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Extending output cable of auto battery charger/maintainer

Discussion in 'Power Electronics' started by Ed Sowell, Apr 19, 2020.

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  1. Ed Sowell

    Ed Sowell

    Aug 1, 2016
    I have a Schumacher SE-5212A-CA battery charger/maintainer with 14AWG DC output cable. To reach the battery while in the car from the charger on a shelf on the adjacent wall, I need to extend the cable about 3 feet. I'd either splice or replace with a longer cable. I'm concerned that this might affect the "sensing circuits" in the charger.

    Anyone here have thoughts on the matter?

    BTW, I sent the question to Schumacher and got a reply from customer service: "The cable is 14AWG." No help at all, I can read that off the cable!
  2. Martaine2005


    May 12, 2015
    Extending or replacing the wires wont affect it. You are only extending by about a metre (3').
    Same for extending the mains input, some people will connect to an extension cord.

  3. bertus

    bertus Moderator

    Nov 8, 2019

    Extending the cables by 3 feet, the voltage drop will be 0.9 Volts per cable so 1.8 Volts over the pair.
    I used this online calculator:
    I used 3 feet and 12 Volts and 50 Amp (the max the charger can give).

    User thicker cables will reduce the voltage drop.

  4. Bluejets


    Oct 5, 2014
    If it's a "smart charger" chances are the charger interrupts the charging routine on occasion to take any readings thus making a change in cable size irrelevant.
    Charger may well be rated at 50A but yet to see one charge at such a high constant rate.
  5. Ed Sowell

    Ed Sowell

    Aug 1, 2016
    Martin, I'd rather add to or replace the output cables than relocate the charger and drag an extension cord.
    Blujets, I think it could be a smart charger but not sure.
    Bertus, most usage would not be recharging a dead battery so it wouldn't often be at 50 amps. And I expect under that extreme condition a 0.9 volts wouldn't have much effect.
  6. Bluejets


    Oct 5, 2014
    Using a mains extension would be the normal accepted method, however if you must and intend to replace the entire length of LV leads, then go heavy.
    Maybe also invest in a pair of HD clamps while you are there.
    Most of these have poor quality clamps anyhow.
  7. Ed Sowell

    Ed Sowell

    Aug 1, 2016
    The Schumacher literature says it is microprocessor controlled to optimize charging rate. Doesn't use the term "smart charger."
  8. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    Schumacher has a web page of FAQs (Frequently Asked Questions) that perhaps @Ed Sowell should read.

    Responders here might want to check this page too.

    Based on what little information has been provided so far, I would suggest extending the existing battery cables with 14 AWG insulated wire. If the charger becomes "hinky" at the distance extended, either use a shorter distance or a larger wire size: 12 AWG or even 10 AWG. I have used 4 AWG welding cable for my home-built "dumb" charger, which was capable of some 200A short-circuit output current, but that seemed a little extravagant even for very conservative me. My welding cable was removed to my day job laboratory, supposedly "on loan" but never returned to me. I now get by with a 4-wire 12 AWG cable, paralleling the red plus white and black plus green wires. The "new" battery charging cable may not start a diesel truck engine (I haven't tried that yet) but it charges an automobile battery PDQ (Pretty Damned Quickly).
    Last edited: Apr 20, 2020
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