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Thread: House battery connector question???

  1. #1
    Member Gundog's Avatar
    Join Date
    Apr 2007
    1250 miles S/O paradise in the lwr 48 dreaming of SE AK

    Default House battery connector question???

    My new boat that is still being built will have 3 batteries, one for starting and two paralleled together for the house. I run an electric pot puller when shrimping and use dual house batteries connected in parallel like one big battery. The system has a battery switch and an ACR.

    My plan is to keep an inflatable dingy on the roof of the new boat and I have an electric trolling motor to power the dingy. I was thinking of connecting the 2 house batteries in parallel with an Anderson connector so I can unplug one battery for use with the dingy avoiding hauling an extra battery. The dingy will not see much use it will be for safety or going ashore on islands in AK. The raft won't be on the boat all the time. I will also use an Anderson connector on the leads of the trolling motor so the battery can be unplugged moved to the dingy and plugged into the trolling motor.

    Now back to the battery being used for the boat through the battery switch the 2 house batteries provide emergency backup power for engine starting through the battery switch. The Anderson connectors are made in different wire size and amp ratings. I am not sure how big I should get to tie these 2 house batteries together. I can get them in most any wire size and in several amp ratings 50amp #6 or #8 wire size. 120 Amp, 175 amps & 350 amps. If you don't know Anderson connectors are what they use on Electric forklifts or jumper cables on tow / service trucks they are very high quality. I will solder and heat shrink the marine grade wire.

    For the amp draw in my house use 50 amp would be plenty but I am wondering when the battery is used for emergency starting I might need to up the amp ratting to 120 or 175 but if I do finding a connector to fit the leads on the trolling motor will be hard but I guess I can solder it.

    What do you marine wiring experts think? Another thing I am wondering is what will happen when I use the trolling motor and run down one of the house batteries and then connect them back together I would think it would drain the other one until they equalized but then they would both get charged again. This system will not see much use this way but on occasion it will be used.


  2. #2


    Size it for starting one engine.
    Here is what is running thru my mind.
    The motor battery went bad on the trip out and I didnít notice it, took my dingy/house battery and went ashore leaving who knows what on in the house. Had a great time on shore, returned to the boat and the only chance I have of starting the boat is a Ĺ used dingy/house battery. Hopefully I noticed this before I hooked it back into the dead system and dumped Ĺ of it into the dead house battery.
    Wouldaah couldaah shouldaah
    From now on Iím going to make sure the engine starts before I hook my dingy/house battery back into the system, I might want to swap it into the starter battery position. If I did this I could size the dingy/house battery wire at Ĺ motor starting or Ĺ normal load whichever is heavier since it will share required load with the house battery and by doing that I can use the smaller connector.
    Marine Wiring Expert = An electrical minded person who loves boats and (a) is more than 50 mi from the job (b) is a has been drip under pressure

  3. #3
    Join Date
    Apr 2006


    I am not an expert on marine electronics, I do know a little about charging batteries and sizing cables. Do you want to size the cable for the trolling motor only, if so you could use what the manufacture recommends? I would not solder the battery connections; if the connector got hot you could melt the solder. I do not think your boat charging system will be able to recharge the trolling battery to 100%.

    If it was my boat I would recharge the trolling battery using the proper battery charger, not the boat. I would also use the boat battery system to keep the battery top off. It you use the trolling battery to help run the house you will not have a trolling battery @ 100% charge. Because it is so importance you know your trolling battery is fully charge, I would also monitor its voltage.

  4. #4



    I just installed a Switch system on my boat this past weekend (see attached). I will admit, I had it all planned out on paper thinking it would limit mistakes and install time. Man, was I wrong! lol.

    It took me all day long to install because I kept mismatching wires - unbelievalbe. It was kind of humorous at times - and frustrating together. But, I got it installed. After installing the circuit breakers, switch and ACR, I measured all my wiring runs and ordered the wires online with lug crimped and shrinked. Man, that was great!

    Sorry, probably of the subject, but hopefully you can learn from some of our mistakes. I will admit, if I didn't have that plan on paper, it would of doubled my install time!
    Attached Files Attached Files

  5. #5
    Moderator Paul H's Avatar
    Join Date
    Apr 2006


    What size cable you use for the starting circuit depends on how long the circuit is. On my boat I mounted the batteries fairly far forward and replaced the cable the engine came with to 4/0 from the engine all the way to the batteries. That is a bit overkill, but the two items that leave boats dead in the water are electrical problems and fuel problems. I figured I didn't want to deal with electrical problems hence the overkill in the cabling. I'd say between 0 and 4/0 cable, it just depends on the length of the circuit.

    I think you'll find shuffling the batteries around will be a PITA, and would advise getting a small gas kicker for the raft.


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