Cranking Batteries

Discussion in 'Boats and Motors' started by guppygill, May 31, 2008.

  1. My cranking battery was completely dead when I went to Erie yesterday. It is a new battery, used about 13 times. Do you guys charge your cranking batteries after EVERY outing? Nothing was left on, ie: lites, livewell, bilge, so why would it be dead. I charged it when I got home and all is well. Should I be looking for something else wrong, it is the first time it has done this? Does the alternator on the motor (50 horse Merc) charge the battery also? We don't have to charge a battery in a car.


  2. freyedknot

    freyedknot useless poster

    after trolling and useing the electronics the RUN back to the ramp charges up the battery even when night fishing. i never have to charge it up at home. i have a volt reading on my fishfinder and watch it when trolling with the small kicker so the electronics don,t drain the battery too low to start it up again,especially during the night bite.

  3. Thanks Frey, I have a separate battery (deep cell) for my trolling motor. Everything else is hooked up to the cranking battery. Could the motor alternator have something wrong with it? So far the battery is keeping a charge.
  4. freyedknot

    freyedknot useless poster

    yes it could have gone bad, or you have a short drawing amps from your battery.
  5. bass


  6. freyedknot

    freyedknot useless poster

  7. if you have a newer lowrance gps 3000 puck it always pulls alittle juice from your battery. the lowrance service pro told me about this, and to put a switch in going to your fishfinder.
  8. Thanks guys, last two questions, I hope, is it any way possible that the alternator on the motor is not working? And can the deep cell battery be used all day for cranking if I run into this again?
  9. Is there a way (other than using the batery several days) to check the alternator on the motor?
  10. ezbite

    ezbite the Susan Lucci of OGF

    sounds like something was left on. good advise on getting a disconnect and i do throw the charger on for a few hours everytime before heading out(just in case)
  11. The charging system on your Mercury is made of the stator and rectifier. The stator is mounted beneath the flywheel, the rectifier is located elsewhere on the motor. The stator produces alternating current and the rectifier converts the alternating current to direct current.

    The easiest way to check the system is with a DC voltmeter. Your next trip on the boat check the voltage of the fully charged battery. It should read 12.6V at full charge. While running around half throttle check the voltage at the battery again and it should read higher than 12.6. I checked mine several years ago and I think it was close to 16 volts while running.

    If the voltage is not higher than 12.6 your rectifier is fried. Rectifiers can easily be damaged by connecting the battery leads backwards, disconnecting the battery while the motor is running, or other wiring issues. Rectifiers are not repairable they must be replaced. Rectifiers are easily replaced but can be damaged again if the original problem is not corrected.
  12. Did you change anything in your onboard electrical shortly before your last battery died? If so, that could be your problem.