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Author Topic:   Fishing after dark: how long 'til a dead battery?
Marsh posted 09-06-2005 06:52 PM ET (US)   Profile for Marsh   Send Email to Marsh  
Any estimates as to how long I can fish with my navigation lights lit before my battery weakens to the point at which it will not start my engine? I would imagine that an all-nighter would kill the battery, but I would be safe for an hour, maybe two.

Any first-hand experiences here? Assume a fully-charged, new battery to begin with, with no other accessories connected.


Buckda posted 09-06-2005 06:58 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Marsh -

I recently anchored out all night in my 18' Outrage with my anchor light, VHF radio, Compass Light, GPS and fuel flow meter on all night. I was also charging my cellular phone at the time with the accessory power.

The battery started at 13V and drained to 12.5V by the morning when I switched the light off.

This was operating on a Group 24 battery (dual cycle) that I bought this spring from Wal-Mart.

I should note that I also have a second battery aboard in case I drained the first.

I don't think it will be a major problem, but if you're anchored, you should turn off your red/green running lights and only have your white, all-around anchor light on.


Speedo66 posted 09-06-2005 07:42 PM ET (US)     Profile for Speedo66  Send Email to Speedo66     
There are a number of companies selling replacement LED bulbs that use extremely small amounts of electricity. If you plan to sit and fish for hours they may be the way to go.

Try for a few examples.


Drisney posted 09-10-2005 08:21 PM ET (US)     Profile for Drisney  Send Email to Drisney     
I replaced the cabin lights, mooring light, and camper interior lights with the LEDs for the energy consumption factor. A white LED is considerably more expensive than red or amber. West Marine (not to start West Marine bashing) had the white LED automotive base light for just under $50. Yes that's right FIFTY DOLLARS. For one! (I think was the name) had them for approximately $15 apiece.
Usual disclaimers, Dave
Cicada posted 09-11-2005 08:31 AM ET (US)     Profile for Cicada  Send Email to Cicada     
I don't see where you'd have any problems fishing with your lights on for an hour or two - for awhile. A lot depends on what type of battery you are using. I had an automotive type starting battery that I was using in the boat and did some fishing / cruising at night. Worked fine for awhile then the battery would not start the motor the next day, then it wouldn't start after a few hours etc. Battery slowly deteriorated until it was basically fried. I started looking at some of the information on this site in the reference section and found that automotive batteries aren't designed for the deep cycling involved with that type of use.

If you only fish at night for an hour or two occasionally then I don't think I'd worry about it. If you fish more than occasionally you may want to consider a different battery like Buckda's, etc.


Liteamorn posted 09-16-2005 05:08 PM ET (US)     Profile for Liteamorn  Send Email to Liteamorn     
I fished many nights with electronics (radio usually off)and nav lights . I never had a problem with my batteries, I always use a deep cycle/starting battery. If you run spreader lights you might have to be carefull and these drain a ton of power. I fish with a headlight on my hat and never use a spreader, you would be surprized how much better your night vision is this way. When you do satert haveing problems it's time to replace them. I try to change one a year when I run duals instead of buying them together if possible, a litle easier on the wallet that way.
jimh posted 09-17-2005 08:00 AM ET (US)     Profile for jimh  Send Email to jimh     
A battery has a rating of Ampere-hours (Ah) which is the amount of current the battery can deliver over a period of time. Typically a battery will be rated at the 20-hour rate of discharge. To determine how much capacity your battery has, discover what its Ampere-Hour rating is, then discover the amount of current you are using to deduce how long the battery can supply that current

For example, if your battery has a rating of 50-Ah, this means that over a 20-hour period you could draw about 2.5 Ampere from it. This assumes you begin with a full charged battery and end with a fully discharged battery. If you draw more current the battery will last a shorter time, and, if you draw less current the battery will last longer.

If you want to have enough charge remaining in the battery to be able to provide power for cranking your engine for starting, you have a more difficult calculation. You'd have to determine what the minimum state of charge in the battery needed to crank the engine. Then you'd have to limit your current draw and time so as not to discharge the battery beyond that point.

If you cannot start your engine manually by a pull-starter, you should not use your engine cranking battery to power electrical devices when the engine is not running. Get a second battery and configure your boat electrical system so that the second or house battery provides the electrical energy for all loads other than engine cranking. This will prevent you from reaching a situation where you do not have sufficient charge in your engine starting battery to crank the engine.

Modern electrical devices such as a voltage sensitive relay (VSR) will help you charge both batteries when your engine is running.

The primary purpose of the engine starting battery is to start the engine, so it should always be kept in reserve for this task.

Here is a good link to understanding electrical loads on a battery in marine applications:

Optima Battery Website

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