New marine install

Greetings, I am installing the following system in a boat and would appreciate any input/comments. The boat has no generator or solar panels.

I have 6 Renogy 170AH batteries paralleled (1020 AH @12 volts) to a 2000 watt pure sine wave inverter/charger. Inverter mfg. recommends 1/0 wire with a 200 amp fuse. I also purchased a 40 amp DC to DC charger from Renogy to help keep the batteries charged while underway with the inboard boat engines (2- 80 amp alternators). The system will supply limited house bank power to the 12 volt systems on the boat and primarily supply the inverter for 120 volt A/C power. The expected draw on the inverter will be 700-1000 watts.

If needed, I can increase the alternator amperage with a replacement alternator, but as the DC to DC charger is only 40 amps, I don't believe this will be necessary.

I also read on the forums that the batteries should be connected with the same length wire to a bus bar or at least have the pos and neg connections on either end of the bank. With the batteries having their own BMS individually, is this still important?

Thanks in advance!


  • billybob9billybob9 Registered Users Posts: 141 ✭✭

    The existing 12 volt DC boat system that is connected to your VHF radio, I would run on a totally separate 12 volt system (emergency) . Depending on your purpose for a bigger power supply you might consider going 24 volts as I did ( big freezer ). The choice of panels will depend on space available for mounting. 250 W panels are pretty big so smaller ones in series might be better. What are you fishing for ?

  • mcgivormcgivor Solar Expert Posts: 3,436 ✭✭✭✭✭

    For the capacity of the battery, 40A charging is not much, but it really depends on when and for how long the loads are actually used. For 1000W at 12V, 83A is required, so for every hour of use around two and a quarter hours of charging is required. Without knowing the details of when the loads are used, for how long and the charging duration it's impossible to say one way or the other if the system would be ballanced.

    The wiring of the batteries would still benifit from diagonal connection for the same reasons as lead acid, although the consequences of not doing so, would probably be less dramatic due to BMS protection, however it would be preferable to have all the batteries at near to equal voltages. If they are all wired to a common point then then diagonal doesn't apply, having all parrallel connections at equal length will ensure each battery supplies an equal share of the load current. Adding a fuse to each battery would probably be a good idea despite there being a BMS, just in case something should go wrong, call it cheap insurance.

    1500W, 6× Schutten 250W Poly panels , Schneider MPPT 60 150 CC, Schneider SW 2524 inverter, 400Ah LFP 24V nominal battery bank 
    Second system 1890W  3 × 300W No name brand poly, 3×330 Sunsolar Poly panels, Morningstar TS 60 PWM controller, no name 2000W inverter 400Ah FLA 24V nominal used for water pumping and day time air conditioning.  
    5Kw Yanmar clone single cylinder air cooled diesel generator for rare emergency charging and welding.
  • littleharbor2littleharbor2 Solar Expert Posts: 1,525 ✭✭✭✭
    edited April 2019 #4

    Invest in a DC clamp meter like this,

    You may find that even with equal length buss to battery connections. A DC clamp meter will allow you to weed out any unequal current carriers.

    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.

Sign In or Register to comment.