have a spec sheet for an all in one charge controller / mppt / inverter.

Under Solar Input Specifications it shows:
Rated Power 8000W
Max PV Array Open Circuit 500VDC
PV Array 90VDC - 450VDDC
Max Charging Current (PV) 120A

I think I understand the first 3. What is Max Charging Current? The solar panels don't charge anything, so why is this listed under Solar Input?
Shouldn't Max Charging Current be listed under Charge Controller?

Thanks

 

[Hedges]

That does mean charge controller output.
(PV) distinguishing from what charge current it would produce from AC input.

There will be an efficiency difference (heat generation, stress on electronics) depending on PV voltage. Some data sheets include a curve. Dropping 450V to 48V has more loss than dropping 90V to 48V.

 

[Supervstech]

So you don’t try to route all solar at 90V?

Keep the maximum amps below 120A.

 

[Mattb4]

Which AIO? Some of these have some rather wonky specs or weird ways of stating them. For instance the first one of 8000w. If under Solar Input you would figure that meant the amount of PV panel wattage. However it could be the inverters AC wattage output side.

 

[Hedges]

Actually, for an AIO rather than an SCC charging battery, higher PV voltage could be more efficient. Many if not most AIO use HV DC rail > 340V (120/240Vrms) or > 170V (120Vrms), so must have buck/boost arrangement to accept 90V to 450V.
If it was straight buck or straight boost, PV voltage close to DC output would be best. I'm not sure whether that is true for buck-boost.

Most of my stuff is AC coupled, so PV goes straight to AC voltage, and battery charging/discharging is an additional step.

 

[SamDeleted]

Max Charging Current (PV) 120A

I think thats the maximum amps it can push into your batteries from the solar panels

 

[SeaGal]

My guess is same as @SamG340 's... 120A sounds a lot to me for the PV side of things. Not sure any PV panels can generate 120A unless they are pre-owned NASA ones?

Let alone the current capacity of an MC4 connector ??‍?

 

[Supervstech]

My guess is same as @SamG340 's... 120A sounds a lot to me for the PV side of things. Not sure any PV panels can generate 120A unless they are pre-owned NASA ones?

Let alone the current capacity of an MC4 connector ??‍?

Parallel panels all add up… the panels would only push what they are rated for, but put 20 in parallel, and wow, does the amps climb…

 

[SeaGal]

Parallel panels all add up… the panels would only push what they are rated for, but put 20 in parallel, and wow, does the amps climb…

Of course, but with 20 in parallel and min 4 in series (to get the volts), you're talking of an 80 panel setup on an inverter rated at 8kW

As a minimum, to have enough in parallel for 120A, you'd need around 8 parallel circuits, then you'd still need min of 4 in series to get enough volts... so still 32 panels on an 8kW inverter... and why would someone configure a system like that?

Maybe it's just a technical limitation, rather than a practical one ?‍

 

[John.DS99]

Thanks for all of the comments. The all in one system I am talking about has the attached spec sheet. My simple thinking has been based on my playing with few panels in series, so I wasn't thinking about how parallel systems are hooked up.

Lots to consider.

 

[EastTexCowboy]

The Max Charging Current is the cap on how many amps it will put back into the batteries. Keep in mind that if you install two of these for split phase 240v it will double the charging amps to the battery, so up to 240 amps. There's nothing wrong with that but you need to make sure you design your system to handle it.

On putting your panels in series, you should manage the maximum input current draw to keep it at or below the 18a specification. The inverter will clip it at or a little below 18a but you're wasting usable panel output so you're losing efficiency. I know because my panels are a little over 10a and I did two strings per array so I end up losing about 10% of the capacity due to my poor planning.

More importantly, you don't want to exceed the max PV array open circuit. With the 500v capacity that should be relatively easy to do but don't forget to allow for cold temps. Your panel specs will include temperature coefficient to let you calculate this.

 

[EastTexCowboy]

I forgot to mention that you can adjust the max charging rate on the inverter, both on PV charging rate and AC charging rate. The default on the AC charging rate is 30 amps, as I recall. So if you only want 80 amps or 100 amps of PV going to charge the batteries you can do so. I still recommend building your system to meet the maximum.