electrical question

coddock

Commander
Joined
Sep 3, 2011
Posts
264
Likes
33
Seems like my bow thruster power supply is not tied into the charging system of my boat. Battery is a group 31 dedicated to thruster and windlass.

Question is... Is it as simply as running a wire from battery to alternator, both + and - to tie in or am I over simplifying it?
 

jerseysportfisher

Rear Admiral
Joined
Feb 13, 2012
Posts
1,181
Likes
149
Location
Communist part of NJ
Boat Make
Bertram 33SF
Tie in to the battery not the alt, using this lil gidget


Automatic Charging Relay (ACR) Explained


ACR%20Diagram.png
 
Last edited:

coddock

Commander
Joined
Sep 3, 2011
Posts
264
Likes
33
The ACR looks like the animal. I presently have 3 batteries;2 wired to a battery switch and the one dedicated for the thruster/windlass. I see I will need 2 ACR units for 3 batteries. How would this play out with this set up?

What are the negatives with simply hooking the battery to alt.with fuse?
 

F/V First Team

Admiral
Joined
Jan 10, 2012
Posts
6,146
Likes
2,489
Location
Narnia
Website
www.otisenterprisesmarine.com
Boat Make
Northern Bay 36 - Modified
Jersey is going to have to slap you on the wrist and berate you online a little bit. It would work. The ACR is just a little better at doing it, gives you peace of mind and it takes care of the voltage drain, if your forward battery doesn't need charging, it doesn't charge it. Kind of like a friend checking up on you when you have the flu, sees if you need some soup, if not they high tail it out of the plague zone.
 

jerseysportfisher

Rear Admiral
Joined
Feb 13, 2012
Posts
1,181
Likes
149
Location
Communist part of NJ
Boat Make
Bertram 33SF
Jersey is going to have to slap you on the wrist and berate you online a little bit. It would work.

sounds like yer gett'n to know me ;)


But to answer the question what are the negatives, other then you just created a parallel circuit and the windlass/what ever else you have there will draw equally across all Bats. you ony need 1 acr, and only a con from 1 bat.
 

jerseysportfisher

Rear Admiral
Joined
Feb 13, 2012
Posts
1,181
Likes
149
Location
Communist part of NJ
Boat Make
Bertram 33SF
Even a proper fuse and block will be pretty close to that, no?

Once you get up to about 100 amps, fuses aren't cheap.


you can get battery terminal blocks for 15 or so, i would fuse it for 10-15amps UNDER the alternator rating, it should not pull no where's near that during a charge
 

greg

Captain
Joined
Sep 3, 2011
Posts
986
Likes
198
Location
Point Judith, RI
I don't know, I still don't see $25 as a huge difference when comparing fuse to breaker.

And don't forget that if your starter is in the circuit, you may need to size to that, as well as any engine pre-heater that may come on. Some people don't fuse a starter. Some do. But the load can be higher than the alt will put out.
 

jerseysportfisher

Rear Admiral
Joined
Feb 13, 2012
Posts
1,181
Likes
149
Location
Communist part of NJ
Boat Make
Bertram 33SF
I don't know, I still don't see $25 as a huge difference when comparing fuse to breaker.

And don't forget that if your starter is in the circuit, you may need to size to that, as well as any engine pre-heater that may come on. Some people don't fuse a starter. Some do. But the load can be higher than the alt will put out.


Thats the whole point of the acr, isolates it from your start batt. If fused right and the circuit is done right, you really have a 3% chance of popping a fuse unless something goes terribly wrong. and being the fuse is on the charging side, chances are even more slim unless you loose the reg in your alt. Breakers are great, but in this particular circuit, its abit overkill. Sure you can get the breaker, it fine.
 
Last edited:
Top Bottom