Inverter: How much power? and how?

Discussion in 'Gen 3 Prius Audio and Electronics' started by andreimontreal, Dec 10, 2020.

  1. ASRDogman

    ASRDogman Senior Member

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    Okay, so you are NOT running them in parallel, but set up as separate.
    So the original battery in not involved in the fridge, etc., but, after the car is running, it will charge up
    the 2nd battery. But what about the original battery? The inverter charges slowly. Do you also have a
    solar charger hooked up?


     
  2. ChapmanF

    ChapmanF Senior Member

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    Not sure which post you're (not) quoting, but you might want to look at #26 above, which gives three stages of things that can happen under different levels of overload (and also says the converter "isn't very likely to be fried"). You might be looking for more explanation after that, but there would be the place to start.

    It could be that you've discovered a difference between the PiP converter and the earlier versions PriusChat members have tested in the past. To be sure of that, though, it would be helpful if you had current-clamp measurements from a few different places, and also the state of the converter's IDH output, under different levels of load.
     
  3. rjparker

    rjparker Senior Member

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    A battery isolator charges two batteries in parallel by closing a relay while the car is charging, which is anytime the voltage is higher than the off state battery voltage. The isolators are commonly used on rv dual battery setups and prevent the "starting battery" from excessive discharge when the charging system is off. With a Prius system constantly charging in Ready, the batteries will remain in parallel unless the 12v drops excessively. The real isolator benefit is when the car is actually off, then the extra battery is running the load by itself. In Ready you have more amp hours through parallel batteries.
     
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  4. ASRDogman

    ASRDogman Senior Member

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    The Prius inverter only puts out a certain amount of amperage, right? So if your 2nd battery is low
    because it's been running all night, will it get more amps to charge it?
    I know on most no hybrid systems the alternator puts out 90 or more amps, but the Prius inverter doesn't.
    Right?
     
  5. ChapmanF

    ChapmanF Senior Member

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    The Prius DC/DC converter has a 125 amp fuse at its output (and serves some other circuits in the car that branch ahead of that fuse, too). There's a limit to its capacity, of course, but it's stouter than some gasser's 90 amp alternator.
     
  6. rjparker

    rjparker Senior Member

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    People have measured 12v charge currents upwards of 70 amps on a Prius. It will quickly taper off as the 12v battery gains charge. The vehicle requires 12v to operate, sometimes large quantities if loads like water pumps, radiator fans, power steering and electric heat are being called. No doubt the inverter can output well over 125 amps for short times.
     
  7. ASRDogman

    ASRDogman Senior Member

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    Interesting... Pretty much everyone says NOT to charge the battery with a charger over 4 amps.
    Or 4.5..... And that the inverter charges the battery in the car very slowly. Low amperage over
    long time is better for the battery. And the battery is only going to take what it needs.
    So you need to drive, or leave the car on for several hours before it fully charges the battery.
    So if you put 70 amps into it, it would seem to damage the battery... Unless it's only for a few seconds
    until the system determines it doesn't need that much.

    That system you have see the weaker battery needs more charge and give it more, and the other one less?
     
  8. rjparker

    rjparker Senior Member

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    First the 4.5amp thing is a warning against putting an old school trickle charger on the agm and forgetting about it. Particularly bad if Dad's old 50/10/2 amp charger was left on 50 or 10.
    BF9A574C-1698-4E06-AEFF-C499EE2599A8.jpeg
    If you have two parallel batteries they should be the same type and ideally the same size. Perhaps the vehicle is off, the battery isolator has them separate and the extra battery is run down to 9 volts. The "starting" battery is 12.5 v.

    Connecting them in parallel is the same thing as jump starting. Assuming no charging is occurring the two batteries quickly equalize in voltage with the higher voltage battery dumping massive amps to the lower charge battery. This is constrained only by the interconnecting cables, internal battery resistance and terminations. A very high current draw can easily go on for ten or more minutes with lower currents well over 10 amps for long periods. Typically a well designed battery isolator prevents this by not allowing parallel operation without a vehicle's charging system. However there are bypasses available to get people into or out of trouble.

