OFF Grid - EV charging from inverter - Grounding issues

DrDnizzy

Hey all, I am having trouble charging my 2013 Nissan leaf from my pure sine inverter. The 24VDC inverter is pulling from a 24V battery bank. The PV system and the battery bank setup is not grounded. I am getting a ground fault reading (blinking green light). After reading some forums, I tried to provide a ground-neutral bond between the AC output of the inverter and the 120V charger. The car indicated it was charging but it did not. The inverter read only 43W output and then read a fault (red light) shortly after.  How do I properly ground the system to get the charger to work right? Thoughts?

BB.

Have you measured the voltage at the AC outlet? Hot to Neutral=120 vac, Hot to ground=120 vac, Neutral to ground ~ 0 volts? Is the AC outlet a GFI type?

How many watts is the AC inverter? Howe large (AH) is the battery bank? How many Watts is the Leaf charger?

-Bill

Ocean

Ground your system.  Get a copper grounding rod, and drive it into the ground near your inverter setup.  Run a ground wire from the rod to the ground bus bar - or at least to the chassi of the inverter.  Neutral-ground bond should only happen once somewhere in your system - it might already be happening in the inverter so check the manual on that.

If installing a ground rod is not realistic at the moment, look for something else which is metal, and buried deep in the ground.. such as galvanized steel water piping, or a well casing.  Ground your system to that.

BB.

In general, while earth grounding is important for lightning control and, to a degree, reduce galvanic corrosion... It does not usually matter to a GFI or random electrical/electronic device.

I do not know about your charger, but some UPS system (uninterruptible power supplies for computers) check to make sure that there is an electrical connection between AC neutral and earth ground (white wire to green wire). If not present, the UPS would not turn on (or required a manual startup).

-Bill

DrDnizzy

Thanks Bill and Ocean, My charger for the leaf does check for an AC neutral-ground bond. The inverter does not have a ground-neutral bond. Using a power strip and edison plug, I was able to create a ground-neutral bond. Then I temporarily grounded the ground-neutral bond to the my house copper ground. This did not seem to work. My inverter may be the problem. It is a cheap chinese version supposedly pure sine but who knows. 
Regarding grounding to PV system. I intend to ground the inverter to the ground bus on the DC breaker box and ground this to copper ground. Will I still need to ground the AC output of the inverter? Could I ground this AC ground to the house ground or is this dangerous? Is it ok to create a ground-neutral bond between the AC output  and charger? Thanks! 
-Dan

BB.

If you have a MSW type inverter, you cannot ground bond the neutral/white wire to safety ground (for almost all MSW inverters--always read the instruction manual). Especially, if the battery bank is ground bonded too (battery negative terminal is tied to safety ground). This will create a short circuit for the inverter and let out the magic smoke.

If the inverter is a PSW/TSW type inverter (pure sine wave), most of them will support a ground bonded neutral/white wire connection (PSW/TSW inverters usually have an isolation transformer on the AC output--again, check the manual).

I am guessing, but if the PSW/TSW inverter is 1,500 watts or smaller, they seem to usually have a floating output (you need to supply the ground+neutral bond, if you need it). If the inverter is >3,000 Watts, those generally have a ground+neutral bond already made internal to the inverter (I think--check manual/wiring/with an Ohm meter).

Sorry for the wishy/washy answer... It is mostly correct, but there are outlier inverters out there that have their own rules/designs that don't follow convention.

-Bill