dead battery

[mercerfisherman]

Hi, not sure if this is the right forum or not but my question regards a battery. I own a 1984 50 hp Mercury outboard. I thought I charged my battery long enough prior to launching my boat but I'm not totally sure. My battery tester did show 2/3 charge. This "marine" battery has about 500+ cranking amps. Approximately 3 years old. It is supposedly the starter battery. However, my bilge pump, navigation lights and my livewell systems all feed off my starter battery. All the connections were tied together that way when I purchased the boat. To make a short story long, the battery started my boat just fine, but a day later it went absolutely dead... Now the battery won't even take a charge. Either my battery tester showed a false charge, or something is sucking my battery power or the battery is just worn out. Could a short in my wires deplete my battery power? I did notice that my bilge pump would turn on for only a few seconds and then turn off. But when fiddling with the knob I could get it to turn on for an extended period of time. Also, I found a mouse living in my boat. I suppose it is possible that the mouse chewed on a wire, causing a short. Lastly, because I have multiple connections to my "main" battery... what kind of battery should I buy and use when I replace my old one? Any thoughts, advice? Thanks.

 

[j_martin]

Re: dead battery

Hi, not sure if this is the right forum or not but my question regards a battery. I own a 1984 50 hp Mercury outboard. I thought I charged my battery long enough prior to launching my boat but I'm not totally sure. My battery tester did show 2/3 charge. This "marine" battery has about 500+ cranking amps. Approximately 3 years old. It is supposedly the starter battery. However, my bilge pump, navigation lights and my livewell systems all feed off my starter battery. All the connections were tied together that way when I purchased the boat. To make a short story long, the battery started my boat just fine, but a day later it went absolutely dead... Now the battery won't even take a charge. Either my battery tester showed a false charge, or something is sucking my battery power or the battery is just worn out. Could a short in my wires deplete my battery power? I did notice that my bilge pump would turn on for only a few seconds and then turn off. But when fiddling with the knob I could get it to turn on for an extended period of time. Also, I found a mouse living in my boat. I suppose it is possible that the mouse chewed on a wire, causing a short. Lastly, because I have multiple connections to my "main" battery... what kind of battery should I buy and use when I replace my old one? Any thoughts, advice? Thanks.

If you pull the battery out of the boat, clean the connectors and put it on a charger, and it won't take a charge, then likely an internal connection broke.

It's a mechanical thing, happens in boats all the time because of the roughness of the ride. Unfortunately, the fix is to replace the battery.

The percentage of charge indication on a battery is just a guess. A 3 year old battery likely has a fairly high finish voltage, and would read high on a charger. If it's a smart charger, you'll note that after it gets to 100 percent it still charges a few seconds quite frequently. Also, the charger indication is a percent of full charge, and full charge (amp hours) dimishes with battery age.

You failed to mention how long you run lights and pumps on one charge. You might want to go up to a group 27 battery if you fish all day.

Also, charge your battery as soon as you can, even if it is only partially discharged. A discharged battery has both mechanical and chemical things going on in it that degrade it rapidly. A charged battery doesn't.

hope it helps
John

 

[bustermin]

Re: dead battery

Your battery tester should have a "Load Test" button on it, that will tell you if the battery is good or not.

 

[Silvertip]

Re: dead battery

Many folks erroneously feel that when their battery goes dead that there "must be a short somewhere". Fact is if there was a short fuses would be blown or wires would be melted. The number of things connected to a battery is of no importance. What is important is how much current (amps) each of those items draws. Lights draw about 1 amp, the bilge pump would draw about 2-3 amps and the live well would draw about the same.. But all of those things draw current only when turned on. When batteries go bad they can do so almost instantaneously or they may degrade slowly. Take the battery to any auto parts store and have them load test it. That will tell your whether it is alive or dead.