Dead battery......why?

[TonyNoriega]

Scenario: Fished last evening for 4 hours - ran engine 1/2 hr of that time. Nav lights (bow only) on while anchored and fishing. Then engine wouldn't crank on starting battery so I switched to trolling deep cycle and it cranked fine.

My GPS/Sonar displays voltage and after cranking/running it was reading 14+volts, going higher when running higher rpm's. With my limited knowledge I believe that means that the stator is generating power ok.

This morning the starting battery reads 12.07v on my multi-meter. The purchase date for the battery is Feb 07.

I have two concerns: that the battery ran down with such little drain in a relatively short period, and secondly, that my 200hpdi wouldn't crank with 12.07 volts.

I certainly would appreciate your opinions.

 

[burroak]

Re: Dead battery......why?

Check for loose/corroded terminal connections on the primary battery.

 

[TonyNoriega]

Re: Dead battery......why?

To add to my description, the cranking main battery is a DieHard 500cca unit. And thanks for the suggestion to check for corroded or bad connections, but the condition of the connections is/was pristine and the wing nuts were firmly secured, so that's decidedly not the problem. This boat is new to me 3-1/2 weeks ago and after writing my post it occured to me that maybe the boat had been sitting unused for a while, so I decided to charge the battery (which I'm doing now) and then see how it holds the charge.

 

[burroak]

Re: Dead battery......why?

To add to my description, the cranking main battery is a DieHard 500cca unit. And thanks for the suggestion to check for corroded or bad connections, but the condition of the connections is/was pristine and the wing nuts were firmly secured, so that's decidedly not the problem. This boat is new to me 3-1/2 weeks ago and after writing my post it occured to me that maybe the boat had been sitting unused for a while, so I decided to charge the battery (which I'm doing now) and then see how it holds the charge.

If you have a Batteries Plus franchise near you, they will check your battery under load at no cost.

 

[dingbat]

Re: Dead battery......why?

Chances are your battery is on the way out. Check its condtion with a hydrometer or have it load tested at your local service station.

Also, do yourself a favor and get rid of the wing nuts and replace them with SS locking nuts. Your electrical system will thank you for it.

 

[gstanton]

Re: Dead battery......why?

I'm curious as to why lock nuts are better than wing nuts? Is it to feed the bilge monster another box wrench?

Just curious......

 

[QuadManiac]

Re: Dead battery......why?

The no-load voltage of your battery doesn't tell you much. Measure the voltage when trying to crank the motor. I'll bet you'll see 8VDC or less. If the battery has a cell that is starting to fail, you will still see good voltage while charging and while unloaded.

As a matter of fact, with a failing battery, you may actually see a higher than normal voltage while charging because the battery is not accepting as much charge current, and so is not loading down the stator as much. (As a disclaimer for you purists, this is much more likely with a charging system that does NOT have a regulator, your mileage may vary and not all applicants will receive this promotional APR, etc., etc,.)

 

[burroak]

Re: Dead battery......why?

As a disclaimer for you purists, this is much more likely with a charging system that does NOT have a regulator, your mileage may vary and not all applicants will receive this promotional APR, etc., etc,.)

I see that you have taken notice of a section of the forum as well.

 

[QuadManiac]

Re: Dead battery......why?

And I'm tired of having someone argue whether it's better to use, for example, 00 wire as opposed to 000. (just a fictitious example, no comments necessary!)

 

[dingbat]

Re: Dead battery......why?

I'm curious as to why lock nuts are better than wing nuts? Is it to feed the bilge monster another box wrench?

Just curious......

Wing nut = hand tight with nothing to stop it from loosening up due to vibration.

Lock nut = tighten with a wrench and has built in vibration protection

 

[jtexas]

Re: Dead battery......why?

12.07 volts is a very nearly dead (discharged) battery. I bet it takes at least 12.4 maybe 12.5 volts to cold start that motor.

state of charge:
12.65 = 100%
12.45 = 75%
12.24 = 50%
12.06 = 25%
11.89 = 0%

Charge the battery with an external charger. Wait a couple hours for the surface charge to dissipate, then measure the voltage with your multimeter. Also check the water. Most car parts stores will load test a battery for free.

Is that a marine battery or automotive? Marine batteries are built tougher to withstand the operating environment.

 

[TonyNoriega]

Re: Dead battery......why?

Here's the latest:

I charged it over night at 2 amps and it came up to 12.93 volts . 7 hours later it read 12.88 volts. 12 hours after that reading it registers 12.83.

In about 12 hours it lost .10v from the highest reading after the charge.

I'll give it another day and test it again. Any thoughts at this point?

If I have the time today I'll take it to Advance Auto Parts for a load test.

Thanks again for all of your expertise......

 

[bassboy1]

Re: Dead battery......why?

If it loses a charge like that, you may have toasted it. We had a go cart battery that we charge, and then left for the whole day, and it overcharged just a wee bit. Luckily, we had been carrying it around in a plastic container, and charged it in that, so when the stuff spilled over, it stayed contained. After that, the battery wouldn't hold a charge.
Also, it can do that if you leave it uncharged to long.

 

[dingbat]

Re: Dead battery......why?

That drop in voltage is normal and is called a surface charge. A surface charge must be removed before testing the battery and typically takes 12 hours or so for it to dissipate.

 

[jtexas]

Re: Dead battery......why?

surface charge is sort of a measurement phenomenon, the battery doesn't really have that extra voltage - some alternatives to waiting 12 hours:

1. apply a load equal to 1/3 the battery's amp-hour capacity for 5 minutes then wait 10 minutes. In a vehicle you could try the headlights on high beam.

2. apply a load equal to 1/2 the battery's CCA for 15 seconds then wait 10 minutes. Rule of thumb says this can be accomplished by disabling the ignition (pull the emergency lanyard is a good way to do this) and turning the engine over (don't forget to hook up the water - or not - depending on your point of view). results may vary

I believe waiting six or ten or twelve hours is considered the most reliable method.

12.83 is good but if it drops down to 12.1 after one or two starts, then its got an internal short (takes a charge just fine, but discharges in a hurry) and needs to be recycled.

 

[QuadManiac]

Re: Dead battery......why?

See what the voltage is WHILE cranking. That's what's really important to you.

BTW, for around $50 you can get a variable load tester at Harbor Freight Tools. Mine paid for itself in one weekend, verifying that several batteries were fine, but one important one was marginal. With the variable tester, I have been able to test everything from deep cycle motorhome coach batteries to 4Ah gel cells. You can get a fixed current tester for around $20, but it's versatility is limited. The variable unit is well worth the difference.

 

[TonyNoriega]

Re: Dead battery......why?

Well, I just returned from the auto parts store and the battery checks out ok. I'll re-install it this afternoon and hopefully the problem is solved, but you can believe that I'll be monitoring the voltage carefully from now on.

I am very grateful to all of you that shared their expertise......not only did I solve the problem but I also gained new knowledge that will surely serve me in the future. Thanks!

 

[Boatist]

Re: Dead battery......why?

Tony
When anchored you should not have your bow navagation light on. You should olny have your white all around anchor light on.

Bow navagation light should only be on when under way. Under way defined as not anchored, aground, or tied to a dock or shore.

Fishing at anchor no Bow light Only white all around light.

Drift fishing then run bow light and white stern light or white allaround light.

 

[TonyNoriega]

Re: Dead battery......why?

Thanks Boatist for passing along that info on the nav and anchor lights. I've been boating on Tampa Bay since '62 but so infrequently go out at night that I can't remember the rules from one trip to another.

Thanks again. Tony