Results 1 to 28 of 28

Thread: Batteries

  1. #1
    RC Competitor
    Join Date
    Apr 2017
    Posts
    81

    Batteries

    Hello everybody, I have decided on going with the castle sv3 combo,(4600kv, or 5700kv, whatever one is cheaper). I would like to know what lipo batteries to get. I think that 2s would be good to start. I have also read that the sidewinder esc needs a battery that is 35c or above, I don't know what that means, but traxxas 2s is only 25c, so I would think that it would be incompatible. Also, the car is a 1/16 summit.

    Thanks!

  2. #2
    RC Turnbuckle Jr. Petertje60's Avatar
    Join Date
    Jan 2011
    Location
    Rotterdam, Netherlands
    Posts
    8,617
    C rating is an indication for how much current a battery can deliver. Just multiply it by the battery's capacity and the result is the maximum amps that it can deliver.

    For example: a 2500mAh 20C battery can deliver 20x2500 = 50000mA which equals 50A.

    There is no official definition for it, just use it as a thumbnail. Bear in mind that not all manufacturers are very precise when giving C ratings. Traxxas C ratings are very conservative.

    To state that an ESC needs a minimum C-rating is nonsense. The ability of the motor demands how much amps you need. The battery must be able to supply that and the ESC must be able to transfer it to the motor. A C-rate without knowing the battery's capacity is non info.

    The 4600 and 5700Kv motors deliver the same power, while the 4600Kv does it on a higher voltage with lower amps.

    No idea what the best choice is for Traxxas 1/16 models today. I have always used SPC 2S batteries or Kypom 3S. SPC is not available anymore, so for 2S I just don't know. Traxxas Lipos are great but on the expensive side of the market.
    Nobody is born with experience

  3. #3
    RC Competitor
    Join Date
    Apr 2017
    Posts
    81
    So the 4600kv motor is a better for battery usage? Does the 5700kv run out of power alot quicker, and get hotter faster? I will have to look around for some other 2s batteries, and then solder a traxxas connector onto them.

    Thanks.

  4. #4
    RC Champion
    Join Date
    May 2002
    Location
    Midvale Utah
    Posts
    1,773
    All else being equal, the lower kv motor will use less power and run cooler to do the same thing (same speed, same acceleration) the only reason to go with the higher kv motor is because your top speed will be higher.
    Dacaur

  5. #5
    RC Turnbuckle Jr. Petertje60's Avatar
    Join Date
    Jan 2011
    Location
    Rotterdam, Netherlands
    Posts
    8,617
    If acceleration is also equal, the neccesary power is also equal. I see no reason why a lower Kv motor would use less power. With the same current and voltage, the lower Kv might even get warm sooner due to it's higher resistance.
    Nobody is born with experience

  6. #6
    RC Champion
    Join Date
    May 2002
    Location
    Midvale Utah
    Posts
    1,773
    Lower kv is equivalent to lower gearing. A lower geared truck would use less power than a higher geared truck during acceleration, right? Same concept with kv
    Dacaur

  7. #7
    RC Turnbuckle Jr. Petertje60's Avatar
    Join Date
    Jan 2011
    Location
    Rotterdam, Netherlands
    Posts
    8,617
    If a truck can accelerate faster due to a lower gearing, that doesn't mean it uses less energy. It's just a matter of more ability to transfer power into movement. Faster acceleration means using more energy which causes shorter runtimes.
    Nobody is born with experience

  8. #8
    RC Champion
    Join Date
    May 2002
    Location
    Midvale Utah
    Posts
    1,773
    Perhaps with a computer controlling everything, accelerating from a stop to 20mph on a lower kv motor vs a higher kv motor in a controlled manner, they would use the same amount of power, when done under a controlled setting.
    That's the difference between theory and reality.
    In reality, where things aren't carefully controlled, all else being the same other than kv, you will get longer runtimes and cooler temps with the lower kv motor, every time.
    The higher kv motor will be drawing more amps at any given trigger (or throttle stick) setting.
    Yes, you will have a higher top speed with the higher kv motor, but unless you are doing speed runs, you would never know.

    This is a fact, take two identical trucks one with higher gearing than the other, and drive them both together. Play Follow the Leader and the lower geared truck will Outlast the higher geared truck in runtime. The higher gear truck simply uses more power at every throttle setting. (Again higher versus lower kv the results will be the same, it's the same basic concept)
    This isn't some crazy Theory, it's a fact known by anyone that's ever messed with the gearing on their electric truck.
    Dacaur

  9. #9
    RC Turnbuckle Jr. Petertje60's Avatar
    Join Date
    Jan 2011
    Location
    Rotterdam, Netherlands
    Posts
    8,617
    Let it be clear that I highly value your knowledge and experience, but if something is posted which is incorrect in my opinion, I have to react. The reason for me to do so was the "all else being equal".

    I know it's hard to bring theory and practice together sometimes, especially with the complex system in R/C cars with Kv rates, voltage, current, gearing and what not. That doesn't mean that theory doesn't apply anymore when you look at pratical experiences.

