battery--here we go again

Discussion in 'General RVing' started by H2H1, Sep 12, 2008.

  1. H2H1

    H2H1 Senior Member

    Ok I now have a new engine battery in the MH, I have also installed a trickle charge charger at 1.5 amp. So when the battery is fully charged what should I read on my volt meter. It has been going up since I installed it. Today it read 12.95 volts, I think that is over charging. I have unplugged it and will wait a few days to check it again. I know I have a drain but can't find it so that why I installed the trickle charger. someone tell me what my 12 volts battery should read once fully charged. thanks ya'll. :laugh:
     
  2. ironart

    ironart New Member

    Re: battery--here we go again

    Hi Hollis and Welcome... :laugh: :laugh: :laugh: :laugh:

    Did you take the reading with the charger attached and running or did you let the battery sit for an hour and rest a little....
    Chargers usually charge at more than 12 volts 13.8 volts for my alternator and charger both.... that is so there is a "Potential difference" in the system which will allow the charge to take place.... 12.5 volts is not unusual for a fully charged battery......Wish mine were that good.... ;) ;) :) :) :)

    To see how it actually is going you need to put a little load on it for a minute or so to dissipate the surface charge and get down to what you actually have in the battery.....any light load (like a light bulb) will do....

    I know that Kirk will give you the full story but this might get you started.... :) :) :)
     
  3. H2H1

    H2H1 Senior Member

    Re: battery--here we go again

    yes Paul it was hooked up when I took the reading. I have been checking it since I installed the TC. I am going to go check it now OK as of now it is reading 12.45 at 8:55 pm, so it has dropped some, but that could be to the drain on it. Thanks Paul
     
  4. ironart

    ironart New Member

    Re: battery--here we go again

    The battery is about fully charged and the "trickle charger" is just putting a very little into it.....12.9 volts with the charger (that is what you were reading on your volt meter) running is a very gentle charge....nothing to worry about.
     
  5. DL Rupper

    DL Rupper Senior Member

    Re: battery--here we go again

    Hey Hollis, I'm currently hooked up to 30 amp, 115 V shore power and my 12 V Vent-fantastic and one 12 V neon light is on and my house batteries are reading 13.5 volts.
     
  6. C Nash

    C Nash Senior Member

    Re: battery--here we go again

    Hollis, do you still have the drain? How often is it killing the battery? Does your MH have a cutoff switch for the engine battery? If not you might want to install one but you really need to find the drain if it's killing the battery in a couple of days. The battery should not overcharge if you are using a trickle charge and have a drain. Just will shorten the battery life IMO. The 12.95 is about right for a trickle charge IMO.
     
  7. Kirk

    Kirk Senior Member

    Re: battery--here we go again



    First of all, if you measure the voltage across a battery with the battery charger connected, what you are reading is not the battery voltage, but the voltage which the charger is required to put out to force more current into the battery, which will always be slightly higher than the actual battery voltage. In addition, a wet cell battery will hold a higher voltage than normal for a period of time after the charge is removed, which has to do with battery design. For an accurate measure of the battery condition, it needs to sit with no charge or discharge for two hours to "rest."

    In practice, as long as there are only very light loads on a battery you can still get a pretty accurate reading and probably after an hour or so for most purposes. A great deal also depends upon the accuracy of the meter that you are using since small changes have significant meaning.

    A good trickle charger has a circuit built into it that monitors the battery voltage and causes it to cycle on and off as the voltage changes.Since the battery voltage rises as it is charged and then slowly falls as it looses charge, the actual timing of your measurement will cause a wide variation in what you will see on the meter, particularly if the meter is very accurate. That is the reason for the stated condition of letting the battery "rest" for two hours so that you have some consistency in reading when compared to condition of the battery.

    Another major contributor is the age and condition of that battery. With a new one there should be a pretty predictable voltage pattern, but only when in the resting condition. The best way to get that is to remove the charger connections and also lift the negative battery cable. Here is a copy of the battery chart that I use.

    Temperature: 77 degrees Fahrenheit

    Percent Hydrometer Unloaded
    charge reading voltage
    100 1.265 12.63
    75 1.210 12.30
    50 1.160 12.00
    25 1.120 11.76
    0 1.100 11.64

    You can also view the complete chart by visiting this link:

    http://www.adventure.1tree.net/rv-living/maintenance/battery-charge-level-chart
     
  8. H2H1

    H2H1 Senior Member

    Re: battery--here we go again

    thanks Kirk for that valuable info.

    yes Nash I still have the drain. the rv shop said they couldn't find, so I am still lost as what it is.
     
  9. ironart

    ironart New Member

    Re: battery--here we go again

    Hollis....There is a method I have used in the past to find these kind of problems.....It is very time consuming and most dealers don't want to get involved. but Here it is anyway......

    Remove the positive cable from your battery......connect a small light bulb (with wires attached) from the positive side of the battery to the battery cable that you removed... (series connection)..... If there is a drain on the battery....the light will light and stay light until you find the problem....

    Now, start to pull fuses in the fuse panel until the light goes out.......Once you have isolated the problem circuit..you can go further into that circuit to find the problem. If the light still stays on with the fuses out then the problem is in the "Feed Lines" to the fuse block, or something that may have been connected later without a fuse..(let's hope not)

    Good Luck
     
  10. Paul235

    Paul235 New Member

    Re: battery--here we go again

    The folks I bought my first MH from said it had a slow drain on the coach battery that they couldn't identify. I used the same technique Ironart suggested using a small digital meter instead of a light bulb and found out the door warmer on the fridge (keeps the door edges from sweating) had been on slowly discharging the battery while in storage. All I did was turn it off and the slow drain ceased. Again it was spotted by removing the 12 fuses one at a time with a helper watching the meter used as an amp meter. Does your unit have a master disconnect switch?
     
  11. H2H1

    H2H1 Senior Member

    Re: battery--here we go again

    yes it does have a battery disconnect. I will get me a small 12 v light with wires and maybe alligator clip to connect up see if I find the drain
    thanks ironart for that very good suggestion, and Paul235 thank you as well
     

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