Pigtails and On board battery charging

Discussion in 'Power - Site Power/Batteries/Generators/Solar' started by Econ, Sep 15, 2021.

  1. Econ

    Econ Well-Known Member

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    My pigtail got damaged and the last 1' plus the plug needs replacing.
    1) any opinion on Hopkins quality as a replacement part?
    https://www.etrailer.com/Wiring/Hopkins/HM20087.html

    2) Wire nuts, copper butt connecters or a terminal junction box for the splice?

    3) The charge goes from the TV alternator traveling about 20' to the 7 way plug then about 15 to 20' to the convertor then back forward about 10 to 15' to the battery.

    That means the charge has to travel 50' ish feet to get to the camper battery as set up now. What IF you could cut 20-25ish ish feet off that circuit? Would it make any appreciable difference in the charge rate while traveling? Would it be worth doing? I will have to make a splice cut at about where the camper battery anyway. ANy ideas?

    Thanks
     
  2. Grandpa Don

    Grandpa Don Well-Known Member

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    I don't know about the battery charging circuit. But the 7-pin plug from Etrailer looks good to me. I trust just about anything they sell. If I had to redo my wiring, I would use a terminal junction box with crimped eyelets on the ends. That would be a neat looking job.
     
  3. kcsa75

    kcsa75 Well-Known Member Gold Supporting Member

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  4. LilRed

    LilRed Well-Known Member

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    Voltage drop is nominal if you have a proper awg cable. Try this site for some guidance, and a chart for reference.
    upload_2021-9-15_19-49-41.jpeg
     
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  5. RonDad

    RonDad Active Member

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    Nice! That’s helpful.
     
  6. SteveP

    SteveP Well-Known Member Platinum Supporting Member

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    I think this is the one I used when I replaced mine. It's lasted for several years.

    I used marine quality butt connectors. I staggered the connectors over about a foot of cable so that I didn't have a big knot in one place. If I had to do it again I might use a terminal box if I could convince myself that it was dust and weather tight.

    I would definitely splice in a pigtail at the tongue on the charging wire, my trailer already had it, to reduce potential voltage drop.
     
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  7. Arruba

    Arruba Well-Known Member Gold Supporting Member

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    MY 2 cents; the nice things about using a junction box are:
    1- if you ever end up with a munched pig tail again, I think it’s easier to replace the tail at the box
    2- if you get another tow vehicle and the wiring sequence needs to change, it’s easier to do at the box

    That said, my Viking doesn’t have one. If I have to someday do a significant fix, I’m putting one on.
    Good luck with your decision.
     
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  8. TSQ

    TSQ Active Member

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    I've used a few Hopkins connectors before and they've been OK. That being said, I prefer the double sided connectors like Bargman uses as they seem to give more reliable connections (especially if you are looking to maximize battery charging).
    Hopkins_end.png Bargman_end.png
    IMHO junction box if you are planning to keep the trailer for a while, or heatshrink marine type butt connectors if not.

    It will depend on your alternator design, trailer battery type, and if you are using a DC-DC charger.

    Assuming your alternator is constant 14.2V, your trailer battery is lead acid, it is all wired with #10 (vehicle and trailer), the vehicle negative goes through the frame with negligeable resistance, trailer negative follows the positive (which may not be true), 20' in vehicle, 18' to converter, 12' to battery, and ignoring additional resistance at connectors,

    Currently (no pun intended):
    At 30A you end up with ~13.5V at the vehicle trailer plug, ~12.4V at your converter, and ~11.5V by the time it gets to your battery.
    At 20A you end up with ~13.7V at the vehicle trailer plug, ~12.8V at your converter, and ~12.2V by the time it gets to your battery.
    At 10A you end up with ~14.0V at the vehicle trailer plug, ~13.6V at your converter, and ~13.3V by the time it gets to your battery.
    At 2A you end up with ~14.2V at the vehicle trailer plug, ~14.0V at your converter, and ~13.9V by the time it gets to your battery.

    So a deeply discharged battery may charge at 30A for a short while but as the battery voltage rises the amperage will drop off rapidly.

