110 VAC inverter installation

This is what it looks like:


INSTALLATION


This is the storage tray over the spare tire and the 12V battery cover. There is a slot the right size for a switch/circuit breaker.


Removing the storage tray reveals several slots in the 12V battery cover that can be used to route cables.


Laying the circuit breaker in the slot, mark the outline and mounting hole.


This is a 120A, 12V circuit breaker with a switch function. Pushing the red button raises the small, horizontal bar, the switch.


Here the circuit breaker/switch is mounted on the 12V battery cover in the slot of the storage tray. The ON/OFF switch is open.


Walmart sell various 4 gauge wire kits that have swaged terminals on each end. The 70" one worked perfectly and I returned the others. In this case, we removed the curved part, leaving the flat battery terminal bolt section. You will need some additional, swag terminals depending upon the final wiring configuration. AutoZone and WalMart both carry them.


The +12V battery terminal cover has a Dremel slot cut so the now flat part of the cable can connect to the terminal and still close the cover.


Here is the storage tray side of the 12V battery cover with cables and the Anderson connector. Granger sells them but they can be found from various sources. This one is rated at 120A. In my case, I used a swag tool to connect the terminals but one could solder with a big-nice person soldering iron. Notice I've used tape and other plastic protectors to identify the B+ cable and protect it from accidental shorts.


Here the 12V cables are connected including the +12V cable using the slot. As for the ground cable, use the frame end of cable to minimize the risk of a small nut on the terminal post clamp falling off and requiring the whole battery assembly to be removed to recover it.


Here is the battery cover, circuit breaker/switch, and Anderson connector ready to go.


A second Anderson connector and the remaining cables used to make a connection to the inverter. BTW, this inverter is way too large. Nothing over 1.2 kW makes sense and even a 1 kW inverter with a 1.2kW surge would be a better match. I'm using a sine-wave inverter because I plan to drive a room air conditioner. Although a modified sine-wave inverter could be used, they are not motor friendly and have to tested with every potential load.



Here is the inverter in the storage tray, powered up and ready for testing.


One of the better test tools is a Kill A Watt power monitor. It can read out voltage, amps, watts and a host of parameters needed to characterize the load.

I have more testing to do including fuel consumption, power and testing with the room air conditioner. However, initial testing revealed:

	Column 1	Column 2	Column 3
0	[th]watts[th]amps[th]comments[tr][td]750W[/td][td]7A[/td][td]Input 13.1 V DC voltage means this is a stable load.[tr][td]1	200W[/td][td]11A[/td][td]Input 12.5 V DC indicates we are probably drawing power from the battery	exceeding the inverter output.[/td]

The static battery voltage started at 12.55 and other sources indicate 12.8 V is the maximum, static battery voltage. If the operational, input voltage is lower than the static, starting, car-off, voltage, the battery is being drained.

I still need to put 1x1 studs on each end to raise the bottom to improve cooling. Unlike my earlier, NHW11 installation, the inverter will be removable but for now I'll probably just carry it in the storage tray with the circuit breaker/switch open.

My next tests will run the 925 W room air conditioner and monitor the 12V battery voltage. Every socket and connection will be temperature tested with an IR thermometer looking for hot spots. We'll also measure the voltage drop across every junction to get an idea of connector power losses. This endurance test will also give some initial fuel consumption numbers per kWhr.

What got me busy on this was helping to jump a stalled car outside of a grocery store. I'm thinking about getting a second Anderson connector, a high current Schottky diode, and jumper cables. If I have to do it again, I'll have a safe set of cables that even if someone should accidently try to reverse jump, nothing will happen. <grins>

BTW, my NHW11, a 2003 Prius, has a similar ~1kW power limitation. I have not done the test but I suspect the NHW20 can also sustain a 1kW power load on the 12V bus.

Since I've got a much larger inverter than a single Prius can drive, I am thinking about how I might augment it. One option would be a power, solar array. Another would be to Schottky connect a second Prius to provide additional amps. I have 'options.'

Comments?
Bob Wilson

 

The NHW11 has a 100A fusible link and the ZVW30 a 125A fusible link. Assuming the amp ratings are there to protect the wiring, I would expect a heavier gauge wire to the battery. We also know the 12V DC-to-DC inverter in the car is variable voltage from the "new car features."

