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hertfordnc's avatar
hertfordnc
Explorer
Apr 21, 2020

Cheap way to isolate and charge gel cell- relay or diode ?

We have a 19 foot Hybrid. We will not do a lot of boondocking. i have a 100 amp Gel cell and a gel cell charger that keeps it properly topped off.

Meanwhile, the campers 12V power supply would damage the gell.

So i want to isolate the gel from the campers 12 volt system when I have shore power.

One option would be a 110V relay that cut out the gel whenever 110VAC is present

A cheaper simpler option would be a diode to prevent the camper power supply from putting voltage to the battery.

But i wonder the battery would charge properly if it also had communication with the rest of the DC system?

Is there an existing product in the RV tool box?


thanks

28 Replies

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  • time2roll's avatar
    time2roll
    Nomad
    Apr 21, 2020
    Title said "cheap way" not "slick fully automatic at any cost"

    There is no off the shelf gadget that does what you want.
  • hertfordnc's avatar
    hertfordnc
    Explorer
    Apr 21, 2020
    In other words "we don't understand your question, we cannot answer your question but we think you are doing it all wrong"


    What has happened to this forum? I've been here a long time.

    Anyway, what i'm doing is pretty basic electrical stuff I just figured someone had already worked it out.


    Doesn't anyone re-engineer anything any more?
  • time2roll's avatar
    time2roll
    Nomad
    Apr 21, 2020
    Cheapest way is to just remove a battery cable. Second cheapest is to just get a battery switch to mount on the battery terminal.

    If the GELL charger is at least 4 amps it could probably replace the converter.
  • Gdetrailer's avatar
    Gdetrailer
    Explorer III
    Apr 21, 2020
    hertfordnc wrote:
    2oldman wrote:
    hertfordnc wrote:
    So the gell would be going through many unnecessary discharge cycles as the small charger tries to keep up.
    How small? You only want this expensive battery for on the road? I'm sorry but this is a bit strange.


    First, I am a bit strange.

    Second, i already have the gell and the charger and the camper needs a new battery so the cheapest solution is to just figure out how to isolate it.


    Sell the gel cell on Ebay or CL, then buy the appropriate smallest RV/ MarineFLA.. I see absolutely no advantage or reason to hold on to the gel battery because you will need to make unnecessary alterations to make it "work" introducing potential points of failure.

    New 100 Ahr gel batteries seem to be going for $189-$240, a used good one surely you could get $100 for it which is more than what it would cost for a new group 24 FLA battery..
  • hertfordnc's avatar
    hertfordnc
    Explorer
    Apr 21, 2020
    2oldman wrote:
    hertfordnc wrote:
    So the gell would be going through many unnecessary discharge cycles as the small charger tries to keep up.
    How small? You only want this expensive battery for on the road? I'm sorry but this is a bit strange.


    First, I am a bit strange.

    Second, i already have the gell and the charger and the camper needs a new battery so the cheapest solution is to just figure out how to isolate it.
  • 2oldman's avatar
    2oldman
    Explorer II
    Apr 21, 2020
    hertfordnc wrote:
    So the gell would be going through many unnecessary discharge cycles as the small charger tries to keep up.
    How small? You only want this expensive battery for on the road? I'm sorry but this is a bit strange.
  • hertfordnc's avatar
    hertfordnc
    Explorer
    Apr 21, 2020
    2oldman wrote:
    I would disconnect the converter and just power the gel charger. You shouldn't have to have a converter running for 12v.


    Everything in the camper is 12V, lights, water pump, furnace, control board for the fridge, etc.

    So the gell would be going through many unnecessary discharge cycles as the small charger tries to keep up.

    Rather, i want the buzz box to provide all that DC power as we use campground power for the Air Conditioner and the fridge.

    But for the drive to the destination, which might take two days, i want the gel to keep everything humming.

    It's perfect for the duty cycle i have in mind, i just to automate the charging and keep the house power supply from cooking my expensive battery.
  • 2oldman's avatar
    2oldman
    Explorer II
    Apr 21, 2020
    I would disconnect the converter and just power the gel charger. You shouldn't have to have a converter running for 12v.

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