Portable Solar inverter and battery system

[David Amon]

At my solar site we have a single axis tracking system by Game Change. The system involves a node controller on each string that is powered by a small panel mounted on the rack with a battery that measures angle and controls angle through a DC actuator. These nodes communicate with a master controller that gets 120 AC power from the Inverter closest to it, but each master also controls about 2 1/2 inverters worth of Node controllers. If power is lost the master has a small battery that basically powers it for up to 4 hours, but after the first 2 hours of no AC power they signal all nodes to go to wind stow position. My problem is when I lose an inverter for a long duration that is powering a master I basically lose tracking for almost 2 other inverters worth of panels and over a month or so that can be a big hit to production.

What I am trying to do is instead of going and getting a gas generator to power the Master controller, I want to get an inverter/battery charger with about 100 AH of batteries at 48 VDC and make a portable solar emergency back up power system that I can mount on a small trailer and just trailer it out to the master and hook it in to regain tracking. Now I picked up a Mrpwr 5000 Kw solar inverter and (2) 50 AH 48 Vdc Lithium Ion batteries. As for panels I will repurpose some of the first solar series 6 panels that are already in the area and once tracking is regained they will also track. Looking at making about 4 strings of 2 panels in parallel. This should make my open circuit voltage in the upper 400 Vdc range and give me 3.5 kW of solar power into the inverter. This should be adequate to charge the batteries and run the load of the master which is has a 10 W standing load with up to a 60 W surge load (Surge load is when it charges it's internal back up battery.)

Now my question is probably a little late as I should have asked this before buying it, but the inverter is a grid tie inverter. In the settings though I can set it up to use solar power first then kick over to battery power with grid being a last resort that would not be available. What I am wondering is should this work as an off grid system? Or did I buy an inverter that will not work in this application? Maybe it will need jump started from an extension cord off the AC plug in the bed of the truck to get synced up to 60 Hz that I can then disconnect and let it run.

I have also considered that when the system is not in use it will still need to be plugged in someplace to float charge the batteries as long periods of time sitting idle for batteries is not good for them.

[solardreamer]

Sounds like you have the wrong inverter. Should use a pure off-grid inverter.

[David Amon]

Sounds like you have the wrong inverter. Should use a pure off-grid inverter.

After much research I found that my inverter is actually a hybrid inverter, so it should work nicely in this configuration. It will allow it to run on batteries and panels only when out in the field and when not in use I can bring it back to the shop and plug it into a power source to keep the batteries charged and float charge them to make sure they do not overly discharge and cause damage when not in use.

Unfortunately, in my crash course in solar the hybrid and off grid inverters were not covered since in a commercial setting of my size grid tie inverters are the only type that are used. It was really confusing me to see two AC connections on the inverter with one being input and the other being output since grid tie only needs one AC connection. I am fortunate that this little project is helping to educate me on residential equipment before I start buying as it would have been easy to make the mistake of buying a hybrid inverter that doesn't back feed grid with excess power when I need an inverter that will back feed the grid with excess power. Granted if you are having trouble with your local power company and the interconnection a hybrid system that does not feed power back onto the grid could be a good way to go if you are just looking at reducing your electric bill.

[solardreamer]

The term "hybrid" is often overloaded with different meaning by different inverter vendors. Without knowing the make and model of the inverter it's hard to know for sure what it can actually do.

[David Amon]

It is PowMr 5000W Solar Inverter 48V DC to 110V AC, 5KW Pure Sine Wave Hybrid Inverter Charger Built-in 80A MPPT Controller, Max 500V PV Input, for 48V Lead-Acid/Lithium Batteries

my panels are first solar series 6 or 6+ depending on where on the site I need power. Planning on 8 panels in 4 series strings of 2 each. If that isn’t enough I can add one addition series string of 2. If the system works as desired the panels will single axis track through a Game Change tracking system as the tracking system is what needs power as the master gets power from a central inverter that is down, but controls tracking for about a total of 3 inverters that are 3.6 Mw. So getting the tracking powered is kind of critical for plant efficiency.

I’ve got two 48 V 50 AH lithium batteries to maintain power overnight and during low irradiance times.

[solardreamer]

PowMr is one of the several companies that abuse/misuse the term "hybrid". Based on the description of the inverter you provided, it's just an off-grid inverter/charger with built-in solar charger (MPPT). It's not a "grid-tied" inverter. The utility/generator input is only used for charging battery. It should work fine for your needs.