Results 1 to 15 of 15
  1. #1
    RC Qualifier
    Join Date
    Feb 2010
    Location
    Twin Cities Metro MN
    Posts
    465

    2s Lipo vs. 7 cell 8.4v NiMH

    Iíve been reading up on Lipoís and considering making the jump. Seems like 3s is a lot for this truck, but what are the advantages/disadvantages to running a 2s, as opposed to a 7 cell 8.4v NiMH? I see the 2s is a lower voltage Ė am I going to see a decrease in performance (speed)?
    Censorship is wrong

  2. #2
    RC Champion
    Join Date
    Sep 2008
    Location
    Edmonton, Alberta, Canada
    Posts
    1,548
    I think Lipo would be a step in the right direction. You will get better runtimes and punch, plus the extra amperage will let you gear slightly higher without putting to much stress on the battery. (almost identical speed)

  3. #3
    RC Qualifier
    Join Date
    Apr 2009
    Posts
    937
    I find my 2s lipo faster then the 7 cells i used to run.. You might think that the voltage is lower, but the Nihm will quickly loose its power where as a lipo is consistant so overall your track times increase.

    Also tis a lot lighter which in turn makes the car easier for the motor to push around and increases your speed

    I wrote a little article about lipos if you want to check it out.. its more of a beginers guide then any sort of in-depth technical writeup..

    http://www.telnets.org/articles/lipo-info.php

    might help you make your decision

  4. #4
    RC Champion
    Join Date
    Jun 2007
    Location
    NOT HERE ANY LONGER
    Posts
    1,852
    The Lipo will provide a consistent amount of voltage over the entire run. A 7 Cell NiMh begins to drop voltage immediately. Some of the better packs level off at a certain point but most of the time the voltage will be below that of even a cheap LiPo.

    Factor in that Lipo's are cheaper and Lighter and it's a no brainer.
    My mother
    Reba Collins 6/30/52 - 3/1/10 1:13pm

  5. #5
    RC Champion
    Join Date
    Nov 2008
    Location
    Halifax County, Nova Scotia. Ca
    Posts
    1,126
    My Low Voltage Cut-off in my VXL shuts my lipos off at about 3.4 Volts per cell, so thats about 6.8 Volts. If I install a Fully charged NiMh 8.4 volt battery and I leave the ESC in Lipo mode, And with the truck off the ground, hit the Throttle full... The LVC will kick in and shut off the truck. I don't run Nimh, but I did this just to show how BAD an 8.4 NiMH will drop voltage. not even 3 seconds and its below 6.8. The 2S 7.4 volt lipo holds the 7.4 almost the entire 20+ minutes
    Always in Trouble for trying to help out.

  6. #6
    RC Turnbuckle Jr.
    Join Date
    Dec 2004
    Posts
    3,630
    If it is a good quality, zapped and matched, EnerG4600, 7-cell pack, it will stomp all over a 2S LiPo pack. And please, I am not talking about a 4600 EnerG Nimh vs a 8000mAh Lipo after 45 minutes into a run. We must be reasonable here; within the runtime capabilities of the 4600 EnerG, 7-cell pack, like what ProMatch sells, it will devastate a 2S LiPo for all out power, especially in the smaller loads we typically see in modest 4WD brushless systems like the Slash 4WD. However, the LiPo will be much lighter in weight and much easier to maintain.

    The talk about Nimh quickly losing power refers to packs of either poor quality or packs with damaged cells or both.
    Last edited by Jakey; 06-10-2010 at 10:34 AM.

  7. #7
    RC Turnbuckle Jr.
    Join Date
    Dec 2004
    Posts
    3,630
    Quote Originally Posted by madkawi650
    My Low Voltage Cut-off in my VXL shuts my lipos off at about 3.4 Volts per cell, so thats about 6.8 Volts. If I install a Fully charged NiMh 8.4 volt battery and I leave the ESC in Lipo mode, And with the truck off the ground, hit the Throttle full... The LVC will kick in and shut off the truck. I don't run Nimh, but I did this just to show how BAD an 8.4 NiMH will drop voltage. not even 3 seconds and its below 6.8. The 2S 7.4 volt lipo holds the 7.4 almost the entire 20+ minutes
    Then your Nimh is of poor quality or has a weak/bad cell. I have tested thousands of matched Nimh packs, some of them at loads of 70-Amps continuous and even at that high load the packs would hold voltage with no problem. I have run good, matched 6-cell, Nimh, EnerG 4600 packs in my VXL Stamepde with the LVC on with no premature cut-off problems at all.

    For the record, LiPo is an overall superior technology for RC use. Light weight and ease of maintenance is a win-win for most of us.
    Last edited by Jakey; 06-10-2010 at 10:23 AM.

