External regulator charging

stmoloudstmoloud Posts: 41Registered Users ✭✭
I have an older vehicle that has an external regulator. The external regulator only charges the start battery.  Ordinarily, the 'floating' led will display after about 30 minutes of travel. The regulator is set at the low end. What I would like to know, if the vehicle is stationary, can I
  • increase the setting of the regulator so to equalize 'deep cycle' batteries
  • not buy a generator for backup, instead, start the engine and use the regulator at a higher setting than usual to fill the batteries. 

160 W, 225 Ah, PWM, grid backup


  • BB.BB. Posts: 28,079Super Moderators, Administrators admin
    Can you tell us what brand/model of car you have? Is it an old vehicle with a "real" generator, or is it an alternator with an external regulator? Sometimes you can get a Marine (boat) external regulator that would interface with your alternator and give you more control over charging voltage.

    In general, car regulators are set for ~13.8 to 14.2 volts or so (at "room temperature"). A true deep cycle battery can be charged at 14.75 volts or so pretty nicely. And float charged at ~13.6 to 13.8 volts or so.

    Equalizing a deep cycle battery with a car--Unless you are on the road 100% of the time, you really should only equalize charge your battery perhaps once a month--Do that at home with a AC powered battery charger with an extension cord from utility power (typically EQ is ~15 volts and a rate of charge of 2.5% to 5% of the battery 20 Hour capacity... I.e., 80 AH battery and 5% rate of charge would be ~4 amps).

    Using a vehicle motor for charging... That may or may not be very economical. A small car engine may consume around 0.1 gallons per hour. A larger car engine may consume around 0.3 to 0.8 gallons per hour (very roughly).

    A Honda eu2000i genset (roughly ~0.1 gallons per hour @ 400 Watts) can output ~400 Watts (or ~22 Amps @ 14.5 volts when charging a 12 volt battery). You may get something like 20 amps from your car's alternator when idling (lots of variables here). The Honda will output around 1,600 Watts maximum @ 0.25 gallons per hour.

    Other issues with idling a car/RV/vehicle is the danger or exhaust fumes getting into the vehicle. A genset you can set 20-50 away with an extension cord from the vehicle.

    And we don't know anything about your power needs... How big of battery(ies) do you have? How many Amp*Hours (or Watt*Hours) do you use per day? How deeply do you discharge the battery bank? Depending on lots of variables, a 50% discharged Flooded Cell Lead Acid battery may take 6-8 hours to fully recharge (that is a long time for idling your engine and/or driving).

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • stmoloudstmoloud Posts: 41Registered Users ✭✭

    I have an ancient Bedford diesel bus about to be retired on some land off-grid.

    The regulator is originally designed for marine.

    At the moment the output is only attached to the start battery. It can easily boil the battery if not careful with the setting.

    So if I dialed up that voltage to boiling point for a couple of hours per month would that do for equalization for both the start battery and the 'house' bank?  Of course, I can get a power supply to do that but that size would be a little surplus to my needs. It would be better if I could double duty the external regulator.

    Re power needs. Presently have 2 x 80 watt panel going into one 85 A/hrs deep cell. It is servicing my very minimal needs at the moment but that is only DC. I am soon about to fabricate a suitable cable to connect to the shore power inlet to the bus for AC power via the inverter.   So I will probably have to buy another battery.  But am trialing this. Will build up as required as at the moment I have the luxury of grid power as a backup.

    160 W, 225 Ah, PWM, grid backup
Sign In or Register to comment.