Battery Cabel Length and Sizing Question

[EpicDay]

Background Info: 22' alumaweld, 200 Mercury outboard, 650 CCA battery

I have relocated the battery from the rear of the boat (about 4' of #6) to the built in battery tray in the front (about 19' of #1/0). As anticipated I am noticing a drop in the starting amps. Per the charts and some manufactures recomendations the correct wire size is in the 000 to 0000 range (very large indeed).

Questions:

1- How to calculate the amp drop between the different wire sizes ? -(Ohms law stuff)

2- To meet recomendations for no loss the wire size is prohibitively large and expensive - How common is it to have the battery located in the front or greater that 19' from the motor?

Thanks
(from a CE that did not take enough EE classes)

[Orca]

I think you are well matched with the 19' of 1/0 relative to the 4' of #6.

You can use this calculator - http://www.powerstream.com/Wire_Size.htm . Pick wire size, 12V, you length, and pick a current load. Say you use 350 amps as your motor starting requirement:

4' - #6 = 1.3 voltage drop, 10.7 volts at end of circuit
19' - 1/0 = 1.5 voltage drop, 10.5 volts at end of circuit

I think that is plenty fine.

[jfa686]

I have found good pricing at welding supply shops on high strand count cable for many differant applications... higher count = less V drop. Disclaimer: just what i have used and is by no means the "right" or only way..

[Danno]

Why relocate the battery?

I would keep it in back if possibles. Our waters are no place for a boat that won't start. Remember that your charging will be affected as well.

For the price of buying all of that new cable, you could buy a second battery of you don't already have one.

[EpicDay]

ORCA: Thanks
The calculator is just what I needed. After going through the calculation I realized I did not account for the entire circuit length (DC Length) => 19' x 2 = total circuit length. (oops)

jfa686: Thanks
Agreed the welding wire is my preferred wire type.

Danno:
This project all got started by checking the condition of the flooring and the under floor foam flotation. The foam was fully water saturated and the flooring showed disturbing signs of rot. During foam removal and flooring replacement I checked the wiring and noticed discoloration at all of the connections. Long story short - I replaced all of the wiring and decided to move the battery up front to the built in battery holder thinking this was the manufactures original battery location. In addition, I thought boat balance and planning speed might be improved.

Admittedly I relocated the battery without really considering the voltage loss issue.

[JuneHog]

if used around salt water, use only listed to UL1426, ABYC and USCG approved cable.
has Type 3 tin coated stranding for adequate corrosion protection. get the type that is gel flooded.

use hvy duty crimp batt. connectors on ends that are then soldered and use the heat glue sealing heat shrink.

non auto bailers are always wet down below

[Hawk JJ]

I keep my main motor battery & two trolling motor batteries in the plastic battery boxes WallyWorld sells, to protect the deck.