12-cell mini

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Lessen

Lessen

Super Awesome!
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Location
Aurora, Ohio (Cleveland)
RC Driving Style
  1. Racing
I've recently been bitten by the 1/18 speedfreak bug. I already have a tricked out Mini-T with a Mamba 8000 but I'm only runnin 6 cells. It's pretty darn impressive and packs plenty of punch for messin around in the house but I wanna try to get this things balls to the wall on the street.

Everything you read is 3 cell lipo this and 3 cell lipo that. I completely understand the logic in running lipos but I just don't want to go that route at the moment. Mainly because I don't have the nice battery charger/discharger that I want (yet). I just don't want to spend money on a charger with only 1 purpose. I can build a 12-cell pack for less than $30 and charge it with the Losi wall charger I already have. Granted, it won't be quite as convenient but it'll work. Besides, you guys know me... I just wanna do something different.:)

So here's the deal... I get 12 GP1100 2/3A cells, make two custom 6-cell packs, connect the packs in series in the car, and BAM!... 14.4 Volts! The largest pinion I've found so far is an aluminum 18T for an RC18T made by RRP. I'm not sure if I'm gonna grab it up or not. I already have a 16T delrin pinion.

here's the battery layout...
[][][] [][][]
[][][] [][][] kinda like this except the outmost 2 cells will be positioned above the middle row and to the outside a bit.

kinda like this when looking from the front...
O........O
.OO..OO.

yeah, I know it's overboard but isn't 50-60mph 1/18th scale ALREADY overboard.. So yeah it'll be quite a bit heavier than 3 cell lipo plus the fact that it's almost all aluminum already, but it will be 3.3v stronger than a 3cell Lipo pack. I'll probably fry a diff or something on the first run but hey, at least I expect it :D
 
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i got a 22 tooth rrp aluminum pinion.. i think its what you need. i dont do electric.. its nip i got a pic if your interested
 
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joey said:
to help you with your pinion problem Try this i used it on my old mini-t and it let me run and size 540 pinion...
you want the 2mm version.
Click to expand...

thanks for the link joey!

I figure first I'll see what I can hit with the stock gearing (14T I think). considering the added weight and extra power I guess it'll be close to the same range as what's normal for 3cell Lipos. So that should be in the 60's hopefully.

I just gotta figure out a way to mount my VSM.
 
i ran a 3 cell lipo on my old Mini-T also with a 8k mamba it was FAST thats all i can say lol.. Good luck..
 
well I dont know much about electroins but I think there is some saftey issues here... First You can still over gear your motor.
and second I am sure that the losi chager is only made to charge 6 cell battery packs... Even my high cost chagers at my house can only change 8 cells.
 
I have an 18t w/ the mamba 8000kv and ran it with 11 cells a few times! 60/12 gearing, Awesome fast! The little truck becomes very hard to control. I had to make 2 packs in order to charge them, one pack was a unitedrc x71 8.4v 7 cell and the other was a gp1100 4 cell pack. I used a y adaptor that ran the packs in a series.
 
dougc said:
well I dont know much about electroins but I think there is some saftey issues here... First You can still over gear your motor.
Click to expand...

right. that's why I will be startin out with a 16t. If I think the ESC can handle a steeper ratio w/o getting too hot I'll try an 18t

dougc said:
and second I am sure that the losi chager is only made to charge 6 cell battery packs... Even my high cost chagers at my house can only change 8 cells.
Click to expand...

that's why I'll be building two 6-cell packs. building 2 seperate packs is for charging purposes only. it'll take 2 hours of charging but that's ok.

BADNBADN said:
I have an 18t w/ the mamba 8000kv and ran it with 11 cells a few times! 60/12 gearing, Awesome fast! The little truck becomes very hard to control. I had to make 2 packs in order to charge them, one pack was a unitedrc x71 8.4v 7 cell and the other was a gp1100 4 cell pack. I used a y adaptor that ran the packs in a series.
Click to expand...

wow, I bet it got up to speed pretty quick with only a 12T pinion. Right now I like a 10T with a 6-cell pack.. lots of torque but still reasonably predictable. Did you use Deans connectors on yours? The other day I realized that you can hook 'em up in series without the extra comlexity of a seperate y-harness. if you put the two female battery ends next to each other and reversed you can cross them with the male esc end and another extra male end that has been wired into itself.
 
With 12 2/3A cells you will have a BIG drag(due to weight) at the speeds you are going to travel.And geared too tall is not the best recepie for max speed unless you have a perfectly flat surface with very little pavement drag(imperfections).

tall gearing + extra weight = YOU NEED A LOOOOONG STRETCH OF PERFECTLY FLAT PAVEMENT
With a LiPo pack you should reach higher speeds,the downfoarce should come from the body.

I have a 6800 and 8000 Mamba tried them in my RC18T and M18 with eight 2/3A GP cells and a three cell LiPo. :flamer: Absolute blasts,the M18 went around 60MPh in a huge newly done parking lot.

damn these tiny things are true road rockets

Good luck with your rocket
 
yes, I know there is a big weight disadvantage but consider the power. 14.4 volts (3.3 volts more than a 3 cell lipo) will be tons of power even with the weight and a 16 tooth pinion. Granted it doesn't make up for the added weight but I'm pretty sure it will be enough to avoid overstressing from taller gearing. This battery pack project is strictly a cost savings solution. There is no reason whatsoever not to use Lipo if I had the means.
 
UPS brought my 12 GP1100 cells today, yipee!

To bad my P.O.S. Integy CVD broke :thumbdown
 
ok, here is the issue. Integy is a freakin PITA. The way they set up their line of aftermarket parts is totally geared for extra sales. Basically, if you use their Ball diff then you have to use their CVD's (the outdrives are too wide to use stock length dogbones, they cause the dogbones to bind inside the outdrives). Oh and don't think of using the hubs that came with your Evo-X conversion kit... the don't work. If you want aluminum you have to get the other set of hubs they make (or use stockers). What a freakin crock. Anyways, for the time being I'm gonna reinstall the stock gear differential, stock dogbones, and stock rear axles. I'm sure It won't take long to rip up that diff but we'll see what happens, it'll be interesting to see how long it lasts, he he he. In the future I'll order the Losi ball diff and a more dependable set of axles, probably those titanium universal shafts I've seen on ebay.
 
ok, not that anybody really cares but here is my first battery pack.. not too bad I think for my first one.

10-18-05_0124.jpg


here it is installed. I could have attached the upper cells inward more but it's ok. It pushes the sides of the body out a bit but it doens't cause a tire rub so I could care less. Add a female Deans and it's done. One more pack to go!

10-18-05_0125.jpg
 
ESC Questions

couple questions.... what do I set the voltage cuttoff at? Still at 4v? Also, I'm gonna be keeping an eye on the temperature of the ESC. What temperature do I need to stay under to stay reasonably safe?

I've had problems fitting both packs once I shrink wrapped them. They fit like a glove when they are not wrapped but I sure don't want to run it only relying on the connection tabs and hot glue. So I've decided to wrap both pack together with electrical tape. at least its blue

10-19-05_1123.jpg


unfortunately, this defeats the purpose of making two seperate packs since they will both always need to be mounted even if I'm only using one.
 
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