Inverter on 12v battery

Discussion in 'Gen 3 Prius Technical Discussion' started by Terrell, Jun 3, 2013.

  1. ftl

    ftl Explicator

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    In all the threads on running a 1kW inverter from the 12V battery no-one has reported any problems with the DC-DC fuse nor with the car wiring.
     
  2. Terrell

    Terrell Old-Timer

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    OK, now I need to open it up and have a look at it.

    Do you know that it's 10AWG? Or are you saying that from what I said?

    I don't plan to pull 100A through it, but I would like to draw 800-900w.
     
  3. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    I don't have a GenIII so the 10AWG is going off of what you said.
     
  4. Terrell

    Terrell Old-Timer

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    I checked the space heater with a meter, and it looks like you are correct. I'm glad you are, because I would have been disappointed if the inverter switched off for just 683w.

    My experience with space heaters is very old school: you'd slap two coils in there, and switch one on for low heat, and both for high heat. I had a very old heater lying around, but I must have thrown it away because I didn't want anyone actually using it, it was a fire hazard.

    Still waiting for the custom cables to arrive so I can hook this up and test it more fully.

    Tomorrow, I have an appointment with Toyota for an oil change. I'll try to get them to tell me more about the wiring to the 12v battery.
     
  5. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I'm sorry for your problems and 10 gauge is way too small: American Wire Gauge
    table and AWG Electrical Current Load
    Limits with skin depth frequencies and
    wire strength
    • chassis wiring limit, 55A * 12V = 660W max!
    I'm going to recommend going to WalMart, automotive section and shopping for 6 gauge, 12V cables with swagged ends. Rated at 101A * 12V = 1212W, this will provide the minimum head room for your installation and the commercial connectors will help a lot.

    Look around for an adjustable heat source including an iron, hot-plate, hair dryer, or a high-intensity light. If you go by a hardware store, you can pickup a dimmer rated up to 250W, a light socket on lead, a 200W heat lamp, a 15A extension cord, and a wall-box. Just rig up the dimmer and extension cord so you can adjust the output voltage. Then plug the lamp into the extension cord. Put 500-600W on one inverter outlet and confirm everything is working. Then add the adjustable load on minimum setting:
    1. Measure 12V voltage at battery connection. If it starts to drop below 12.8V, stop the experiment, that is the maximum, sustained, 12V load!
    2. Run for 1 minute - carefully touch test the 12V cable at the connectors to feel for any heat. If hot, stop and properly reconnect the 12V cable. DO NOT OVER TORQUE!
    3. Verify the cable itself is cool to touch.
    4. Verify the inverter is not hot, verify where the heat is dumped.
    5. Increment the load, repeat steps 1-5.
    Bob Wilson
     
  6. Terrell

    Terrell Old-Timer

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    Today I was at Toyota for an oil change, and asked the service guy if he could tell me the gauge of the wire from the DC/DC inverter to the 12v battery. He had no idea, so he called someone to ask. He also had no idea, so I went to the parts shop, they looked it up, and said they see all sorts of info, but nothing about the wire size or capacity. Then I asked the service manager if he knew of anyone who knew, he checked around, and finally came back to me saying Toyota probably doesn't want to let people know things like that, but if he finds out, he'll tell me. He also was unable to tell me how much power the DC/DC inverter can supply to an inverter. He handed me an article he'd found on the web about the guy who powered his home with an 850w inverter during an outage (one of the many I'd already read). Hopefully my cables will arrive later today, and I can do some more serious testing.
     
  7. Terrell

    Terrell Old-Timer

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    I'm not good at guessing wire size, so it may be heavier than that. It's fused at 140A at the battery. I see from the table you mention that the chassis wiring limit is 55A for 10 gauge wire. I'll try to have a better look at it, and see if I can get my calipers on it to measure it to see what size it really is.

    There seem to be many others who are using a 1000w inverter, so I hope this will work.

    I've ordered 4 gauge cables, which I hope will arrive today.


    Bob, you've left something out in step 2: "Properly reconnect the 12v cable" - reconnect?

    Sounds like some good testing tips, Bob.
     
  8. szgabor

    szgabor Active Member

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    I have successfully tested such setup (connecting to the 12V battery pictures in the other thread) and found that TV lights were fine but the fridge tripped the inverter 1000W (2000W surge) pure sine wave. The compressor motor in the old fridge just too much inductive load.

    I have not used it continuously ... but remember some members did can someone comment who did use it for some time?

    I do understand the concerns 2K 1Toster but this is just theory at this point. btw I fused the input cable to inverter 85 A so I am not even trying to get 1KW. But hoping to run internet TV and hopefully the water pump of the heating system in emergency.
     
