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08-30-2007, 06:01 PM
| #1 |
| RCC Addict Join Date: Apr 2005 Location: Eden Prairie, MN
Posts: 1,225
|  7.4v LiPo vs. 8.4v 7-cell NiHM Here's my dilemma... I have this new tuber that I want to get a new battery for. I just recently got a Novak Rooster Crawler and the battery limits are 4-7 cells nicad/nihm or 7.4v lipo. I have virtually always run 7-cell nihms in my TLT's. The tuber is a bit top heavy, so I'd like to reduce the weight. I could switch to a 7.4v lipo, and that would cut the battery weight by almost half, but i would loose a volt in power (1v). I've run 7-cells in the past because I like to have some wheel speed, and still keep the gearing pretty low for the torque aspect. I know I could run the lipo and bump up a tooth or three on the pinion or spur to regain my wheel speed, but I don't necessarily want to loose much of the 'torqueiness'. Or do I keep the gearing and sacrafice the wheel speed for a lighter battery...?... I'd like to keep the battery in the same position as it currently is, too. I want the buggy to look 'clean'. As of right now, I'm leaning towards getting a LiPo. Have any others had to make a similar decision? What way would you lean? Thanks in advance for any help in making up my mind...   Some specs of the truck: B3 tranny Novak Rooster Crawler - to be installed (currently running a Futaba 230cr) Integy 55t (soon to update to a Hard Line 'Dominator") Hitec 645MG servo I've been running a 7-cell 1400mah 2/3 pack... old, now ~1000mah Pics of the battery position in the tuber: |
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08-30-2007, 06:46 PM
| #2 |
| I wanna be Dave   Join Date: Oct 2005 Location: Columbia TN
Posts: 6,172
| Just jump up to a 35t. |
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08-30-2007, 08:13 PM
| #3 | |
| RCC Addict Join Date: Apr 2005 Location: Eden Prairie, MN
Posts: 1,225
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08-30-2007, 09:02 PM
| #4 |
| Web Wheeling  Join Date: Jan 2005 Location: Twin Cities
Posts: 2,837
| Why not go brushless? You can gear up for more wheel speed, and increase your low end power at the same time. And you can run more voltage all at the same time. |
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08-30-2007, 09:08 PM
| #5 | |
| Quarry Creeper Join Date: May 2005 Location: Wisconsin
Posts: 268
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08-30-2007, 10:38 PM
| #6 |
| I wanna be Dave   Join Date: Dec 2005 Location: Hawthorne, Florida
Posts: 2,568
| You could lose a lot of weight up on the chassis by going to the lipo. Could probably get at least a 2100 pack in there. I run a MM, 55 turn, 3s lipo. Great low speed, great wheel speed. |
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08-31-2007, 12:18 AM
| #7 |
| Quarry Creeper  Join Date: Jun 2007 Location: MESA
Posts: 455
| I Ran Into This Same Decision Recently On My Tuber. I Went With The Lipo 7.4 2100 And A 45t Motor. It Was Still A Little Bit Lacking On The Wheel Spin. I Jumped Up 2 Teeth And It Seems To Be A Nice Compromise. I Ran It Yesterday For Over An Hour And My Lipo Was Still At 7.6. I Also Saved Weight By Not Using A Rx Pack And Just Using A 6 Volt Regulator To Power My Servo From The Lipo. |
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08-31-2007, 06:54 AM
| #8 |
| Quarry Creeper Join Date: Nov 2004 Location: Mid TN
Posts: 411
| I would go LiPo. In reality, a fully charged LiPo cell is at 4.2 volts, so a two cell is really 8.4 volts peaked. I realize that's still not as much as a 7cell limh pack peaked, but it's not bad. Plus, as you drop weight, you'll be able to get more out of your electronics, so you can probly gear up a little to keep wheel speed. Then, as has been mentioned, you could just go brushless... |
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08-31-2007, 09:44 AM
| #9 |
| owner, Holmes Hobbies LLC   Join Date: Nov 2004 Location: Volt up! Gear down!
Posts: 14,854
| I would agree here. Your goal is to save weight on the chassis. A 2 cell or 3 cell lipo will still be lighter. Even if you go with a 2 cell you can either gear up or get a faster wound motor. Any any rate, you will increase your sidehilling with a lighter pack. |
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08-31-2007, 09:50 AM
| #10 |
| RCC Addict Join Date: Aug 2005 Location: Akron
Posts: 1,764
| I ran a 2S lipo and 35t in my WK. It had a ton of wheelspeed and the low end was decent. They do peak out at 8.4v. I ended up going to a 65t motor with the 2S and like it a lot. |
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08-31-2007, 11:58 AM
| #11 | |
| Rock Stacker Join Date: Aug 2007 Location: South Central Mississippi
Posts: 93
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08-31-2007, 06:06 PM
| #12 |
| Quarry Creeper Join Date: Jun 2007 Location: MESA
Posts: 455
| It Is A Thunderpower 7.4 2s 2100mah. Last Night I Tried The 65t And Didn't Like It...way Too Slow. I Put The 45 Back In And Again Last Night Was Crawling For Nearly 2 Hours Without Any Loss Of Power. I Wasn't Sure I Would Like The Regulator Instead Of A Rx Pack But The Space & Weight I Saved Are Worth The Trade Off. |
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