3s to 6s Vrx Cobra
02-11-2021, 02:43 AM
#1
3s to 6s Vrx Cobra
Hi all.
I recently purchased a budget vrx cobra 1/8 brushless. I am in the progress of upgrading the standard ESC to a 150amp so I can run a 6s setup. Only cobra to my knowledge that runs a 6s.
To utilise my current 3s batteries I will be doubling them up to get the 6s (same brand and ratings). What I want to know is has anyone ever done this to a car set up for a 3s, and have you had any unexplained issues?
My first problem is fitting them into the current battery holder. Then I have the weight issue. They would be located on one side, not sure how this will effect the balance.
Thanks. If anyone has any pics of their stacked battery setup please post.
I recently purchased a budget vrx cobra 1/8 brushless. I am in the progress of upgrading the standard ESC to a 150amp so I can run a 6s setup. Only cobra to my knowledge that runs a 6s.
To utilise my current 3s batteries I will be doubling them up to get the 6s (same brand and ratings). What I want to know is has anyone ever done this to a car set up for a 3s, and have you had any unexplained issues?
My first problem is fitting them into the current battery holder. Then I have the weight issue. They would be located on one side, not sure how this will effect the balance.
Thanks. If anyone has any pics of their stacked battery setup please post.
02-11-2021, 03:55 AM
#2
Suspended
Don't do it. Just don't. Best case it'll be undrivable and not fun, worst case you'll just break it the first time you even think about giving it some throttle.
The reasoning:
1: If you only upgrade the ESC, you'll likely fry the motor, maybe even also the new ESC.
2: If you don't fry anything, the added weight will make it handle worse.
3: The extra weight will also put more stress on all drivetrain components.
4: Extra stress on drivetrain components due to weight + way too much power = unlikely to last even one battery.
If you really want more power go 4s first, it'll be more than enough.
I know the RTR scene has become a pole measuring contest where only "how many cells you runnin'?" and "how fast does it go?" count, but believe me, it won't be a good time.
The reasoning:
1: If you only upgrade the ESC, you'll likely fry the motor, maybe even also the new ESC.
2: If you don't fry anything, the added weight will make it handle worse.
3: The extra weight will also put more stress on all drivetrain components.
4: Extra stress on drivetrain components due to weight + way too much power = unlikely to last even one battery.
If you really want more power go 4s first, it'll be more than enough.
I know the RTR scene has become a pole measuring contest where only "how many cells you runnin'?" and "how fast does it go?" count, but believe me, it won't be a good time.
02-11-2021, 04:58 AM
#3
Tech Regular
iTrader: (2)
2x what kawasaki161 said. 6s speed is no joke as to the damage you will do to your car in crashes. Also the raw power can simply destroy driveshafts, diffs, wheel hexes.
I have not heard of your VRX Cobra, so I looked it up. ( Is THIS your truck?) At first glance, it looks like a smaller truck that has been scaled up to make it 1/8 size. Plastic chassis, Plastic shock towers, 12mm hex wheels. I can only guess on the diffs, but if they didn't bother to upgrade the wheel hex, I doubt the diffs will handle more power...
Motor is a 3660 size 3000kv. Good motor for a 3s runner 1/10 MT or SCT, but I bet it is already overworked in proper 1/8 truck. 6s will send it to a quick grave - both from over-revving (3000kv is too much for 6s) and overheating. So, you will really need a new motor too.
So lets assume you get a "proper" 1/8 setup - 150a 6s ESC, a 4075 2000kv motor, and a big 6s battery. Now you have a 50-60mph truck. Congratulations. But the first time you have a +45mph crash, all that plastic will be smashed and spread across three counties. That is assuming the diffs don't blow or the 12 mm wheel hexes don't round out the first time you goose the throttle.
I am not spelling this out to be negative, but just to show there is a lot that goes into a big high power truck. There is good reason a Arrma Kraton is $600, and it still sometimes breaks (50mph crashes are brutal, they don't care about brand). I have been down this road, and all I got was heart break, an empty wallet, and a dead RC.
If you can't afford the $400 - $600 buy in of something like a Redcat Kaiju or Arrma Kraton, don't be afraid to look used. Yes, there are a lot of folks wanting like new price for their used trucks, but have patients, and you will find a good truck for about half of new price, and it will probably come with spare parts and a battery or two.
I have not heard of your VRX Cobra, so I looked it up. ( Is THIS your truck?) At first glance, it looks like a smaller truck that has been scaled up to make it 1/8 size. Plastic chassis, Plastic shock towers, 12mm hex wheels. I can only guess on the diffs, but if they didn't bother to upgrade the wheel hex, I doubt the diffs will handle more power...
Motor is a 3660 size 3000kv. Good motor for a 3s runner 1/10 MT or SCT, but I bet it is already overworked in proper 1/8 truck. 6s will send it to a quick grave - both from over-revving (3000kv is too much for 6s) and overheating. So, you will really need a new motor too.
So lets assume you get a "proper" 1/8 setup - 150a 6s ESC, a 4075 2000kv motor, and a big 6s battery. Now you have a 50-60mph truck. Congratulations. But the first time you have a +45mph crash, all that plastic will be smashed and spread across three counties. That is assuming the diffs don't blow or the 12 mm wheel hexes don't round out the first time you goose the throttle.
I am not spelling this out to be negative, but just to show there is a lot that goes into a big high power truck. There is good reason a Arrma Kraton is $600, and it still sometimes breaks (50mph crashes are brutal, they don't care about brand). I have been down this road, and all I got was heart break, an empty wallet, and a dead RC.
If you can't afford the $400 - $600 buy in of something like a Redcat Kaiju or Arrma Kraton, don't be afraid to look used. Yes, there are a lot of folks wanting like new price for their used trucks, but have patients, and you will find a good truck for about half of new price, and it will probably come with spare parts and a battery or two.
Last edited by JerryRigged; 02-11-2021 at 09:11 AM.
02-11-2021, 12:22 PM
#4
Thanks guys for being honest. I’m by no way a racing guy, only in it for the fun. Being on a budget is why I opted for the vrx cobra. Yes that picture was the one however I got the brushless upgrade to the 2000kv motor.
good thing about this car, parts are very cheap. Already replaced the center diff, cost $15. I know going to a 6s seems crazy but I’m only in it for the fun. I don’t race it, only go to ovals with rolling hills, sometimes to a bmx track.
weight and balance is going to be an issue but also a challenge 🤪
once I convert it I’ll try out the 6s, if no fun I’ll change back to the 3s.
good thing about this car, parts are very cheap. Already replaced the center diff, cost $15. I know going to a 6s seems crazy but I’m only in it for the fun. I don’t race it, only go to ovals with rolling hills, sometimes to a bmx track.
weight and balance is going to be an issue but also a challenge 🤪
once I convert it I’ll try out the 6s, if no fun I’ll change back to the 3s.
02-11-2021, 12:26 PM
#5
Tech Regular
iTrader: (2)
6s is not for racing, Bashing only. Racing is 4s - it is about controlling your power, 6s is about uncontrolled power. 
Having the big battery on one side is not really an issue, this is the way most of 1/8 buggy/truggies are designed.
Good luck, and have fun!
Having the big battery on one side is not really an issue, this is the way most of 1/8 buggy/truggies are designed.
Good luck, and have fun!
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