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Discussion Starter · #1 ·
Ok so I have a 21 ft venture from 1978, we went out this weekend and I couldn't get the outboard to crank so I ran the trolling motor when the wind died. After about 4 hours of running my battery was completely dead. So I am looking into creating a power supply to run more than just the trolling motor and outboard. Does anyone have a good diagram? I have no electrical system in this boat what so ever. I will be wiring a VHF radio, cd/radio, 4 speakers, GPS, and the motors. Can you guys help me at all? Any info would be greatly appreciated! Photos, diagrams, whatever. I wanted to use solar power to charge my battery banks but I'm all new to this boat thing. I have don't plenty of car working before.
 

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You will need:
big battery
solar panel
MPPT solar charger
circuit breaker/fuse panel
Good crimpers
Ancor wire
good terminals
fuse on positive battery post
two buss bars, one for the positive, one for the negative.

Not sure just how good an outboard can charge the battery.
I like buying my electrical needs from Marine Wiring, Boat Cable and Electrical Genuinedealz.com
 
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Discussion Starter · #3 ·
What do you consider a big battery? I have a the following:
Super Start Marine - Starting Battery
$65.99 Each
1 year limited warranty
Battery Type: Starting
Cold Cranking Amps (CCA): 460 CCA
Marine Cranking Amps (MCA): 575 MCA
Cranking Amps (CA): 500 CA
Group Size (BCI): 24
Height (In): 9-3/8 Inch
Length (In): 10-3/4 Inch
Voltage (V): 12 Volt
Width (In): 6-3/4 Inch
Group Size (BCI): 24
Cold Cranking Amps (CCA): 460 CCA
Cranking Amps (CA): 500 CA
Reserve Capacity (min): 70 Minute
Voltage (V): 12 Volt
Length (In): 10-3/4 Inch
Width (In): 6-3/4 Inch
Height (In): 9-3/8 Inch
 

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There are several good books on 12 volt marine electrics... or portions of Don Casey's or Nigel Calder's books. The subject is too big for meaningful advice in a forum.

What you need to do is not rocket science, but does take some knowledge and planning. The battery you've described is not optimal, you'd do better with a deep-cycle design instead of a starting battery. But it should suffice till it wears out (unless you really stretch it with heavy trolling motor use).
 

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You will need:
big battery
solar panel
MPPT solar charger
circuit breaker/fuse panel
Good crimpers
Ancor wire
good terminals
fuse on positive battery post
two buss bars, one for the positive, one for the negative.

Not sure just how good an outboard can charge the battery.
I like buying my electrical needs from Marine Wiring, Boat Cable and Electrical Genuinedealz.com
I had a 21' Victory and setup a simple electrical charging system.

If your battery is big enough, you can use a small-enough solar panel without a charge controller. Slow charging in this way will mean the battery is topped off for your weekends, but it's not for more for heavy daily use.

big battery (normal car size, but "deep cycle", not "starting" and not "dual-use"
solar panel
fuse panel (they sell 6 fuse units at West Marine)
Good crimpers
Ancor wire (West Marine sells, "Ancor" makes good marine wire. It must be tinned, don't use automotive wire which is not tinned.)
good terminals
fuse on positive battery post
for the two bus bars, the fuse panel may have places you can attach wire to.

Captain Meme actualy has a good list, you could possibly tweak it slightly by leaving out the charge controller. You'll want the panel to be 12 volt and 20 watts maximun, I think. That will give you over an amp of charging and won't hurt the battery even if it's already fully charged.

You're better off with a charge controller, but they can be expensive, IMHO.

Regards,
Brad
 

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" leaving out the charge controller. You'll want the panel to be 12 volt and 20 watts maximun, I think. That will give you over an amp of charging and won't hurt the battery even if it's already fully charged."

Wasn't too long ago this subject was debated on this forum. While I don't believe in consensus to settle technical matters, a good charge controller has three stages, charge, absorption and float. One can purchase a controller for less than $50 that will
limit the float voltage.
 

