Battery Management

Discussion in 'Electrical Stuff' started by Chip S, Feb 18, 2020.

  1. Chip S

    Chip S Member

    70
    Jun 17, 2019
    Bordentown, NJ
    1993 Sea Ray 200 Overnighter
    1993 Mercury 150 hp Black Max Outboard
    The 200 Overnighter I recently purchased had a second battery installed by the previous owner. The 1/2/Both switch is wired to the engine so the battery selected starts the engine and receives charging from the alternator. The electrical bus and bilge pump, however, are hardwired to Battery 1. I plan on rewiring the electrical bus to the battery switch eventually, but until I do I'm debating how to manage my batteries. I'm considering running primarily on Battery 1 and using Battery 2 as an emergency backup only. I would run on Battery 2 now and then to keep it charged but primarily run on Battery 1. I'm concerned about running for long periods of time with the radios, etc. running off of Battery 1 while Battery 1 is not being charged by the alternator. It's a stupid way to hook up a battery switch but I've found that when buying a used boat it usually takes 2-3 years to find all of the "stupid" and fix it.
     
  2. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Don't understand the "stupid" comment. When running, you run on both. When on the hook pick 1 or 2.
     
    Stee6043 likes this.
  3. Stee6043

    Stee6043 Well-Known Member

    Jun 1, 2015
    West Michigan
    1997 Sundancer 400
    7.4L Gassers
    I think your boat is wired quite correctly.

    Bilge pumps should not be switched, they are correctly wired directly to a battery (with a fuse, of course).

    Typical use of your switch would be running the boat on "both" so both batteries are being charged by the alternator. When at anchor select 1 or 2 to only deplete one battery. Before starting to leave your favorite anchorage switch it back to "both" to again charge both. Rinse, repeat. Quite common...and I wouldn't recommend "fixing" it :)
     
  4. sbw1

    sbw1 Well-Known Member

    Oct 10, 2006
    West Michigan
    This is listed in my signature
    This is listed in my signature
    IMG_4230.JPG I used to alternate batteries when I owned a boat with this set up. If we anchored or beached the boat we would switch to the opposite battery after we got to our destination to save the other one. Our boat was in a slip and we would switch to BOTH and the charger when not using the boat. That way we always had fresh batteries.
     
  5. Chip S

    Chip S Member

    70
    Jun 17, 2019
    Bordentown, NJ
    1993 Sea Ray 200 Overnighter
    1993 Mercury 150 hp Black Max Outboard
    The wiring of the bilge pump will not be changed. That is correct. The wiring for everything else in the boat (radios, gps, lights, etc.) is currently connected to Battery 1 irregardless of the switch position. Currently I can have the switch in the "Off" position and still use everything in the boat except the engine. If Battery 1 dies my radios are dead even if Battery 2 has a full charge. Putting the switch to "Both" with a dead Battery 1 will give me a short period of time to use the radios but a dead Battery 1 will kill a live Battery 2 very quickly. Best practice is to be able to run the electrical bus off of either Battery 1 or Battery 2.
     
  6. scoflaw

    scoflaw Well-Known Member

    Aug 10, 2011
    cape cod mass, cape coral fl
    1999 Powerquest legend 260 sx
    502 mpi Bravo 1
    Well that's not correct but a quick fix to make it right.
     
  7. paulswagelock

    paulswagelock Well-Known Member

    Oct 25, 2010
    pa
    2018 SDX 270 OB 300 Verado
    Verado 300
    The house load should be on a separate battery than the engine, but it also should be switched, not hardwired. Then a VSR or ACR is used to charge that battery while the engine is running. Bilge pumps etc get hardwired directly to the battery.
    The cheaper solution used by many builders is to put the house load and engine all tied together, and have the battery selector simply pick which battery(s) supply the source to that combined load.
    You should get a two battery switch that turns them both on or off, with an emergency parallel switch, and keep everything isolated. This one would be what you need:
    [​IMG]
     
  8. Stee6043

    Stee6043 Well-Known Member

    Jun 1, 2015
    West Michigan
    1997 Sundancer 400
    7.4L Gassers
    Ahh, I see. Your original post didn't exactly read that way.

