Forum Discussion

jeffwhite's avatar
jeffwhite
Explorer
Aug 25, 2018

Monitor Battery Level....

Camping World doesn't seem to have much, but I'm looking to monitor my battery situation (4 6v us2200's) with minimal work. I'm pretty sure I could purchase a meter and wire it inline and put the monitor in the coach somewhere, but.....couldn't I just plug something into the cigarette lighter (coming from the battery pack) and have it register?
I've seen some things like this, but they are set up to install from scratch. Is there something I can purchase and just "stick" it into the cigarette" lighter (for the tv connection) and have it tell me the level? Or, are these just crappy? Or, is there something that limits the accuracy in that situation? Or, do I just need to run something from the batteries and wire it into the coach as a separate item? jeff
Class A
  • Ed_Gee's avatar
    Ed_Gee
    Explorer II
    Aug 25, 2018
    jeffwhite wrote:
    Camping World doesn't seem to have much, but I'm looking to monitor my battery situation (4 6v us2200's) with minimal work. I'm pretty sure I could purchase a meter and wire it inline and put the monitor in the coach somewhere, but.....couldn't I just plug something into the cigarette lighter (coming from the battery pack) and have it register?
    I've seen some things like this, but they are set up to install from scratch. Is there something I can purchase and just "stick" it into the cigarette" lighter (for the tv connection) and have it tell me the level? Or, are these just crappy? Or, is there something that limits the accuracy in that situation? Or, do I just need to run something from the batteries and wire it into the coach as a separate item? jeff


    Really! Campingword seems to have exactly what you are looking for: Battery voltage monitor
  • jeffwhite's avatar
    jeffwhite
    Explorer
    Aug 25, 2018
    No kidding!!! Your right. When I searched, I didn't get that. Thanks. jeff
  • KD4UPL's avatar
    KD4UPL
    Explorer
    Aug 25, 2018
    Anything you can just plug will not be very accurate. It will be some version of a volt meter. Voltage is not that useful tellin gyou the condition of your batteries. A fully charged battery under a heavy load will have a low voltage. A poorly charged battery under a light load will also have a low voltage. A fully charged battery will have a high voltage, so will a bad battery hooked to a strong charger.
    To really know how much battery capacity you have left you need a meter that includes a shunt wired inline with your large main negative cable. This measures amps in and amps out over time. You tell it how many amp hours your battery bank is and it calculates how full it is.
  • jeffwhite's avatar
    jeffwhite
    Explorer
    Aug 25, 2018
    Ok, so what would a unit like that look like? I would just intercept the negative cable and wire it directly into the coach? I've got 4 6V batteries that I'm running series/parallel to get the 12V. jeff
  • older_fossil's avatar
    older_fossil
    Explorer
    Aug 25, 2018
    The only time that voltage is a good indicator of state-of-charge is when it has "rested" with no load or charging for at least 4 hours. This is not practical in real life. As stated above, a meter that uses a current sensing shunt is much more useful. A unit like Victron BMV-712
  • rgatijnet1's avatar
    rgatijnet1
    Explorer III
    Aug 25, 2018
    As long as 4 batteries are connected together, any volt meter will be giving you a reading that has very little to do with the actual condition of an individual battery.
    I prefer to monitor my charging system to insure that it is working properly. As long as it is working properly, and the water levels are properly maintained on all batteries, then that is the best that you can do to get the longest life from your battery bank.
  • Sam_Spade's avatar
    Sam_Spade
    Explorer
    Aug 25, 2018
    jeffwhite wrote:
    ....couldn't I just plug something into the cigarette lighter (coming from the battery pack) and have it register?


    Yes absolutely....as long as it is a digital display.

    All you REALLY need to know is the battery voltage.
    But some folks here will likely write a whole book asserting that is not true at all.
    Trust me.

    Available at most any auto parts store or RV dealer.....for about $15. I have two of them. One on the coach and one on the chassis.
  • Sam_Spade's avatar
    Sam_Spade
    Explorer
    Aug 25, 2018
    jeffwhite wrote:
    Ok, so what would a unit like that look like? I would just intercept the negative cable and wire it directly into the coach? I've got 4 6V batteries that I'm running series/parallel to get the 12V. jeff


    You are falling for some BAD information here......at least as it applies to an RV. All of that is NOT necessary and may actually be confusing and counter-productive......for most people.

    Try the $15 solution first. It does take some thought when interpreting the reading at any given time but that is fairly easy.

    Edit: You can not really tell the condition of each battery without splitting the string and testing each one individually.
  • jorbill2or's avatar
    jorbill2or
    Explorer II
    Aug 25, 2018
    If you want accuracy you want , as said , to install a battery monitor not just a volt meter . Something like a Trimetric TM 2030 -RV .this has been the go to for years but there are others Volt meters are not very useful in determining battery Heath. The monitor can be programmed with total amps in the bank and then counts all amps in and out. After 24 hours it will be a accurate battery level meter.
    Batteries have a wide range of voltages even fully charged with a substantial load will show volts in the mid- low 11’s the only way a volt meter is helpful in battery state is a battery that is “ off line “ resting with no load on for a couple hours.. not practical in a rv that’s in use.
  • Sam_Spade's avatar
    Sam_Spade
    Explorer
    Aug 25, 2018
    jorbill2or wrote:

    Batteries have a wide range of voltages even fully charged with a substantial load will show volts in the mid- low 11’s the only way a volt meter is helpful in battery state is a battery that is “ off line “ resting with no load on for a couple hours.. not practical in a rv that’s in use.


    That statement is totally misleading.

    Given a similar situation, a set of batteries does NOT show "a wide range of voltages".

    After a full charge, with a minimum load they will have a "normal" voltage.

    After XX hours of "normal" daily (or nightly) RV use, they will have a "normal" voltage within a fairly narrow range.

    A simple voltmeter will also instantly tell you if the present situation is charging, floating or discharging.

    And charts are readily available that tell you the approximate SOC based on the lightly loaded voltage.

    This is not rocket science and does NOT have to be difficult or expensive. But you can make it both difficult and expensive if you want to. I have better things to do with my time and money. A simple voltmeter serves me quite good.

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