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05-05-2009, 07:28 AM | #1 |
Newbie Join Date: Jun 2008 Location: Sliema
Posts: 44
| LiPo - Electronics setup
Dear all, i just ordered 2 x Novak Goat Kits with the 18.5 turn motor up front and for the rear a 21 turn. Now i need 2 Li Po battery but prices are so different. I found the following and would like to know if they are good for crawling due to their Burst Rate : 15C here is the item http://cgi.ebay.com/2x-7-4v-4000mAh-...3A1%7C294%3A50 Thanks |
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05-05-2009, 08:34 AM | #2 |
Rock Crawler Join Date: Mar 2009 Location: Victoria BC
Posts: 988
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15c seems to low to me, from what i have been reading for crawlers you want a minimum of 20c with 30c burts , check out maxamps.com they have a big selection and you should find exactly what you need
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05-05-2009, 08:43 AM | #3 |
owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down!
Posts: 20,290
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For crawling that 4000 pack will be fine at 15c discharge.
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05-05-2009, 08:51 AM | #4 |
RCC Addict Join Date: Jan 2008 Location: Mount Juliet
Posts: 1,287
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John knows his stuff... but I am just curious where you are going to mount a pack of that size??? It is huge. If it was me in a comp rig, I would be using this pack: http://www.hobbycity.com/hobbycity/s...0C_Lipoly_Pack I run the 3 cell version of this pack in my Bully and it provides plenty of juice...never even gets warm (Dual 45T handwounds). It would be nice if the Goat could use a 3 cell, but alas...No. A pair of these would cost $50 after shipping. |
05-05-2009, 08:53 AM | #5 | |
Newbie Join Date: Mar 2009 Location: Wilmington
Posts: 15
| Quote:
Novak rates the 18.5T motor at 119 watts while the 21.5T is rated at 85 watts. Those two motors combined will put out 119 + 85 = 204 watts and can theoretically demand that much power from the battery and ESC. Even with the two batteries wired in serial, which would give you 8000mAh of capacity, they would only allow 8 x 15C = 120 watts of power output, which is just barely enough for the 18.5T motor, let along the two motors combined. Having written all that, it is still possible to use these batteries with the two motors you propose. The motors will likely not reach their peak performance, but they'll work...the batteries might get a little warm, just keep an eye on them. I run dual Novak Goat ESCs on one of my supers, which demands a theoretical max of 119 + 119 = 238 watts from my Lipo while my battery is only rated at 4.5 x 25C = 112.5 watts; that combo has been running well without any problems, knock on wood. On my other super I run dual Novak Rooster with 55T motors with 3S 1500mAh 25C batteries which allow a max output of 1.5 x 25C = 37.5 watts and that system runs just fine as well, knock on wood. | |
05-05-2009, 10:20 AM | #6 |
owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down!
Posts: 20,290
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It would be 60 amps, not 60 watts.
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05-05-2009, 10:36 AM | #7 | |
RCC Addict Join Date: Jan 2008 Location: Mount Juliet
Posts: 1,287
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Assuming the formula of (AMPS = WATTS / VOLTS) and that the volts are constant at 7.4volts (2 cell lipo), then: The GOAT 18.5 would be AMPS = 119 watts / 7.4volts or Amps = 16.1 The GOAT 21.5 would be AMPS = 85 watts / 7.4volts or Amps = 12.1 Running one of each of these would pull a total of 28.2 amps. So if he was to purchase the 4000mah 15C batteies that could produce 60amps....the would have plenty of capacity. But that battery is HUGE. Using the Zippy battery from my previous post, that battery can produce approx 43.5 amps (1.45 x 30c) continuous and burst at about 58amps (1.45 x 40c). This could easily support 2 Goat systems. The smaller size of this type of pack allows for flexible placement...that huge eBay pack would be a bear to place low....if even possible. | |
05-05-2009, 10:55 AM | #8 |
Rock Crawler Join Date: Dec 2008 Location: With the ATL Crawlers
Posts: 707
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I figuring what battery I should run for my ax10. This is very helpfull info. Thanks |
05-05-2009, 01:01 PM | #9 | |
Newbie Join Date: Mar 2009 Location: Wilmington
Posts: 15
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05-06-2009, 06:48 AM | #10 | |
Newbie Join Date: Jun 2008 Location: Sliema
Posts: 44
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05-06-2009, 07:05 AM | #11 |
RCC Addict Join Date: Jan 2008 Location: Mount Juliet
Posts: 1,287
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Only ONE battery is needed. I run my one battery on my rear axle on a homemade tray....then built an adapter to split to each ESC. I only stated the 2 quantity because you were pointing to an ebay ad for 2 batteries.
