Battery cables

[ghostlymoron]

I'm re-locating the batteries on Cobblers and need longer cables. Can anyone advise what size I need for a Dynastart ? The length will be about 5'

 

[savageseadog]

25 or 35mm^2

 

[VicS]

Need to know the max cranking current. Maybe your engine manual contains the information

But assuming 5ft means 10 ft total positive and negative cable length

20mm² would be suitable for 100amps. Double the cross-section for double the current ie 40mm² for 200 amps Interpolate for current in between.

 

[ghostlymoron]

The manual states that the starter motor output is 1hp but I can't find a reference to CCC. The existing battery cables are 10mm o/d (including plastic sheath) which works out as 50mm2 assuming the insulation is 1mm - this seems excessive. Total there and back length is 10' as you correctly assumed.

 

[savageseadog]

The manual states that the starter motor output is 1hp but I can't find a reference to CCC. The existing battery cables are 10mm o/d (including plastic sheath) which works out as 50mm2 assuming the insulation is 1mm - this seems excessive. Total there and back length is 10' as you correctly assumed.

1HP is 62A at 12V. There is a notable surge current which will be limited by total resistance. I would go 25mm^2. The cable can't be too thick but practically 25 will be fine.

 

[VicS]

The manual states that the starter motor output is 1hp but I can't find a reference to CCC. The existing battery cables are 10mm o/d (including plastic sheath) which works out as 50mm2 assuming the insulation is 1mm - this seems excessive. Total there and back length is 10' as you correctly assumed.

1HP is 62A at 12V. There is a notable surge current which will be limited by total resistance. I would go 25mm^2. The cable can't be too thick but practically 25 will be fine.

1 Hp is the maximum mechnical power output The electrical input will be significantly higher.

some figures I have for an ordinary 1.1 hp starter motor are:

no load 30 - 50 amps
loaded 185 - 225 amps
stalled 400 - 490 amps

I would allow for something in the range 150 to 200 amps

 

[ghostlymoron]

I've ordered some 25mm2 cable rated at 170 amps.

 

[nigelmercier]

The existing battery cables are 10mm o/d (including plastic sheath) which works out as 50mm2 assuming the insulation is 1mm ...

How did you figure that? Are you doing π ((10-2)/2)² - if so it doesn't take into account of the gaps between the cores, it's more likely to be 35mm².

 

[JumbleDuck]

1HP is 62A at 12V. There is a notable surge current which will be limited by total resistance. I would go 25mm^2. The cable can't be too thick but practically 25 will be fine.

If it's 1hp out mechanically it'll be around 1kW in electrically - 80A @12V. I recently rewired my 1GM10's 1kW starter using 30mm² for the earth (because it's shared with everything else) and 25mm² for the supply. I also replaced the old screw-clamp battery terminals with stud type and proper terminations on the wires. The engine now bursts into life first press whereas before it always took a few press-thunks before it would deign to turn over.

My cable runs are about 3m each way.

 

[ghostlymoron]

How did you figure that? Are you doing π ((10-2)/2)² - if so it doesn't take into account of the gaps between the cores, it's more likely to be 35mm².

yes, I ignored the gaps. pi x d x d /4 = A