    If you get it down to 20' vehicle plus 8' to battery:
    At 30A you end up with ~13.5V at the vehicle trailer plug, and ~12.9V by the time it gets to your battery.
    At 20A you end up with ~13.7V at the vehicle trailer plug, and ~13.3V by the time it gets to your battery.
    At 10A you end up with ~14.0V at the vehicle trailer plug, and ~13.8V by the time it gets to your battery.
    At 2A you end up with ~14.2V at the vehicle trailer plug, and ~14.1V by the time it gets to your battery.

    Now you can charge at 30A until your battery is close to 13V, and when the battery is ~13.3V you are charging twice as fast (20A vs 10A). By the time the battery gets up to 13.8V~13.9V you are charging five times as fast (10A vs 2A).

    Will this matter? Depends on how you camp. If you use your vehicle to charge your trailer battery while driving or at the campsite you will notice a difference. If you are leaving home with a full battery and just keeping it topped up while driving then you won't.

    Note that to truly charge a deep cycle battery (to 14.4V) from your vehicle you will need a DC-DC charger with a multistage charging algorithm. These will maximize usable capacity and battery life, minimize charge times, and protect wiring and connectors from overcurrents. But like everything, only worth it if you charge from the vehicle a lot (and camp a lot).
     
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  9. Econ

    Econ Well-Known Member

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    Thanks to everyone who responded. Your ideas and opinions have been considered. The decision is to use a junction box.

    We use minimal electricity except DW's CPAP and its a hog. We are not campers. We are hikers and tourists. Staying in camp is wasted time so we try to minimize it. Babysitting a generator is not desirable and interferes with the important stuff so my mind is always thinking of ways to minimize generator time and it's effect on scheduling. <GG> On a recent trip we moved 100 miles picking up minimal net charge.

    Solar is not an option except in the winter then the sun is low.

    Its been raining for 4 days and long range is 7 more. That tropical storm has decided to park so I am locked inside waiting it out. Atleast all the paperwork is caught up. <GG>

    @TSQ

    The Honda dealer I buy parts from for the past 40 years offered an opinion. Officially the mileage minder dictates maintenance. They recommend that the tranny, VTM and be changed every 20K and engine oil every 5k if towing. The TV is a 2012 5 speed 4WD.

    I have not found a Bargman connector expect one with 25' of cable connected.
     
    Last edited: Oct 14, 2021
  10. TSQ

    TSQ Active Member

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  11. Econ

    Econ Well-Known Member

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    That pisses me off. Called Etrailer last week and specifically asked for a Bargeman and asked if I just overlooked it. They assured me the only Bargeman they carry was the 7 way with a 25' pigtail. Amazon didnt have Bargeman last week. Now the day after the damn thing arrived they are recommending a Bargemen instead of the brand I got. Thanks Etrailer

    @TSQ Thanks for the heads up.
     
  12. TSQ

    TSQ Active Member

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    I'm sure the Hopkins will work just as well for you.
     
  13. Econ

    Econ Well-Known Member

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    Thanks @SteveP , @Arruba , @TSQ
    The deed is done. Junction box under the battery on the frame inside. The time consumer was supply runs.

    Etrailer and RV Works show the pigtail exiting the inside of the frame by going up and over the frame rail. My had the pigtail going under the frame rail. Any Reason???????

    The plug and 6" of wire was salvaged.

    Now teach me. If I go from the junction box to the camper battery I would be wiring the camper and TV battery in parallel. The alternator would charge the TV battery and that would charge the camper battery ?????????

    Since the pigtail plug is salvage can it be put to use. As a CPAP maintenance man I'm always thinking about keeping the camper battery charged.
    Without adding a DC-DC charger con you plug the spare plug into the TV socket when you go on thiose little 100 mile side trips.??

    Thanks
     
  14. SteveP

    SteveP Well-Known Member Platinum Supporting Member

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    Less risk of road abrasion with it exiting over the rail. Mine is long enough to exit over the rail, wrap around the jack post and still reach the TV plug with plenty of slack.
    That is correct.
    As long as the battery is LA, either AGM or FLA, you should get the same charge you get to the battery on the camper tongue, maybe a schose more. You would need the DCDC charger for LI batteries.
     
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  15. Econ

    Econ Well-Known Member

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    @SteveP
    Thanks
    Planning and trip development just informed me we have the last 5 day in a row camping space at Smokemont leading up to T_Giving. T-giving will stay somewhere with power

    Building batterybox that will house the battery. charge controller, misc solar tools, multimeter,etc distilled water. Will wire the junction box and Bargeman too.
     
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