I was wondering if I could use 2 Lithium CR2 batteries (3v each) instead of a hump pack. What are possible problems in the future? I understand these aren't rechargeable but I have a few available and they're supposed to last long. Any ideas?

They are Energizer Lithium Photo...

They will not supply enough current for servos.

What do you mean by current? I'm assuming mah? How much do these put out?

Says that it's rated at 800 mah each... Here's the spec sheet:

http://data.energizer.com/PDFs/CR2_EU.pdf

My bad, I was thinking about the disk batteries, CR3s.

Two of these would be equiv to a 1600mah hump pac. Just wonder how they'll do when the mah is made mostly of current since RC servos pull more current than a camera. The discharge graph says these should work, but the voltage is going to always be below 6v.

Depending on what servos you're running, the max discharge of 1amp may be a prob. Since you've already got them, give them a try, don't see anything that it can hurt. Check the temps on them after running a little while. If they're having trouble with current demand, they'll prob start getting hot.

Nice. I think I'll give em a try. Just gotta figure out how I want to make the two connect to the receiver...

I've seen DIY's on packs but can't find any... Anyone mind leading me in the right direction?

Prob 1st thing to do is to tape or glue the two cells together with the ends reversed to each other - neg and a pos at the same end. I use shoe goo since its strong, dries pretty fast and is easy to remove.

Then take some 16-18ga wire and connect the 2 cells neg to pos on one end. Use a servo extension and cut the fem end off and solder the remaining ends to the correct ends of the two batteries. Red is pos.

Its usually typical to rough up the ends of the cells where you'll be soldering. I wipe them off after that with a rag wet with motor spray to make sure there's nothing to interfere with the solder sticking. Use some flux while soldering.

There's a bunch of pack making DIYs on Utube.

Connecting those batteries together in series as described will create an 800mah, 6v pack. In order to make a 1600mah 6v pack, he'll need 4 of those set up in 2s2p configuration.

What's 2s2p configuration?

2 in series, 2 in parallel. The 2 in series give you 6 volts, the 2 in parallel give you 1600mah. Put them together and you have a 6v, 1600mah pack.

had to quote this because it is the only way..
if you ignore this you will end up with a run away unit or just not enough current left for a response back to the transmitter...
1) crashes due to poor response time..
2) runs off a clif because all the juice left the battery's...lol
sometimes stock setup in the end for receivers
is the way to go unless your looking for lighter faster moving stuff...lol

Sorry, I don't understand. If I connect 2 in series and 2 in parallel... How do I connect the pairs together? I see this...

[+ -][+ -]
[- +][+ -]

Sorry.. I'm not much of an electrician...

I'm just trying to use the smaller batteries cause 1. I have a few available and 2. they're much lighter than a hump or the 4 AA's..

After you connect two in series (+to-), think of them as a single cell, since essentially, now they are. Build two of those. You'll have a + & - left over on each.
Now connect the +'s of each together (remember, they are each considered one cell now), and connect the -'s together.
Again, the whole contraption can be considered once cell, albeit a little bigger and with wires hanging out all over.
Connect your receiver leads to the appropriate terminals and.... done.

What is the weight of a 5s hump or 4AA alkalines compared to 4 of these Lithium cells? How about size?

So this is what I'm looking at graphically (minus all the text)...