A 4s4p LiFePO4 (Lithium Iron Phosphate, for those that don't know) would measure about 36mm tall x 70mm wide x 144mm long, and this would be for a side-by-side configuration (like what I use). If you did a shotgun style, it would be 36mm tall x 72mm wide x 140mm long.

It's all your choice as to what to get. Each type have their advantages and disadvantages (relative to each other), and both are better than NiMh.

I'm still unsure of the charging.

Why can't I buy just any Lipo and charge it at 2C? Also, if I bought 2 different packs, say a Kokam and LiFePO4 both 6s 3500mah, will they take the same time to charge at 2C?

Lipos usually can't handle 2C without dramatically reducing the number of cycles that they will run for. As newer and better technology comes out, Lipo cells are starting to be able to be charged at greater than 1C (but still only a few are capable).
A Kokam and LiFePO4 will finish the CC (constant current) phase of the charge at the same time, but the LiFePO4 will finish the CV (constant voltage) phase way ahead of the Kokam, just because its normal CV voltage is 3.65v and it is being pushed with extra charge all the way to 4.20v.

Thanks,

Since I'm in the UK, I've been looking at these:
http://www.flightpower.co.uk/proddet...p?prod=4200016

My Triton (by Great Planes) can do 4s lipo @ 2.5a max. So I can charge a pack at time. I thought I want to try Lipos before buying a new charger to do them faster or more cells at once, seems logical.

If I did 2.5a for 3300mah, is that like 1.5C? What else would I need to charge, any sensors or anything? Does the Triton detect when it is charged and stop, safety etc?

Accually nick it is not 1c for the 3300 mah at 2.5 amp. It would be 3.3 amp for a 3300 is 1c.

Whats the price of that in US dollars? And do they ship in the US, I might look into those also.

Would it be better to get a 3s and 2s or just one 5s pack if I wanted to run 5s total? Or in other words, if I wanted to run 5s now and 6s later with a different motor, could I get the 3s and 2s now and just get another 3s later to make 6s? Or would that 1 3s pack being older and run more cause conflicts? However looking on that website, I dont see them in a 2s configuration. What would I do there?

2500ma /3300mah = 0.76C.
A balancer would be nice to have, and is a good investment since it will keep the cells at the same resting voltage, which will increase the overall life of the pack.

Instead of getting Flightpower from the UK, you can get Hyperion or Polyquest XP or Duralite or Impulse in the U.S. Any packs that are almost the same size/weight at the same capacities from these vendors will use the same cells as the Flightpower packs.

If you want to run 6s later, why not just get it now? It isn't a good idea to mix and match new/old packs in series during discharge because the older pack will hit LVC sooner than the newer pack.

Well I'm running a 7xl right now. I think 6s would be a bit too much. I was thinking abou getting like a 9 or 10XL later on thats why I wanted the possiblilities of 6s. You got links for those manufacturers?

http://www.hobbypeople.net/mfr/IMPLSE01.asp
http://duralitebatteries.com/batteries-egold.html
http://aircraft-world.com/shopdispla...o+%2D+HYPERION (the ones in the blue wrapping)
http://www.brchobbies.co.uk/?page=sh...ory=4&start=24

There are lots of other sites, these are just a few of the ones I know of.

I'm looking for a charger now, the Astroflight looks good, anyother? Wanting to be able to have high amps (Astroflight does 7.5), for future flexibility but only around 8s cell limit.

Looked at the Schulze but they don't provide any information except how many cells they do.

Man, my LHS handles the Polyquest XP packs for the air crowd. I was looking at them yesterday in the glass cabinet, couldnt see them well but thats them. They have the 3s 3700mAh pack atn$137 and I didnt see the 2s price. They also have the Triton charger. What kind of balancer would I need to get?

Personally, I'd be wary of the AF109 for high cell counts. I've read multiple stories of it "switching" the cell count, and the user not being able to stop it unless they unplug the battery.

For chargers, there's the Super Brain 989 that can do 8s Lipo (not sure how many amps):
http://www2.towerhobbies.com/cgi-bin...?&I=LXLTW4&P=7
Or, there is the Multiplex LN5014 that can do 5s Lipo at 5amps:
http://www.rc-monster.com/proddetail...531lipocharger

IMO the Triton isn't a good Lipo charger. Only 4s up to 2.5amps. You can get a $50 charger with those capabilities.