Results 1 to 12 of 12

Thread: 2nd Battery Wiring Diagram

  1. #1

    Default 2nd Battery Wiring Diagram

    Anybody see any problems with the attached diagram ?

    It is basically the same as my existing single battery setup with a second battery and the 2 cables from the battery as shown.

    Not sure if you can run both engines at the same time without the alternator(s) having a problem. I presently run both at the same time and don't have a problem with the single battery setup as shown.

    Have seen lots of posts on this, but have not seen this particular diagram.
    It seems simple enough (too simple ?)

    Seems like a cheap easy way to use your old battery as a backup whenever you replace it with a new one (which I do every 3 years).
    Attached Files Attached Files

  2. #2

    Default

    I don`t see an issue with both running. Is there any reason why you are not using the 'common' on the switch for accessories? Using the lug would allow a true all-off scenerio. I know alot of people leave a few things hot all the time but I don`t...just curious I guess.

  3. #3
    Member
    Join Date
    Apr 2006
    Location
    Anchorage
    Posts
    3,246

    Default

    With your circuit I do not see how you can ever have a fully charge battery. Not knowing how long you run your boat, charging current and battery drain I may be wrong. You could do a power audit to determine if you have a problem.

    When you are charging battery #2 only, battery #1 will be discharging threw your electronics, this could cause you problems with #1 battery.

    If you are running both engines at the same time only one alternator will be charging your battery if itís the trolling engine you could have a negative current drain.

  4. #4

    Default

    On your diagram questions
    A) correct
    B) you are correct IF the battery switch is in the off or #1 position, moving the accessories + to the switch common would allow you to, 1) have nothing connected to the batteries with switch in the off pos 2) use either or both battery's as a house battery or a starting battery
    c)
    D) Correct, however if you have drained down one battery by using it as a house battery consider using only the full battery to start the motor since the both position will allow a drain from the full battery to the lesser charged battery + the starting load
    E) correct
    F)

    If you have not yet purchased a kicker get one that the pull start function is a ready to use recoil not one that you need to use a rope that is tucked away some place. If you get to the boat and find both battery's down because someone left the battery switch in the wrong position (never happens) the kicker makes a nice generator to recharge with.

  5. #5

    Default improvement

    I agree that moving the navigation/accessory hot lead to the Perko common pole is a better way to go. Normal operating procedure would be to head out on the #1 battery and return to port on the #2 battery thereby charging both but never draining both.

    Sounds like nobody sees any problem with both engines running at the same time (i.e. both alternators) thereby charging the same battery ?

    Thought I read somewhere that one engine can damage the alternator on the other (I assume the larger alternator would damage the other one).

    In other words, is an alternator (or some other freaky engine electronics)damaged when there is another charging current entering the same battery from another alternator ?

    If nobody knows for sure, then I will probably check with the mechanics at Dewey's & Marita for the Mecrury main and the Yamaha kicker respectively.

    Of course my kicker is a remote control with no pull start feature (Yamaha does not sell a conversion kit to add a pull start, otherwise I would get it !)

  6. #6
    Member
    Join Date
    Apr 2006
    Location
    Anchorage
    Posts
    3,246

    Default

    [QUOTE=titobandito;733316]I
    Sounds like nobody sees any problem with both engines running at the same time (i.e. both alternators) thereby charging the same battery ?

    QUOTE]

    I see a problem.
    "If you are running both engines at the same time only one alternator will be charging your battery if itís the trolling engine you could have a negative current drain."

    You don't think a negative current drain is a problem?

  7. #7

    Default alternators

    Moose:

    My understanding is if the kicker was the only one charging a battery then the house load running off that same battery could exceed the charging current supplied from the kicker. That is the same as what I have now with the single battery setup and so far it has not caused a problem under my normal operating conditions.

    The part I don't understand is how only one alternator will be charging if both engines are running. This is where I wonder about one of the alternators getting messed up when both engines are running and connected to the same battery. My existing setup has both engines on one battery, and I have run them both at the same time. I run them both only for a short time when switching over and wanting to make sure that something is running !

