Norman_E
Well-Known Member
My boat has three "house" batteries of 110 amp hours each, of which two are close to the engine and the third is in the forward lazerette, and is connected to provide power to the anchor windlass and bow thruster, and linked to the other two via a pair of heavy battery cables which must be about 10 metres long. Until I get to the boat I cannot measure how big they are but from the appearance they look to be about 35mm cables. I really want to move the heavy battery back as it adds quite a bit of weight where it is not wanted. I am going to fit a NASA BM2 battery monitor which has to have its shunt connected to the negative battery terminal with all load flowing through it. I plan to move the forward battery back to join the others and power the heavy equipment forward by means of the existing link cables. The heaviest load is the bowthruster which can draw 250 amps, but only for a maximum of 30 seconds at a time. The 1000 watt anchor windlass only draws a fraction of that and is not used at the same time. If my cables are 35mm and 10 metres each are they adequate? If they are smaller (say 25mm) can I double them up rather than replace them?
EDIT. I just found an online DC cable size calculator which shows that it is totally impractical. It calculates that I would need 500mm cable! Given that all the other loads are relatively small ones, provided I put the new inverter up front I am now thinking of connecting the shunt up front and putting in a negative link from there to connect back to the rest of the equipment.
EDIT. I just found an online DC cable size calculator which shows that it is totally impractical. It calculates that I would need 500mm cable! Given that all the other loads are relatively small ones, provided I put the new inverter up front I am now thinking of connecting the shunt up front and putting in a negative link from there to connect back to the rest of the equipment.
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