So having pre-ordered an 80mm 2000kv motor, I now need to decide which batteries O_o

I'm currently running 4s2p A123, but at 640g, they're pretty fat. I just weighed my cars again and my nitro ST-RR is about 400g lighter with fuel in, than my electric ST-RR.

In the first post, I said the weight difference was 150g. The only change I've done since I weighed the cars back then was to remove my home brew aluminum battery tray and replace it with the custom made RCM tray that finally arrived (thanks Mike :)) I remember thinking that the bottom plate and tray were quite heavy, but 250g is pretty huge lol.

I will remove the battery tray and weigh it separately tonight to make sure, but I might have to make up a better aluminum tray to save some weight.

The whole point of this exercise was to make my setup as light as possible while maintaining a battery/motor combo that can make at least 15-20min of driving time.

The batteries I am looking at are the Zippy packs from Hobby city. I was originally going to go with 4s 5000mAh packs as they were slightly more capacity than what I have now, and slightly higher voltage so I figured I'd get around the same run time (13 min) maybe slightly more with a better motor. There should also be much less voltage sag under load, and so my top speed should be slightly increased to what I have now.

Magman mentioned going up to a 5s 4000mAh setup, and gearing down to maintain the same speed, but to go down to the 1600kv motor. Unfortunately, as I've already ordered the 2000kv, would I be able to get away with a 5s pack with the 2000kv motor and gear down with a 16t or 17t pinion (running 15t atm)?

I also might have a lead on some 5s TP 5000mah packs which are only slightly used, but are the same size as the Zippy ones.

Is that the right use of the terminology by the way? Gearing down = gearing to reduce top speed with bigger pinion, gearing up being the opposite?

Anyway, the 5s 5000mAh packs are 659g, so essentially, the same weight as what I have now....

A 5s 4000mAh pack is 581g, or 60g lighter than what I have now.

They have a 3300mAh 5s pack which is 443g and much lighter than what I have now, but what sort of run time would I get with only 3300mAh?

thanks for all the help/advice so far guys :D Much appreciated