Charging trolling motor battery from big motor

[GrizzlyAdams]

First of all can I charge my trolling motor battery from the big motor? Secondly how can I do it? I don't want to leave it hooked up to the big motor all the time but was thinking about hooking up some alligator clips to one end and connecting the other end to the motor battery. I suppose jumper cables would be the same thing. Is this possible and how would I go about doing it. How long would it take to fully charge the battery back up? Anything that I should be putting in line such as a fuse, etc? I will be running a 12 volt trolling motor. Thinking the minnkota power drive V2 55#. Thanks for the help.

[PerchJerker]

You can get a DC on-board charger like the Dual Pro Charge On The Run series or the Minn Kota DC charger.

They're easy to install, they mount in your boat (and stay there) and connect to your starting battery and your trolling batteries. The alternator on your outboard chargers the trolling batteries.

Positives are that they are convenient, not too expensive, and will charge your trolling batteries. Negatives are that they are really dependent on your outboard motor's alternator --- high output and long run times will do more to recharge your batteries than low output and short run times. Bottom line is that if you're not running your outboard a lot you're not putting much charge into your trolling batteries.

You can check them out HERE at Pro Fishing Supply if you want. Hope this helps.

[GrizzlyAdams]

Thanks pj. That is what I was looking for. I have a 1989 90 horse mercury. What would you suggest to be the best one to get for this motor? Can they also be connected to AC for charging at home also. I would like a good one for trips up north. I want to be able to troll all day if possible. I plan on having 2 separate batteries for the trolling motor so that I can switch them when one dies or should I connect them together? How long would I need to run to get the batteries back to a full charge or so? I will be getting the trolling motor in a couple weeks and trying to figure out in advance the best way to hook it up to get the most use out of it. How long does a charge on a battery usually last on the mentioned trolling motor? It will be a bow mount. Never owned a bow mount before so pretty new to these. I had a smaller trolling motor for the back of my little boat and that one never really did last too long. What type and size of battery should I be looking for for this also? Does a certain brand work better than most others?

[Whoaru99]

Thanks pj. That is what I was looking for. I have a 1989 90 horse mercury. What would you suggest to be the best one to get for this motor? Can they also be connected to AC for charging at home also. I would like a good one for trips up north. I want to be able to troll all day if possible. I plan on having 2 separate batteries for the trolling motor so that I can switch them when one dies or should I connect them together? How long would I need to run to get the batteries back to a full charge or so? I will be getting the trolling motor in a couple weeks and trying to figure out in advance the best way to hook it up to get the most use out of it. How long does a charge on a battery usually last on the mentioned trolling motor? It will be a bow mount. Never owned a bow mount before so pretty new to these. I had a smaller trolling motor for the back of my little boat and that one never really did last too long. What type and size of battery should I be looking for for this also? Does a certain brand work better than most others?

If your batteries are both in good shape and of the same size, I'd put them in parallel rather than use them individually. Reason is that the batteries will give more power in total (longer run time) when they are drained more slowly. With two batteries in parallel each will see roughly 1/2 total demand thus give up more total amp-hours, and amp-hours are the ticket to run time.

I think the alternators on the Mercs of that size are around 15A or 20A and that will be split between running the engine and charging two or more batteries. So, if everything was perfect (and it won't be), it would probably take anywhere from 5 hours to 10 hours of strong running to fully, or nearly fully recharge the batteries, IMO.

Of course, it will help extend your run time, but I think you'll have to run the big motor a lot to recharge them.

It's hard to say how long the batteries will last because it depends on their condtion, capacity/size, wind/waves, boat size, trolling speed, etc.

[GrizzlyAdams]

The batteries will be brand new so they will be equal right away. Is it worth doing the dc charger then or better to just get an AC charger and do it at the dock. We will usually spend from sun up to sun down on the water when we are up north. Not to say that the entire day will be spent trolling though. Just wondering roughly how long will batteries last for trolling. I know conditions will have an impact on it but looking more for an idea of how long we would be able to troll with 2 batteries in a days worth of fishing. We also like to drift spinners too. So again the trolling motor would not be used the entire day. But if trolling is working good we may troll til the batteries die. Thanks for the replies so far.

