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Using 3S lipo on a brushed motor buggy

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Old 03-05-2014, 10:29 PM
  #1
romandesign
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Question Using 3S lipo on a brushed motor buggy

I have a few planes and lipo batteries. I want to get some low-priced hobby grade RC buggy or truck to have fun with my daughter. I found a good one for the price: Mad Gear Racing Desert Wolf Baja 1/10 2WD RTR RC Buggy - sells for $100 on Amazon. It has a brushed 540 motor and runs on 7.2V 1800mAh NI-MH battery. ESC is definitely lipo-capable (has a jumper switch), and according to one review it also can handle 3S lipos.

I have 4 2600 3S lipo batteries. I'd like to use them instead of buying a whole bunch of new ones (don't have budget for this now). Apparently electronics can handle it, but I'm not sure the motor can.
  • Is there a cheap and safe way of reducing lipo battery voltage or somehow taking some voltage off the motor?
  • Can this motor handle 11.1V if I don't run full throttle for a long time?
  • If I burn the motor, what is a cheap brushed upgrade that CAN handle 11.1V?
  • What would be a cheap upgrade to a brushless motor + ESC that would be suitable for those batteries on this car?

Any advice appeciated. Thanks.
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Old 03-06-2014, 05:06 AM
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I don't think there is any brushed systems that can handle 3S. Even if this one could, you'd stripping and replacing gears and diffs extremely often in the truck. See if you could just use the NiMH pack until you have money to buy a 2S LiPO or another couple of stick packs;
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Old 03-06-2014, 05:26 AM
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All you need to do is use an in-line resistor to drop the voltage going to the motor. However, it will get hot. Another option is to adjust the throttle EPA down to 50% or so, effectively limiting the current going to motor. This second option assumes the esc can support 12 volts
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Old 03-06-2014, 07:29 AM
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What kind of a resistor would be able to handle the load without self-destructing in the process? Also, what would be a resistance value needed? I guess I could strap it to a small CPU heatsink or something like that to dissipate heat. I only need to know what resistor would I use for that...

I only have one reviewer as a source for that info, but he specifically said "The esc is well protected (but not very accessible) and capable of running 2s or 3s lipos which is great!", and the specs do say that it is lipo-ready (there are some jumpers for that).
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Old 03-06-2014, 12:31 PM
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Seriously the cost of the resistor you would need, and size it would be cheaper to buy a cheap 2S battery lol
I have one that sinks 2-3 amps for my fishtank lighting, and that sucker needs a CPU heatsink, and fan to dissipate the heat now imagine one that would be 10-15X larger (assuming the RC would only pull 20 amps which is not very likely) Hell I think I paid somewhere around $4-$7 for the resistor lol
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Old 03-06-2014, 01:00 PM
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that cheap of a RC will come with a ESC and motor that will not handle 3s.
in fact, even a 2s could overheat the ESC and shorten the life of the motor.

if they die, you can get a traxxas xl5 and a decent motor for around $50.

if you wanted to upgrade the ESC and motor to brushless, youll spend around $100....plus youd have to upgrade the buggy itself to handle the power.

I know the perfect buggy for your girl, the thunder tiger phoenix XB. you can get one on tower hobbies for $200 shipped. it is brushless, lipo ready, tough and handles decent. the radio has a duel rate for the throttle....this means you can adjust the top speed right from the radio.
this buggy is a re-branded team associated B3, which is a older buggy but is known as a decent racer and for being durable (as durable as buggies get anyway)
tbone racing makes a nice front bumper for the TT phoenix that ups the durability a fair bit.

this buggy ive owned and have run 3s. but honestly you will want to buy a $35 2s pack from hobbypartz.com, as a 3s is simply too fast for young kids.

