battery or alternator?
 

So last night my wife is driving the 2001 discovery ii, 102,000miles. She tells me while driving, the battery light went on. Then when she came to a red light the vehicle became sluggish and the dashboard lights flashed on. She was able to get it into a parking lot, when she came back 1/2 hour later the truck would not start.
Is this the sounds of the alternator? or battery?
I know I need a new battery, anyway.
The truck is about 18 miles from my house, 30 miles from my mechanic. Tow is too far and I don't want to bring it to "just anyone".
I have a new battery to install, but if it is the alternator will a new battery last to get me the 30 miles.
Any advice is appreciated, thank you.

Alternator most likely.

Put the fresh battery in, drive it home, don't kill it until you get there.

Thanks.
Yeah, that's what i figured. 15-20 min ride on a new battery

x2 leave everything you can off in the truck, you could make 30 miles. not in stop and go.

Thanks. I changed the battery, quickly, and made it home.
Truck ran fine, but the red battery light was on.
Is this an indicator for the alternator?
I did not seat the battery properly as I was in a bad spot. I did not clean the wires or put the gel on the anodes. The negative lead needs to be adjusted and was a bit loose...can this be the reason for the battery light to be on?

you should certainly clean all that stuff up, at test the output of your charging system.
but if the battery died while it was running then your alt. was not charging your battery, could be lose / bad connections if your luckily.

Gonna check it out, thanks.
BTW is the alternator a tough DIY?

Should be pretty easy. Slip the belt off the pulley, remove two bolts, loosen the wires, you're done.

The worst part will be wrangling the belt, which is a pain in the ass on these trucks until you've done it a few times. An extra set of hands always helps.

thanks

I'm with drowssap: although not likely, make sure all alternator connections are good before replacing the alternator, but I'm leaning toward the alternator as well.