  9. bwilson4web

    bwilson4web BMW i3 and Model 3

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    We run it at least once per year but in April 2011, we ran 4 days and 6 hours.

    Prius - UPS Project

    We have a similar setup using a sine-wave inverter rated at 1.5kW continuous. I've tested it up to ~960W only to find the 120A, 12V circuit breaker and the Anderson connectors lose too much power. I am confident we can go to a sustained, 1kW once I take them out of the circuit.

    Bob Wilson
     
  10. szgabor

    szgabor Active Member

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    So if I understand this you were running sustained using the chassis wiring to the 12V battery without "melting" that ...

    And also others run similar setup. Final good solution when Toyota decide to provide OEM next to the 12V port seem to be a 120V size plugged opening in my 2012 Prius :)

    Yes 1KW over 12V even small resistance is brutal as I said my goal is more 750W top with this setup.
     
  11. bwilson4web

    bwilson4web BMW i3 and Model 3

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    I'm pretty careful about my wiring, especially power wiring. I'm a great believer in using non-contact thermometers early and frequently. We can't 'see' heat and you never want the smoke to escape.

    Bob Wilson
     
  12. Terrell

    Terrell Old-Timer

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    Thanks, it's encouraging to hear from others about this.

    This evening, I climbed into the trunk and measured the outside of the white wire that goes to the 12v battery at .28-.30, then tried to measure the insulation to subtract that (I can't get a good cross section to measure, because they crimped the wire so it's flat where it comes out), but it looks to be about .10-.11, so the wire would be .20 at best, and .17 at worst, or around 4-5 AWG, and possibly even 6 gauge. The wire is aluminum (why did they do that?! Just to save a few ounces of weight? Or to keep it from corrosion, because it runs along the bottom of the car? Both?)

    Maximum Ampacity for Aluminum 6 gauge is 50A, and for 4 gauge is 65A.

    If the DC/DC inverter supplies 14.4v, that would give 720w for the smaller wire.

    My cables from the battery to the inverter are 4 gauge copper, and a total of 53" round trip (4.42'), so there will be a voltage drop of .112v into the inverter, or 14.288v into the inverter, so now it's down to 714w. (I don't know how the Anderson connectors will affect things.)

    The 1000w inverter says it's approximately 85-90% efficient, so that leaves me with 607w (assuming the smaller wire size of 6 AWG) that I should be able to draw safely (and maybe more, if that white wire is bigger than 6).

    If there's a short surge, the battery will cover the surge temporarily.

    I have a 100A ANL fuse in my cable from the 12v battery to the inverter. There's a 140A fuse built into the 12v battery post connector to the DC/DC inverter. So I think I'm good as long as I keep my power draw to around 600w.

    Any serious flaws in my thinking, folks?

    Our refrigerator is fairly new, and Kill A Watt says it runs at 100w, but the sticker on it says 6A, so the start up draw must be huge compared to just running. So if it will start up, this setup ought to keep the refrigerator running. We also have a small chest freezer (100w running, but needs 653w to start up) that I hope to be able to back up, and the furnace, but I think the blower in it is going to be way over the top (I've not measured it yet).
     
  13. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Just a couple of load related things to consider:
    • Inverter surge - typically ~300 ms., 15-20 cycles, this is the inverter peak power rating. So my 1500/3000W inverter can provide power up to 3000W for a couple of hundred milliseconds IF the 12V supply can provide the current. If the battery bank is large enough and the conductors heavy enough, 3000W/12V ~= 250A. This is within the 'cranking' amp range of even our 12V battery yet brief enough the cables won't melt . . . but a fuse.
    • Load inrush - typically ~300-600 ms., this load can trip the 12V low. Many electronic power supplies including laptop power-bricks, are bad about having a diode bridge feeding a large capacitor. The inrush can be so bad that the plugs arc just plugging them in without a load! For this, I've used an inrush thermistor that starts high resistance but as it warms the resistance drops. The problem is the thermistor has to stay hot and that wastes power.
    • Motor startup - typically 1-3 seconds, this load can trip the 12V low. Induction and synchronous electric motors found in compressors and furnaces often have a somewhat complex startup load. If the 12V battery and cables are already running high loads, this can trip the 12V low circuit.
    I once left the house with the lights, an inrush risky TV and cable box, a box fan, all running on the 1.0/1.2 kW inverter. While I was out, something triggered a fault and the inverter and load went into a 3-5 second, loop: all on; 12V low trip, and; auto-reset back to all on. I thought it was funny but my wife did not appreciate the humor.

