House Battery Location

[alaska_av8r]

Looking for some thoughts on this setup. I have a 30 foot boat with the house batteries currently sitting in the engine room. The boat has twin engines (so two alternators), I have a genset and a 20amp xantrex true charge battery charger.

I want to move the house batteries and locate them under the front bunk (3 AGM's), the reasoning behind moving them is to put some more weight in the front of the boat and make more room in the engine compartment for an additional water tank. The water tank would be much easier to install in the engine room than under the front bunk.

Now the boat has a windlass that has large gauge cables that run from the engine room under the front bunk to the windlass contactor. I would love to install the house batteries under the front bunk and use these large windlass wires as the power feed to send power back to the electrical panel for the house supply. I would rewire the windlass with a shorter cable of course.

Now my battery charger is back in the engine room, and of course my alternators are there as well. My question is what kind of voltage drop could I expect trying to send that charging current an additional 20 or so feet through that large gauge cable? Is it going to be significant? Is it going to kill my alternators or battery charger trying to charge those batteries thru 20 feet of wire?

Also am I missing something in this thought process?

thank you

 

[RickJ6956]

Re: House Battery Location

A quick search turned up this page.

You need to know the gauge and length of the wires feeding the windlass and the current draw.

 

[alaska_av8r]

Re: House Battery Location

Thank you for the reply that is some good information.

 

[seabob4]

Re: House Battery Location

One thing to consider when installing the batts in living spaces is the out-gassing of hydrogen gas during the charge cycles. I've done many a windlass where I've installed the dedicated batt under the dinette or v-berth. What I do is mount the batt in a closed battery box, install a 3/4" t/hull in the lid, then plumb it to a 3/4" t/hull in the hullside installed nearby. Haven't had any problems yet...

 

[alaska_av8r]

Re: House Battery Location

I have AGM's that supposedly aren't supposed to gas since they recombine within the battery itself, but from what I am gathering is that with be battery charging sources (both alternators and charger) 25 feet away from the batteries the batteries will take much longer to charge etc.

 

[RickJ6956]

Re: House Battery Location

Electrons don't care how far they have to travel. They care about traveling in comfort, which means plenty of space to move without bumping in to others -- which causes heat and voltage drop. That's why correctly-sized wires are a necessity.

 

[alaska_av8r]

Re: House Battery Location

Well I am not exactly sure what size the wires are, they are large however as they are the feed from the engine room to the windlass, but wouldn't there be some resistance even though the wires are larger? I certainly would love to stick these AGM's up there, but like I said the voltage drop is my biggest concern, I guess I could mount the battery charger up there with them but then that means I have to run a power wire up there. I used a voltage drop calculator and get values of 0.8% voltage drop.