    Once the vehicle is started, the vehicle raises the charging voltage above either batteries voltage, typically 14.8 volts to begin. This causes current to flow from the vehicle's charging mechanism to the batteries.

    If they are significantly discharged, it will be very high current. Both batteries charge at the same voltage however the amps into each may be different.

    At some point the battery voltages rise close to nominal and full gorilla charging quickly tapers down. The inverter's water cooled dc to dc breathes a sigh of relief but it still carries the vehicle's "12v" load including a float voltage of around 13.4 to the batteries. Which is low current for as long as the vehicle is on.

    So is adding a 1000 watt 85 amp inverter a good idea on a Prius? Not really. The inverter's dc to dc is carrying the load anytime the car is in Ready, increasing thermal and power stresses on that expensive part. Offline use of the secondary battery will take life off of it over time, however agm and other high discharge chemistries are designed for that kind of application. Finally the factory agm will last seven or eight years when used as designed, eg as a standby low current demand float battery.
     
    #48 rjparker, Jan 7, 2021
    Last edited: Jan 7, 2021
  9. ChapmanF

    ChapmanF Senior Member

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    Those things are all true about the charging system in Gen 1 and Gen 2, where the DC/DC output voltage is limited to about 13.8. I measured a Gen 2 recharging a severely empty battery and it never went over 8 amps, and dropped fairly soon to below 5.

    If you have a Gen 3 (this is the Gen 3 forum), you'll have noticed that the DC/DC output voltage is sometimes as high as 14.7. That extra volt makes a huge difference in current into the battery, leading to the charging currents AHetaFan measured.

    But another thing that changed in Gen 3 is there is a temperature sensor over the aux battery. Gen 1 and 2 didn't have that.

    This is one of those areas where it matters to keep the differences between generations straight.
     
  10. ASRDogman

    ASRDogman Senior Member

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    (y)
    I just take it for granted NOT(assUME) since this is the 3rd Generation chat room, that people talk about
    the 3rd generation. :whistle:
     
    #50 ASRDogman, Jan 7, 2021
    Last edited: Jan 7, 2021
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  11. ChapmanF

    ChapmanF Senior Member

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    Then you should have been totally unsurprised by talk of 70 amp charging currents.
     
  12. andreimontreal

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    Yes. While reading here it crossed my mind how some of you are looking at these things and I felt that "passion" itch . Funny but that's slightly freaking me out - you mentioning it :eek: ; I have experience with experience - I know I'm dumb as a brick when it comes to the topic so I ask enough to the point where I pull through. The goal is to get done on this to focus cinema: writing, photography, film making - got my hands full with that and a specific plan/message which I must translate into stories - otherwise I'll blow up.

    I like the topic of electronics though.

    If I had about 2 lives, I'd def do what you said.

    A
     
  13. rjparker

    rjparker Senior Member

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    Engineering is more of a sure thing with plenty of divergent opportunities. The more you know the more you know you don't know. Which makes you more effective.
     
  14. andreimontreal

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    I it was never about the money - but it so happens the financial gains and stability are ridiculously high in entertainment. I would literally do it because I like it so much - physics (especially electric and vectorial, I found it so easy and I loved every bit of it). Not to mention my crafting skills got me into renovation/fine finishing and a contractor bud keeps calling me to help with work; I got plenty of streams of revenue it seems and not enough time for them; been neglecting the film side of it a bit too much in fact - need to finish this car and put the time into my craft. I could work half a year and take a vacation the other half no prob. With my lifestyle downsizing I could prob work 1 month a year if I needed the time to write and whatnot - my idea of bliss: freedom. Just what I needed . Other keeps telling me I'm a different breed - I tried to explain to them that I'm taking the path of the least resistance towards my goal: but it looks like madness for regular folk (imagine wanting to downsize your life to a Prius camper and maybe a 5 by 5 storage space for depositing extra if ever; here's my project at an early stage ).

    Wisdom 110%. I like to torture my brains and hands. Bro in law asked me why I do the mechanic work on my car since I can afford one - I said "experience" - he grew up in Romania, street savvy with an education, charming fella' - he went "oh, alright", everything was understood. Maybe I'm a cheap bastard too, I'll admit to that a bit, but having experience with anything: I value that a lot.

    A
     
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