Should add the boat is a 1983 Lund tyee 4.3 16'. It is a deep boat. "v" front

[Whoaru99]

I'd think two good batteries in parallel will get you most or all of a full day of fishing as you describe it, maybe more, but for good battery life it's VERY important to recharge batteries as soon as possible after use. Don't let them sit partially discharged. That's hard on the battery.

If you have the option of AC powered charger over night or duing mid day rest/break, I'd go that way no questions before choosing the alternator charger method, IMHO.

[jeffreyd]

I would if you decide to charge the batteries off the start battery, while using the motor, as i understood your comment, would put a battery isolator in line between the start and troll motor batteries. Even tho you will be adding to the power that is available by having the extra battery, it will still draw it down at the same rate considering they are all of equal charge and condition.

If one of the batteries is weaker or not in the same condition as the others, when the motor or charger is put on the system, that weaker battery will be taking as much as it possibly can from the output. Over time this will only cause the other batteries to become weaker and less productive.

A battery isolator is similar to a check valve. it however will allow the charge from the alt or charger to go through the system and charge all the batteries but it will not allow the use of the energy from the starting battery. Not sure that i would want to chance being stuck someplace with a dead start battery because the use of a troll motor.

I would also put inline a reset type breaker, if you look at the various types out there, the ones that have the button on top that when pushed releases a small bar and breaks the current. Also the distance that you will be running from back to front will require a certain size wire. You do not want to go too small as the draw will overheat the wiring and cause problems, and too large is just a waste and pain to hide.

I will look to see if i can find the name of the breaker and isolator that i have used in past.

the breaker is made by Pollak and is listed as

Single Rate Thermal Type Breaker- Type III Switchable Manual Surface Mount

The isolator is made by Cole Hersey.

I found both at their respected websites.

[GrizzlyAdams]

Thanks guys. My concern as you mentioned is not to drain the starting battery by connecting to it. I am just looking mainly for the best way to hook all this up to get the most out of all of the batteries. The depth finder (Soon to be a HB 858c), lights and radio are hooked up to the starting battery. Is this the proper way for them to be hooked up? There was only one battery when I bought the boat a month or so ago. I am adding the trolling motor and the HB in a week or 2 with 2 new batteries for the trolling motor. What size and type battery should I be looking at. I don't want to go cheap as I like things to last but don't want to spend so much I have to give up my first born. All your help and advice is greatly appreciated.

[BobT]

I would suspect you might be a little disappointed at the results of using your outboard to maintain your deep-cycle batteries. Not saying you can't do what your asking but the amount of time it would take to recharge your deep-cycles will be too much for you to benefit much this way.

Suppose you use your electric trolling motor for an hour and you used it rather heavy so it was drawing roughly 30A on average for that hour. If the outboard could put out 30A it would take an hour to recharge the deep cycles alone so you'd have to run your boat for an hour to recharge the battery(s).

[jeffreyd]

bobt, i think you are correct but the perfect world example is just that, it does not take into acct voltage drop or resistance in wiring so that 30 amps output by the time it hits the battery is less. if it were mine, i would put 3 batteries for the troll motor and wire as i described above reserving the start battery for just that. but this is me, and my experiences with low voltage equipment.

[GrizzlyAdams]

I am glad I asked. I figured there would be more to it than just charging it up with a quick cruise.

Should my depth finder and lights be hooked to the same battery as the starter or should they be on a different battery? My older depth finder didn't take much juice and am wondering if the hb 858c will take a lot more juice. I would think it wouldn't be enough to drain the starting battery.

How much will the lights wear down the battery at night with the depth finder also attached?

Sorry for the questions, I want to know these things now rather than find out the hard way out on the water and not be prepared.

[harvey lee]

Craig, I have three batteries in my boat. One for the motor, one for the trolling motor and one for the extras.