    I simply disconnected the inrush load, minimized the other loads, started the fan to get it running, re-connected the inrush loads one at a time (laptop, cable box and then TV,) and added the rest of the loads.

    When you realize how startup and inrush loads, you can 'camp out' at home. But it helps to test with the loads before a real outage. That is not a good time to be testing.

    Bob Wilson
     
  14. Terrell

    Terrell Old-Timer

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    Got it installed! I'll do a write up with pictures soon.

    Sorry I've not done this yet, I've been really busy. We've had lots of rain, and a flooded basement to clean up.
     
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  15. Danders

    Danders New Member

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    IMG_0667 (1).JPG I would like to see how you ran wiring from battery. I trial ran some
    #8 wire, also got a deal on a 1000W used inverter. I'm planning on
    using to charge RC plane batteries, instead on transporting heavy 125
    amp hour deep cycle. Also will use a power back up, just to run gas fireplace
    fan, TV and a few lights. <500 watts I also plan on maxi blade fuse 80 amp
    near + terminal.

    Advise gladly accepted, Thanks
     

    Attached Files:

    #35 Danders, Apr 23, 2016
    Last edited: Apr 24, 2016
  16. ILuvMyPriusToo

    ILuvMyPriusToo Senior Member

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    Thanks for sharing the details of this set-up. I am looking forward to the pictures. Are you planning a quick connect/disconnect?
     
  17. Terrell

    Terrell Old-Timer

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    Sorry to be so slow in getting back to this. I've made a video here on YouTube showing how I did it, complete with supplies and where I got them, and you can see wiring. Hope it's helpful!
     
  18. ILuvMyPriusToo

    ILuvMyPriusToo Senior Member

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    Thanks for the helpful video! Nice install!
     
  19. ChapmanF

    ChapmanF Senior Member

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    Hm, old thread I didn't see at the time!

    That fat white wire going to the single plug is not the one from the converter; that is in fact the wire back to the 12 volt battery itself. (Unplug it, when the car is off, and things will all go dark.)

    If you look just to the left of where that plugs in, there is a kind of square cover set diagonally. That cover can be lifted up if you squeeze the right things, and underneath it there is another fat wire ending in a zany spade terminal clamped under a nut. That is the wire from the converter.

    In between those two is the 125 amp "DC/DC" fuse. It is a royal pain to get to. It is bolted to the front of that largest module making up the fuse box. You have to take the box apart, as detailed more here.

    [​IMG]

    That white integration relay replaces a number of other smaller fuses (such as for the low-beam headlights, horns, etc.) with non-fuses ... the thing's electronic, and apparently has some self-resetting current limiting built in. But the big 125 amp fuse is separate.

    A lot of posts in this thread are using ampacity tables for household wiring. Ampacity isn't a fixed property of a certain thickness of metal wire, but a function of how much heat that wire will produce, what temperature the insulation on it can handle, and how well heat can get away from it.

    Household wiring typically uses fairly low-temperature insulation. For example, 2k1 refers to 60 ℃ wiring here, which is low even by current residential standards:

    House wiring you can buy at the local big box has been more likely to say 90 ℃ for some decades now.

    Automakers routinely use wire gauges that seem insane by residential ampacity tables, because they use wires with insulation ratings that can be 125 ℃ or 150 ℃ or so. And are generally not surrounded by insulation blown into the walls of a house.

    Whatever gauge is that fat white wire from the front to the back of the car, given that Toyota put a 125 amp fuse on the front end of it and a 140 amp fuse on the back end, somebody signed off there that it isn't going to turn into a string of dripping goo at 125 or 140 amps. Your main concern will be voltage drop, just figuring out what voltage you will be seeing at the point where you've tapped off, when pulling the current you expect to pull.
     
  20. Terrell

    Terrell Old-Timer

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    Yep, that's an old thread -- but it's nice to have it awakened again. I've been using my 1kW inverter for camping (small microwave to cook meals, plus a rice cooker, but not at the same time!), as well as to power some of the key things in the house during a power outage. Interesting that the large chest freezer in the basement runs just fine, but the refrigerator's startup is too much for the inverter to handle. In addition to running the chest freezer, I hook up our internet (router, modem), phones, and computers. Unfortunately, the blower motor on the furnace also has too much startup surge to run.

    Earlier, someone asked about a "quick connect." I do this through Anderson connectors.

    The longest I've run it was about seven hours, when a big tree limb fell on our house lead-in wires. That was the time power was shut off for them to fix the bent mast and replace wires. Otherwise, power failures here happen once or twice a year due to storms, but the power is restored pretty quickly. Just about the time I've hooked up all the extension cords and vented the exhaust out through the garage door the power comes back on.
     
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