12 -24 without losing the 12

[dbkerley]

I currently have a 12v system and am considering adding some 24v trolling motors. How do I pull the 24v out of my dual battery setup without it crossing into my 12v system? If this was AC I'd already have it. I just haven't developed any mutivolt DC systems. Maybe using an inverter and breaking it off my AC system would provide the best backup isolation or I could add another set of batteries. Ideas please.

 

[dbkerley]

Re: 12 -24 without losing the 12

BTW - I did look at the stickies at the top and I thought the 3 battery setup would work. However, as almost everything on the boat is 12v, I thought it would overwhelm the single starting battery and could create charging problems as well. Obviously I am missing something in that diagram.

 

[Silvertip]

Re: 12 -24 without losing the 12

Puzzled: Adding SOME 24 volt trolling motors?????? Just how many would that be?? How you add just ONE 24 volt troller depends on how your 12 volt system is configfured. 1) How many batteries do you currently have. 2) What type are they? (AGM, deep cycle, starting?) 3) Does the current system use a dual battery switch, ACR, VSR, Isolator, or any combination of these? 4) Do you currently have a 12 volt trolling motor? If so, which battery is it powered from.

You can provide 24 volt and retain the normal 12 volt boat system but nobody can tell you how to incorporate it until we know what you have now.

 

[dbkerley]

Re: 12 -24 without losing the 12

I currently have 2 deep cycles with a isolation switch (1-both-2). I also have 30a 110v shore power and a Guest 30a (?) single bank charger.

I am wanting to add the 160# thrust trim-n-troll tabs made by Minn Kota. I also want to add a gender. The best estimate I can get is they will draw 106amps @ 24v.

One suggestion was to add 2 more batteries as an independent 24v circuit and replace the charger with a 4 bank unit.

 

[Silvertip]

Re: 12 -24 without losing the 12

You are looking at some serious current draw and adding two "huge" deep cycle for the 24 volt system will be sucked flat in very short order if you draw 106 amps for any length of time. Plus that takes some huge wiring. You were given good advice to leave the current system as it is and add a totally independent 24 volt system. That said, I have one more question. What's a "gender". In the English languge it is what distinguishes a male from female so i doubt that's what you intended to type. If you mean "gener -- as in generator" then we have another scenario to deal with. The existing single output on-board charger can remain in the boat system. If it is connected to the COM terminal of the dual battery switch, leave the switch set to BOTH and both batteries will charge. Otherwise, set the switch to "1" or "2" and only the selected battery will charge. Setting the switch to OFF means NONE of the batteries will charge. If you do add a 24 volt system, you only need a two-output charger, albeit a big one, since you will need multiples of 2 batteries in this system depending on how much capacity you need. If you add a generator, then the generator can feed the AC side of the system which will in-turn feed the on-board chargers.

 

[dbkerley]

Re: 12 -24 without losing the 12

It should have said genset instead of gender. But, this phone is too smart. Sorry for the delay. My grandson and I were adding an inverter to the van so he could connect his ps3 to the existing entertainment system. It is now riding in the seat behind me connected to a 100 amp line I ran through the baseboard to power our fridge and micro while on the road.

The reason for the large trolling motors is so they can act as a wing engine in an emergency or provide additional maneuvering options in the marina or when loading and unloading from the trailer. Weight is fuel and I am trying to keep it down.

Well, I'll be back on the road until my wife spots another Starbucks.

 

[Silvertip]

Re: 12 -24 without losing the 12

I take it these will electric motors will not be used more for docking purposes more than they would emergency propulsion so that throws a little different light on things. However, electric power for emergencies on a larger boat are going to be energy hogs so I hope IF you have an emergency it is not more than a couple miles from land and that you will not have rough water to deal with. You might want to consider adding an outboard bracket and a suitable outboard for emergency propulsion. Depending on the size of the boat a 9.9 to 20 HP might serve you better.

 

[dbkerley]

Re: 12 -24 without losing the 12

If I mount a kicker on the swim platform, handling would be a real pain as there is no reasonable way to tie it in to the helm and my wife would have to stand out on the bow shouting directions to me.

I really want a simple solution that provides reasonable backup safety without adding another 3k pounds to the stern. The boat is a Formula F26 PC. Almost 31' overall and it will spend 90% of it's time on inland lakes without available tow services.

