Electrical amperage question

[Tagg]

I am putting in a second battery.
Off that battery is a fuse block ( from a wrecker).
All the electrical mods will come off that fuseblock to keep them separate from the factory wiring.
I have a forklift plug on the front bumper so jumper cables can be "plugged in" without opening the hood.
I want to use a relay so the cables are only "live" when the button is being pressed. I found a relay rated 80 amps but I don't know if that is a high enough rating for the application. Batteries have 800 CCA.
I don't understand how the two numbers are connected?
Can someone help me out?

[w squared]

I am putting in a second battery.
Off that battery is a fuse block ( from a wrecker).
All the electrical mods will come off that fuseblock to keep them separate from the factory wiring.
I have a forklift plug on the front bumper so jumper cables can be "plugged in" without opening the hood.
I want to use a relay so the cables are only "live" when the button is being pressed. I found a relay rated 80 amps but I don't know if that is a high enough rating for the application. Batteries have 800 CCA.
I don't understand how the two numbers are connected?
Can someone help me out?

80 amp relay is less than I would want for booster cables. 800CCA = 800 "Cold Cranking Amps" = 800 amps is what the batter y is rated to provide under optimal conditions. I would look to find a relay that has a beefier rating than that. The other problem is that if your vehicle needs to be boosted, you won't have the juice to operate a relay...meaning that you can't use your forklift plug. 

How often do you plan to boost or be boosted? Opening the hood for jumper cables is not a really big deal. I'm not trying to slam you here, just save you some grief.

I get the value in having an external plug for boosting, but I'm not sure that it's worth prioritizing unless you are going to have people that you don't trust boosting your vehicle on a regular basis.

[cLAY]

WE have a simial plug on all our light fleet vehicles at work for boosting. Works well but we don't have any kind of relay. Its just straight to the battery, live all the time and we've never had a problem with one.

They are great for plugging in accessories as well.

[w squared]

WE have a simial plug on all our light fleet vehicles at work for boosting. Works well but we don't have any kind of relay. Its just straight to the battery, live all the time and we've never had a problem with one.

They are great for plugging in accessories as well.

Yup...fleet vehicles are the one time/place where plugs make sense.

[Tagg]

I was thinking of boosting anyone else off a second battery. I'm safeguarding the primary battery to start my rig. It's not wise to leave the connection between two jeeps for too long so I thought connecting a relay with a button to activate it would be ideal. However the 800 amp relays are something like $150 so at that price I'll live with the live-all-the-time plug.  What is a starter relay rated for?

[esi]

There should be no issues with leaving two vehicles hooked together for a while unless one has a real bad short, providing that your vehicle is running while boosting another. A different option would be a battery isolater (PA on sale right now around $50) or you get a master shut off switch and run it on the postive cable out to your plug. The isolater will let you run one battery down and still have a full one to start your rig.

[i_go_commando]

another thing i would consider would be a simple staring solonoid. there not rated for constant high load, but for a short load like starting or jumping. cheep at a wrecker or a parts store. im also of the opinion to keep it simple though. may not realy be needed...