Battery Spark

[eric416]

I hooked up 2 batteries to a battery selector switch today and when i crank the engine i get a spark on one of them from the negative post to the negative post with the wing nut on it. Also should i have both batteries grounded to the block?

 

[NYBo]

Re: Battery Spark

Sounds like a loose connection.

Yes, both battery negative leads get grounded to the engine block. The instructions for the battery switch should have a basic wiring diagram indicating this.

 

[ADKoutboard]

Re: Battery Spark

....And get rid of the wing nuts!!!!! use a star washer on the battery first, then cables, then a Nut with a nylon insert.


Tarren

(still trying to come up with a cool catch phrase.)

 

[eric416]

Re: Battery Spark

sorry, it was sparking between the positive posts. All connections are tight as can be.

 

[Silvertip]

Re: Battery Spark

Sparking between the positive posts and what?

 

[wire2]

Re: Battery Spark

....And get rid of the wing nuts!!!!! use a star washer on the battery first, then cables, then a Nut with a nylon insert.


Tarren

A star washer is a good mechanical "hold" device but is not very conductive electrically. High current needs lots of surface area, a star washer doesn't provide it, too irregular and made of steel. It will heat up during cranking.

It's better to put the cable lug directly on the bolt, then a plated flat washer, then a nylox nut. With a film of grease on all parts to prevent oxidization.

 

[wire2]

Re: Battery Spark

sorry, it was sparking between the positive posts. All connections are tight as can be.

How long have the batteries been in place?
The positive post of a battery can eventually develop a black film of oxidization between the post and cable clamp.

Oxide is non-conductive, and as the connection is compromised, it will cause a spark during high current. Remove the clamp, clean the black film off with sandpaper or a wire brush, apply a film of grease, put the clamp back, tighten.

 

[eric416]

Re: Battery Spark

the batteries are brand new. when i crank the motor i see a small spark between the 2 positive posts on one of the batteries.

 

[wire2]

Re: Battery Spark

the batteries are brand new. when i crank the motor i see a small spark between the 2 positive posts on one of the batteries.

Is this a combination battery, with GM side mount and classic top posts, to have 2 positive posts? And there's a spark between them?

 

[Silvertip]

Re: Battery Spark

A battery does not have two positive posts. One positive and one negative. There may be a standard auto style battery post and threaded terminal but they are both common.

 

[wire2]

Re: Battery Spark

A battery does not have two positive posts. One positive and one negative. There may be a standard auto style battery post and threaded terminal but they are both common.

Yes, they're bridged by a lead bar and electrically common.
I'm asking the OP to confirm what he has, and what the spark is from/to.

Eric416, is this the style of batteries you have?
http://s7d5.scene7.com/is/image/CanadianTire/0107590_1?$medium$&defaultImage=image_na_EN

 

[eric416]

Re: Battery Spark

this is the style battery i have and the spark was between the 2 red posts

http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?productId=130143&catalogId=10001&langId=-1&storeId=11151&storeNum=10109&subdeptNum=10548&classNum=10549

 

[wire2]

Re: Battery Spark

The only way that setup can make a spark is if the cable end is not electrically solid on the post, and there's an arc when the current peaks. The arc will cause a tiny bit of metal to vaporize and shoot off. (Like a spot welder) In this case, it just happened to shoot towards the other post.

Eric, pull the wire off the battery and have a close look at it? I think you'll find evidence of an electrical arc, (some metal burned away on the cable end and/or the threaded post).