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Old 10-13-2009, 07:57 PM   #1
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Default help me pick a battery for rc8e

I am just about to finish my assoc rc8 buggy. And I could use some help with picking a battery. is it better to use 1 or 2 would would 2 2cell 5000ma be 14.8v 10000 ma or 5000ma and what is the best bang for the buck ? this is my first ele. car I could use any help I can get.
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Old 10-13-2009, 08:03 PM   #2
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2 2cell is the same as one 4cell if you look at it this way.

A single pack is 2S1P - 2 cells in series built 1 parallel.
That is 7.4v for the pack.
To run 1/8 scale, you "usually" run something like 4S1P. So you would wire 2 2S1P packs in series to make one 4S1P "pack". This pack is 2x7.4 or 14.8v but it is the same mAh as the original cells.

2S1P (in series) 2S1P = 4S1P of the same capacity. If both are 5000mAh (and should be the same size) - then the wired in series "pack is 5000mAh".
If you wire them in parallel you have 2S2P at 7.4v of 10,000mAh

You need to consider motor choice before you determine which battery is best. In your conversion - what motor will you be running and what kind of track - and what kind of runtime do you need to have with the buggy?
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Old 10-13-2009, 08:32 PM   #3
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I run 2-2s hard packs wires together, I chose the 2s hard packs b/c I can run them in another car when needed.

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Old 10-13-2009, 09:28 PM   #4
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I chose the mmm 2200 I need 15 min of run time.
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Old 10-13-2009, 09:40 PM   #5
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the track is fairly short with lots of turns and some big jumps right after them a hard pack most of the time
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Old 10-13-2009, 10:17 PM   #6
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Look at hobby city. You can pick up 2 5000mah 30c packs for $80 - $100 dollars shipped. Same for a 4s pack.
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Old 10-13-2009, 11:50 PM   #7
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Does it have to be 4s?
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Old 10-14-2009, 12:51 AM   #8
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If your using a 2200kv motor, by looking at the Lipo Power to Motor kv, your sweet spot would be a 4s pack.

This would give you an RPM of around 32,000 approx. Similar to a nitro engine.

I run the CC MM ESC & 2200kv motor in my Losi 8ight 1/8th.
I race this and can make a 15min final on my setup.

The battery you would be looking for is:

4s 14.8v Battery
5000mAh
and i wouldn't go no less that 30c

For your track, i would recommend a gearing of 45/12 :-)
The gearing is just as important as the battery, you need to keep heat down. Less heat, more efficient, more run time.

No you can choose to run x1 Single 4s pack or x2 2s packs in series.

Hope this helps.

Ben
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Old 10-14-2009, 03:44 AM   #9
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Quote:
Originally Posted by cozmo View Post
I am just about to finish my assoc rc8 buggy. And I could use some help with picking a battery. is it better to use 1 or 2 would would 2 2cell 5000ma be 14.8v 10000 ma or 5000ma and what is the best bang for the buck ? this is my first ele. car I could use any help I can get.
After choosing your battery, make sure you have a good charger that has the appropriate balancer leads for the brand LiPo you plan to run.
Sounds like a fun project.
--Glenn
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Old 10-14-2009, 04:59 AM   #10
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Ben's got good suggestions (above).

So, you asked is it best 1 or 2 packs. If you don't use any other cars that need 2S1P packs, then consider a 4S1P pack at 5000mAh capacity. That way, you have less wires to mess with, only need one charger and one 4S1P weights less (fewer wires and cases) than two separate packs. Lightness counts (adds a little to your runtime).

On a small track, you accelerate more but you are not on full-throttle much - so you should get 15 minutes runtime with 4S1P 5000mAh. Nice thing is, that is almost a "standard" size and you can pick from dozens of vendors who offer that type of battery.
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Old 10-14-2009, 06:17 AM   #11
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SMC's new 50c 5200mah 4s fits perfect in the ae tray
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Old 10-14-2009, 09:26 AM   #12
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Quote:
Originally Posted by CBHVR6 View Post
SMC's new 50c 5200mah 4s fits perfect in the ae tray
Do you have a link to that pack?
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Old 10-14-2009, 09:33 AM   #13
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Do you have a link to that pack?
They are brand new and my normal site doesn't have them on yet. Here is a link to the older 40c version

http://spcracing.com/index.php?productID=85

If you want the 50c 4s, call brian at SMC and he can get it to you fast!
540-298-7706

i know that he has them in stock along with 2s 50c if you would want to run dual 2s packs
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Old 10-14-2009, 05:40 PM   #14
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thank you all people around here are kind of tight lipped I say come one come all, it's good for the sport...
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