Starter Motor Cables for BMC 2.5 litre Diesel

[PGC]

Does anyone know the CCA for a BMC 2.5 litre diesel please? I want to fit new cables to replace the welding cables on the boat I bought a few months ago and need to work out the cable cross section. I've read the workshop manual that came with the boat and phoned several suppliers of reworked engines with no joy.

Any help gratefully received.

Cheers,

Paul

 

[caiman]

Hi
In my Operators manual it says' CAV 6MT17 batteries 2off.I will be fitting a 12v battery to mine.The AH quoted in the manuel is 108.Presumably this is when the 6cv batteries are coupled to get 12v.The bigger the cable the better IMHO.I cannot see a CCA in the manuel.
Hope this helps.
Cheers

 

[Baddox]

CCA is usually the battery spec. and how much current it can supply. Instead, you need to know how much current the starter motor draws. Then, work out the length of cable required to run from the battery to starter AND back.
Armed with the number of amps and cable length, you can then look up on one of many websites to identify the cable size required. It’s also worth having a look on ebay for hydraulic crimpers if you want to prepare the cables yourself. Is there a problem with the welding cables? Their fine wires make them a popular alternative to similay but fully tinned cable.

 

[vyv_cox]

I used 35 mm2 for my 2.2 litre BMC. The cable runs are short, maximum 2 metres. No evidence of a problem. The cables on the 2.5 litre Fiat engine in my previous motorhome were amazingly small, probably only 25 mm2, again with very short runs.

 

[lw395]

The best starting point may be the nominal wattage of the starter motor.
Then design for around 1V total drop.
The cable does not need to be continuously rated.
Bigger cable is always a nice idea, but getting good connections is important too.
I found jump leads to be a cheap source of fairly fat cable.
The fine wires of welding cables make them prone to corrosion if they are not kept properly dry, don't let water wick up the cores.

 

[VicS]

The best starting point may be the nominal wattage of the starter motor.

I think if you find that it will actually be the ( mechanical) power output of the motor.

The electrical power consumption will be significantly greater.

The only figures I have are for a 810 watt (1.1hp) motor on a 2.1 litre petrol engine.
They are
Unloaded: 30-50 amps at 11.5 volts
Loaded: 180 - 220 amps at 9 volts
Locked: 400 - 490 amps at 7 volts

If cable runs are short current carrying capacity might be a more important consideration than volts drop.
However, they do not have to be rated to withstand the expected current continuously.

The battery cable on the above appears to be 50mm²

 

[PGC]

Thanks for the help!

Thanks to all of you for the inputs. I'm working on the boat this weekend and will use your responses to work out a cable size.

Cheers,

Paul