    Typically everything should run through your switch (sans the bilge pump) so you can run all loads on either 1, 2 or both. It's very common and should be easy to accomplish.
     
  9. Wylie_Tunes

    Wylie_Tunes Active Member

    768
    Oct 26, 2012
    Lake Wylie NC area
    N/A
    N/A
    With a 1/2/BOTH style switch, I prefer to have ALL loads wired through the switch, except a few that are more crucial like auto bilge, CO, etc. This means when the switch is off, the boat is off, except those essential loads we want voltage to all the time.

    SO get that re-wire done. Next, I want to know what type of batteries are in there. If you have pair of cranking or dual purpose, then you can alternate between their use. If you have one cranking and one deep-cycle, then you should use them as such. Its ok to crank and run on BOTH, but you would want to click over to which ever is the deep-cycle when you drop anchor. This isolates the cranking bank for starting, as well as you will get the most out of the batteries, by not using the cranking as a house battery. And you get the most life out of a deep-cycle when its not used a main cranking.

    With everything wired through the switch, you will only draw from the bank you've switched to. With loads circumventing the switch, that bank can get drawn down while the is running, if the switch is not put on that bank or BOTH.

    Running on BOTH, especially after pulling anchor, allows the engine(s) to put some juice back in that likely run down house bank.

    If you have a large house bank and plan to use it for any length of time while on the hook, you should depend on shore charging to replenish the house bank, once the boat is back home. Dont rely on the engine alternator and dont leave the bank down when the boat is put away.
     
    techmitch likes this.
  10. Chip S

    Chip S Member

    70
    Jun 17, 2019
    Bordentown, NJ
    1993 Sea Ray 200 Overnighter
    1993 Mercury 150 hp Black Max Outboard
    Thanks to everyone for the insights. Both batteries are cranking batteries with 125 min reserve. At this point I'm leaning toward running on Battery 1 most of the time and running on Both now and then to keep Battery 2 charged. Once I get the electrical bus wired to the battery switch it won't be an issue but it might take a few months before I get that job done.
     
  11. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    Your boat originally came a single battery with no switch - not even an on/off switch. At some point point someone simply added the switch and cables to get the redundancy of two batteries for starting the engine. Basically still a stock system with an extra battery on standby for the engine.

    Since you have two starting batteries right now, you really don't have a "house" battery. You'd be better off just splitting time equally between the two batteries on a regular basis. When charging, pick the battery that needs it, rather than splitting the charging juice between two batteries. It'll charge up better that way.

    An easy way to split time between the batteries is use #1 battery on odd days that you boat and #2 on even days.
     
  12. BillK2632

    BillK2632 Well-Known Member GOLD Sponsor

    Jun 25, 2009
    Lake Norman, NC
    1999 185 Bowrider,
    Mercruiser 4.3, Alpha I
    I have two batteries and a 1/2/both switch. Everything except the bilge pump is wired through the switch. I have two starting batteries and just alternate between them. At the end of each day I just switch to the opposite battery. Even running the stereo for hours I have never run the battery down. I rarely run on both, maybe if I am going on a long run and want to charge both batteries - problem with both is if one battery is really low, it will pull the good battery down.
     
  13. Chip S

    Chip S Member

    70
    Jun 17, 2019
    Bordentown, NJ
    1993 Sea Ray 200 Overnighter
    1993 Mercury 150 hp Black Max Outboard
    With the nice weather today I went down and moved the electrical bus wire from Battery 1 to the battery switch output post. Now the electrical bus is getting electricity from whichever battery is being used. I'll just switch between Battery 1 and Battery 2 when I use the boat. I had a boat with this setup before so I know how to manage it.

    What I don't get is the electrical bus wire was long enough to reach the battery switch. I only needed to put a larger ring terminal on the end of the wire. I originally thought the person who installed the battery switch didn't run the wire to the switch because the wire wouldn't reach, but that wasn't the case. Whoever installed the battery switch had a very limited understanding of the boat's electrical system.
     

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