One thing I think everyone should carry is a simple plug in cigarette 12V meter.

I read far too many posts about "won't start battery is good".
How do you know the battery is good?
The Spyder has nothing to tell you this.

Some have replaced the analog gauges and added a volt meter gauge. If so then you don't need this cheap tool.

Before I installed a permanent 12V gauge I got one of these.
Simply plug it in your trunk cig lighter socket and you know your voltage.
When the key is turned on you can see how much it drops under a light load.
When you hit the starter you can see how much it drops starting.

This simple $4 device will give you much more knowledge of what is going on.

http://www.ebay.com/itm/12V-24V-Digi...lUglHj&vxp=mtr

Bob