I have been in RC for over 27 years and know nothing about ''Lipo'' but here is a few facts that I have found to try and help you a little.
Quoted from: GSMnow from RCCA
1) what is your skill level? Have you raced a very high speed RC car before, and can you handle careful throttle control? I have been racing for manyh tears and I still had a huge hurdle when I added brushless power to my truck. The extreme power available makes your trigger finger more important than the steering. It takes alot of practice to use the crazy power unless you just do long straight shots. A turn at 50 mph could turn the truck to a pile of scrap.
2)Where are you driving? Size of space and surface? If you have a huge parking lot with nothing in your way, sure GO FAST!! but if you have a confined space and setup a course you need to drive through, smoother control will help alot.
If you have only driven brushed RTR's before, I would start off with a good 6 cell NiMh pack with stock gearing and get a feel for the way it drives. You should get well over 10 minute run times and over 35 mph top speeds which is still quite fast. This is very close to the Mamba Max setup I race with in my Losi XXX-T. IT is really more power than you can use on a tighter track. When I bashon the street with my smaller tires, I can gear up for more than enough speed to keep it interesting.
Personnally I am very happy with ProMatch battery packs. They are now selling the EP4200 cells in 3 grades assembled or loose. I run the middle grade (team) cells. They are not cheap, but they run very hard without quitting and they realy stand behind their pruducts.
If you have been racing FAST RC cars and feel you are able to carefully control the throttle (you should be running the IFMAR worlds) then you certainly can jump in with a faster setup. NiMh cells are current limited compared to the latest LiPo stuff, but with higher voltage they can still make serious power. The EP4200 cell can pump out over 40 amps continuous and surge to over 75 amps. The VXL ESC is rated to 3S LiPo, that would be a max voltage of over 12 volts. If you can figure out a way to jam them in the chassis, you could run up to a 10 cell NiMh pack without hurting the ESC. With NiMh cells I would not gear it for more than about 50 mph as the currents will be incredibly high. I would have to do some math to get a solid pinion size for that, but looking at the Rustler VXL ad, it looks like a 28 tooth pinion will get you in the 50 mph area.
The thing you need to understand about a good brushless setup (I have not driven a VXL so I can't say how it compares with the Mamba Max) is that they can make much more torque over a wider rpm range than a brushed motor. This makes it able to pull much harder at speed where a brush motor hits hard slow and tapers off as you accelerate. My MM 5700 XXX-T can pull a wheelie even after I am already going over 30 mph. And that is just on 6 cells geared for 35 mph.
Do yourself a favor and start with a modest speed setup. 35 mph is very fasy. 70 mph is crazy. Ride in a car on the expressway and try to focus on one of the lane dashes(reflector, whatever you have there). How long can you focus on it?? Now picture your truck going past at that speed?? Now turn it around in the width of a residential street!
Hope this helps you a little it clues me in a little.
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