These are also two different installation approaches. The NHW11 has the inverter permanently mounting in the trunk on a hinged, plywood side-wall using the shortest, possible directly connected cables and the NHW11 used a different model, 12V battery.

In contrast, the ZVW30 inverter is removable. I tried to find a place to mount it but the storage tray needs to be removable to access the spare tire and the corner over the battery didn't work either. Since it is removable, the cabling has three connectors that my NHW11 does not have:

1. Circuit breaker/switch junction
2. B+ Anderson connector
3. Ground Anderson connector

Part of my testing will measure the voltage drop across each junction using my VOM and also the voltage drop across the 4 gauge cable. This will also let me judge the quality of my swaged terminals.

If my testing shows excessive voltage drop, I may go with a set of permanent cables and a 'stand' on the cable end. The inverter would store in the storage tray yet one could pull it up and stand it upright over the battery cover when accessing the spare tire. This would eliminate the connectors and use a 100/125A fuse for the circuit breaker. But I would also want a second, chafing shield around the B+ cable.

A second option would be to mount the inverter to the battery cover. There would be some loss of hatchback volume, the corner over the battery. However, it would minimize the cable lengths and could still be laid on the spare tire when the battery needs replacement. This would also protect the cables so a chafing cover would not be needed.

The inverter has its own cooling fans and the 1x1 mounts will provide air space under the unit. It has thermal protection so I normally don't worry about it.

Bob Wilson

 

Hi Richard,

As much as I like the idea of running from the traction battery, I still have problems getting accurate information about the internal, power bus of UPS units. My fundamental problem is not having the circuit schematics.

To my thinking, the best solution would be spoofing the MG2 inverter with a switch that ties either two or three legs to 120/220 VAC outlets, and a microprocessor that handles the resolver inputs. The software would spoof the inverter to generate the synthetic AC. Everything is there but the connectors and software to drive the MG2 inverter. Power would be limited by the amp ratings of the sockets more than anything else. Three independent, 15-20A circuits, separated by 120 degrees would be available.

I have a spare, NHW11 inverter that someday may be my test article.

Bob Wilson

 

An interesting thought:

When the cargo cover is in place it provides some additional structural support for the rear floor. I don't use it but had never considered its secondary purpose of reenforcing the hatchback floor area. But I prefer having emergency power when the lights go out. <grins>

Bob Wilson

 

None that I'm aware of.

My NHW11 testing indicated the earlier one had no problem. I only observed a voltage drop when the current draw got in the 89-90A range. I've already put a 1.2kW load on the inverter and the voltage dropped to 12.5V suggesting we're in the battery buffer range.

It is hard to tell from the image the model Prius. It is substantially different than the NHW11 and I suspect it is not the ZVW30 inverter.

The schematic shows a 125A fusible link so I suspect it can handle the current.

Bob Wilson

 

We are thinking along the same lines. Sad to say, only my wife's ZVW30 has an electric compressor. But I suspect it is an adaption of a commercial compressor and likely to be using a Japanese-style, AC source, and probably at a fixed frequency.

Bob Wilson

 

Sad to say, initial testing with the existing air conditioner failed. I suspect the overload protection circuit in the inverter shut it down before the compressor started. I was hoping the 1.5kW inverter with 3kW surge could handle it. Once running, the AC current draw is only 9.25A but the AC compressor inrush may be too much and go on too long. I'll have to break out my instruments and take some measurements.

First I need to measure the startup load of the air conditioner and then see what happens when the inverter tries to crank it up. The solution may be as simple as a soft-start circuit that limits the startup load to 1.5kW for some finite length of time. Since the compressor normally cycles, it needs to be a little smarter than the normal circuit.

I also have a second air conditioner, an earlier, smaller unit, that may work. It certainly is worth a quick test.

Last year, I saw an even smaller unit at Home Depot last year and if they still carry it, a quick test. During a summer power outage, we only need one room cool enough to sleep.

The last option is the 5,000 BTU window unit.

Bob Wilson

 

Nicely done!

I tried to read the watts but no luck. I also checked the current Cobra web site and it looks like they now have LCD read-outs. What I didn't find was whether these are modified sine-wave (price suggests they are) and their rated efficiency.

How long have you had it?

Thanks,
Bob Wilson