House battery not charging?

Discussion in 'Electronics Q&A' started by wahoo76, Jan 26, 2018.

  1. wahoo76

    wahoo76 New Member

    Jan 3, 2016
    Sydney, Australia
    2006 Searay Sundancer 315
    twin 4.3 MPI
    Hi All
    Hoping someone can help. So my 280/315 has 3 batteries. 2 starting and 1 house. Starboard engine and battery run alone. The port engine starting battery (new) keeps going flat when overnighting and luckily I have the switch to bank over and start the port engine after I have started the starboard engine.
    Now the port battery charges after running the boat. 65amps per hour on the V6 mercruiser.
    SO WHAT IS THE HOUSE BATTETY DOING??? it’s new also. Deep cycle 120amps.
    I don’t have the luxury on leaving on shore power.
    Can someone please advise?
    Thanks in advance.
  2. NotHerDecision

    NotHerDecision Well-Known Member PLATINUM Sponsor

    Jun 28, 2016
    Houston, Texas
    2001 Sea Ray 460 Sundancer
    2014 Seadoo 155 LTD
    2105 Seadoo 130 SE
    2013 Mercury Dinghy
    Cummins 6CTA 8.3L
    Do you have a generator?
  3. MickT

    MickT Member

    Aug 5, 2016
    australia - newcastle
    2006 sundancer 300
    twin mercruiser 5.0 mpi w/bravo III
    What do you mean by ‘what is the house battery doing?’

    The house battery should not have any effect on your starting battery.

    You need to find out what is drawing power from the starting battery. Do you switch the batteries off? Does it still go flat overnight when switched off? Could be a faulty bilge pump, could be a faulty alternator, could be something else wired up wrong....
  4. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    I'm not quite sure what you're asking, either, but it sounds like you're saying that it seems like your house battery is "not in the loop", so to say? Are you using the port battery switch properly to select which battery you want to use for house loads? The same goes for picking which battery you want to charge. You can also select the house battery to start the engine, fyi... although it's best not to make a habit of using a DC battery to start the engine.
  5. Wylie_Tunes

    Wylie_Tunes Active Member

    Oct 26, 2012
    Lake Wylie NC area
    Staying overnight on the boat, on the hook, I would not be surprised by this. This battery could very well be part of your house bank. This is part of why there is a means of using the running engine's battery to crank the other engine.

    That 3rd battery could be wired in parallel with your port engine battery, making up the house bank.

    1st thing I would do, learn exactly how the system is configured and how it works under normal conditions. 2nd, Check the voltage level of all the batteries with a DVOM meter. Fully charge and retest any that are low. 3rd, with the engine(s) running, test for alternator charge voltage at each battery. Including that #3 battery. Need to know how it gets a charge while underway. 4th, if there is an on-board charger, test at each battery for charge voltage when the charger is plugged in/on.

    Dont assume a battery is good or bad, dont assume it is or is not receiving a charge and dont use the helm volt gauge for diagnostics. Pick up an inexpensive digital volt ohm meter from the hardware or auto parts store.
  6. northern

    northern Well-Known Member

    Jan 17, 2007
    West coast Vancouver to Alaska
    380 Aft Cabin 1989 GPS and Charts by Nobeltec
    Twin 454 strait shaft
    Our boat is set up so house (12 volt) and one engine are on the same batteries. One engine is set up to be stand alone. With engines off turn on 12 volt lights then turn off the main switches to the batteries to see what engine runs the house batteries. If you only replaced one battery and the other is old it can damage the new one. Lots on batteries in various threads on this site.
  7. CliffA

    CliffA Well-Known Member GOLD Sponsor

    Dec 29, 2009
    Lake Norman, NC
    2001 Sea Ray 340DA
    Name: 'Happy Place'
    4.5kW West. Generator
    Purchased Nov. 2014
    Fresh Water Use
    Twin Merc. 6.2L (MPI)
    Raw Water Cooled
    V-Drive Transmissions
    as i understand it you should always replace all batteries that are wired parallel in a 'bank' at the same time because the output of the bank will only be a strong as the weakest battery in the bank....

  8. Wylie_Tunes

    Wylie_Tunes Active Member

    Oct 26, 2012
    Lake Wylie NC area
    Only batteries wired in series or parallel in a single bank, need to be the same age, size and type. An old batter in a different bank, will not harm or effect a new battery installed in a different bank.

    With that said. If you suspect one bad battery and they are all the same age and more then 3 years old, id look hard at all of them and consider replacing the rest along with with one suspect, just to same time and near future issues with the remaining.
  9. bobeast

    bobeast Dance the Tide SILVER Sponsor

    Oct 22, 2017
    Isleton, CA
    2002 310DA
    350 MPI w/V-drives
    1 bank shares house and starting duties with two batteries wired in parallel. The other battery is starting only. At least that's how my 310 is wired. It sounds like your 2 battery bank is wired to your port starter, with would explain why your port engine isn't starting after being on the hook.

    Really there's not much magic involved. You need either more battery or less load. Also if you don't have shore power ever, its very possible your batteries are never getting fully charged from your alternators, depending on how long you run the engines between going on hook.
  10. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor

    Apr 21, 2009
    Someone please feel free to double check me, but I believe Mick's battery setup is such that the two "port" batteries are NOT wired in parallel. Instead they are hooked into a 1-2-Both-Off switch. Although, of course if "Both" was selected on the switch, then they would running in parallel. The Stbd battery is wired to a simple On-Off switch.

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