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Using Jump Leads

Two days after receiving WW April addition I discovered by starter battery did not have enough power to do its job. So the article on boaters tool kits was well timed. With modern cars it is quite dangerous to their electrics to use jump leads if you don't know the correct routine. Are there any risks on the average narrow boat, En Avant has the usual compliment of kit. I would propose to leave as many units as possible turned off at the control board, my concern would be for the battery monitoring system. Would the same apply if using a shore based petrol generator to recharge said battery. Thanks in anticipation of your help. Keep up the good work with WW.

Asked by: Nigel James  | 10.10am, Monday 24 March


WW says:

I am sure that Mark and Rupert can give you all the information you need on this but, if the battery is starting to give problems, it may well mean that it is nearing the end of its useful life. It might be a lot simpler and cheaper in the long run to replace it. You will also be safe in the knowledge that it should not give you any more problems for the next few years.

Graham Booth  | 11.09AM, Monday 24 March

When the typical electrics on boats was fairly simple, a flat starter battery could be quite easily jumped across from the domestic battery by the simple expedient of using a single jump lead to connect the positive terminals of both batteries together.
The more complicated electrics fitted to many narrowboats these days do not preclude this action, but if two jump leads are used the shunt used by the battery management system will be bypassed by the negative lead. This should be fitted first ensuring good connections and will protect the shunt from the high starter current. Connect the positive jump lead next and attempt to start the engine; when the engine starts leave the cables in place for a few minutes then disconnect them in the same order, negative first.
If you use another fully charged battery, connect it directly to the starter battery using the jump leads. There is not usually a shunt fitted into the starter circuit, so normal precautions are satisfactory. The same is true of temporarily using a mains battery charger whether it is powered from shore power or a generator. More care does need to be exercised if jump starting from another boat; only connect the starter batteries, and connect the positives first since the boats already have a weak negative connection through the water and hull contact, then the negative.
It is always important when using jump leads to ensure that any inadvertent connection is not made, however transient, as this can cause sparks. The electronic systems should be robust enough to cope with jump starting; however it would be well to check the manual for any particular safeguards recommended by the manufacturer.

Rupert Smedley  | 12.51PM, Monday 24 March


Readers say:

Thank you for a prompt response.I think that Graham has the right idea as I now realise that the battery is probably 7 years old. Thanks again

Nigel James  | 9.41AM, Thursday 27 March

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