second 12 volt battery - 2020 edition

Discussion in 'Gen 3 Prius Main Forum' started by geedub, Apr 27, 2020.

  1. Johnny Cakes

    Johnny Cakes Active Member

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    At some point of adding other things, I'd definitely agree with you. As for the actual Prius specs, the DC to DC converter is rated at 120 amps but has a 100 amp in-line fuse.


    Nice. Obviously a fuse is a good thing!!

    Personally, for my camping setup, I have a LiFePO4 battery that is independent of the car battery. My stuff is connected to the LiFePO4 battery. If I have access to 120v AC, I plug in and the battery is charging while my stuff runs. If the car is in READY, then the car charges the LiFePO4 battery while my stuff runs. If neither, then it just discharges while my stuff runs until it depletes 40Ah. Automatic switch prioritizes AC when present.
     
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  2. ChapmanF

    ChapmanF Senior Member

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    I think at some point car makers were thinking of adding auto shutoff after some period of time, for those people who park their hybrid in their enclosed garage and don't realize they left it READY. I don't know if that ever happened in Gen 3. I've never known my 2010 to do it. But 2012 was a refresh.

    The "certain amount" is better than a hundred though. geedub is hardly the first PriusChatter to add electrical loads to the car, and those are modest compared to what other people have been adding in all generations of Prius for as long as I've been on this forum.

    For some people contemplating heavier loads, I've always suggested monitoring the converter's IDH signal (an output where the converter says Uncle! if it is feeling overloaded). In the car as stock, the only thing that pays attention to that signal is the HVAC (if the supplemental electric heat is on and the converter says Uncle!, the HVAC controls will drop the electric heat). Not that I've ever known anyone to take the suggestion. :)

    For the loads geedub is adding, there'd be no point.

    By the way, is your inverter cooling pump pumping well?
     
    #62 ChapmanF, May 22, 2020
    Last edited: May 22, 2020
  3. geedub

    geedub Member

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    Can you recommend a particular battery? I've been looking at power stations with built-in inverters. I like the Dometic LiFePO4 but it has no inverter.
     
  4. geedub

    geedub Member

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    The evaporative cooler? That's helping a little. I'm getting 5 - 10°F of cooling although the output is limited to a small area. Combined with the roof sprinklers i can maintain a little below ambient temperature.

    I don't have a pump for the cooler. I run water to it for several minutes and it retains it for about an hour.

    The water for both come from a well that the camp operates. It stopped working yesterday and the temp in my screen room jumped 10°F in minutes.
     
  5. ChapmanF

    ChapmanF Senior Member

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    No, I meant in the car, the little pump that circulates pink coolant through the inverter electronics.

    Those pumps do sometimes wear out, which can lead to the inverter getting warm depending on the electrical load, and sometimes saying "all right, enough of that" and shutting down.

    I'm still kind of grasping at explanations of the unexplained dropping-out-of-READY. A hot inverter ought to be accompanied by a trouble code.

    Will be interesting to hear if that happens again.
     
  6. geedub

    geedub Member

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    No error code. I see the coolant circulating.
     
  7. Terrell

    Terrell Member

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    Yes, they should be. The Dometic CFX28 barely fits behind the passenger seat between the center console and the right side wall if you raise it up on 2x2 blocks of wood. That's the secret to making it fit. The blocks of wood give a bit of air circulation room, plus they make the top of the Dometic just the right height so that when the back seat is reclined, the Dometic makes a level surface. To drop the Dometic into that spot, put the 2x2's in place, move the passenger seat all the way forward, then with the handles down, the Dometic should squeeze right into place. Lower the back seat, and you've got a level sleeping area. Set the passenger seat in the upmost position, and slide it almost back to the Dometic, but not quite all the way, or you cannot open the top of the refrigerator. Dometic may have changed their dimensions. WoodBlocksDometic.jpg
     
    #67 Terrell, May 24, 2020
    Last edited: May 24, 2020
  8. Terrell

    Terrell Member

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    Which is why I added a second 12V battery to my Prius. I was camping, had solar hooked up, but had three days of rain. The Dometic automatically shut down when the battery got too low. I didn't realize it until later when I found food had gotten warm.
     
