using a starter battery and a deep cycle battery in a vehicle

steve9856steve9856 Registered Users Posts: 1
i may sound a little over ambitious in this project but i think it can be done i want to put a stater battery in my truck and keep it independent from the rest of the electrical system while the vehicle is off and only have it connected to the starter. then i would like to have a deep cycle battery connected to the lights, radio ect so i can power the radio and sub with the vehicle off but when the vehicle is running both batteries need to charge and be connected to the alternator. I have some knowledge about electrical components and any ideas would be appreciated. thanks.


  • AguarancherAguarancher Solar Expert Posts: 302 ✭✭✭
  • littleharbor2littleharbor2 Solar Expert Posts: 1,525 ✭✭✭✭
    Look up, Battery Isolator Kit. I think that's what you are referring to. Lots of different choices available.

    2.1 Kw Suntech 175 mono, Classic 200, Trace SW 4024 ( 15 years old  but brand new out of sealed factory box Jan. 2015), Bogart Tri-metric, 700 ah @24 volt AGM battery bank. Plenty of Baja Sea of Cortez sunshine.

  • BB.BB. Super Moderators, Administrators Posts: 30,737 admin
    You can also find some DC to DC battery chargers. And here is an interesting guy... Allows up to 15 amps of charging current between otherwise isolated batteries:

    One of the bigger issues with the typical automotive alternator is that they can output >100 Amps pretty easily--For a few minutes, but the quickly fold back on output voltage and current... Typically somewhere between 13.8 and 14.2 volts.

    For Sealed batteries (like AGM), 14.2 to 14.4 volts (at the battery terminal) for charging is OK. If you are using flooded cell deep cycle batteries, if you do not charge them at ~14.75 volts, it will take longer for them to charge and reach full charge (and ~15 volts for equalization).

    Depending on your energy needs and personal situation (where you park the truck, etc.), you might want to look at a second good quality AC charger for the "house" bank. When you park overnight/for a few days, the AC charger can bring the deep cycle battery bank back to nominal state.

    Also, if you have limited time during the day to run the truck motor (you pull the deep cycle battery to 50% state of charge, you usually need on the order of 6-8+ hours to fully recharge it... Running the truck for 3 hours during the day at 14.2 volts charging is not going to get the second battery full until there have been a few days of driving).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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