Something killing battery---did not happen before

« **on:** August 25, 2012, 09:30:14 PM »

So, I almost always put the charger on my battery for a while before I take out the boat---1 battery, alot of sitting around with the radio on. Today, it was totally dead when I put the charger on,--like dash lights don't come on "dead" I took off the positive battery cable, and put a volt meter between it and the battery, and it was showing full battery voltage. It showed no amp draw. I did unhook the radio so the clock, and memory were not drawing any voltage, and of course had the key off. I started to narrow down systems that could be shorting out by totally disconecting them one at a time. I found that the alternator seems to be what it shorting out, and draining the battery,--I THINK. It still makes power like it should when it is running for the reccord. My question is... do they go bad like this?-
by bad I mean an internal short? How would one test for this before replaceing the whole thing?---and will a regular automotive alternator work instead of a higher priced marine one? Thanks in advance!

« **Reply #1 on:** August 25, 2012, 10:13:01 PM »

Quote from: iloveitloud on August 25, 2012, 09:30:14 PM

So, I almost always put the charger on my battery for a while before I take out the boat---1 battery, alot of sitting around with the radio on. Today, it was totally dead when I put the charger on,--like dash lights don't come on "dead" I took off the positive battery cable, and put a volt meter between it and the battery, and it was showing full battery voltage. It showed no amp draw. I did unhook the radio so the clock, and memory were not drawing any voltage, and of course had the key off. I started to narrow down systems that could be shorting out by totally disconecting them one at a time. I found that the alternator seems to be what it shorting out, and draining the battery,--I THINK. It still makes power like it should when it is running for the reccord. My question is... do they go bad like this?-
by bad I mean an internal short? How would one test for this before replaceing the whole thing?---and will a regular automotive alternator work instead of a higher priced marine one? Thanks in advance!

With the key off, it should not be showing any amperage draw.

Most parts stores have battery load testers, maybe the easiest way to check the battery. For that matter you should be able to take the alternator and have it tested.

I wonder if there is a connection issue in the circuit? You can measure voltage across the two battery terminals,, then leave the meter on one terminal, and use the other meter probe to check the system at each connection point, looking for a large difference in what you read across the battery. That can identify a point of high resistance.

If the dash lights don't come on, but yet there is battery voltage, I would not immediately suspect a bad battery.

« **Reply #2 on:** August 26, 2012, 06:36:07 PM »

Battery seems ok,---i ran the boat later in the day after the battery had charged for a while. started many times, and sat around with raidio on for a long time. I was just mentioning the dash lights to indicate how dead the battery was. boat had not been run in 2 weeks before yesterday. Now, I pulled off the + battery cable, so whatever is wrong can't keep draining the battery. i also plan to check battery voltage after it has been sitting for a few days.

« **Reply #3 on:** August 27, 2012, 06:36:04 AM »

How old is the battery? have it tested with a full charge.

« **Reply #4 on:** August 31, 2012, 09:33:43 PM »

with everything turned off your meter should read zero between the cable and the post. diodes in the alternator will go bad and bleed power to ground. disconnect the alternator and check your meter again, if not zero start pulling fuses or unpluging your different accesories one at a time untill it does read zero

iloveitloud

Something killing battery---did not happen before

obnoxious001

Re: Something killing battery---did not happen before

iloveitloud

Re: Something killing battery---did not happen before

renegade

Re: Something killing battery---did not happen before

Wayne Zighter

Re: Something killing battery---did not happen before