I do not know if I would hook my trolling motor batteries up to the outboard. I think it would take alot of hours of running time to recharge.

I simply use an onboard charger and plug it in at the end of the day.

[harvey lee]

Craig, I have three batteries in my boat. One for the motor, one for the trolling motor and one for the extras.

I do not know if I would hook my trolling motor batteries up to the outboard. I think it would take alot of hours of running time to recharge.

I simply use an onboard charger and plug it in at the end of the day.

I use to have my livewell pump hooked up to the motor battery and while catfishing for an extended time, I drained my outboard battery.

My outboard battery is just for that.

[Wish-I-Were-Fishn]

Sounds like a job for the Flux capacitor.

I also wish there was a way to charge from the motor, but there is just to little juice to do the job IMO. However every little bit helps I would think.

[GrizzlyAdams]

Quote:

My outboard battery is just for that.

That was what I thought as well. The most important battery is the starting one. Atleast I can get back to shore even if the others are drained.

I just want to make sure I hook everything up right the first time. I don't like learning the hard way. lol..

[BobT]

Most boats by design are wired with lights and other accessories wired to the starting battery. I guess I've never been out long enough using interior lights, anchor light, sonar, and maybe aerator to the point that my starting battery was unable to turn over the outboard. Most of these accessories draw pretty low power from the battery. If you use a dual-purpose battery for your starting battery it will have enough reserve capacity to handle these low power loads and still maintain enough umph to start the outboard after hours of idle time.

I would just use separate battery(s) to handle high power loads like electric trolling motors.

[PerchJerker]

I agree with the others, connect everything except your trolling motor to your starting battery. The things that will put the most drain on the battery are constantly running pumps and radios, especially CD players. Lights and electronics and occasional use of your pumps should not drain down your starting battery.

And even if you go with a DC charger, you will still need an AC charger overnight to get your batteries back to full charge. And it sounds like you have AC power available? If so I'd make sure you have a 10 amp or better charger for each of your batteries, and plug them in over night. If you're worried about not making it a full day on your battery, get a second battery to put in the boat (maybe you can even borrow one from someone for a short trip)?

[GrizzlyAdams]

Most of my use will be local and home for the night, so yes I will have AC. What then is a good ac on board charger?

Up north could be a different story though. not sure how many places will have ac at the dock but if all else fails and I have to pull the boat out of the water and plug in at the cabin it would be ok too.

I do plan on having 2 batteries for the trolling motor.

What are the best batteries for the trolling motor and what size??

[BobT]

The highest capacity deep-cycle batteries you can fit in the location. Use deep-cycle for your trolling motor, not dual-purpose. You'll get much better results.

Dual-purpose are a cross-breed between deep-cycle and starting batteries and are a good choice for your outboard starting battery because they can handle your accessory loads better than a plain starting battery.

[PerchJerker]

What then is a good ac on board charger?

Dual Pro and Minn Kota are as good as it gets for on-board chargers. Get a charger that has a bank for each battery in your boat --- ie. if you have 3 batteries then get a 3-bank charger. 10 amps per bank is the most popular size but most guys would get by just fine with 6 amps per bank too ---- it all depends on much you've drained your batteries, and how long you can leave the charger plugged in before you go out again.

Battery Chargers At Pro Fishing Supply

As far as deep cycle batteries, I agree with BobT --- get deep cycle batteries (not dual purpose batteries), and the batteries with the most reserve capacity minutes will last the longest. I've got InterStates in my boat and have been very happy with them.

[yaggie]

You will be able to set your bird unit to alarm you if your starting battery drops to a set level before it is too low to start the engine. I have had this happen fishing smaller lakes where you just have short run time with the outboard. A two to three minute run doesn"t charge the battery back up. On larger lakes where you run for ten minutes or so its not a problem. Most boats are set up with the trolling batteries only powering the trolling motor.

[GrizzlyAdams]

Thanks for all the info Gentlemen. It is greatly appreciated.