If it takes roughly 1hr to charge a 2s 5000mah batt at 5amps. Then if you get a charger that can charge at 15-20 would it then only take around 15-30 min and does it harm the batt to charge it that fast. Also if i am anly going to ever run 2s batts is it worth it to get highend charger for higher than 5amp rates is there a benefit other then faster charge times.

Well if the baterys says it can be charged in 2c or 3c or 5c that is no problem.
1c is the actuall mahs of the batery. 2c is the double of the mahs of the batery.

A double C means half the time to charge.

Minium 100w charger for you if want to charge at 1c, that is more then an hour....
if you want to charge in 20minutes you need a 400w or even higher charger!

I charge my 5s (18.5V) lipo with a 50w AC/DC charger, and select 5.0A...but the charger only charges at 2.5A and gets extremelly hot...so i need a new charger to charger faster and cooler! :P

Those numbers only match for your 5s, not the 2s the OP asked about :

1C always takes about 1 hour. (Ok, when balancing it may take a little longer).

And for 2s you certainly don't need 100W for 1C. Since 8.4V (fully charged, no load voltage)*5A (=1C for a 5000mAh battery) is just 42 Watts... so a 50W or 60W unit should be enough.
To charge in 20 minutes instead of 1 hour, you'd need 3C (15A), since 20 minutes is one third of an hour. And for that 8.4V*15A=126W is all you'd need (plus a little reserve) - but you don't need 400W - not even close to that.

Only when you charge 5s instead of 2s, those numbers become true - but again: the OP asked about 2s, not the 5s you use.

Of course. Fully charged, no load, a 5s has 21V... so a charger with 50W can only charge at 2.38A (=50W/21V)... about the 2.5 Ayou said. Setting it to 5.0A cannot work, you'd need 105W (plus a little reserve) for that at least. And it gets hot, because it is at its absolute limit!

So does it harm that batt to charge in the 15amp range, will it cook the batt or get it really hot

Example

FMA's all-new Cellpro 10XP builds on the foundation laid by their popular 10S charger, adding multi-chemistry charging capability and greatly increasing the output power, while still retaining the use of the peripheral components such as balance boards from the 10S platform.

Even with all the new features added on, it's still an FMA Cellpro charger, and that means safety, reliability, and ease of use are assured.
*
Specifications

Maximum charge power capacity: 645W at 32V DC, 234W at 12V DC
Charge current range: 0.01-15.0A
Input voltage range: 10-32V DC
Current drain for balancing: 500mA
Balance accuracy: 78µV
LiPo/LiIo/LiFe: 1-10 series
NiCd: up to 28 cells (non-balanced)
NiMH: up to 28 cells (non-balanced)
Lead Acid: up to 24V
Intelligent temperature control: Yes
PC Connectivity: USB port
Weight: 575 g
Dimensions (LxWxD): 168x92x44 mm

So if i got that charger for example, and a buddy has a 350 watt ps he can get me, it would be able to charge at the full 15 and not need the 645 it also has listed to do it, i take it it need the 645 if i was doing 4S range and up type batts. Also hw do you get full potential of these DC Chargers if your out in field running on a car battery,

Most battery manufacturers say you can charge at twice the "C" rating (5000 @ 10 amps) safely. I've been charging 1 cell and 2 cell (good Batteries) for years at 15-17 amps and no issues. You're gaining charging time yes, hurting the battery, not as much as you would think. I've done this weekly over the whole winter months and run time losses and voltage drop-off are minimal. Cheap batteries may not be so lucky! Running a battery down to cut-off voltage and re-charging would take 1/2 hour for sure. With the new breed of chargers out there, you can charge up to 40 amps if you have the b---s!!! jmo

I charge a 6500mah 2s at 2c and it takes about 15mins including balancing. How low are y'all letting your batteries go that it takes 30 mins on 2c? Mine hit cut off at 3.4 sometimes I'll pull them at 3.5.

3.2

It will explore or fire, if your lipo battery don't support to charge with 3C...Ask the dealer, before you charge like this.

I know I'm starting the Battery Temperature Topic again; but it's important.

To put it in short: -don't charge your Ni-MH batteries over 95°-100°. -If the batteries get hotter than 95°-100°; you could be beat'n-up the battery.

Take Care