Charging Marine Batteries

[gonefishin]

Hello, I'm a new boat owner. I recently bought a JetCraft with a Yamaha 110 outboard. I put in a battery switch so I can charge two batteries at once. However, the salesman told me not to charge a marine battery off the Yamaha 110. I'm hoping for comfirmation of this and any info on why? I would like to run my accessories and elec *****ing motor of a marine battery, but if I can't charge it then...

Thanks in advance,
John

[tripleb]

Hello gonefishin,

Well, that makes no sense ..... Did the salesman tell you how to disconnect the charging circuit of the outboard?

The outboard is going to charge the batteries when underway and even when at home running on earmuffs.

Perhaps you misunderstood the salesman.

[Ken]

John,
I'm not familiar with the Yamaha 110, but I assume it has an alternator/rectifier/regulator output that is capable of at least 20 amps. - and that's plenty to charge a "marine battery" - I don't know what the heck your salesman is talking about.
You really don't want to try and charge two batteries in parallel - it can be done, but not recommended. There are several ways to go with the batteries, depending on whether you have a 12 or 24 volt *****ing motor.
In general, you want a pure "starting" or "dual purpose" battery for your starting battery. For pure "starting" type, you don't want any accessories on it - just used for "starting" and console gauges only. If dual purpose, you can put a few accessories on it, like a radio, depthfinder, livewell pump. You have to be careful with accessory load in that you would not want to run your starting battery down below its capacity to start the motor when needed - like you might encounter if you ran accessories all night w/o recharging with the motor alternator.
For your *****ing motor, you want a "deep cycle" type battery(s) - you can also put other accessories on the deep cycle.
If you want the motor to charge more than just the starting battery, then I would recommend an onboard charger like the one offered by Stealth Technologies (www.stealthcharging.com). It's purely solid state and monitors the condition of the starting battery - when it's fully charged, then the solid state circuitry swithes over to other batteries and charges them - pretty neat idea, but expensive - go take a look.
Tell me what kind of ***** motor you have and what kind of accessories you want to power and maybe I can be a little more specific for your application.
Good luck,
Ken K

[gonefishin]

Hey Tripleb, thanks for the reply. Well, the salesman seemed to imply that the alternator could not handle charging a marine battery and may damage it. I'm no mechanic, but I've always understood that alternators put our a max current, unlike generators that try and meet the demand. so the only thing I could maybe expect is that the batteries wouldn't fully charge. Do you think it is possible to damage the alternator this way?

gonefishin

[tripleb]

Hey gonefishin,

Should not hurt the alternator. I have been running a Deep Cycle battery on an Evinrude for 15 years (Evinrude went belly up this year) and never had a problem with the alternator. Deep cycle needed for *****ing motor.

As I understand it, most outboard motors have a "max" alternator output. That "max" is usually at WOT. At less RPM's the output of the alternator is less.

Certainly, you cannot expect the alternator to keep the Deep Cycle battery at full charge if you use your *****ing motor a lot. I always would take my Deep Cycle battery out of my boat every couple of weeks for a proper charge.

[gonefishin]

Ken,

Thanks for the info and reassurance. I'll look into the Stealth Technologies charger, sounds like a good idea. However, for now I'm using a Pergo switch...I'll be sure not to charge both batteries at once. I don't currently have a *****ing motor, but will be getting one soon. Currently I have everything hooked up to a single battery:

Fish finder
GPS
down riggers
live well pump
Stereo (500w amp)
Spot light
boat accesories (bilge pump, running lights, etc.)

I figure everything should be hooked up to the marine battery. What is the most common configuration?

[Ken]

John,
There are many ways to go with this - but probably the most common configuration is to have a pure starting type battery dedicated to the motor. This will start the motor and also power the usual console gauges, running lights, bilge pump, and maybe a depthfinder and gps (these are accessories that you run normally when the motor is running, and the alternator can handle the load). You just want to make sure you don't pull the starting battery down below, say 12 volts, so that it will start the motor when needed. There are battery voltage monitors available that sound an alarm when a preset voltage level is reached.
For other (heavy load) accessories that you want to power when the motor is off, then go with a heavy duty (size 27 - 100 amp-hour min) deep cycle or dual purpose battery. You can use the battery switch to manually switch over to the deep cycle and start the motor (assuming it has enough power at that point) and recharge with the motor alternator.
When you add the *****ing motor - well, that is going to be another configuration that depends on whether you go with 12 or 24 volts. Let me know when you decide, and we will discuss your options.
Good luck [img]smile.gif[/img] ,
Ken K