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05-06-2009, 09:11 AM | #12 |
Newbie Join Date: Jun 2008 Location: Sliema
Posts: 44
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But splitting a 7.4 batt between 2 ESC wouldn't that split the voltage aswell?
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05-06-2009, 09:19 AM | #13 |
RCC Addict Join Date: Jan 2008 Location: Mount Juliet
Posts: 1,287
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Nope. This is how I have been running my rig for the past bunch of months. No loss of power. No shortage of power. Think of it like this...in your 1:1 vehicle if you were to connect 2 devices to the cigarette lighter/accessory plug would either of those devices get 1/2 of the 12 volts supplied? Or do they get all of the 12 volts? They get all of the 12 volts....they just drain the battery faster than if only one device was in use. BOTH devices get the full 12 volts. IF the battery could not supply enough AMPS to feed the devices, then there would be problems. See the AMPS calculations above. The battery choices described have enough to supply the AMPS required.
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05-06-2009, 09:38 AM | #14 |
Newbie Join Date: Jun 2008 Location: Sliema
Posts: 44
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I see, i thought of going for the following ProTek R/C Li-Poly Receiver Battery Pack (7.4V/2000mAh) http://www.amainhobbies.com/product_...ducts_id/13508 Is its spec any good and if i stop crawling i can always use them on my truggy / buggy lipo setup What about installing two batteries, is there some sort of issue with that? or its just weight and space? Thanks everyone |
05-06-2009, 09:39 AM | #15 |
I wanna be Dave Join Date: Dec 2005 Location: Tax Nation
Posts: 2,289
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as long as you connect them in PARALLEL not in SERIES you will be fine. All the red wires go to positive All the BLACK wires go to neg Edit: the receiver pack you are looking at might not be the best idea. The wires running to the connector are not heavy enough to handle the amp draw and thus may melt/short/catch on fire. Last edited by jetboat; 05-06-2009 at 09:50 AM. |
05-06-2009, 10:13 AM | #16 | |
Quarry Creeper Join Date: Oct 2008 Location: In the basement...
Posts: 473
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This has a VERY low discharge rating ans WILL NOT support your usage - check out holmeshobbies.com for the correct batteries. Quote:
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05-06-2009, 10:51 AM | #17 | |
Rock Stacker Join Date: Sep 2007 Location: east mich
Posts: 49
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05-06-2009, 11:38 AM | #18 |
owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down!
Posts: 20,290
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Those elite 2200s are killer cells, I have some myself. Great price for the product too. Obviously a good enough deal for me to buy.
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05-06-2009, 01:39 PM | #19 |
Quarry Creeper Join Date: Dec 2008 Location: other side of the track,the bad side
Posts: 241
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ckrc has 3s 1500 mah with a 25c/35c rating for $40 I belive. A friend of mine just ordered 2 for hs berg
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05-06-2009, 03:23 PM | #20 |
Newbie Join Date: Jun 2008 Location: Sliema
Posts: 44
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Can anyone kindly explain to me whats the diference between 2s & 3s is it cell count and if i remeber reading correctly you can't run a 3 cell on a goat esc right?
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