really large battery cable diameter

[bomdia]

I'm replacing the battery cables in our hunter 375, and the battery cables from both the domestic and engine batteries (12v system) are AWG 2/0. This equates to nearly 70mm2 in metric.
As well as being twice the cost, do they need to be that big?
I was thinking to replace them with 40mm2. I don't have any huge current draws apart fridge, radar, GPS etc, nothing that would ever come close to requiring that size wire i thought.
Yanmar also say that for a cable run of 4m, a 40mm2 diameter wire is adequate for engine starting.
Can anyone advise on this matter?

 

[sarabande]

it's important to know the length of cable required on the engine circuit.

40mmsq is looking a bit small for 4 m length, especially if for any reason you had a sustained cranking problem.

Do you know the starting amps for the engine ?


These people

http://www.vehicle-wiring-products.eu/VWP-onlinestore/cable/batterycable.php

seem to do a good price on tinned cable at all sizes.

 

[neale]

I'm replacing the battery cables in our hunter 375, and the battery cables from both the domestic and engine batteries (12v system) are AWG 2/0. This equates to nearly 70mm2 in metric.
As well as being twice the cost, do they need to be that big?
I was thinking to replace them with 40mm2. I don't have any huge current draws apart fridge, radar, GPS etc, nothing that would ever come close to requiring that size wire i thought.
Yanmar also say that for a cable run of 4m, a 40mm2 diameter wire is adequate for engine starting.
Can anyone advise on this matter?

Before changing the size of the cable you really need to understand the relationship between cable length, power draw and voltage drop due to resistance. There are a number of websites where you can tap in the relevant info and find out the right size cable. If in any doubt, i'd leave as is.

 

[Stu Jackson]

Usually 2/0 cable is used on recreational boats our size (mine is 34') for transferring power from a battery bank to an inverter. From the inverter the power goes either to the boat's AC panel, or just uses the receptacles on the inverter itself.

Do you have an inverter? Did the PO? If you don't, and if they're not in the way and are useful, leave them in for a time when you want to install an inverter. Check the condition of the lugs at each end before reuse.

You say "cables from..." in your post. Yes, but to where?

 

[andythilo]

Replace like for like.

http://cgi.ebay.co.uk/WELDING-CABLE...ltDomain_3?hash=item1c089a4ccf#ht_2108wt_1165

I used this place to buy some 25mm2 cable for my boat, pretty cheap if you ask me. Although you will need access to a hydraulic crimp tool to put the ends on.

 

[mitiempo]

I don't think I have ever seen battery cables that were too large but I've seen many that were too small. I'd stick with 2/0. Tinned of course and with adhesive heat shrink over lugs that are properly crimped.

 

[markdj]

When calculating the distance of the circuit, be sure that you measure the entire circuit from battery positive post to starter and from starter negative or engine earth to battery negative post so both positive and negative cables.

What engine do you have? if you have the engine manual, what is the cranking amps of the starter and what is the recommended size of battery in CCA?


Mark
www.boatdoctorni.com