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  1. #1
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    Batt/ESC/Motor temps.

    So yesterday I put in the 15 tooth pinions and went around the tall grass and driveway and street for what ended up being 3319mah worth of battery. Pair of 7 cell IB3800s to be exact. With the 19 toothers I didn't like the motors heat when done with a run so I went 15. Mission accomplished, sorta. I felt the motors after the run and was really pleased. I took Eva inside and put it on the bench. Hottest point on the motors was 115 degrees, ESC was 97. But my batts were a little warmer, most cells were 122-135 degrees and at least one was showing 152 degrees. I have the Duratrax Flashpoint so I am not 100% sure of it's accuracy, but it seem to be pretty close. What are your thoughts on this?

  2. #2
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    I've found that with mine last summer, the 19t pinions were just too big and things were getting just too hot for my liking. Have to admit, that's one of the best parts with the 775 swap, I've run even steeper gears and not had it get as hot as it did with the 550's!

  3. #3
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    I would say the batterys cant handly the amp. Was the trucked pointed the hole time in the tall grass?

  4. #4
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    I was usually WOT in the grass to get throught it, but wasn't in the grass the whole time. I just didn't figure the motors would be so cool and the batts so hot.

    I have a pair of LiPos to use as well, and I will be getting some from ********* when the 5000s come in stock...

  5. #5
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    Really nihms are good up to 160, though I like 120. #1 reason of nihms getting hot is running to long. Stop your run 3 minutes earlier and all will be good. 75% of rated capacity is really all you should run of nihms.
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  6. #6
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    Oh wow, I thought since I've been told to stop charging when they hit 120 that that would apply to a running temp as well.

    And I got about 87% of capacity out of them and was pretty bored with the driveway/road/yard. So that can deffinetly be cut down.

    Cool Beans Guys!

  7. #7
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    I was looking for some info on how long to run my Nihms. I wasn't sure whether running them till they were completely depleted would help them to get a full charge. Rather than leaving them with still some juice. I had a pair of 2400 that I ran dry and when I opened the battery compartment they had ballooned.
    Last edited by Cooleguana; 04-30-2009 at 10:14 AM.

  8. #8
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    Quote Originally Posted by Cooleguana
    I was looking for some info on how long to run my Nihms. I wasn't sure whether running them till they were completely depleted would help them to get a full charge. Rather than leaving them with still some juice. I had a pair of 2400 that I ran dry and when I opened the battery compartment they had ballooned.
    Was it the shrink wrap that puffed from the heat or did you actually inflate a cell-or-two?

    It seems rediculous to me that your not supposed to run them until they are depleted. Why state a capacity that younot suppose to use?

  9. #9
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    All the shrink wrap peeled away. Looked like the batteries turned into the Hulk! The batteries them self didn't seem to swell up too much. I'm thinking they got extremely hot. I didn't have a sensor to check it and I wasn't about to touch them.

  10. #10
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    Not planning to run 2400's just had some kickin around and my 5000 were charging. Thought I'd see how the 2400 would perform. I think the Revo drained the live out of them.

  11. #11
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    Quote Originally Posted by Cooleguana
    Not planning to run 2400's just had some kickin around and my 5000 were charging. Thought I'd see how the 2400 would perform. I think the Revo drained the live out of them.
    Gotta feed it well, not give it little snacks!!!

  12. #12
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    Yeah that Revo get mighty hungry. Oh well live and learn. I'll leave the 2400's to the 1/16 hoppers I have

  13. #13
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    Hey I noticed you were in the other thread "Which are the best batteries to buy for my first EREVO?" Have you made up your mind to got Lipo or stay with the Nihm's?

  14. #14
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    Quote Originally Posted by Cooleguana
    Hey I noticed you were in the other thread "Which are the best batteries to buy for my first EREVO?" Have you made up your mind to got Lipo or stay with the Nihm's?
    I currently have a pair of 7 cell NiMH and a pair or 2s 4000 LiPos. I am planning to get 4 of the ***** 5000 2s when they come in stock. Unless something else comes along that is close to the price and output.

    I had 5 batteries for my Slash so I could run about all I wanted. Now with this dual battery monster I am limited to a pair of pairs. But four of the *****s should make my NiMH a thing of the past.

  15. #15
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    Quote Originally Posted by koolwhipman
    I currently have a pair of 7 cell NiMH and a pair or 2s 4000 LiPos. I am planning to get 4 of the ***** 5000 2s when they come in stock. Unless something else comes along that is close to the price and output.

    I had 5 batteries for my Slash so I could run about all I wanted. Now with this dual battery monster I am limited to a pair of pairs. But four of the *****s should make my NiMH a thing of the past.
    That is sort of where I am. I had a bunch of hoppers (4) and 2 pairs of 2400. So lots of runtime/swapping. I bought 1 Venon 6cell 7.4 5000. Shortened the need to swap. Then I bought my eRevo Brushed. Bought another 6cell to pair up. Bought a pair of Venom 7cell 8.4 to get more runtime/punch. Now I'm debating what to purchase next.