 

[Silvertip]

Re: 12 -24 without losing the 12

Short of towing a dingy I guess all I can suggest is that you run current consumption numbers and figure out for yourself whether you can get any reasonable distance in an emergency from this setup using two batteries. Remember, two batteries in series does not double the available current. It doubles the voltage. Two batteries in parallel doubles the current but voltage stays the same. So, figure out the AHr rating of the batteries you have room for and divide that number by the maximum current draw of this power system and that will be the absolute maximum range that system will provide. You could also add four batteries consisting of two 24 volt banks connected in parallel. Where you came up with 3K as the weight of a small outboard (which is 75 - 150 pounds depending on HP). You will have nearly that much in batteries alone. I guess the simplest solution is to keep the boat properly tuned and you won't need the emergency power. If you installed a 24 volt high output generator, then the generator could power the motors directly. You just don't see many 24 volt generators. Perhaps a military surplus store might have one.

 

[dbkerley]

Re: 12 -24 without losing the 12

The 3k I was referring to was the weight of a wing engine with additional fuel tank. I understood your suggestion regarding a kicker. While I have room to drop one below deck; I just couldn't see it being practical unless it was connected to the helm somehow. I'll continue working on the troll set up. It amazes me that they get nearly as much for the engine mount version as the ones with tabs.

 

[Silvertip]

Re: 12 -24 without losing the 12

Not being one to give up easily on a problem, let me attack this from one more perspective. You mentioned your boating is primarily on inland lakes. In a 90% of the time situation, should you have to rely on this electric propulsion system, what would be the maximum range you would need to reach wherever it is you need to get to? Consider the bodies of water you are on very carefully. Are they remote, long and narrow, big and round/oval, river systems that connect multiple lakes, etc. My point in asking is that unless these are very large bodies of water, help is a matter of getting to shore which may be less than a mile in the vast majority of your trips. Having that same system help with docking is a complicating factor. Combining the two makes either one less than ideal. My feeling is still that for emergency propulsion, even a 9.9 outboard would be the most practical, would have unlimited range (based on fuel available) and yes -- they can be tied into the main outdrive and have separate controls at the helm but I also feel that is not necessary. You have an emergency! So what if your wife or another passenger needs to help in maintaining direction. You are not naviagating through a lock so this should not be a major issue. As for docking assistance, short of bow and stern thrusters, a simple electric wired or wireless trolling motor would be far more useful than an engine mounted electric motor. You don't need to carry a different fuel supply for the outboard if it's a four-stroke althugh a two stroke would be much lighter. A small 3-gallon portable tank of two stroke fuel would run that motor for about three hours at wide open throttle. Keep the fuel supply treated with Stabil or SeaFoam and it will stay fresh for six months or more. The long and short of all this is that unless your boating activities have some very unique distance or location considerations, I'm wondering if you are not being overly concerned about the need for a backup system. Inland lakes tend to have a fair amount of other boaters. Hailing a passing boater would result probably result in a tow to shore, to someones dock, or to the nearest marina/bar/restaurant. So the most practical and least expensive backup plan might consist of a hailer and a twelve pack of adult beverage. Save the other money for fuel.

 

[dbkerley]

Re: 12 -24 without losing the 12

You are probably right and I tend to make 10year plans for 5 year projects. I just hate to have to backstroke due to a lack of thought. I had a problem with my other boat last season and was towed back to the ramp by another fisherman. Then it started and I loaded it up and went home anyway.

 

[Silvertip]

Re: 12 -24 without losing the 12

Fresh fuel (treated), a properly maintained engine with a properly functioning electrical system and a properly maintained outdrive should result in not having to deal with a tow at all. Paying attention to instruments can tell a great deal about the health of the engine and its systems. Can you still have an issue? Certainly! But you could drop dead in an instant as well. Some things you just can't plan for. As they say -- "stuff happens".

 

[dbkerley]

Re: 12 -24 without losing the 12

I know that somewhere inside me. The OCD side of me says all things can be caused or prevented. We just have to keep looking until we find the solutions that fit the desired outcome. Doubt in any form messes with my ability to enjoy anything. A lot of what I end up doing on the boat has more to do with satisfying a mental need than physical problem the boat has.

 

[dbkerley]

Re: 12 -24 without losing the 12

They come with a remote that is similar to the copilot. It steers through varying or reversing the thrust at the tabs. It also has a return to center option that you press and it will straighten out mid turn.

BTW - Silvertip - Thanks for being the sounding board on this. Thinking through it by myself was becoming irritating. I'm still wanting the setup though despite it ultimately being impractical. I think the silent running factor would be pretty cool.