  8. #8
    RC Champion
    Join Date
    Sep 2008
    Location
    Edmonton, Alberta, Canada
    Posts
    1,548
    Quote Originally Posted by madkawi650
    My Low Voltage Cut-off in my VXL shuts my lipos off at about 3.4 Volts per cell, so thats about 6.8 Volts. If I install a Fully charged NiMh 8.4 volt battery and I leave the ESC in Lipo mode, And with the truck off the ground, hit the Throttle full... The LVC will kick in and shut off the truck. I don't run Nimh, but I did this just to show how BAD an 8.4 NiMH will drop voltage. not even 3 seconds and its below 6.8. The 2S 7.4 volt lipo holds the 7.4 almost the entire 20+ minutes
    This is because you are tricking the ESC into thinking it's a 3s Lipo. The speed control will detect the voltage of the battery when in Lipo mode, and decide whether it is a 2s or 3s. A peaked 2s should be exactly 8.4v. A peaked 7c Nimh will be over that, which the ESC will interpret as a dead 3s.

  9. #9
    RC Turnbuckle Jr.
    Join Date
    Dec 2004
    Posts
    3,630
    Quote Originally Posted by Super Dude
    This is because you are tricking the ESC into thinking it's a 3s Lipo. The speed control will detect the voltage of the battery when in Lipo mode, and decide whether it is a 2s or 3s. A peaked 2s should be exactly 8.4v. A peaked 7c Nimh will be over that, which the ESC will interpret as a dead 3s.
    Agreed, a peaked, 6-cell Nimh will be close to to 9 volts and I have to discharge some of the voltage off before the ESC will recoginze the pack when in the LVC mode. A 7-cell Nimh would really confuse the same ESC when in LVC mode.

  10. #10
    RC Competitor
    Join Date
    Jan 2010
    Posts
    60
    Weight is also a big factor between lipo and nimh. Lipo is about half the weight of a nimh.
    Last edited by slash_48; 06-10-2010 at 11:45 AM.

  11. #11
    RC Enthusiast
    Join Date
    Apr 2010
    Posts
    21
    I wasnt sure about switching to lipo until I measured how hot my nimh was getting and I realised that I was pushing it to the limit. I got a 5000 2s lipo and am so pleased I did, more punch, more run time, no temp issues and light to boot. Just get one.....

  12. #12
    RC Racer
    Join Date
    Apr 2010
    Posts
    180
    My venom 4200 8.4v weighed from memory around 425g. My venom 40c 5000mah 2s Lipo weighed in at around 250g or thereabouts. Big weight difference.

    Top speed on 13/54 : GPS read, no body, street runs.

    Nimh 8.4v 4200. 32mph
    2s Lipo 40c 5000mah . 30mph

    I also measured about 10 minutes into the run.

    Nimh 8.4v 4200 . 29mph
    2s Lipo 40c 5000mah, 30mph.

    Total runtime on nimh is 16-18 minutes
    Total runtime on Lipo is 26-28minutes

    I get about another 12 minutes of solid runtime with the 2s Lipo as well. I've kept the venom nimh for wet conditions or just all out bashing and a good spare battery to have in the tool box.

    The other benefit of the lipo is I can run 15/54 and the motor and battery handle fine and I get around 38mph.


    IMO if you get a better quality NIMH high mah capacity it would probably be a better choice for general bashing + not worrying about charging issues e.t.c I recently went to lipo batteries and if I had a good 7 cell high mah nimh I would be happy to alternate between that and the Lipo 2s. Overall as I only bash the benefits with Lipo are probably only longer runtime and more punch towards the end of the pack.

    Going to 3s is a totally different game altogether - at least borrow a friends pack or something just to see what the truck can do on it!!
    Last edited by bcr07; 06-10-2010 at 09:32 PM.

  13. #13
    RC Turnbuckle Jr. asheck's Avatar
    Join Date
    Nov 2007
    Location
    Kansas City
    Posts
    7,361
    I recently did some testing in my Pede, between an older Matched EnerG 6c and some Misc 2s lipos. They all ran out within a few MPH of each other. Between 32-35mph. The nihm did lose about 1mph faster then the lipos, but was also stronger then a 4000mah lipo, at all times till lvc kicked. I would challenge anyone to tell a difference, if just handed the controller.

    Anyways, a quality 7c should easily handle a 2s lipo. A shotgun pack nihm, isn't gonna handle much, before the build shows it's limits.

    I don't see how anyone is gonna be disappointed with lipo. However, if your currently running good quality nihm packs, you might not see the performance increase you hear about.
    _
    _
    _ 3 lines are all that's allowed in a sig.

  14. #14
    RC Champion
    Join Date
    Mar 2010
    Location
    Ontario, Canada
    Posts
    1,249
    Nimh, fades with use, its a great battery, safe to charge and handle.

    2s Lipo goes as strong till it hits LVC and its usually lasts slightly longer.

    saying that its rare to buy a 3000mah lipo, usually its a 5000-6500mah 2s lipo and you end up with min twice run time and consistant till very end.
    MMM/2650, E-maxx Body=FUN !
    3 Slash 4x4
    Pede 4x4

  15. #15
    RC Turnbuckle Jr.
    Join Date
    Dec 2004
    Posts
    3,630
    Quote Originally Posted by akesj1
    Nimh, fades with use, its a great battery, safe to charge and handle.

    2s Lipo goes as strong till it hits LVC and its usually lasts slightly longer.

    saying that its rare to buy a 3000mah lipo, usually its a 5000-6500mah 2s lipo and you end up with min twice run time and consistant till very end.
    A good, matched, EnerG 4600, Nimh pack fades no more than does an equally sized LiPo pack.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •