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Old 11-04-2007, 07:59 AM   #1
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Default High amp draw and lipos

I thought i'd start a new thread about using lipos in a high amp draw situation. I race dirt oval on a high bite track running a Mamba max 7700 and a Schulze u-force with a 6 turn hacker. Recently I have had a couple issues with a few lipos. The first was a cheap e-bay pack rated at 20c 4000 milli pack. I ran 3 minutes and it started slowing down. I stopped running it right away and it was hot and way out of balance. Then i told a friend i was not going to run it anymore and he loaned me a orion hardcased 3200 to try.It did the same thing. So does anyone have any idea what's going on? Am i just drawing to many amps or what. If so should i go with more milliamp battery to be able to draw more amps or what? When this happens to a lipo is it damaged? Any input is appreciated. Thanks
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Old 11-05-2007, 10:16 AM   #2
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I suggest you go to this link. Very much information about batteries in general. http://www.batteryuniversity.com/
Hope you figure it out.

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Old 11-05-2007, 10:19 AM   #3
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try running 2 packs in parallel, as it will halve the current draw to each pack. it may increase in weight, but with lipo this is no problem.
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Old 11-05-2007, 10:21 AM   #4
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on an Orion 3200 with a 20c discharge you can pull 64 amps continuously, I would say you need a bigger battery or stronger discharge rating 25c or 30c. If you use an Orion 4800 with a 20c discharge you would be able to pull 96 amps continuously.

Keep in mind that you normally want to set up to use about 80% of your continuous discharge rate.

At least thats the way I set up my electric boats
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Old 11-05-2007, 04:37 PM   #5
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My touring car is drawing about 45 amps average for 5 minutes. I had to increase the size of the pack from 4000 to 4900 mA-h in order to accomplish this. Although a pack is rated 20 C this is not very helpful as the pack may dangerously overheat if discharged at that rate. Another limit is 140 F. Much over that and the pack will start to swell. I am using an FMA pack the Revolution cell. It runs cool, but is slightly oversize for car use. It fits in a TC5 with a new battery strap. 6000 mA-h 2s1p Lipos are available from Max Amps.

Motor type-Some motors draw more current for their output than others. In my test a coreless motor (you look inside and there is what looks like a big wad of semi organized wire, no steel) is less efficient than a cored motor like the LRP or Novak which have wire wound around a steel core. This coreless type of motor will overheat the batteries and cause you to dump quicker.
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Old 11-05-2007, 04:46 PM   #6
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Im having the same issues, only closer to the end of the pack. mamba max esc, vortex 7.5.

Getting a bigger lipo will solve this problem for sure. Max-amp 5000 or higher, New orion 3600 with 25C rating. Im about to get a premium power 4700mah, ill let you know how this handles high amp draws!!
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Old 11-05-2007, 04:57 PM   #7
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<Shameless plug for the CORE 5000mah pack here>

It's discharge capability exceeds the capability of that ESC and motor, so you'll have no worries with the pack anymore. I thermalled a Max system in one of our 8th scale onroad cars, and the CORE pack was 10deg above ambient temp.

CORE lipo (and general lipo) FAQ/info here:
http://www.secureonlineshopping.biz/...&pagewidth=550

<end shameless plug>
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Old 11-05-2007, 05:16 PM   #8
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Thats a good read, but when are they coming back in stock, need 2 of them
-
nevermind, I see they are listed twice, is there a difference between the two?
CR004 CORE RC - 5000mAHr 7.4v LiPo In Stock $139.99
G752 Core RC 5000mah 7.4 LiPo - core Out of Stock $139.99

Quote:
Originally Posted by Shawn Palmer View Post
<Shameless plug for the CORE 5000mah pack here>

It's discharge capability exceeds the capability of that ESC and motor, so you'll have no worries with the pack anymore. I thermalled a Max system in one of our 8th scale onroad cars, and the CORE pack was 10deg above ambient temp.

CORE lipo (and general lipo) FAQ/info here:
http://www.secureonlineshopping.biz/...&pagewidth=550

<end shameless plug>
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Old 11-05-2007, 05:17 PM   #9
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They came in last week - we're all good anytime you want to order

http://www.racing-cars.com/usa/produ...ecnumber=47902
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Old 11-05-2007, 05:43 PM   #10
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I have run a novak 3.5 on the orion 3200's on lots of different occasions. No problems. The most I had to put back in the battery was 2100 mah, and that was for any type of racing I was doing

cant imagine what the problem is. you over geared real bad? I know about 9 out 10 people I see w/ the MM7700 are way over geared. Just a thought
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Old 11-05-2007, 06:29 PM   #11
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the core says to charge at 1c, Since I have not run lipo yet, how long does it take to charge at 1c?
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Old 11-05-2007, 07:21 PM   #12
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Charge time from totally empty at 1C is around one hour depending on the charger.

I charge after each race, and charge times back to full can be as little as 20 mins.

The G752 is an early part# and not valid (not sure why it's still on the site). Use the CR004 part #.
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