    #68 Terrell, May 24, 2020
    Last edited: May 24, 2020
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  9. geedub

    geedub Member

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    Thanks Terrell. Did you not want to leave your car in ready mode?
     
  10. ChapmanF

    ChapmanF Senior Member

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    Well phooey. The latest greatest CFX3 line doesn't include a 28. Smallest is 35. Doesn't sound promising, unless it's a Tardis and only bigger on the inside.

    I think the big deal for the CFX3 line was supposed to be increased efficiency. Not sure how big the difference is, but I notice on Dometic's site that the CFX3 units have their running amphours/hour listed, and the CFX ones ... don't.
     
  11. Terrell

    Terrell Member

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    I suppose I could have, since it uses so little fuel. But I was in a camping area, and having the car cycle on and off all night is frowned upon. :)
     
  12. Terrell

    Terrell Member

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    A quick look at the Dometic web site shows that they still sell the CFX28. I wouldn't want anything larger for the Prius. The web site is a bit clunky, but if you scroll down the CFX3 page you'll find the 28.
     
  13. ChapmanF

    ChapmanF Senior Member

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    Yeah, I did find it there; I was just pointing it out that it's in the older CFX product line. The CFX3 line is the new hotness, apparently because they have done even more magic with efficiency. A CFX 3 in the 35 size has a published draw 0.98 amphours per hour, under the specified stable conditions, 90 °F outside the box and 39 °F inside.

    I can't tell you how much better that is than the older CFX family, because when I look for those figures among the specs for a CFX 28, say ... they aren't there.

    Their efficiency improvements in CFX3 may have pulled them ahead of Engel for efficiency (see #4, this thread).
     
  14. geedub

    geedub Member

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    Yeah, I wanted a CFX3 but I definitely wanted something to fit behind the passenger seat. It came down to the CFX28 or another brand but for that size limitation I didn't see anything better. After about one week I'm very happy with the unit.
     
  15. ChapmanF

    ChapmanF Senior Member

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    Can you post some data on how much it draws over time, under stable conditions?

    Are the ambient conditions up around 90 °F by this time of year?

    Have you noticed your profile location says "Flordia"? :)

    Is there a comparable Engel that also fits behind the seat, and how do the prices compare, if you looked at them?
     
  16. geedub

    geedub Member

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    How would I gather that data?

    This Engel fits but too small for me: LINK

    Yes, I'm in Flordia.... 90º isn't unusual this time of year.
     
  17. ChapmanF

    ChapmanF Senior Member

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    These kinds of things come in a lot of flavors now.

    Thanks! Engel seems to publish more thorough performance data.

    The numbers Dometic published for the CFX3 (for 90℉ ambient, 39℉ inside, or equivalently 32℃ and 4℃) would compare best to Engel's middle graph here:

    mt27f.png

    Under those conditions, 0.98 Ah/h for the CFX3 35 compared to Engel's 1.46 Ah/h for a smaller unit looks like quite the feather in Dometic's cap.

    I wonder if the CFX 28 has comparable data published anywhere. I didn't find any in a cursory search, but maybe it's buried somewhere.

    Where is this Flordia of which you speak?
     
  18. Johnny Cakes

    Johnny Cakes Active Member

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    Hey geedub, I sent you a private conversation message. Thx.
     
  19. geedub

    geedub Member

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    Sure! Just got back to camp and it's pouring so I'll get with you in a bit..
     
  20. geedub

    geedub Member

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    Not that I don't want to buy that thing just to help you out, but what else can I do with it....? ;)

    It's in an alternate universe where 6 foot tall synthetic mice and plastic flamingos don't exist...
     
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