  8. #8

    Default

    Both engines running will not harm anything, one alternator will not cause a drain on the other.

    Usually dual alternator systems have a paralleling circuit to keep both alternators running at the same voltage so they both stay on line.

    Your boat with two outboards doesnít have anything to balance the alternators so the one producing the most voltage will bully the other off line. As the stronger alternator reaches its max amperage output the voltage will start to drop, when the voltage drops to the potential of the weaker alternator they will run together until the load requirement causes them to split voltage again and then only the bully will be on line.

    The one problem you could run into is having one running and on line while starting the other with a weak battery, if the second motor's starter draws more current then the low battery and running alternator can deliver it will blow the alternator output fuse on the running motor. I have heard of some people replacing that fuse with a resettable circuit breaker for this reason.

  9. #9
    Member
    Join Date
    Apr 2006
    Location
    Anchorage
    Posts
    3,246

    Default

    Quote Originally Posted by Jonsboat;733492[COLOR=black
    Your boat with two outboards doesnít have anything to balance the alternators so the one producing the most voltage will bully the other off line. As the stronger alternator reaches its max amperage output the voltage will start to drop, when the voltage drops to the potential of the weaker alternator they will run together until the load requirement causes them to split voltage again and then only the bully will be on line.[/COLOR]

    ]
    Excellent answer Jonsboat.

  10. #10

    Unhappy alternators

    Quote Originally Posted by Jonsboat View Post

    The one problem you could run into is having one running and on line while starting the other with a weak battery, if the second motor's starter draws more current then the low battery and running alternator can deliver it will blow the alternator output fuse on the running motor. I have heard of some people replacing that fuse with a resettable circuit breaker for this reason.
    I think this is the crux of the problem.

    I have not yet had a problem in the existing single battery arrangement which must mean I have always had a battery that had sufficient charge to feed whatever house load was on and also start either engine when the other was running thereby not overloading either alternator.

    However, it appears I have been lucky due to my always charging the battery at home before heading out on every trip.

    The manual says the 150 HP Mercury alternator puts out 40 amps at 5000 rpm (max) and requires minimum starting amperage of 465 MCA (1000 MCA when ambient is below 32 fahrenheit !! ) .

    The manual says the T8HP Yamaha alternator puts out 80 Watts (6.6 amps @ 12V ) and requires minimum starting amperage of 245 CCA or 323 MCA.

    Clearly starting either engine off a noticeably drained 650 CCA battery while the other engine is running could blow the alternator output fuse on the engine that is already running.

    Conclusion:

    (1) I will use the simple redneck backup battery wiring system of having a second battery with only the kicker connected to it
    (2) The big engine and house load (less than 40 amp due to existing breaker on house lead) connected only to the other battery.
    (3) If the main battery goes dead, then use redneck failsafe manual battery switch over method of just taking the kicker off line and connecting the main to the kicker battery. This system will be bullet proof, and cost me nothing in additional parts except for the second battery.

    Hopefully this info is useful to others, I can't be the first one to have wanted to try the proposed 2nd battery system.

    Thank you Jonsboat.

  11. #11
    Member
    Join Date
    Apr 2006
    Location
    Anchorage
    Posts
    3,246

    Default

    I respectfully disagree your system is not bullet proof, will it work yes, but itís not bullet proof. A battery system that are recommended by manufactures are also not bullet proof, they are a better design system for the average boater. Itís extremely hard to design a bullet proof system with out knowing all the details.

    Just my opinion.

  12. #12
    Member Dan in Alaska's Avatar
    Join Date
    Feb 2007
    Location
    Anchorage
    Posts
    854

    Default

    This is a better set-up, in my opinion. I hate the 1-2-Both type switches.
    Blue Sea Add-a-Battery System

    With this system, you put all of your electronics on one battery, and all of your engines on the other battery. A voltage sensing relay makes sure both batteries get charged when the engine(s) are running, and isolated when the engines are shut off.

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •