Power sockets only 10 amps. Is this "normal?" What's it fused for?

Thanks much for the suggestion. I'm left wondering if I might rig a pigtail extension to wire the existing two outlets in parallel with 15A fuse and a heavy duty connector? Would that do?

 

Not generally a good idea; the two paralleled circuits will only "share" current very approximately, reflecting any resistance differences in the wiring or connections to each, and there's an undesirable failure mode when one of them develops high resistance (poor connection, say), both heating up and shedding more of the load onto the other one, which is then overloaded.

It's like the hot-weather electrical grid cascading failures, where multiple transmission lines serve an area, they start getting hot from all the current running people's air conditioning, the copper expands and the wires sag between poles. Eventually one sags into a tree, tripping its circuit protection. Now the same load is shared over n-1 wires, they heat up and sag even more, the next one goes, and ....

Does your oxygen concentrator only accept 12 volt input, or does it also have the option of running on house current? I would recommend making a proper connection at the battery with appropriate fusing in any case, but if going to that trouble anyway, I'd suggest putting in an inverter. You could easily run your concentrator if it has a house-current input, but you'd also then have great flexibility to plug other stuff in. Just adding a fat 12-volt circuit specific to the concentrator, not so much.

-Chap

 

No, sorry, I certainly wouldn't. It might work. But it could end up with either damaged wiring (or much worse). With the complexity of wiring on any modern car, it's not something to guess about. Plus, attempting something like that would have your insurance underwriter wiping their hands of any responsibility for any incident.

I'd be engaging an Auto Electrician to rig up a unique outlet for the machine.

 

Is there a safe way to tap the traction battery by stepping the voltage down and avoid having to go through the firewall with 10 gauge wire? I very much appreciate your sound advice on these matters.

 

The voltage is not like house current AC where you can step down with a transformer. D.C. requires some high voltage circuitry to lower the voltage.
I have worked with high voltage equipment and I would not attempt to do this.

 

No. DC voltage is easily reduced with a resistor based voltage divider. Notice I said easily, not efficiently. There are other, probably better, methods.

There is at least one oxygen concentrator that I can find, the Inogen One G3, that specifies 10A DC power draw. For that, a separately wired high-power circuit should do the trick.

 

A voltage divider only works if the current draw is consistent. You would also have the heat from the resistors to deal with.

 

...oh the traction HV battery...that's an advanced topic but I seem to recall some few have tapped into that, in some threads long ago. If I recall the reason for tapping in there would be to get more watts of power for the home emergency case.

Far more common and safe I would think is to hook an inverter on the 12V.

 

And flexible! Surely you can get an oxygen concentrator that has a regular plug for 120 AC. And then you can easily plug in all kinds of other stuff too, unlike if you worked out some single-purpose setup to run one particular DC oxygen concentrator.

-Chap

 

As you have asked the question if there is any way to step down the traction battery I assume you don't have the knowledge required to do that safely.

Yes, there is a way, using a specialized inverter, such as, coincidentally, the one in the car. This is NOT for "general public" messing. 200V DC WILL kill you. The output from the traction battery is protected from connection to chassis by GFI on -both- the positive and negative leads so you would have to try very hard to kill yourself, but DON'T DO IT!

The only reason anyone would have to access that voltage would be to get the high power it can provide. I understand one or two companies have made such inverters, including Toyota, for use in Japan. That one provides 100VAC 50 Hz, which is not suitable for North American appliances (voltage too low and frequency wrong). IF you could actually buy one, which you can't from my understanding.

We are stuck with the 12V DC output from the inverter that supplies the 12V system in the car (the battery, lights, and electronics). You can get about 300W continuous from that system (12V at 25 Amps), and maybe a little more. If you draw down the 12V battery or put in a bigger 12V battery and draw it down you can get more power from it for a short time. A 50 A-Hr battery would deliver around 600W for an hour. With the car on you could draw around 1000W for about an hour. After which the 12V system would need some time to recover, and you might overheat some major system parts in the process (it's not designed to supply such power). You WOULD have to properly engineer such a modification. We're talking a draw of around 85 Amps at 1000W. Voltage drops and resistive heating would be serious.

