Forum Discussion

bkenobi's avatar
bkenobi
Explorer
Feb 26, 2018

Electric jacks and power

My 2007 NL has Happijacks installed on it. I've found that when raising and lowering the camper that the process can really drain the battery and the dealer confirmed with some numbers. I thought that perhapse disabling the batteries with shore power would be a good way around the problem, but then the jacks don't work at all. From reading and talking to the Happijack, the batteries are required due to current draw.

That sounds legit...except that I left the camper at the dealer for 2 months and the battery was flat. They plugged in a shore line and had no problem loading. I didn't notice if it was 30A or 15A.

Also, how can the jacks pull that much current when the DC wiring is all tiny? A car jumper cable is designed for heavy current and is very thick, but the jack wires in my unit are fairly small by comparison.

http://assets.bluesea.com/files/resources/newsletter/images/DC_wire_selection_chartlg.jpg

Acording to this chart, if the wore was 10awg and allowed to drop below 30A, it could be up to 30ft. But the claim I've heard is that the jacks can draw more than double that. If so, that would require 6awg or 4awg. I know the wires aren't 1/4" thick plus insulation.
Truck Campers
  • Gripnriprod's avatar
    Gripnriprod
    Explorer
    Feb 26, 2018
    Happi Jac calls for 40a supply from the battery to the circuit board. Assuming each motor draws equally (they won’t due to the differing weight each jack lifts), the individual current being drawn would be 10a.
    No explanation for “flat” battery being able to run the jacks unless the battery charging circuit is good for ~40a.
  • Terryallan's avatar
    Terryallan
    Explorer II
    Feb 26, 2018
    I'm betting that the battery has to be inline to provide power to the jack. IF you unhooked the batter when you disabled the battery. You broke the current flow.
  • mkirsch's avatar
    mkirsch
    Nomad II
    Feb 26, 2018
    Even though the battery was "flat" the jacks were still connected to the battery. It's a circuit logic thing not a voltage thing.
  • work2much's avatar
    work2much
    Explorer
    Feb 26, 2018
    40 Amps for the 2-4 minutes running the jacks shouldn't drain the battery. 4 minutes is less than 3 AH of capacity.

    You may want to have the battery tested to see what your capacity/health of battery is. It could be that the voltage sag on the battery is too much for your battery.

    Above is correct. The batteries on all of my previous campers have needed to be installed for the jacks to work. Plugging the camper in will deliver amperage to the batteries allowing jacks to work through the boosted battery.
  • deserteagle56's avatar
    deserteagle56
    Explorer II
    Feb 26, 2018
    work2much wrote:
    Plugging the camper in will deliver amperage to the batteries allowing jacks to work through the boosted battery.


    ^ This. I notice a big difference in how fast the jacks work if I plug the camper in to shore power.
  • monkey44's avatar
    monkey44
    Nomad II
    Feb 26, 2018
    Not sure about your problem here - but something to know if your camper battery is low.

    When that happens to us occasionally when camping with no HU, we just pull the truck next to the camper and plug it in. Keep the truck running and lift the camper, works fine.
  • Ski_Pro_3's avatar
    Ski_Pro_3
    Explorer
    Feb 26, 2018
    My jacks, while lifting my 3,000+ pound camper, draws only 15 amps. I use a clamp-on amp meter to measure the total load with everything else turned off.
  • bkenobi's avatar
    bkenobi
    Explorer
    Feb 26, 2018
    Clamp meters only work on AC, so I assume you are connecting the clamp at the TC panel or house panel or something? A Kill-A-Watt would worm too. I suppose I could do the same with a fuse buddy. But that wont test what's going to the jacks, only what's being pulled from shore. And since ground power is 15A unless you have a 30A outlet, I wouldn't expect you to pull more that 15A on a 15A circuit.
  • Ski_Pro_3's avatar
    Ski_Pro_3
    Explorer
    Feb 26, 2018
    bkenobi wrote:
    Clamp meters only work on AC, so I assume you are connecting the clamp at the TC panel or house panel or something? A Kill-A-Watt would worm too. I suppose I could do the same with a fuse buddy. But that wont test what's going to the jacks, only what's being pulled from shore. And since ground power is 15A unless you have a 30A outlet, I wouldn't expect you to pull more that 15A on a 15A circuit.


    Nope, clamp meters come in both AC and DC. Mine has both. I have a FLUKE 365 detachable jaw meter. The detachable makes it easy to get deep into an area where the wire you are attempting to measure lives and still be able to read the display.

  • bkenobi's avatar
    bkenobi
    Explorer
    Feb 26, 2018
    Well I learned something new! Last I checked, DC clamp meters were technically available but the typical price point made them out of reach for all but the professional ($$$$). I'd still have to think about $2-500, but that's certainly closer to a hobbyist price.

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