Inverter dilemma

[Bandannaman76]

Greetings! I've recently installed a power system. My inverter is a Sun Gold Power LPF series 5kw, controller is Epver tracer series 10415AN 5kw and running 8 Amerisolar 250w panels for 2kw with the option to upgrade to eight more for a total of 4kw, and my battery bank consists of 16 12v 150ah gel sealed batteries ran 48v series/parallel. Inverter has grid tie capability, but for now I just want to isolate my shop to cut energy costs. When my shop is disconnected from the main and I power up my system everything seems to work as I'm getting power and have no issues with controller or inverter, but when I turn on my air compressor it will not function and the overload warning on the inverter kicks in. Battery bank is is at 57-58v, so it's pretty much fully charged. My question is do I need to hook up to grid power even though I don't want to use that power? The inverter display does show an error message that it does not sense 240v input as it's not hooked up to it. I'm thinking that since inverter does not have any AC input as a baseline, it defaults to keep battery bank charge as primary and AC power out as secondary, thus minimizing amps. Inverter manual does state that it will run power tools including air compressors, and electric motors up to 5hp. Compressor motor is 5hp and the amps at 15. Thanks for any any all help!!!

[Mike90250]

....... Inverter manual does state that it will run power tools including air compressors, and electric motors up to 5hp. Compressor motor is 5hp and the amps at 15. Thanks for any any all help!!!

That's a pretty big claim for a 5kw inverter. Sure it will run them, but I doubt it can start much more than a 3hp motor. The starting surge requirement is likely well beyond what the inverter can manage. Somewhere in your inverter specs, should be some peak output/overload graphs, and that will tell you what it can start.

The power factor (PF) of the motor will also increase the demand on the inverter


XWsurgeSpecs.gif

XWsurgeSpecs2.gif

[Ampster]

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I'm thinking that since inverter does not have any AC input as a baseline, it defaults to keep battery bank charge as primary and AC power out as secondary, thus minimizing amps. Inverter manual does state that it will run power tools including air compressors, and electric motors up to 5hp. Compressor motor is 5hp and the amps at 15. Thanks for any any all help!!!

Your thinking is correct that the inverter is minimizing Amps to not overly discharge the batteries. I am not familiar with that inverter but it may be configurable based on the size of your pack. If not it may just need some surge capacity from the grid to start those power tools then it will probably run off batteries. It only needs that capacity for a few seconds at the most.

Mike summarized it well above.

[Bandannaman76]

Thanks for the input. There is no "surge current" rating in the manual, just states that it can run up to 5hp motors. I figured that there needs to be an ac input for baseline. I'll hook up input, fire the system up and throw the breaker and see what happens. I'm hopin' that once the inverter initially senses ac input it will use that data and when I isolate my shop it will continue to base that initial data to keep peak load output.

[Bandannaman76]

Forgot one thing... inverter specs do state that surge rating is 15kw for 20 secs, but nothing anywhere about amperage load capacity.

[Ampster]

At 240v that would be 60 Amps AC. I am sure that would work when on the grid. The issue I would want to explore is whether there a limit on battery Amperage. At 48 volts that same 15kW would be 300 Amps DC. Let us know how your experiment works out.

[Bandannaman76]

Well... hopefully I'll never see the peak wattage, just stating what the inverter rating is. I have a 150 amp breaker on the bank. Just out of curiosity and ****z & giggles, what if the 240vac input comes from the inverter via sub panel that is powered 240 vac from the inverter via batteries? Most of the time the shop is idle so there would be minimum demand. Would the system along with solar keep itself charged, and when I'm pulling a higher demand working in the shop the inverter would sense an input voltage drop and then priority the batteries to take the load? Better to ask a stoopid question than make a stoopid mistake.

[Bandannaman76]

OK, I replaced the 4000w/12000w peak inverter with a 12000w/36000x peak and viola, my 5hp compressor will start and restart when air pressure drops, and inverter demand is around 34-36% at that time. Now what happens is my 150a 12v dc circuit breaker pops off about a minute after the compressor restarts to top off . All of my cables are 2awg, but I bought some 4/0awg for the bank to inverter thinking the problem is the bottle neck there. The problem now is that the terminals on the 4/0 are way too big to attach to the breaker so I'm looking for any suggestions for a compatible breaker for 48vdc battery bank?

[Mike90250]

Midnight is my go-to for large DC breakers, but they are not cheap, here's 3 of them

http://www.midnitesolar.com/productPhoto.php?product_ID=202&productCatName=Breakers&productCat_ID=16&sortOrder=15&act=p

http://www.midnitesolar.com/productPhoto.php?product_ID=578&productCatName=Breakers&productCat_ID=16&sortOrder=3&act=p

( this only goes up to #2 wire )

http://www.midnitesolar.com/productPhoto.php?product_ID=364&productCatName=Breakers&productCat_ID=16&sortOrder=19&act=p

[Bandannaman76]

Great! Thanks for the info. I'll order one and update progress.