To get such power it's best to stop, unload your "Honda generator", and do your thing at 115VAC or 220VAC from the generator.

 

I’m not sure anyone outside of Toyota does, because the safety and longevity of the hybrid vehicle (HV) battery may depend on protections implemented by the HV ECU, which would be defeated by connecting a load directly to the HV battery that the HV ECU could not monitor or control.

For the 1500-watt inverter that Toyota offers as an option in Japan (page in Japanese), the output frequency is selectable between 50 Hz and 60 Hz with a jumper, as you might expect in a country that uses both frequencies. Here are the other specifications for Toyota’s inverter, from the Japanese edition of the New Car Features book:

Accessory Outlet (AC 100 V)
Output Voltage [V]: AC 100 ± 10%
Output Waveform: Sine Wave (With 1000 W resistive load connected, distortion within 5%)
Output Frequency [Hz]: 50 ± 2/60 ± 2
Maximum Output Power [W]: 1500​

The inverter (8624A-47020, ¥74,200), outlets, etc., are probably available from parts exporters, but I don’t know if they would work in a U.S.-specification car. I have no idea if the HV ECU in a Prius sold here implements the input (HCIV) and output (NOAC) signals required for inverter control, without which the battery protection would be compromised. The inverter is also incompatible with vehicles having a spare tire, by the way.

Agreed. Unless whatever you’re doing is properly integrated with the built-in protection features, trying to use a Prius as a stationary power source is just asking for expensive trouble.

 

As I said, not efficient. And the current draw should be relatively constant assuming the unit concentrates oxygen all the time. I can't imagine there is a way to store it in so small a unit.

 

[QUOTE="This is why Amateur Radio people are encouraged to wire directly to the battery, with an inline fuse at the battery. Heavier wire (#14 minimum, #10 prefered), proper connectors rated for the current etc. makes a big difference. ......................

Install a proper cable from the battery, with inline fuse at the battery, to be used ONLY when the car is in "ready". You can even install a relay in line with this cable, closed by "accessory" voltage, ensuing the cable won't work unless the car is on. Something I always do.[/QUOTE]

I would like to attach an inverter directly to my 12V battery. (2004 Prius) I'm a little wary of scouring the internet for the best way to do this. Is there a definitive 'how- to' source for doing this? So far I've gleaned that a 'pure sine inverter' is best....use proper wire gauge (above). Love to see an 'idiot's guide' on this. Any suggested sources? Thanks!

 

Here was the most recent detailed post I made on that topic.

Quick takeaways: near the battery in a Gen 2 is an easy and convenient place to tap, but you don't have to be obsessive about tapping at the battery posts; in fact, it's better if you don't. The reason is you'll be keeping the car in READY most of the time you're using power, and then the power you're using isn't coming from the battery, but rather from the converter at the front of the car.

Your inverter's negative input doesn't need to go on the battery negative post; you can follow the battery negative cable to where it screws to the car body. Put a proper ring terminal on your inverter negative wire and clamp it under that same screw. You now have a good ground connection and it is closer to where the power is coming from (the converter) than it would be at the battery end of that same wire.

Kind of the same for the positive wire. Instead of right at the battery positive post, put a ring terminal on and have it share the cable end of the large fuse that is built in to the battery positive clamp. Now your tap is (a) closer to where the power is coming from (converter at the front of the car), and (b) protected from the battery by a robust fuse. (There's another such fuse at the front, converter, end of that cable, so by taking your tap there, you have protection on both sides.)

Others may approach it differently, but that's my preferred arrangement.

Pretty much any inverter you might buy will have a manual showing how to calculate your wire gauge based on the load and necessary wire length, and you can probably read the manual on the web before even buying the inverter.

 

I've been using my Viair p70 rated 15A max and getting away with it. Maybe I'll throw some spare fuses in there as well. 70P Portable Compressor | VIAIR

 

I'd ask the question on the GEN 2 FORUM - there have been very significant changes since your car was produced. The GEN 2 owners would give more reliable answers.