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Author Topic:   Battery Type for Montauk?

swist posted 10-06-2005 08:31 AM ET (US)
I noticed my new (to me) 2004 Montauk came with a starting battery. These batteries are like car batteries - they depend on being pretty much up to charge all the time, with little drain if the engine is not running.
Even in a small boat, this is not quite the same usage model - there are lights (anchor in particular), electronics, and bilge pump which could be running quite a bit with the engine off. I would think that either a deep cycle or combination deep cycle and cranking battery would be a better choice. You don't really need the cold cranking reserve of a starting battery to deal with a 90 hp motor in mainly warm weather. And you will shorten the life of such a battery very quickly if you regularly run it down, even partially, between charges.
Deep cycle or combination batteries seem much better suited to the task at hand.
Chuck Tribolet posted 10-06-2005 06:52 PM ET (US)
A combination (aka dual-purpose) battery is probably the
right one. Deep cycle batteries aren't designed for high
current. I'd keep that starting battery till it dies, then
put in a combination battery.
How long are you not running with the electicals on? That
load is only a couple of amps.

Chuck
jimh posted 10-07-2005 12:00 AM ET (US)
When the door is opened on a modern luxury car, there are about a dozen lamps that come on in the interior of the car. I bet the current drain of all these bulbs exceeds the current drain of a typical GPS, SONAR, and VHF radio.
In addition, most cars (with transverse mounted engines) have electric fans which will run for radiator cooling, drawing considerable current. Also, cars have very powerful fans for circulating air in the passenger compartment, and these draw very significant amounts of current.
In fact, the electrical load in vehicles is increasing at a rapid rate, and in most cases is probably significantly higher than the typical small boat. Yet, I have never heard of anyone recommending that their automobile engine starting battery be replaced with a deep-cycle type battery.
The primary purpose of the engine starting battery is to start the engine, and I think that the battery should be chosen with that in mind. If your boat has very high electrical loads, you should isolate them to a second battery (a house battery) and provide it with charging current only after your engine starting battery has been restored to full charge by the engine.
swist posted 10-07-2005 07:44 AM ET (US)
The car analogy is a bit off. Sure if you have devices that drain current for short periods of time just before starting or just after shutting down, it's not going to be a big deal.
In a boat, you could have your anchor light on all night, along with your VHF and other electronics, and possibly things like spotlights and deck lights. Night fishing comes to mind.
If you leave an interior light on all night in most cars it will run down the battery - perhaps not to the point of needing to jump start it, but if you do it over and over on a battery not designed to be discharged significantly, it will reduce your battery life and recoverability considerably, and you will find that eventually leaving that light on all night *will* result in a dead battery....
jimh posted 10-07-2005 11:40 AM ET (US)
There is much prior discussion. See:
http://continuouswave.com/ubb/Forum6/HTML/000561.html

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Author	Topic: Battery Type for Montauk?
swist	posted 10-06-2005 08:31 AM ET (US) I noticed my new (to me) 2004 Montauk came with a starting battery. These batteries are like car batteries - they depend on being pretty much up to charge all the time, with little drain if the engine is not running. Even in a small boat, this is not quite the same usage model - there are lights (anchor in particular), electronics, and bilge pump which could be running quite a bit with the engine off. I would think that either a deep cycle or combination deep cycle and cranking battery would be a better choice. You don't really need the cold cranking reserve of a starting battery to deal with a 90 hp motor in mainly warm weather. And you will shorten the life of such a battery very quickly if you regularly run it down, even partially, between charges. Deep cycle or combination batteries seem much better suited to the task at hand.
Chuck Tribolet	posted 10-06-2005 06:52 PM ET (US) A combination (aka dual-purpose) battery is probably the right one. Deep cycle batteries aren't designed for high current. I'd keep that starting battery till it dies, then put in a combination battery. How long are you not running with the electicals on? That load is only a couple of amps. Chuck
jimh	posted 10-07-2005 12:00 AM ET (US) When the door is opened on a modern luxury car, there are about a dozen lamps that come on in the interior of the car. I bet the current drain of all these bulbs exceeds the current drain of a typical GPS, SONAR, and VHF radio. In addition, most cars (with transverse mounted engines) have electric fans which will run for radiator cooling, drawing considerable current. Also, cars have very powerful fans for circulating air in the passenger compartment, and these draw very significant amounts of current. In fact, the electrical load in vehicles is increasing at a rapid rate, and in most cases is probably significantly higher than the typical small boat. Yet, I have never heard of anyone recommending that their automobile engine starting battery be replaced with a deep-cycle type battery. The primary purpose of the engine starting battery is to start the engine, and I think that the battery should be chosen with that in mind. If your boat has very high electrical loads, you should isolate them to a second battery (a house battery) and provide it with charging current only after your engine starting battery has been restored to full charge by the engine.
swist	posted 10-07-2005 07:44 AM ET (US) The car analogy is a bit off. Sure if you have devices that drain current for short periods of time just before starting or just after shutting down, it's not going to be a big deal. In a boat, you could have your anchor light on all night, along with your VHF and other electronics, and possibly things like spotlights and deck lights. Night fishing comes to mind. If you leave an interior light on all night in most cars it will run down the battery - perhaps not to the point of needing to jump start it, but if you do it over and over on a battery not designed to be discharged significantly, it will reduce your battery life and recoverability considerably, and you will find that eventually leaving that light on all night will result in a dead battery....
jimh	posted 10-07-2005 11:40 AM ET (US) There is much prior discussion. See: http://continuouswave.com/ubb/Forum6/HTML/000561.html