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1st can I say sorry its fir my MGA not the Triumph. Im replacing the twin 6v batteries with a single 12v (50ah 480cca) Ive just received the new leads and they look a little smaller than the old originals. They are rated at 110amp 16mmsq. Im told they are suitable but would like an expert opinion please.

 

Regards Paul

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If you assume peak starter current as around 300 A , 16mm^2 cable will give a voltage drop of around 0.6v per metre. In your case that would give a loss of about a 1.5 volt on the feed (plus and an unquantifiable loss on the earth return) and of course worse if the starter takes more current than that. You might not notice anything in the summer but very cold winter starting might be affected.

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So the 170a 25sqmm cable would be better and up to the job. If so Ill just order some

Not strictly necessary but I would personally for a run of that length.

Edited by RobH
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Temperature will not really be a problem for the short time you are cranking, so using a short length of the thinner stuff should be OK. (A 300mm length will drop about 0.18 volts at 300 A and dissipate 54 watts in heat so a 5 second cranking will barely get it warm)

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I seem to recall that the MGA (and MGB) have the batteries in the floor behind the seats, which accounts for the long run. For this reason, and to allow the starter to receive as many volts as possible, especially in cold weather, the beefier cable (170A) should be used for the long run. For the very short part of the run, the 110A cable would suffice.

Luckily for us, TRs have the battery very close to the starter motor.

Ian Cornish

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