Will my alternator maintain my 12 volt deep cycle battery at full charge?

[Tomcat]

I need some help please. I recently purchased a new 15 HP four stroke manual start Honda outboard. The spec sheet says the motor's alternator will output 6 amps at 3000 rpm. I telephoned the Honda technical department and they said that the alternator will output 1 to 2 amps at trolling speed (90% of my fishing day will typically be at trolling speed).

 

First question

 

If I connect the alternator cables to my 12 volt deep cycle battery, would I be able to maintain my deep cycle battery at full charge while my deep cycle battery is dedicated to powering a colour sonar unit which draws 1.5 amps per hour? Note that I have always recharged my deep cycle battery (6 years of operation) at 2 amps.

 

Second question

 

Are there any connection caveats when I connect my sonar unit to my deep cycle battery (that has connections to my motor's alternator)?

 

Thanks in advance.

[aplumma]

The deep cycle battery has an amp rating on it that is like 600 or more amp hours. Divide that by your power draw and you have more than enough power to run the depthfinder for a long weekend without charging from the motor.The problem that some people have is the charging circuit from some outboard motors will give you feedback on the depthfinder and create clutter and false signals. If you want to see how well your motor is chargng the battery it should read 12.65 volts at full charge charge it till it is then take it out for the day and then check it again at the end of the day if should still read 12.65- 12.00 volts at the lowest. Less than that means you are pulling more out of the battery than you are putting in.

 

Art

[Terry]

if it's only the fishfinder on it it will more then keep it charged...

it would run for weeks without the motor charging it

[fishboy]

As has been mentioned, you can run a sonar unit of a fully-charged battery for a weekend easy.

[Tomcat]

Thanks for the input guys. However, I'm confused.

 

Presently, I run a Lowrance X-85 during a week's fishing trip (Sat to Sat) off a 12 volt 33 Amp hour deep cycle battery without having to recharge the battery. My X-85 draws only 400 milliamps/hour with the back light off (90% of the time) and 700 milliamps per hour with the back light on (10% of the time).

 

However, I'm considering upgrading my sonar unit to a colour unit (and maybe a GPS combo unit). Typically, such units draw 1500 milliamps per hour. My existing 33 amp hour battery would theoretically last just a little over two 10 hour days. Consequently, I've got to either purchase a bigger deep cycle battery or somehow recharge the existing battery. The latter possibility is why I asked my original question about whether my 15 HP Honda, outputting 1-2 amps at trolling speeds, could maintain my existing battery at or near full charge while powering a sonar unit.

 

My neighbour advised me that my Honda had no chance of recharging my deep cycle battery because the output would have to be at least 10 amps to initiate the charging process. Any comments on his advice?

[Terry]

1500 milliamps, doesnt that = 1.5 amps per hour....

 

and without a doubt it will keep charged

you will never need to take it out of the boat to be charged

[tonyb]

The colour units do draw a significant amount of power compared to monochrome. I would have to believe that the alternator in the Honda would do a fine job. Sounds like you are getting the color unit anyway (great choice) so let us know how it goes.

 

Tony

[OhioFisherman]

All the electronics on my boat run off the starting motor battery, two sonars, livewell pump, running light. My electric trolling motor has a separate battery. Never had a problem with the staring motor battery running down.

 

I have fished all nite using the running lights and running the sonar.

[hawg_hauler]

It is benificail to slow charge a deep cycle. High amperage current can damage a deep cycle. I see no problems in your set-up.