    1) Buy another set of 7cells ($90 CDN)
    2) Buy some Lipo's compatible with the EVX-2 ESC and a cut off switch
    3) Change my ESC (MMM) and buy Lipo's that won't fry my 550 Titans

    How much more runtime do you get from the Lipo' compare to the Nihms?

  16. #16
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    Quote Originally Posted by Cooleguana
    That is sort of where I am. I had a bunch of hoppers (4) and 2 pairs of 2400. So lots of runtime/swapping. I bought 1 Venon 6cell 7.4 5000. Shortened the need to swap. Then I bought my eRevo Brushed. Bought another 6cell to pair up. Bought a pair of Venom 7cell 8.4 to get more runtime/punch. Now I'm debating what to purchase next.

    1) Buy another set of 7cells ($90 CDN)
    2) Buy some Lipo's compatible with the EVX-2 ESC and a cut off switch
    3) Change my ESC (MMM) and buy Lipo's that won't fry my 550 Titans

    How much more runtime do you get from the Lipo' compare to the Nihms?
    I got about a minute and a half of runtime with my LiPos.

    I could only use them in the basement because it's been raining or wet all four days I have owned the thing.

    I got the LiPo cutoff with Eva from my LHS. I hope that sticking with 2 x 2s will keep my Titans alive, especially with 15/68 gearing.

    I know that in my VXLed Slash the same LiPos gave me a noticable performance gain and a noticable longer runtime, but I never put a timer on. I do know that I won't buy another NiMH, but I will use the ones I have until I get some (probably)*****s my bowling league prize money next week. And of course I'll use the NiMH while I wait for the intercontinental shipping.

  17. #17
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    Too bad about the weather. Here in Toronto, Canada we have been getting on and off rain. So you just have to pick your times. It has kind of worked out the best for me. We have a skate park being put in close to where I live and they still haven't put down any concrete. So there are some great dirt jumps and half pipes. With all the rain the workers stay away! So I get to run till all my packs are dead. Then back the next day.

    Driving a Revo in the house=Disaster waiting to happen!

    I'll keep watching for your posts on the outcome of the lipo run. I'm still running the stock gearing. So if your getting good times.... mine should be even better with less aggressive gearing.

    So are you still running the stock EVX-2 ESC? Just with the cutoff for safety of the Lipo's?

  18. #18
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    One other question bout the Lipos. How is the time for charging. I find with my Nihm 7cell 8.4's charging at 4amps it takes about 1.5hrs to charge. It would be nice it Lipos were less time to charge. Never heard anyone talk about that.

  19. #19
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    It depends on the battery...most LiPos are only safe to charge at 1C (1 amp per 1000mAh), but some allow you to charge them at 2C (2 amps per 1000mAh), but there are some out there that can be charged at 3-5C.

    So, charging a 5000mAh LiPo at 5 amps, would take anywhere from 30 to 45 minutes I would think.
    Project: BL Revo Race Quad & BL G-Maxx G3R CF Revo

  20. #20
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    Quote Originally Posted by Cooleguana
    One other question bout the Lipos. How is the time for charging. I find with my Nihm 7cell 8.4's charging at 4amps it takes about 1.5hrs to charge. It would be nice it Lipos were less time to charge. Never heard anyone talk about that.
    Charging a LiPo pack from near empty to full, takes over an hour at a 1C rate.

  21. #21
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    Most people don't discharge their LiPos to near empty like they do their NiMHs, though, so charging takes less time...in fact, a lot of people only discharge their LiPos to around 1/3 capacity or so, which means the pack can be charged in 30-45 minutes or so...that is why I stated what I did. But, yes, a near empty pack will take an hour or more to charge.
    Project: BL Revo Race Quad & BL G-Maxx G3R CF Revo

  22. #22
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    Great thanks for the reply on the charge time Revoš,Jakey. Well it sounds like it would be less time then the Nihms. How ever slightly less....less is still good.

  23. #23
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    Quote Originally Posted by Revoš
    Most people don't discharge their LiPos to near empty like they do their NiMHs,
    Nimh should not be discharged near empty either! Over-discharging is the number one cause of Nimh battery pack failure.
    Quote Originally Posted by Cooleguana
    Great thanks for the reply on the charge time Revoš,Jakey. Well it sounds like it would be less time then the Nihms. How ever slightly less....less is still good.
    Actually they take longer to charge than do good quality Nimh packs.

  24. #24
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    Well, in my Slash with the VXL, I would run my 4000 mah Lipos until the LVC kicked in. When I charger the batt I remember some times of 1:05, 1:15, 1:17, and usually just over an hour. That was at 4 amps on a 4000 on a Venom Pro charger. The Mah that went into the pack was always in the very high 3800s to 4100.

    Was I doing something wrong? I don't think so, I was running to the LVC then charging until it was full.

    Why would you only run a third of your batts capacity? Lipo's can be discharged to 3 volts per cell. When you charge it from there to full to get the total Mah it is considered to be, ya? So that's what "size" it is.

    And NiMh are supposed to be cut off at .9 volts per cell.

