So I left the interior lights on in my new Mk1 MX5 and have flattened the battery.

 

Tried to jump start it last night but had a few issues and was pushed for time, so didn't get it done. Basically I got sparks when I tried to connect the negative lead and this freaked me out. Admittedly it is a looong time since I jumped a car.

 

Here's what I did:

1) I connected the positive lead to the flat battery (really awkward to reach on the MX5 as it's tucked under the bodywork in the boot! Didn't help there was limited light).

2) Connected the positive lead to the second car's good battery - Hyundai i20.

3) Connected the negative to the good battery.

4) Lastly when I went to connect the negative to the flat battery it sparked quite a bit so I took off both of the leads.

 

Did I do something wrong?

I read you should connect the negative to a bit of bodywork rather than the battery, should I have done this instead? 

It was my understanding you could do either, I'm sure in the past I connected + & - to both batteries.

 

Cheers

Andrew

 

You worried for no reason. Sparks is normal.

Last lead to connect should be NEG to body so the spark is away from the battery.............in a health and safety type way!?

Sparks are normal when connecting (upon completion of the circuit). Not so once already connected, as that would indicate a poor connection.

 

The thing of connecting it to the body away from the battery is to prevent the 'possible' explosion of hydrogen from the battery vents. And that is generally the same level of 'possible' as hitting a hole in one from the back door of a C-130 flying over a golf course

Edited 28 October, 20169 yr by Huskoda

Thanks for the replies.

 

Turns out it was slightly more simple explanation and rather stupid on my part.

 

The problem was the battery on the MX5 was not colour coded for positive and negative. I thought the negative was the positive as it had a thick red lead to it!

 

So the sparks were because I was connecting a negative to a positive..

ouch. hope all is ok.

Sparks are normal when connecting (upon completion of the circuit). Not so once already connected, as that would indicate a poor connection.

 

The thing of connecting it to the body away from the battery is to prevent the 'possible' explosion of hydrogen from the battery vents. And that is generally the same level of 'possible' as hitting a hole in one from the back door of a C-130 flying over a golf course

Initial sparks are normal. The mistake a lot of folks make is in thinking that a pair of normal jump leads with normal clips will carry the start current . What you need to do is to let the jump car charge the jumped battery to let it get a degree of charge. It's helpful if you check the battery terminals on both cars for hot connections, as this means a bad connection.

3) Connected the negative to the good battery.

4) Lastly when I went to connect the negative to the flat battery it sparked quite a bit so I took off both of the leads.

I would have connected these in the opposite order.

 

ie, to the flat battery first.

On my mx5 if the battery is flat I tend to use the boot latch striker plate as the negative connection...

On my mx5 if the battery is flat I tend to use the boot latch striker plate as the negative connection...

 

I did that very thing.. since the negative is so difficult to access. Luckily didn't cause any damage by the whole - to + balls up.