Electrical problems

[Bob7963]

Im having a peculiar electrical problem. Prior to taking the boat out of the water I was having a starting problem (all wiring, panels, breakers, and engine is new since 2005) in that it wont start on battery # 1, wont start on Battery #2 but it will start on both. The other and perhaps unrelated problem is that the am/fm raido (which has a constant power lead direct from the battery) works only intermittently. battery # 1 is a single 12v starting battery (walmart = 6 years old) Battery # 2 is 3 12v 75amp hour deep cycle marine batteries (6 years old).
I removed and cleaned all terminals and cables. Still the same. Both batteries showing 12+.
I replaced the battery switch, worked okay for a while, and them same problem since I took the boat out of the water.
There have been no electrical problems at all since the boat was rebuilt.
I am guessing its one or more of the batteries have failed.
Before I haul the batteries out of the boat, I was looking for any other thoughts.

 

[Rich Stidger]

Healthy fully-charged batteries should show a voltage of 12.65 to 12.75 volts. If yours are lower than this range and you know they are fully charged, one or both are probably toast.

Pull the batteries and have them tested after fully charging them at home.

The other possibility is that you still have a bad connection that you have not cleaned. Your am/fm radio could be a separate problem because it draws very little power and even with half-dead batteries or a corroded connection it should still work. Engine starting is a high current draw situation where a corroded connection or bad batteries simply will not work consistently.

 

[Maine Sail]

Even batteries with no usable capacity left in them can still trick a voltage reading or a specific gravity reading.

Voltage and specific gravity only tell you when the batteries are "full" but not what the "capacity" of "full" is at that point in their life. I have a battery in my shop right now that has a resting voltage of 12.66 and shows good SG but it will only muster about 100 cranking amps when it should supply about 700CCA...

 

[KD3PC]

the other thing I have seen more and more is that the cables and terminations "look" fine, yet the internal corrosion is such that the cable will not pass enough current to start or feed a load.

Pulling back the heat shrink, cutting back a little more insulation or a strong mechanical pull on the lug are the only way I have discovered the damage.

All else "looks" good, even the idle voltage and SG.... and your comment about everything working after the switch replacement (moving, yanking pulling on that end of the cable) points to some issue with the cable...

check each/both ends thoroughly, even if you buy new batteries

 

[Stu Jackson]

And check the ground connection at the engine, too (i.e., "both ends" as suggested).

 

[Bob7963]

I removed everyone of the battery cables when I cleaned them and wire brushed both the cable and terminal, and used anti corrosion spray on all of them. They visible corrosion was really minimal, as I check and clean them every year. They are all bolted connections and I am sure I got all of them. So I have ruled out the cables and the three way switch. I forgot to mention in my first post that the bilge pump is doing the same thing the radio was. The bilge pump is also hot wired (switched and fused) to the battery and will not come on when activating the bilge pump switch. It should activate when you manually switch to on, or when there is adequate water in the bilge to activate the pump, even when the 3 way switch is off. It will only come on when the the switch is set to "both" now. Off the top of my head I cant remember if the bilge is wired to battery bank # 1 or Battery bank #2. The Radio is wired (hot wire) to battery bank #1.

The pump is new this year, and worked as designed for 4 or 5 months, as did the radio and everything else.

I am only reading the volatge of the meter oin the panel, so I cant say if it is exactly 12 volt, slightly more, or slightly less, and I didnt have my meter with me so I am just not sure what the exact voltage is.

So I am thinking one more more batteries has a problem. and I guess I will have to lug all of them to the battery store to get an opinion. Anyone have any thoughts to the contrary?

 

[Bob7963]

PS all of the cables, including the battery cables are soldered and heat shrinked. I checked all of them (12 connections)

 

[Barnacle Bill]

My guess is if your batteries are each 6 years old, they might be toast. Make sure you have fluid in them too, if applicable. But, 6 years is a long life span for a boat.

 

[Robert 47]

B Bill is right. Sounds like your beating a dead battery. If just one cell in either battery is dead, it will bring the other cells down with them, as well as the other battery. I know what you are thinking. I don't really want to buy two new batteries. :cussing:
I am in the same boat so to speak. Mine are 6 and 7 years old, and they will be replaced in the spring. Not even going to try and salvage them another season. The radio can be a source of drain. I only use ours when we are at the boat. So when the battery switch is off, so is the radio. In our auto repair business, I see alot of people come in for electrical checks. All checks out good until you ask them if they leave their GPS, phone charger, or the good one "the 900 million watt boom box" plugged in over night, and the answer is usually "yes". Some of these appliance cords are not that good and cause an electrical drain on the automotive battery. I don't say this is your problem, but I thought I would mention it here as a problem for batteries.
The hard start issue has got to be a connection somewhere that you missed. Did you look on the starter terminal? Just taking the boat out of the water in my mind would not cause this kind of a problem. Good Luck.