Battery Charger

J

JGrider

New member
Hello guys, I hope you are not to busy today and don't mind talking about batteries on more time.
I am just now replacing a guest 5/5 charger. I recently got a great deal on a Xantrex 2 40 amp charger. Now that I have had time to reflect I think this is a little to much overkill. I am still going to install this and later I want some refrigeration so I intend to add a couple of batteries just for that.
I now have one battery in each lazarette.

1. My longest wire run is 15 ft. Do you believe #6 wire is large enough for this?

2. One chart I have been looking at calls for an 80 amp breaker at each positive terminal if I use #6 wire. Should I use a breaker for wire size or just the 40+ max output of the charger?

3. The location I have chosen for the charger is the back bulkhead under the stove. This will make the AC feed wires about 9 feet long. Do I need to install larger wires for this length and is a incoming fuse required since this fed from the shore power panel.
 
I was really disappointed that no one offered any reply to my questions but it did make me search for the answers on my own. You learn something everyday.
 
The shore power panel should have a breaker on the main input to the panel (110v) which should probably be 30 amps. and each output (110v) circuit, sized for the appropriate load. E.G. if you have a 110v refrigerator that draws 5 amps, a 7.5 amp breaker should be fine. If the fridge also runs on 12V (they usually have an automatic changeover (will run on 12v unless 110v is present) it's 12V circuit should have a breaker also. I'd look and see how much 12VDC it draws and size it appropriately.

The 40 amp charger is probably overkill, as you said, but you can use it. 40 amps @ 12volts equates to ~5 amps or so of 110VAC. If it feeds two 40 amp charging circuits, a 15 amp breaker should be fine. I think you could have that breaker, and a couple of other 5/10 amp breakers on the 110VAC feeding 110v appliances on the boat. Don't forget that they won't all be hot using full current all the time so they don't need necessarily to add up to the 30 amps on the input breaker (but they shouldn't add up to much more than that..)

Boats usually have a 12v negative buss bar that all the ground wires run to and a positive buss bar near the batteries and one large 12V breaker on this hot (+) side. Typically for a house circuit, it will be a 50amp breaker (nominally)

That large + wire usually goes forward to a DC distribution panel near the helm where the small DC breakers/switches are. Sometimes they are a breaker that acts as a switch, sometimes it's fused with a switch to turn the DC load on and off.

Some DC loads are connected directly to the battery with a fuse and no switch (like a bilge pump that's automatically switched on with rising water and you never want it to turn off unless the battery is dead). Some, because they need full voltage (like a Wallas Stove/Heater) are also connected directly to the battery and have a fuse/switch separate from the DC Distribution panel (usually right under the stove).

Now, as you're probably thoroughly confused, ask some more questions and we'll attempt to enlighten you. I welcome corrections and additions from the marine electricians in the crowd.

Charlie
 
Thanks Charlie,

What I cant seem to grasp is why the installation manual says I need a #2 wire for a round trip run of 30 feet for the output of the charger. It also shows a breaker on each positive lead that is to be matched to the wire size. Before I buy this wire I wanted to get some input from someone with more experience than I have.
The A/C wire run is only a few feet and is not all that expensive.

http://www.powerstream.com/Wire_Size.htm

Does this link apply to battery Chargers?
 
West Marine has, in their catalog, and on line I think, some of the best info on wire sizes. Have not delved into the one you have but most ofr these usually have a big safety factor built in (not that I'm not in favor of safety) and, if they also sell wire, have a vested interest.

Try West Marine!

I've got 80 amps running from the house to the pier/boats. It's buried cable, used #2 copper 4 cables (120-0-120) plus a ground. It was very expensive but I've never noted any voltage drop that's significant at the pier. And that was about a 425' run!!

Charlie
 
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