How many mah do I need for dual BL 21.5t 4ws ?

[shannow]

Hello,
I know there's a lot of topic on this but not for my specific system :( (or 2BL motor at least comparable) .
My setup I'm building is berg fitted with a double ESC with two 21.5t LRP brushless (148watts each max) and two 7954HS hitec servos for 4WS .
I already have batteries from my touring cars/buggies but they are quite big ... 4200mah and voluminous (hard case) but even tho I'm currently drawing my frame on CAD fitting these in the Berg is a merry game ... unless I just stuff them anyhow but I'll will be expensive on my CG ...
There are relatively cheap lipo that are very small in comparison and plenty of crawler uses them (1200mah+ aircraft looking) but on my system will it still be ok ?
The ones I'm looking at are 1800-2200 mah , will it provide at least 20minutes of runtime ? Each motor as a 148watts capacity but I won't bash with it . Just smooth and easy crawling .

thanks you very much for your time

[indiana mudcat]

I would get almost an hour from packs that size in my Axial with a 18.5 on 2s, not sure how much time the double ESC and servo's are gonna sap but I'd guess about half an hour. You'll still want high C packs to feed all the power the motors can pull though I'd try to find 50A cont and 100 A peak or better, I'd go for more amps if you can find a pack that fits, esp if your gonna run 3s.

[oldhippie]

I get over 15 min with my 850mah 3s. With your setup ya need a battery that can discharge at least 60 amps (ah x C). Something like the HYPERION G3 VX 1100 MAH 3S 11.1V 35C/65C would be a good choice.

[shannow]

thanks a lot . I'll have a good thinking session then
One of my possibilities is to have two tiny 1000-1250mah 7.4v 30C pack run in parallel to get the amps (60-75amps) .
I still have to think were to put them . Perhaps on top of the front and rear servos or in between the links I don't know yet .
thanks again