    I have 14x 3800s in my truck with a 12.5 volt cut off. I ran 3319 Mah out of them and was still popping wheelies from a dead stop. ((meaning massive throttle bursts and drain on the batterys' voltage)) They didn't trip the LVC. They still had enough power left in them to go for longer.

    And a 1C charge will take an hour. Regardless of what it goes in. Thats what makes it a 1C charge. But when I charge my LiPos and the voltage gets to 8.4(this was for a single 2cell) the amperage starts to drop. That makes it less than 1C for the last 3/4 of the charge or so, therefore resulting int e 1 hour and 15 minutesish times. My NiMH charge at the same amps(other than the pulses at specific intervals) so they take around an hour for a complete charge. I usually don't run them down to a full discharge because they drop a little in performance sooner than that.

  25. #25
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    Hey Thanks koolwhipman for the detailed charging description! That give me a really good idea of real world times. I know there are lots of variables but this at least hits in the ball park.

  26. #26
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    I didn't say most people only use 1/3 of their battery's capacity, I said they usually only run them down to a 1/3 of their capacity, which means they only use 2/3 of the capacity...the "average" user does this with their LiPos because they are scared to death to puff their LiPos...so when they charge, they charge in less than an hour. Face it guys, it's true.

    And I know NiMH are "supposed" to be cut-off at .9v, but do most people stop running them at that point? No, they dont...they run the vehicle until it just stops, I have watched it happen many times, even with experienced racers who still use the "NiCD Memory" mentality. Again, face it, this is fact.

    Guys, chill out, and hop off my back...it isn't about you, and just you, it is about everyone in the sport...which is why we work with "averages". It's about what the people of the sport as a whole do, not each individual user. Sure, those of us who do know better are the exception, but 99% of the RC community just does as they please, so we have to generalize, and work with averages. Just because you don't fit into the "average" doesn't mean everyone else doesn't. Enjoy the sport, do what's best for you.
    Last edited by Revoš; 05-01-2009 at 11:40 AM.
    Project: BL Revo Race Quad & BL G-Maxx G3R CF Revo

  27. #27
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    A good quality 4600mAh Nimh charged at 6-Amps takes 46 minutes to charge, far less than 1 hour. And before someone relplies saying a 6-Amp rate is too high, I'll add it is not too much for a good matched pack and does not harm the pack in any way.
    For the record a 0.9 volt per cell cutoff is too low for Nimh when discharged in series.
    Last edited by Jakey; 05-01-2009 at 11:47 AM.

  28. #28
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    Yeah my Peak charger only goes to 4. But I was looking at one that is rated at 7amps. That might speed things along.

  29. #29
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    I agree with Jakey here, a quality NiMH pack can be charged at higher than 1C...and when we are speaking of cutting off NiMH at .9v, we are meaning .9v per cell.
    Project: BL Revo Race Quad & BL G-Maxx G3R CF Revo

  30. #30
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    Again, a 0.9 volt per cell cutoff is too low for Nimh when the cells are discharged as a pack in series. A good quality Nimh pack is 95% or more discharged at a 1.1 volt per cell cutoff, therefore there is no reason to go any lower and risk pulling a cell down to potentially damaging levels.

  31. #31
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    That's true...what would you suggest for a 6-cell pack, maybe 6.6v, and 7.7v for a 7-cell pack? Or 6v and 7v respectively?
    Project: BL Revo Race Quad & BL G-Maxx G3R CF Revo

  32. #32
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    Quote Originally Posted by Revoš
    That's true...what would you suggest for a 6-cell pack, maybe 6.6v, and 7.7v for a 7-cell pack? Or 6v and 7v respectively?
    6-cell pack; 6.6V ...... 7-cell pack; 7.7V

  33. #33
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    Cool deal, thanks.
    Project: BL Revo Race Quad & BL G-Maxx G3R CF Revo

  34. #34
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    There is no cutoff on the EVX-2 ESC so how would you monitor the Nimhs. Or do you just stop when you notice a performance drop. Does the MMM's cutoff work on Nimhs too?

  35. #35
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    Most people just stop when they notice a decrease in performance, yes.

    As for the MMM having a cut-off for NiMH batteries, I am not sure...never looked that deep into mine since I don't run NiMHs with it.
    Project: BL Revo Race Quad & BL G-Maxx G3R CF Revo

  36. #36
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    A cut-off is a cut-off. It doesn't care what power source the power is coming from. They typically cut off at a level that is suited for LiPos. My Novak 4s Smart Stop is set to act at 12.5 volts. That is 3.25 per each LiPo. or with NiMH/NiCD 12 cells feeding it that would be 1.04 volts per cell. Two 7cells is 0.89 per cell. For 5 A123 cells that is 2.5 per cell.

  37. #37
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    A good quality Nimh pack works very well with a LVC. The exception being the LVC on the VXL system. A fully charged, good quality, 6-cell Nimh pack exceeds the upper voltage limit of the ESC when set to the LiPo mode; same goes for an equivalent 9-cell pack.

  38. #38
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    Thanks guys great to know

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