Battery jumpers

[CLS]

A question to all.

If out at sea and one battery dies, can you jump start with jumper leads from one battery to another without disconnecting the good battery, should the motor be running or off ??. Does the same apply if on land any you jump from a car ?? can it do any harm to the electronics etc. ??.

 

[benniejordaan]

CLS wrote:

A question to all.

If out at sea and one battery dies, can you jump start with jumper leads from one battery to another without disconnecting the good battery, should the motor be running or off ??. Does the same apply if on land any you jump from a car ?? can it do any harm to the electronics etc. ??.

It is never good to jump start any battery, at least not continuously. But like with cars, you can do exactly the same. Use your jumper and remove them as soon as the engine is running. The engine produces enough power to keep it running. Keep the motor with a good battery running before cranking the motor on the dead battery.

You should always keep a set of jumpers on board!

 

[Fanie]

If you use a contactor you can connect the batteries together temporary when you desire it. You can buy them from auto spares shops and they can switch enough current. They are about the same size as the starter solenoid you find on most outboard motors.

The ones I bought drawed only about 2A to switch the contactor, you get ones that draw a lot more, which you don't want. It is desirable to first make the contactor before you crank the dead motor. It will reduce arcing on the contacts of the contactor and it will last a lot longer.

When you parallelled the batteries, if possible do not start right away, but allow the low battery to gain a bit of power before you crank it's motor. A few minutes makes a big difference. Otherwise the good battery will not only have to start the motor, but will also attempt to charge the low battery at the same time, so less power to start the motor.

You can work it with a pushbutton switch without leaving the helm. Don't use an on/off toggle switch, you don't want to forget the batteries in parallel. Use a decent push to make relese to break switch.

As Bennie said, it is in any case a good thing to have jumpers aboard. Buy the thick cabled heavy duty truck starter ones, the thin ones is a load of junk.

 

[Fanie]

Needless to say the negative battery terminals should be connected together and also through decent cables. The cables should be tinned copper wire, avoid the bare copper ones like the plague, and the cables should be fine multi cored flexible cable, available from wholesale electrical shops. The battery negatives can be connected together permanently.

As short as possible cables and solder the lugs in a solder bath. You can find a component assembly house, they should have solder baths. I'd use leaded solder and not unleaded solder.

You hook a piece of SS wire through the eye of the lug, then while in place over the cable end dip in a thinner based flux then into the solder. The SS wire will keep the lug from falling off when you dip it. Don't hold too close, it gets hot very quickly. Don't use the acid based plumber flux.

 

[PH]

Fanie wrote:

Needless to say the negative battery terminals should be connected together

I heard, when jump-starting cars, the negative cable (black) should be connected to the body of the car with the faulty battery and not to the negative pole of the dead battery. Is this true? (If so, why would it make a difference? The negative pole is anyway directly connected to the bodywork)

Thanks.

 

 

[Fishton]

CLS wrote:

If out at sea and one battery dies ..............

Never get caught with a flat battery again ..............

 

[CLS]

Thanks all, when you thought all was simple, makes you think a bit, changing a battery with wet hands and deck wakes you up.

 

[Fanie]

I heard, when jump-starting cars, the negative cable (black) should be connected to the body of the car with the faulty battery and not to the negative pole of the dead battery. Is this true? (If so, why would it make a difference? The negative pole is anyway directly connected to the bodywork)

When you jump start you always want to connect directly to the battery pole, even if the body is also connected to same. The reason is simly you get voltage drops over wires and parts which is undesirable. Many times the 'earth strap' is only to make sure the unit, ie an engine is connected to ground although the power to the unit ie starter must still be supplied through a cable.

Thanks all, when you thought all was simple, makes you think a bit, changing a battery with wet hands and deck wakes you up.

Add a bit of rough water and fading light... things never go wrong in perfect weather. When they do however it's almost certain to trigger a list of things.

 

[L Hooker]

Yip always keep jumpers on board ...In May launched at Ponta went up to Milibangala hell of a far...My old man cut the engines as i was into a decent fish, landed fish then tried to restart motors, left motor dead dead dead...If i had not had the jumpers i would have been in the sh!t... If for what ever reason you don't have jumpers one can always swap the batteries start one motor and then do the same for the others!!! my 2c

 

[CLS]

L.Hooker.

I have been there done that, thats how I know wet hands + wet deck + live battery = shocking experience. ha ha ha . I had heard mixed opinions- some for some against regarding starting motors using jumpers thats why I have asked for advice.

I will source a decent set for the boat, hope I will never need them.