battery discharging

[brakedancer]

I have a problem with my cranking battery...when I go on a trip my battery goes dead even though I am running the big motor enough that it should be able to keep that battery charged and within 2 days the battery does not have enough juice to turn the motor over..without chargeing the battery all winter it still had kept a charge all winter...I have tryed 2 different new batteries with no help...we have disconnected everything connected to that battery..put a meter on the motor and its says it is charging 14 volts..somewhere I have read about diodes or something like that could be bad...anybody have any ideas..

[wmw]

on my boat if i came back in from fishing and left the night running lights plugged in the sockets with the switch off the battery would drain so i just had to make sure i unplug the lights when i wasn't using them.

It could take some time but you could remove one fuse at a time until you find the system that's causing the drain. or if you have to use the boat as is disconnect the battery when your not using the boat.

it has to be some thing your doing or using on the water and not in the driveway. I hope you find it.

[SkunkedAgain]

You need to do more sleuth work. There are only two possibilities, either the battery isn't getting charged or it's not holding the charge. Since you've swapped batteries we know that it's not the battery itself. The battery also holds over the winter, but we don't know if the battery is left connected in the boat or that's indoors. I'll assume that it's indoors, which leaves the door open for a drain in the system. A multimeter will help you determine if the battery is still under light load when you think that everything is turned off.

The other possibility is that it isn't getting charged by the alternator. You said that it's putting out 14 volts so I'm inclined to believe that you've eliminated this possibility, but it also seems like the most likely cause. I'd double check the alternator output. If you rule out the alternator, then it's got to be a battery drain.

[ClownColor]

Mine took longer to die (like a week or two) but my culprit was the radio. It would slowly discharge my battery as it took power to keep the clock and internal settings set. I put it on a accessory switch which now my battery is always full but now it resets my clock and stations every time!

[brakedancer]

well I just got my boat back from a different shop than I normally use...Same story everything seems fine...I thought maybe between the troops on here and a different mechanic we could come up with something..nope..no drains on battery..and motor is charging..hmmm..maybe its time for a new boat..

just getting tired of running jumper cables from my deep cycle batteries to my cranking battery on day 3 of a trip..I've gotten so I don't even use the radio or the live well if the need isn't there..so the only drain is the depth finders..and still have issues..

[jac714]

If you have not done so check the resistance of the positive and negative battery cables, it is possible to have 14 volts but not enough current to charge the battery. I would first check the cables and then have the alternator load tested if you have not done so.

[boatfixer]

BD,

What engine? What are running off that battery (engine, electronics?, lights?) and when you say you are running it long enough, could you describe duration, rpm etc?

Ive got a few guys up here that troll Pokegama at night that cannot keep batteries charged. Idle speeds typically are not enough to put out enough to charge.

[brakedancer]

its is a 1997 Merc 90 horse..I guess I'm talking running up at Winnie or Rainy River WOT for 15-30 minutes at a crack..

the battery going dead had happened with only depth finders running.maybe an occ bilge pump start...never trolling with the merc..

[98prosport]

here is a quick easy test to see if there is a draw on the battery when not in use. simple disconnect all neg wires off the battery, put a 12 volt test light in line between the cable end and the neg post. If it lights up, you have a draw. If the light does not light, then no draw. do this with each ground wire connected to the battery that goes to devise.