Battery cable size

[vintagescubaman]

Now this is a very basic question, I want to renew my battery connecting wiring to balance the batteries, I have four 110amp leisure batteries and one starter battery. I am also fitting a large inverter that requires 180amp cable, am I right in thinking that 110 amp cabling between batteries is suitable, as the load drawn by the inverter is split between all batteries? 180 amp cable between batteries seems a bit on the heavy duty side. I have looked at the forum, but havent found an answer to this specific question.

 

Many thanks

[bottle]

Someone will come along that actually knows, until then found this via google.

 

http://www.solosol.net/DC_Cable_Sizing.html

[Justme]

Dont size cable by amp rating for low volt high amp applications.

 

Sizing that way is all about cable heating.

You need to be concerned about voltage drop in the main.

 

The easiest way I have seen was posted on here a few years back.

 

max amps X cable distance one way / (divided) 12 (or 10 to make it easier & give a lower v drop).

 

So if you need 180amps & the distance is 3m (one way) then you need 45mm csa cable (or 54mm csa if div 10)

 

25mm csa is rated at 170amps but would cause more v drop.

40mm csa is rated at 300amps.

[Keeping Up]

The BSS requires you to use cable of at least 25mm² between batteries.

[Gibbo]

Now this is a very basic question, I want to renew my battery connecting wiring to balance the batteries, I have four 110amp leisure batteries and one starter battery. I am also fitting a large inverter that requires 180amp cable, am I right in thinking that 110 amp cabling between batteries is suitable, as the load drawn by the inverter is split between all batteries? 180 amp cable between batteries seems a bit on the heavy duty side. I have looked at the forum, but havent found an answer to this specific question.

 

Many thanks

 

180 amp cable seems a bit limp to me. Depending upon the spec used and the manufacturer, 180 amp cable would be about 25sq mm. Most people use a minimum of 35 or 40sq mm. Big installations often use 70, 90 or even 120sq mm.

 

As Justme pointed out. The current rating is pretty much irrelevant for this purpose. It's the volt drop that matters.

 

http://www.smartgauge.co.uk/cable_type.html

[journeyperson]

The BSS requires you to use cable of at least 25mm² between batteries.

 

I've just had to re-cable to 25mm between batteries to pass the BSS and I couldn't understand how the cables came to be undersized because the boat has passed inspection since 1993. I can only think that the guy who owned it before me and only had the boat for 2 years must have renewed the cabling in the wrong size after its last BSS when he changed to batteries with different sized terminals. He was an HGV driver and maybe it was good enough for a truck but the examiner told me they were in danger of overheating. If I'm right it was the only change he made to the boat and it was wrong.

[Gibbo]

If I'm right it was the only change he made to the boat and it was wrong.

 

You seem surprised?

[journeyperson]

You seem surprised?

 

Relieved he didn't do anything else.