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Smells like low tide.
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Discussion Starter · #1 ·
I am planning on putting together a system for charging my trolling motor battery while driving between fishing areas while on the road. I know such stuff exists, as for charging up deep-cycle batteries in RVs, etc. I suspect one would need a battery isolation switch, some battery cable, and maybe some sort of voltage regulator (unless the one already in my truck is adequate/safe for the job).

However, before i attempt to re-invent something that already exists and has the bugs worked out, does anyone know of such a charger add-on that I can just go buy at a RV supply store and easily install? I'm not much of an electrical engineer, but I can do basic wiring.

Thanks!!! - Jimbo
 

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Alpine trout is right, you will not need an isolator. Not sure if you can get a kit to do what you want, but not many parts involved anyway. Are you gonna run the wire thru your exsisting trailer plug?? The "flat four" rubber plug will not do this. If you have the round style plug with 5 or more terminals will work. The most important part of this will be the FUSE. ANy auto parts store will can supply you with a fuseholder, get one for a blade style (ATC). Battery cable not required, 10 gauge wire will be more than enough. Put fuse holder at battery, run wire under rig attatch to frame etc as you go. RUn to boat battery hawever you want. NOw when truck runs, it will be charging boat battery. Even when off, will be trying to "balance" the two batteries. Now when you unplug whatever you have tween the truck and boat, you will have a very hot wire coming from the boat battery, I would fuse this also at the boat battery. A 20 amp fuse should be enough, you might have to go to a 30 amp but I would bet not. The lower fuse rating the better. Now the bad news...have been an auto mechanic 26 years ( hence the "wrench") have seen many vehicles burned up, alternators smoked, batteries melted etc from trailer wiring poorly installed. Your truck;s alternator was designed to run the TRUCK and nothing else. Anytime you add anything to a vehicle you are potentially creating problems!! GOod luck and if yo need more ino let me know.
 

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Smells like low tide.
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7,951 Posts
Discussion Starter · #4 ·
NFR: Charging deep-cycle batteries from alternator...

Thanks Alpine Trout and Wrench.

I don't have a trailer or trailer connections, just car-top my square-butt canoe.
I was thinking along the lines of running the wire to the bed of my truck where I would have connections for the deep-cycle battery. Also some kind of switch so that after I start the truck with the vehicle battery and let it get charged back up, simply throw the switch and re-route the juice to the deep-cycle battery. (That's where I thought the isolator might come in, but now I see that I only need a simple "A or B" switch).

Wrench, what you said about the alternator only being designed to run the truck makes good sense. The deep-cycle would probably be in a discharged state when hooked up and cause quite a draw for however long it takes to charge it up. However, I don't run any other auxillary stuff in my truck, and it seems like the existing alternator/charging system should be able to handle this.
But as I have little experience in these matters, I'm not sure about it. I certainly don't want to damage my alternator or deep-cycle battery. I do want to keep it simple. And safe.

A friend of mine once bought a used car and noticed the fuse to the radio was burnt out. Wanting tunes for the drive home, he bypassed the fuse, rocked out all the way home, parked and went inside for a beer and to give me a call and say, "Hey Jimbo, come on over and check out my new chariot." By the time I got there, the fire dept. was just finishing hosing down the burnt hulk.

Thanks guys. Any further guidance would be most welcome.

Jimbo :thumb
 

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Smells like low tide.
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Discussion Starter · #6 ·
NFR: Charging deep-cycle batteries from alternator...

Thank you! Not being electrically inclined, I was under the erroneous assumption that the voltage regulator somehow switched the system to run off the alternator once the vehicle was running. So you say it runs through the battery and the alternator keeps it charged.
So an on/off switch for only the extra battery seems to be what I want to install.
One more question: Is the vehicle's voltage regulator sufficient to prevent overcharging of the extra battery? Seems like it should be, but since some of my other assumptions were wrong, I would like to be certain.

Thanks again!
Jimbo:thumb
 

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NFR: Charging deep-cycle batteries from alternator...

OK, You want to run a wire from the pos of your truck battery, with a fuse, to the deep cycle pos. Then run a wire from the deep cycle neg he truck bed, or better yet, back to the truck battery neg. Do try to modify any of the trucks original wiring. ( what kind of truck??) If you want to switch this settup, put a switch in the wire going from one pos to the other, get a simple two pole toggle switch that will handle 30amps, just checked my parts books, Carquest # DS214, DS175 or DS167 would all work. Deep cycle batteries charge slowly, so do not suck up the amps like a standard battery. Takes them HOURS or DAYS to fully charge if they are discharged, do not expect a 50 mile trip tto fully charge your battery, although it will help. Your trucks regulator moniters the voltage, when it gets high ( what kind of truck??) it begins to decrease the current to the alternator field circuit, and the amperage out put of the alternator goes down. Yes, odds are it will charge boththe truck battery, run the heater a/c lights etc and charge your deep cycle without a real problem, but you are loading more than it was intended. Your biggest potential problem is that wire running back to the deep cycle. It has to stay safe, and once unhooked from the deep cycle, is now HOT unless switched off, and sooner or later Murphy's Law will be applled. Use the lowest amp fuse you can. My bet is the deep cycle, run down, will suck about 15 amps, start with a 20amp fuse. Just for contrast, your truck battery, discharged, will suck easy 80 amps as it charges up. Hope some of this makes sense......
 

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Smells like low tide.
Joined
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7,951 Posts
Discussion Starter · #9 ·
NFR: Charging deep-cycle batteries from alternator...

Thanks for the advice. I have a '88 Mazda B2200, no a/c.
Lights and wipers and radio would be only extra draw as I don't use my fan. Also, I usually have two batteries in the canoe for all-day excursions, so i can switch to the fresh one before I draw the 1st one all the way down. When fishing solo sitting in the back of a canoe, two batteries (plus anchor)in the bow help keep the canoe balanced. Can troll/explore a larger lake or river all day from dawn til dusk without getting too far into the second battery.
I have a charger designed for deep cycle batteries and it rarely takes more than 5 hours to charge up a fully discharged battery. Partially discharged tops off much quicker. Of course, I try to conserve power and make the batteries last.
Was thinking this charging setup would come in handy for road trips with long drives between destinations where I would be camping with no available electicity to plug in my regular charger. Probably only use it a few times a year at most.
Thanks again!:thumb

Jimbo
 
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