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would it be ok to use a 7-cell nimh with the stock ae-2 esc?

Discussion in 'Newbie Q & A' started by Spence123, Feb 19, 2015.

  1. Spence123

    Spence123 Studio Forums Elite
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    Hi all, since my lipo packs are so old, I got better run time with some nimh's, and i only have two 7-cell traxxas nimh's. Will they work? And not possibly damage my esc? I mean the esc says on it: 2s lipo or 6cell nimh


    Thanks,
    Spence
     
  2. Spence123

    Spence123 Studio Forums Elite
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  3. Antho11

    Antho11 Studio Forums Elite
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  4. Spence123

    Spence123 Studio Forums Elite
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    Guys, I looked at the thread, and I was just wondering without a separate bec if I can run a 7cell nimh pack. I mean also, packs are underrated in voltage. For example, a 3s lipo pack is labeled as being 11.1v, when it is really 12.60v when fully charged. The 7cell nimh packs are labled as 8.4v, and are really closer to 11v when fully charged(checked with volt meter. So would this be fine, or should I just buy a 6/cell nimh pack, or get another 2s lipo(as my current ones are shot with over 400 cycles on them) and an lvc alarm?
     
  5. 68camaro

    68camaro Studio Forums Elite
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    I ran a 7 cell in mine for a while like 4 years ago before I had lipo's , no issues at all
     
  6. Spence123

    Spence123 Studio Forums Elite
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    I mean even after a full nimh pack(I ran it just to see what would happen) the esc wasn't even warm to the touch, so its for sure hardly even under any load. Just asking if it will hurt my bec or blow up my esc because the nimh 7-cell packs are closer to 11v when fully charged compared to the advertised 8.4v
     
  7. Ragnar

    Ragnar Studio Forums Elite
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    if u want longer run time u can put two 6 cells in parrell. that wld double run time. if its an option. 2 batteries plus to plus and minus to minus
     
  8. Spence123

    Spence123 Studio Forums Elite
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    Still just asking, can I run a 7-cell nimh without blowing up my esc or bec? And also the stupid thing is the cheaper ae-5 esc can run on 3s out of the box, plus its waterproof!
     
    #8 Spence123, Feb 19, 2015
    Last edited: Feb 19, 2015
  9. Ragnar

    Ragnar Studio Forums Elite
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    that will depend on the esc. if u want send me any info or pics of it and ill chk it out for u. my 1st thght is yes itll handle it, but dont hold me to it. i hv an old mechanical speed controler and run 11.4 thru it. gets hot but keeps going.
     
  10. Ragnar

    Ragnar Studio Forums Elite
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    my old msc is supose to only b 6 cell
     
  11. Spence123

    Spence123 Studio Forums Elite
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    Well axial rates the ae-2 at 2cel lipol/ 6cell nimh or nicad packs, and well, would running it 1 nimh cell over the limit really kill it?
     
  12. drzoo2

    drzoo2 Studio Forums Elite
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    Unfortunately, since the ESC is not spec'd at 3S, there is no good answer to this. I have read that as long as you use an external BEC you will be ok. Your not going to get a definitive answer, yes or no. Your only going to here from people that have used it with or without indecent.

    There are two main parts to be concerned with. The FETs that make up the motor control and the internal BEC circuit itself. Since Axial rated the ESC at 2S, is it because of one or both.

    With the motor control FETS, it comes down to whether the voltage rating is within the supply voltage (battery) and if they are able to handle the extra current without overheating. You have answered the temperature part. The unknown is the voltage rating. If I had the FET part numbers I could look up the spec's and give a better answer. I don't have one to look at.

    The internal BEC is what I feel is the real reason this ESC is rated at 2S. The AE-2 employes a linear voltage regulator rated at 2amps. The way a linear regulator works is by "burning off" the extra voltage in heat. At 2S this is about 7watts. This increases dramatically on 3S, 15.2 watts when trying to feed a 2amp load. In order to maintain the same thermal margin, the output current on the ESC/BECwould have to be deraited to 800mA. Linear BECs are insanely inefficient and where I fell Castle (the actual maker of the AE-2) falls flat.

    So with all that said. Maybe with an external BEC.
     
    #12 drzoo2, Feb 19, 2015
    Last edited: Feb 19, 2015
  13. Spence123

    Spence123 Studio Forums Elite
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    how cheaply can I purchase an external bec? Well, I know that I can find pretty cheap 2s lipos, so I may just stick to that. Could I buy a cheap bec, and then run a 2s lipo? I mean if I wanted to do a 4 wheel steering mod in the future. I may just buy that cheap floureon 3300mah 2s....... It can't be that bad for what I am doing right?
     
  14. drzoo2

    drzoo2 Studio Forums Elite
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    Yes. A BEC can be found for as low as $10. The best external BEC is made by Castle. Maybe they realize their internal BECs suck and felt compelled to put some effort in an external.
     
  15. Spence123

    Spence123 Studio Forums Elite
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  16. drzoo2

    drzoo2 Studio Forums Elite
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    I can't really answer that. I have never used a Floureon LiPo. You will have to go by eBay ratings. It's cheap so give it a shot. Let us know how they are.

    I have only used the Castle BEC but I found this one on eBay...

    http://www.ebay.com/itm/HOBBYWING-R...527?pt=LH_DefaultDomain_0&hash=item51c5a4a087

    I haven't used this BEC but I have use Hobbywing parts and find they are good quality. It's $5 shipped....
     
  17. Spence123

    Spence123 Studio Forums Elite
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    Alright, i will give that pack a shot. I just need to come up with the doe to buy it(cash) I keep spending my money faster than I can earn it lolz
     
  18. drzoo2

    drzoo2 Studio Forums Elite
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    Stick with Hobbywing. Same price and they usually make quality parts. I have a diagram on connecting a BEC. I'll have to find it. It's easy.

    Your just going to remove the red wire from the ESC, place the external BEC plug in the battery channel on your receiver. It will then power the receiver and the Servo. The ESC will power itself.
     
  19. 68camaro

    68camaro Studio Forums Elite
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    dude your fine, ran it for a year with 7 cells. Everything will be fine
     
  20. Spence123

    Spence123 Studio Forums Elite
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    Will it really be fine on 7cell nimh? I want my rc to last as long a possible. I think I may just stick to a 2s lipo. Keep things simple and safe
     

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