I usually ran 2s, and when my girl wanted to drive I would just turn the throttle duel rate knob on the radio down and hand it to her, knowing it would be slow enough for her to safely drive. it is a good buggy for the money, you wont find a brand name, brushless buggy for less.
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Old 03-06-2014, 01:14 PM
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I read about using "power diodes" to lower voltage. I'm thinking about a voltage suppressor diode (similar to P6KE20A), but not sure which one. I read diodes reduce 0.7V each, so I would need four in series, but I'm not sure which ones to use and how exactly. I'd love to hear some advice...
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Old 03-06-2014, 01:18 PM
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diodes and such is overcomplicating it my friend.

I get you want to be able to use the lipos you have, but buying an extra nimh or a decent 2s pack will run you $30-$35. You don't want a bunch of complicated wires and Gerry-rigging on a rc for your kid.

and 3s is just way more power than a kid needs. a brushed buggy like the one you linked plus a 7.2v 5000mah nimh wont cost more than $150. A TT phoenix xb plus a decent 2s lipo will run you $250.
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Old 03-06-2014, 01:59 PM
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The included battery (1800 NiMh) only lasts for 10 minutes. Buying another 3 decent batteries will be more expensive than I like. Diodes would only cost a few dollars (if that can work which I'm not sure yet) and I'll be able to use 4 powerful lipos... I'd like to explore that option if possible...
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Old 03-06-2014, 02:06 PM
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http://www.ebay.com/itm/200A-POSITIV...-/280961661775 here ya go buy 3...
Remember most brushed ESC's are rate 300Amps so that might not cut it even. Personally I wouldn't trust it either, but hey you want to save a few bucks, and those diodes are so much cheaper then the alternative of buying a few cheap 2S packs for $20ish a pop, and not risking blowing the ESC out...

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Old 03-06-2014, 02:10 PM
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the thunder tiger phoenix plus a pair of 2s 5000mah lipo packs will get you almost an hour of runtime. 2 such packs will run $70.

if you burn up the stock esc, youll have to spend $30 for a used losi or traxxas esc, or around $60 for a new one.

what is your budget?
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Old 03-06-2014, 02:20 PM
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Quote:
Originally Posted by nitrosportsandrunner View Post
the thunder tiger phoenix plus a pair of 2s 5000mah lipo packs will get you almost an hour of runtime. 2 such packs will run $70.

if you burn up the stock esc, youll have to spend $30 for a used losi or traxxas esc, or around $60 for a new one.

what is your budget?
wouldn't these fit the TT? http://hobbyking.com/hobbyking/store...dProduct=14976 if so the packs wouldn't even set him back $50 vs the alternative of trashing an ESC, and then having to buy the packs on top of it(along with the junk he is attempting which won't work right)
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Old 03-06-2014, 03:23 PM
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they will fit, tho youd have to use Velcro or something as the stock battery bar would sit right over the balance plug's wire.
granted, the TT phoenix is twice the cost of that other buggy, but it is twice the buggy and it can run lipos, has duel rates for the throttle and will get much better runtimes and last longer. I put my phoenix threw bashing much harder than any young girl will.
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Old 03-07-2014, 04:47 AM
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You guys really don't get it he don't want to spend any money.

'
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Old 03-07-2014, 05:29 AM
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Sorry to say... IMO there is currently no diode in existence that's going to do the required task.
generally a diode only limits the the direction that the current flows.
Yes there is voltage suppression diodes but they are not designed to drop the voltage, they are designed to protect against over voltage.
they can only do this for a short period of time before they reset or fry

all we can do if offer advice, it's up to the OP if he listens

if he is dead set on running 3s lipo's... The only way to do it is significantly reduce the gearing. But the costs of a GRU unit would out way the cost of a 2s lipo.....