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" leaving out the charge controller. You'll want the panel to be 12 volt and 20 watts maximun, I think. That will give you over an amp of charging and won't hurt the battery even if it's already fully charged."

Wasn't too long ago this subject was debated on this forum. While I don't believe in consensus to settle technical matters, a good charge controller has three stages, charge, absorption and float. One can purchase a controller for less than $50 that will
limit the float voltage.
Ageed on the value of a charge controller. With a charge controller (and the bigger panel that it will keep from frying the battery) you could then use the boat more often.

Regards,
Brad
 

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I'm going over this whole area right now.

My boat already has an electrical system, but it's a combination of the 40-year-old original wiring and some bodges to add a 24v segment to run a trolling motor.

The 24v part complicates it, and I may end up spending $200 for a controller. On the other hand if spending an extra hundred for the controller can make the batteries last a couple years longer it's probably worth it.

Just a note on using a trolling motor: I have two group 27 batteries and a 74-pound thrust motor. My math tells me that I can run the motor for about an hour to get to 50% battery (and I understand it's not a good idea to deplete them below 50%). On flat calm I can make 3.2 knots, so my setup give me a range of 3.2 nautical miles on a calm day. This works fine to get me on and off my mooring, but it would be pretty limiting if you had to make any distance.
 

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Most starting batteries (refered to as "SLI" starting, lights, ignition) can only be totally discharged a very low number of times, like 4-6, before they are killed. So you really don't want to use an SLI battery for long term trolling. They're intended to be discharged only about 10% in real use.

Marine deep cycle batteries do better but typically are only intended to be discharged 30% to 50%, the number of charge cycles plummets after that as well.

Using a trolling motor to move the sailboat? Lots of batteries and a charging solution, and putting a small gasoline powered genset on board is a whole other topic. Better to fix the outboard, unless you want to do the whole electric boat thing.
 

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" leaving out the charge controller. You'll want the panel to be 12 volt and 20 watts maximun, I think. That will give you over an amp of charging and won't hurt the battery even if it's already fully charged."

Wasn't too long ago this subject was debated on this forum. While I don't believe in consensus to settle technical matters, a good charge controller has three stages, charge, absorption and float. One can purchase a controller for less than $50 that will
limit the float voltage.
Do I Need A Solar Charge Controller ?? - SailboatOwners.com
 

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Actually, you can just get buy by knowing you limitations.
You now know you trolling motor will only get you about 4 hours of motoring. Your OB will also have limited range or time of use.
Don't sail further from dock than the range of your combined auxiliary power.
I had a 3 gallon tank. Wouldn't last a week of vacation time sailing three times a day from the vacation house. I had to motor about 40 minutes for each trip. I changed to a 6 gallon tank and installed an hour meter on the OB. I can now calculate my range pretty well and stay within it.
I never sail further than I can motor back.
My back up plan is TowBoatUS.

If you do want a full electrical system, it sounds like you got some good advice here already but a cheaper solution is possibly just a second battery and battery switch. When the first one dies switch to the second. Then take the first one home and charge it.
 

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...a cheaper solution is possibly just a second battery and battery switch. When the first one dies switch to the second. Then take the first one home and charge it.
With respect, that's not a good way to do it. Hooking up both batteries in parallel with give more than twice the range and the batteries will last longer. (It's the Peukert effect.) And the other way means a lot of lugging heavy batteries down the dock.

Peukert's law - Wikipedia, the free encyclopedia

Just get a small flexible panel, mount it on the coach roof, add a controller, and forget about it.

Regards,
Brad
 

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Two engines, 12 volt batteries, solar panels, charge controllers, etc. seems rather complex for a 1978 Venture 21 that was considered "fully equipped" with a compass and paddle when new. The functions required and desired by the OP could be fulfilled with: One engine that starts when you pull the rope, a portable VHF, a cell phone and Bluetooth speaker.
 
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