Jump Start

[normanr]

Hi All
Happy new year to all the forum members,I am asking this question on this forum although I have sold my Mercedes because the expertise regards information on this site is the best.
What I would like help on is on Boxing night I travelled 25 miles to my Daughters and parked the car at 1.30pm when we went to leave at 11pm the battery was flat and would not even turn the courtesy lights on I have never had a problem with the battery before that,called the RAC out and the report was assist battery start test alternator past ok,check battery discharge -0.12a-ok,test battery failed.
I drove the car back home and went to get a new battery yesterday but had to order one but in the meantime the battery is holding it's charge fine the car starts first time every time so can't understand why it has not discharged again if as the RAC guy says it is Kn-----d.
So I don't get caught out again (had to wait nearly 3 hours) are these jump starts safe to use with the modern cars only heard they could damage engine ECU due to the boost they put out can anybody advise on this only if this is the case surely there should be some sort of warning on them.
I think something drained my battery for some reason to loose charge that quick but it has not happened again so would like to get a booster charger in case .
Thanks
Norman

 

[rf065]

You can buy jump leads & starter packs with built in surge protection, they will cost more but will not fry the ecu or anything else.

Russ

 

[normanr]

Hi Russ
Could you give me some information on what to buy and where to get them.

Norman

 

[Dieselman]

I don't believe that any booster packs can damage the ECU due to the current they can output as a battery gives a lot more than they will.

The problem is thet when connecting a sudden spike is created, especially if you don't make a clean connection stright away. There are jump leads available with surge protecting capacitors built in for this.

Having jumped cars, even recently I'm not convinced of the requirement though.
If the Ign is off how will the ECU recieve any power.?

As you say, the RAC jumped started your car.

 

[talbir]

Surging can occur both when connecting and disconnecting. Allow the engine to idle for 2-3 mins once started before removing the jump leads.


talbir

 

[Uberwagon]

I don't believe that any booster packs can damage the ECU due to the current they can output as a battery gives a lot more than they will.

The problem is thet when connecting a sudden spike is created, especially if you don't make a clean connection stright away. There are jump leads available with surge protecting capacitors built in for this.

Having jumped cars, even recently I'm not convinced of the requirement though.
If the Ign is off how will the ECU recieve any power.?

As you say, the RAC jumped started your car.

I've seen it happen on some of our development vehicles and even on an electronic governor for a large generator, it definitely happens.

I've even seen electronics get fried when all the circuit breakers have been open while welding has been taking place, I put it down to Voodoo.

Dave!

 

[Dieselman]

I've even seen electronics get fried when all the circuit breakers have been open while welding has been taking place, I put it down to Voodoo.

I'd never weld with electronics such as an alternator connected because the constant spiking and inverting of current effectively flash tests the diodes many times a second. After a few thousand flashes they give up.

 

[Uberwagon]

I'd never weld with electronics such as an alternator connected because the constant spiking and inverting of current effectively flash tests the diodes many times a second. After a few thousand flashes they give up.

This is the issue, nothing was connected, all the breakers were open for the auxillaries and also the engine itself.

It's very rare but still happens.

Dave!

 

[jaymanek]

Surging can occur both when connecting and disconnecting. Allow the engine to idle for 2-3 mins once started before removing the jump leads.


talbir

we use jump packs every day and this is the best advice... leave it on the car for a few mins once started.

 

[normanr]

Thanks guys
Good information once again.
Norman

 

[Dieselman]

This is the issue, nothing was connected, all the breakers were open for the auxillaries and also the engine itself.

It's very rare but still happens.

Breakers being open isn't the same as disconnected at the apparatus. You need to disconnect locally if not you get inductive and capacitive surges due to the cable still connected.

 

[Uberwagon]

The confusing part was that Woodward themselves said there is no way it could happen and then said we had made a mistake.

When you mean disconnected at the apparatus, do you mean remove the ecu completely?

Dave!

 

[Dieselman]

When you mean disconnected at the apparatus, do you mean remove the ecu completely?

I'm confused now. I thought we were talking about alternators connected when welding.

ECU's aren't normally an issue, was the welder's earth contact a good one.? It sounds like you had some serious spiking going on there.

 

[Uberwagon]

I'm confused now. I thought we were talking about alternators connected when welding.

ECU's aren't normally an issue, was the welder's earth contact a good one.? It sounds like you had some serious spiking going on there.

My alternators are 25 tons so we wont damage them.

I mentioned it as an example of how careful you have to be as electricity works in mysterious ways.

I haven't jumped mine successfully yet, when I did the battery needed half an hour on a trickle charger before it would do anything. I have a Cetek now instead.

Dave!

 

[grober]

Any welding arc will produce a strong local RF [radio frequency signal]signal. (think giant unsuppressed spark plug! )This may well induce currents in circuitry in close proximity causing damage without any direct electrical connection.

 

[crockers]

What damage can be done if you connect the leads to wrong terminals? i.e. + to - ....

 

[c240yaz]

What damage can be done if you connect the leads to wrong terminals? i.e. + to - ....

Battery explosion, fire ?

 

[rf065]

What damage can be done if you connect the leads to wrong terminals? i.e. + to - ....

There is a thread on the other forum where someone has done just that, it sounds like an expensive mistake.

Russ

 

[Dieselman]

Theoretically it could do a lot of damage to electronic components, but the reverse polarity relay should offer a decent level of protection as it won't supply power if reverse connected.

 

[MBManInKen]

What damage can be done if you connect the leads to wrong terminals? i.e. + to - ....

You could damage the electronics including those of the donor car. In a worst case, the battery could explode and that could cause injury including blindness.

While most people seem to understand that they need to get the polarity right, a lot of people still make the mistake of connecting the negative cable to the negative terminal of the battery rather than to a clean metal part of the car. That can cause a spark too and you don't want sparking near the battery where hydrogen gas can build up...