How to run power to electric trolling motor

[Cevin c Taylor]

Hello:  I picked up an electric trolling motor (32 lb thrust or so) that I'm going to try out on my '83 CP16 next sailing season.  The boat's all buttoned up under a tarp at present, but I'd like to start planning things.  I'm wondering how you run the power to the motor.  It seems like the battery should probably be in the bow of the boat due to weight distribution issues.  Do you then run the power along the inside berths and have the cord come out the lazarette?  Is there a better way to do it?  I would appreciate any help you might have.  Thanks!

[Billy]

I have the same problem but opposite. I need to run power FROM my engine. It has an alternator.

If you are just "trying" the motor, would don't do anything permanent until you know you like the motor. My batt is on the starboard side. I would try moving the batt around until you are happy. A shorter wire will also save you some juice.

[capt_nemo]

wolverine,

I agree with Billy - make sure you like the performance of the motor first. Then consider where the best place is to locate the battery or batteries keeping in mind that the shorter the distance the better. In our boats, midships and as low as possible is usually best.

Wherever you locate the batteries make sure you run cables large enough to carry the current demand and minimize loss of voltage presented to the motor. Any good electrical reference will have tables that recommend wire size given the current expected and round trip distance from battery to load and back again to battery for only a 10% or 3% loss.

If you have difficulty finding the information, send me a personal message with current and round trip distance and I'll provide the recommended wire size for you.

capt_nemo

[JBC]

I have tried several arrangements for running cable from a battery to an electric motor, and decided to think out of the (battery) box: I use 2 batteries.  Both are half the size of a regular marine battery and weigh about 24 lbs ea, closed gel design, 12 volt.  One I use in the bow to power lights, etc.  The other I keep at the stern, under the lazarette, and I can hook it up directly to the motor's cable when needed.  Because these batteries are fairly light, I don't worry now about heavy weight in the stern area, or a long cable connection.  And if I think a battery is about to run out of juice (which really hasn't happened the way I use the motor to get away from and back to the dock), I'll simply switch to the other one.  Costs more (about $80 per battery), but I sure like the trade off.

Jett

[skip1930]

Two battery hook-up in series I'd over cable with '0' cable in bulk from any parts store with hefty lugs bolted together.
Try the set-up first before making anything permeate.

skip.

[Pacman]

There are several considerations here:  Battery location, cable length and routing, and cable size.

Battery locations forward seem to be best from a weight distribution standpoint.

In theory, a battery should be located near the motor to avoid power loss due to internal resistance in the battery cables.  However, we are not discussing a 100' extension cord here. 

At distances of less than 12 feet, the difference in line resistance should not be enough to make battery cable length a major consideration.  Also, the larger the cable, the less resistance there is.

Cables should be routed where they won't interfere with other stuff,

I probably would locate the battery in front of the compression post and use large gauge battery cables with cable ends that can accept bolts and wing nuts for ease of hook-up and removal.

I have thought about using bolts through the aft cockpit wall as terminals for a trolling motor.  The cables would be bolted to the inside wall under the lazerette cover and the trolling motor clips could be attached to the ends of the bolts that protrude into the cockpit.   Insulating covers would be used to keep things safe.








m

[brackish]

If you do a search there are some very nice waterproof connectors that are designed to mount permanently to a bulkhead with a plug on the motor end that will neaten up your installation and you have a minimum length of cable on the motor itself.   Then a permanent routing of the battery to connector cable, hidden but accessible.  As others have suggested a trial for location and ampacity and voltage drop consideration for the sizing of components.

[Cevin c Taylor]

Thanks!  This has given me a lot to think about.  I'll definitely try the arrangment first before making anything permanent.  I've made that mistake too often.

[JTMeissner]

Wolverine, I run a 40-lb thrust MinnKota Endura C2 on my 1975 ComPac 16. 

I connect to the battery using a MinnKota Charger Extension Cable (15 ft) which is sized for the load with a 30 amp inline fuse on the positive and negative wires.  I put a male quick disconnect on the leads from the motor, and a female connection on the cable (had to clip the connectors that come with it). 

My battery sits in a MinnKota Trolling Power Center, a plastic box that puts both a cigarette lighter outlet and battery posts on the external surface, as well as a simple battery meter to check charge and 60 amp circuit breaker.  The battery box sits nicely in the storage area right in front of the compression post. 

The motor, cable, and power center all came from Amazon (full names used above if you want to search for those items to examine), the quick disconnects were from Bass Pro Shops. 

For a weekend sailing trip, I put the battery up front and attach the cable, then open the lazerette and connect the motor.  The motor cable doesn't appear to pinch even with the lazerette lid down, and the connectors are well inside.  When done sailing for the day, I usually secure the motor but leave the battery in place as it has never gone below 70% charge on a 4-day weekend of day sailing.  On my last night at the lake I pull the battery and charge it overnight in the camper (you can charge in the power center).

The fifteen foot cord gives you plenty of slack to decide if you want to go straight along the keel or run the cable up and along one of the hull seams.  I may eventually decide to put a through-hull port for the motor, but that is pretty low down the list of projects for the boat.

-Justin

[Pacman]

Justin,

That sounds like the best idea yet. 

It addresses all the considerations very nicely and with some added features llike the battery meter, in-line fuse, line connections, and a cigarette lighter outlet too.

Thanks.

[MKBLK]

Wolverine - Great timing for your post! I actually started a project to move my battery (it currently, no pun, lives in the stern well) to amidships under the entry hatch on my CP16. Part of the plan was to also make it convenient to operate my bilge pump. My MinnKota is only 28 lbs./thrust, but has been more than adequate on relatively STILL water.

I cut out a piece of 1/4" marine plywood about 12" by 24" that straddles the pair of scupper pipes coming from the cockpit. I mounted the pump on this platform with the intake fabricated from PVC pipe angled down into the bilge. The pump came equipped with alligator clips for temporary operation which is how I use it. Adjacent to the bilge pump, I'm installing a pair of brass studs with appropriate washers and nuts to accommodate the recycled jumper cables that will go forward to the midship battery. I simply cut off the old clamps and replaced them with a pair of ring connectors and a pair of lug connectors (lugs to make it easy to quickly remove the entire assembly). When finished, I'll be able to simply hook up the MinnKota via its alligator clips or the bilge pump when necessary. Easy, peasy!

And Justin, thanks for the tip on the MinnKota Trolling Power Center. Looks like a great product! There's definitely one in Pegasus' future! I found a heavy duty battery booster under the tree this Christmas and I plan to use it for nav lights and pumping up the rubber dinghy. It also is big enough to supplement the regular battery in a pinch.

Can't wait to get back in the water!

Marty K.