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Thread: How many accessories before needing a 2nd battery?

  1. #1

    Default How many accessories before needing a 2nd battery?

    I have an 18' G3 with a 90/65 jet. At present time I'm running a gps/fish finder and a marine UFH emergency radio (which usually is off).

    I need to add a power outlet for a spot light for hunting season and wire in a bilge pump. Do I have to have another battery with a switch before I can install the extra accessories? I was told my engine's alternator put out about 23 amps so there shouldn’t be any issues… wanted to check out other opinions before getting to work.

    Money's tight before leaving on a moose hunt as today I flew over the area checking things out. Hopefully, someone here can help out.

    Thanks.
    "He should have been packing a more powerful gun...you have to be a very good shot or very lucky to stop a brown bear with a .357 Magnum." - Rick Sinnott, Alaska Department of Fish and Game biologist after a double attack by a grizzly.

  2. #2
    Member theultrarider's Avatar
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    You need another battery to run what you are wanting to run. However, I will never have another boat with just one battery for pice of mind. Be very careful in using your spotlight without the motor running. Most of those things draw alot of juice and can drain a battery very quickly. Good luck on the hunt.

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    Moderator Paul H's Avatar
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    A second battery won't allow you to run more accessories while the engine is running, as you are limited to the output of the engines alternator.

    What you need to figure out is what you will be running while the engine isn't running, as that's where your battery(s) capacity becomes an issue.

    I'd say any place you run a boat where a dead battery would be more than an inconvenience, a second batter is a necessity.

    A cheaper alternative than a permanently installed second battery is to pick up one of the those booster/jump start battery packs from an auto parts store.

  4. #4

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    The lights and bilge pump would only be running during times the engine was running which is how I run my gps. At most, I can see the gps and lights being on at the same time for the trip to/from camp during darkness. The alternator was reported to being more than enough to maintain capacity for all the items with only one battery (per Deweys)... just wanted another source of information before I started wiring up everything.


    Nothing on my boat is used while the battery is off. The fish-finder is just something the GPS has as a feature... not really needed or used on Alaska's river's where you take a jet boat.


    The booster/jump start battery pack idea is a good backup in a situtation where the battery did in fact fail. Thanks, I'll look in to that. Last thing I want to do is install a second battery the day before I leave - if I have to I will, but I really don't want to spend the time or expense if I don't have to.
    "He should have been packing a more powerful gun...you have to be a very good shot or very lucky to stop a brown bear with a .357 Magnum." - Rick Sinnott, Alaska Department of Fish and Game biologist after a double attack by a grizzly.

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    Member wolfkiller's Avatar
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    Default Second battery

    Is second to a battery switch. The more stuff you add the better the chance for a paracetic draw. I run 2 batterys with a 1-2-both-off switch. I have a little bigger boat. In your case I would put in a good battery switch that shut off everything then use it whenever you are parked.
    I added lights to my boat last year. My hunting partner bumped the switch when grabing somthing out of the boat at camp. We didnt see the lights untill it started to get dark. By then it was too late. Someone came by the next day and we got a jump. As soon as we got back home I put in the second battery and switch.
    In your case just a on off switch would do.
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    Member theultrarider's Avatar
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    Quote Originally Posted by theultrarider View Post
    You need another battery to run what you are wanting to run. However, I will never have another boat with just one battery for pice of mind. Be very careful in using your spotlight without the motor running. Most of those things draw alot of juice and can drain a battery very quickly. Good luck on the hunt.

    Boy I screwed this up by tyiping too fast. I meant to say that you do NOT need another battery to run what you have in mind.......then the rest. Like was said the quick starts are handy or even buy your second battery and do not wire it in the night before. Just have it charged and in the boat....just in case.

  7. #7

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    Thanks guys, I'm going to take a second, charged, battery and just wire in the spotlight and pump. I'm not a 'wire' guy, so I don't want to install a switch in a set up already done by Deweys... hate to screw it up and I leave Friday. The second battery will have to do... just in case.

    Thanks for your help - will report back how the trip goes upon my return (and will then have a second back-up installed before I upgrade my boat).
    "He should have been packing a more powerful gun...you have to be a very good shot or very lucky to stop a brown bear with a .357 Magnum." - Rick Sinnott, Alaska Department of Fish and Game biologist after a double attack by a grizzly.

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    Member AK DUX's Avatar
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    I'm not a electrician, but from past experience....make sure you have an in-line fuse when you wire accessories directly to the 2nd battery.

    Back in the 70's (when CB's were the thing and I was in high school) I wired a CB directly to the battery without a fuse. It worked fine, but one night at a drive-in movie, for some reason the wiring to the radio caught fire...right in the middle of not watching the movie if you catch my drift. I'm out there with the hood up, smoke rolling out & pulling red hot wiring with my bare hands...didn't do much for my esteem

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    Member breausaw's Avatar
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    How many accessories before needing a 2nd battery?

    Zero, you need a 2nd battery.

    Glad you desided to get one, hooking up to duel bat switch is not that hard to do.
    Jay
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    dual battery switch is definitely the way to go.. what I have always done is run the switch on battey one during one trip and battery two every other trip.. This assures that you always have one good battery and that a backup is always there... The diagram for setting them up is self explanatory and included in the PERKO battery switch box, whick is the best battery switch made... Check it out.

  11. #11
    Member Maast's Avatar
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    Look into something called an "automatic charging relay" the most common ones are by a company called Blue Sea Systems. They're pretty bulletproof by now.

    Basically, the ACR will engage a relay to the second battery(s) when the engine is running and allow it to charge, and then disengage it when the engine is off. This allows you to keep your starting battery full no matter what state of charge your house battery does.

    A 120 amp Blue Sea ACR runs about $70.

    IMO the best bang for your buck for your house batteries is the $60 6volt 200 amp-hour golf car batteries at Sams Club, they're made for moving vehicles. Two of these wired in series will give you your nominal 12 volts.

    The reason that I recommend such a large house bank is that even deep cycle batteries should only discharged to a 50% depth-of-discharge, thus leaving you with 100 amp-hours of juice, which you can go through surprisingly fast.

    BTW, dont use incandescent lights; use the compact florescent lights for general lighting - they're a heck of a lot more efficient and'll make your batteries go a lot farther, if you need a really bright light use at least a halogen, they still lose most of their energy to heat, but they dont stink as bad as a regular incandescent bulb.

  12. #12
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    A person should always have a 2nd battery in a boat as a back up. Your charging system is
    capable of charging two starter batteries because only one is used for a few sec.
    If you are going to add a 2nd battery, to run your cabin you also need to make sure you are able to recharge the cabin battery, you may need a larger alternator or a 2nd one depending on how much power you are using, size of your alternator and running time.
    It never simple.

  13. #13

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    I carry 3 batteries in my boat. Two are hooked together, and one is isolated for emergency
    use only. Cheap insurance.

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