Dual Battery Banks

  • December 31, 2013 2:08 PM
    Message # 1465757
    Deleted user
    I have recently had the pleasure of a brand new Beta 38 in TAMZIN.  With this new found reliability I'm starting to make plans for  more extensive cruising vs just day sailing and overnights in the past  because I was afraid to get too far from home with the old Volvo.  It has dawned on me that the basic Beta wiring harness supplied with the engine only charges the starting battery as the two systems are isolated.  The house battery only receives a charge while at the dock on the 120v charging system .  To date that has not been a problem however on an extended cruise it obviously would be.  My question is,  there does not seem to be any 'intuitive' means of charging both batteries while motoring. Could I simply use small jumper cable between the positive posts (while motoring) or should I look into a more sophisticated system? and if so how would it be wired ?  thanks  Larry
  • December 31, 2013 5:26 PM
    Reply # 1465840 on 1465757
    Larry, if you have a battery combining switch installed right now and are able to combine your starting and house bank, you will charge both banks when the switch is in the both position. There are other ways but this is very simple and effective
  • January 01, 2014 12:34 AM
    Reply # 1465922 on 1465757
    Anonymous member (Administrator)

    Larry:  I have the Beta 38 HP also and do love the engine.  I would recommend Nigel Calder Boatowners mechanical and electrical manual  (I think the 3rd is the latest edition) as a good place to start researching the issues with multiple battery charging. 

    I found that on the Beta - you could turn off the key w/o the engine being shut off.  Since I wasn't sure how Beta handled the alternator output with the key off and the engine running - I rewired the output of the alternator to always have a load ( battery in this case).

    There are also issues with mutliple batteries connected to a common charging point -- if one battery is weak - then the strong batteries will try to charge the weak battery - running all the batteries down etc.

    Look into battery isolator ( there are two types - diode and relay) - a way to charge seperate batteries from a single output (your alternator in this case) .

    Galvanic isolators are nice addition also.

    Also there are multiple types of batteries and each has it's own charging needs/rates etc. 

    Nigel does a good job with explaining and offers schematics etc. as this is a complicated subject. 

    Here is a link to a battery watering forum topic.

    Hope this helps - and Happy New Year!


    Last modified: January 01, 2014 10:51 AM | Anonymous member (Administrator)
  • January 01, 2014 7:08 AM
    Reply # 1465996 on 1465757
    I am not a fan of battery osolators.  The reason is that there can be up to a volt drop to the batteries from them.  That leaves them in a constant state of discharge.

    In my opinon, a better alternative is a battery combiner.  a simple system that combines the house and start batteries with there is charging current.

    after the charging current is gone the battery banks disconnect.

    Always keep an eye on electrolyte and you will know when there is a weak cell.  it will get low first (from the charge mostly going to that cell).

    good luck!


    sv jasmine
  • January 02, 2014 10:29 AM
    Reply # 1466636 on 1465757
    Deleted user
    Hello Larry -

    Reading up on Nilgel Calder's electrical guide before proceeding I think is an excellent suggestion. 

    I too have a recent BETA engine (75) install.

    Have been using 'Sterling Products' diode isolator for the two bat banks and Sterling's 4 stage 'pro' charger to manage charging while underway. The pro charger compensates for the 1 volt loss the split charge isolator creates.

    Procharger works with (overides)  existing BETA alternator internal regulator but also allows the basic internal regulator to exist as a back up to the pro charger.

    At the dock we are using 
    Sterling Power Pro Charge Ultra - 12 Volt, 20 Amp Marine Battery Charger - 3 Bank Battery Charger

    Have been operating all three above with success for over three years.

    Have a Xantrex inverter/charger in another application and having to replace my second defective unit in 1 year.

    Best, Tom
    Last modified: January 02, 2014 5:15 PM | Anonymous member (Administrator)
  • January 03, 2014 4:27 PM
    Reply # 1467545 on 1465757
    Looks like a sweet charger. Wish I would have known about that 3 years ago. And for the Xantrex. Yep! POCrap.  Run and don't look back at anything Xantrex. Just my experience.
  • January 05, 2014 3:03 PM
    Reply # 1468287 on 1465757
    Deleted user
    Thanks all.  I spoke with the tech guys at Beta and their recommendation was to run the cable from the starter to the common on the battery selector switch.  Then cables per normal to #1 and #2 battery banks.  Per Beta start the engine on Battery #1 run for about 20 minutes which should be sufficient for a full charge and then switch to Battery #2. Do not ever switch to the "OFF"  position while the engine is running.  Basis this I ran a cable from the #2 selector post to a single throw (0n/0ff) switch then to the house buss board.  Since most of my sailing is day sailing interspersed with long stretches of motoring on the ICWW (ie lots of auto pilot and chartplotter usage) this seemed like a good set up for me.  Again thanks for all the info and suggestions.   Larry
  • January 05, 2014 10:54 PM
    Reply # 1468454 on 1465757
    Deleted user
    Here's one other way.  Our house bank directly (fused) feeds a bus bar which feeds everything else.  The main panel, Ham, refrigeration, watermaker etc. have individual breakers except the main panel.  

    The selector switch common is fed from the motor/alternator, #2 feeds the house bank and #1 from the start battery instead of having everything fed from the common switch terminal which is normally done.  This allows us to start the motor and have everything running like electronics, refrigeration, etc without the fear of a voltage spike. We also run our Lofrans windless from the start battery and it could possibly cause a voltage surge when being used although we have never heard this to happen. After awhile we switch the #2 setting to charge the house bank if necessary.

    I like not having to worry about surges and spikes.

    P.S. I just saw this also what Beta has said.

    Last modified: January 05, 2014 10:56 PM | Deleted user
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