Next option would be to convert it to brushless.... But it's going to be "stupid fast" on 3s. Not something I would recommend for a child
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Old 03-07-2014, 06:59 AM
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Thanks for all the advice. It seems that the only option is a DC-DC voltage regulator, which for the ~20A current would cost about the same as a set of 3-4 new 2S lipos. So buying new lipos looks like the most logical way to go. I was hoping that there is a simple solution for reducing the voltage, but it's more complicated than I thought.
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Old 03-07-2014, 07:18 AM
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Or... Get a 540 or 550 motor that's rated for 12v... Or 14v....

http://www.trossenrobotics.com/store...Motor-12V.aspx

http://www.robotshop.com/en/banebots...-19300rpm.html


ottle bit of "out of the box thinking"
for the price it's worth trying at least

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Old 03-07-2014, 08:17 AM
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I've ran a 3s lipo on a 380 size motor in a Losi Mini-T. It did not self destruct, but it lit up when full throttle was applied.
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Old 03-07-2014, 08:38 AM
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New motor is an interesting option. Thanks.
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Old 03-07-2014, 09:27 AM
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Quote:
Originally Posted by ughturtle View Post
You guys really don't get it he don't want to spend any money.

'
Its the complete opposite we get it, just saying what he wants is not really feasible, and will cost more in the long run. Trust me I'm one of the people that go the cheapest route possible on most things, just in this case the only viable options would be getting something like an ESC out of something like a summit(not sure even then that would work on 3S) which costs around $100, a cheap Brushless setup for $70ish, or cheaper $24 2S batteries like I linked.

Hell on one of my mini RC's I even went the voltage regulator route with a 5A regulator to make a 2S work just to watch the voltage regulator explode(figured as it ran on 4 AAA's 5A should have done it fine) so its not like I don't get where he is coming from sure it worked fine at 1st, but once I hit full throttle Poof let out the magic smoke.
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Old 03-07-2014, 06:00 PM
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Quote:
Originally Posted by cumminspower5.9 View Post
I've ran a 3s lipo on a 380 size motor in a Losi Mini-T. It did not self destruct, but it lit up when full throttle was applied.
My bet is the brushes dident last long especially if it was arching that bad...

my first lipo powered vehicle was a HBX Bonzer with a brushed 13DT modified motor... On 11.1v it was mental.... Only problem the brushes would only last one battery pack.... 3 sets of brushes later I went to brushless.

generally 3s is ok on a low KV brushed motor... Say my 80t motors in my clod are fine.
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Old 03-07-2014, 06:12 PM
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I get he doesn't want to spend a lot, I certainly know what it feels like to enjoy this hobby and have a tight budget!

but trying to make a $100 brushed RTR run on 3s lipo will cost MORE money than just buying a $200 brushless RTR. Even if he found a cheap brushed ESC that would handle 3s....the stock motor wouldn't, and likely the driveline would have issues with the brushed motor on 11.1v.

only brushed motor that will handle are high turn, crawler type motors....and that's because the high voltage still doesn't result in very high RPMs. even so, 3s will wear out the brushes faster than they would on 7 or 8v.

id love to offer a sub $200 RTR brushless, but to my knowledge they don't exist (at least not in 1/10 scale)
you can sometimes find a used brushless, like a redcat epx pro for $100.....but that can offer its own list of headaches depending on how the previous owner treated it.
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Old 03-07-2014, 09:42 PM
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All sub $200 including postage

http://www.ebay.com.au/itm/New-SRC-R...fd333ae&_uhb=1

http://www.ebay.com.au/itm/1-10-4WD-...f311e62&_uhb=1

http://www.ebay.com.au/itm/1-10-SCAL...55e6b14&_uhb=1

http://www.ebay.com.au/itm/2-4GHZ-1-...2925f4b&_uhb=1

http://www.ebay.com.au/itm/1-10-SCAL...5a99b03&_uhb=1

http://www.ebay.com.au/itm/1-10-BRUS...2924ae0&_uhb=1

I haven't really look through them, I just thought I would quickly share what I found
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Old 03-08-2014, 05:11 AM
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I think all that HSP, redcat exceed stuff here will cost $200-$230 shipped. and while I like the 4wd epx pro truck and buggy, the $200 TT phoenix is a better buy. it may not include a battery, but has a much nicer radio, better aftermarket support (since it is really a B3) and youll have a better chance finding spare parts at hobby shops for it than the ones you linked.

again, I personally like those models but they are not always the best quality.
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Old 03-09-2014, 12:54 AM
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^talk about spam in a can..... 8 messages of random statements. IP Check...
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