    When you take two identical trucks except the gearing, your example is very true, but only if the higher geared truck is overgeared. If the lower geared truck is undergeared, the opposite will be the outcome.
    Shorter runtimes are caused by inefficiency, which can be caused by a wrongly chosen gearing or wrongly selected motor.

    Back to where it was all about: I think on average the 4600Kv motor will be the best choice for a mini Summit. The 5700Kv will only be better when you are looking for high top speeds.
    Nobody is born with experience

  10. #10
    RC Competitor
    Join Date
    Apr 2017
    Posts
    81
    Thanks for helping out with this issue. I will look around for a 4600kv and see what i find. I would be doing some small bashing and some speed runs, and I think that the 4600kv would be probably the best for that. I also saw a review on the castle sv3, and the guy said that he could not use his batteries because of the c rating. So, should I look for one with the appropriate c rating just to be safe?

    Thanks!

  11. #11
    RC Competitor
    Join Date
    Apr 2017
    Posts
    81
    Also, any lipo chargers that you recommend?

  12. #12
    RC Champion
    Join Date
    May 2002
    Location
    Midvale Utah
    Posts
    1,773
    You just need to be sure your batteries can handle what you are asking if them. C-ratingXcapacity = rated current. This is really just a rough guess, which is always weighted toward "better than it really is", but it's all we have.
    The advantage to running​ two packs in parallel, is you can use less expensive packs with lower c ratings and still get good performance.
    For a brushless mini revo or summit, I would aim for at least 50 amps of "rated current".
    As for chargers, I like my imax B6, and they can be had for well under $50 on Amazon or eBay.

    One last note on the gearing/kv conversation above. All my arguments assume both high and low gearing are still within the right gearing range. Over and undergearing are completely different things.
    Consider that a truck with higher gearing pulls more amps when accelerating vs one with lower gearing (both in the right range though) that's an indisputable fact. Not talking electrical there here, I'm talking go out and accelerate as hard as you can without flipping.More amps means more heat, and heat is nothing more than wasted power.....
    Dacaur

  13. #13
    RC Competitor
    Join Date
    Apr 2017
    Posts
    81
    So does the imax b6 work with traxxas batteries? And would a 2 cell 25c battery be enough for the sv3 combo?

  14. #14
    RC Turnbuckle Jr. Petertje60's Avatar
    Join Date
    Jan 2011
    Location
    Rotterdam, Netherlands
    Posts
    8,617
    Imax B6 is not the best charger. I have used two of those for a while and never had problems, but when I stepped to a better charger, life became a lot easier.

    A 2S 25C says nothing about the amps it can deliver (you need to know the capacity).
    Bear in mind that the 25C that Traxxas puts on it's batteries is a lot different than a lot of other manufacturers. I agree on dacaur to find a set of lipos which can do 50A together. I bet the 2200mAh 25C Traxxas ones will do a fine job (except for your wallet but hey, good quality is rarely cheap).

    To the discussion: when you have a car that has the ideal gearing for a certain acceleration, that means every other gearing is either over- or undergeared.

    When talking about a car that accelerates towards the flipping point, you will see no difference in current as long as you use the same voltage. When you do it right, you use a higher voltage with a lower Kv motor which results in a lower current. So I am afraid we have to agree to disagree on that point.
    Nobody is born with experience

  15. #15
    RC poster
    Join Date
    Aug 2015
    Posts
    6
    Don't get the IMAX B6 mini or the B6 becuase they require a dc power unit.(You can get the ac power supply convertor sold seperately). Get the the IMAX B6AC V2, if anything.(Make sure you get the GENUINE skyrc chargers with the verification sticker.) These IMAX chargers are good but they don't come with a traxxas plug so you would need to solder some on or get an adaptor. They come with an XT60 and deans plug.

    Because you're a begginner I'm guessing, go with the Traxxas EZ peak plus. It's very easy to use, and you can't really mess up any settings cause they're aren't many. It's also backed up with Traxxas Lifetime Warranty so if something does go wrong, Traxxas has you covered.

    A 2s 25c battery would be fine with the sv3 4600/5700kv. The Castle Sidewinder SCT is a much better combo imo but your using it in a 1/16 scale so you should be fine. Also, I would like to point out a few problems with the sidewinder esc:

    - The switch is just awful and the car kept turning off on me and I had plenty of unintentionally crashes. I'd suggest you solder the switch for a closed circuit and that problem will go away. Now the car will automatically turn on when you plug in a battery

    -I'd highly suggest you get Castle Link or get a Lipo Alarm Buzzer cause the Sidewinder Esc Default auto lipo mode cut off is at 3.2volts per cell which is far too low in my opinion. This can shorten the lipo life in the long run. I got Castle Link and set it to 3.7volts per cell which will be the best voltage for lipo longevity. You can also tweak with a bunch of settings.

    -Sometimes the motor wires will become loose where the motor connects to the ESC and it wouldn't fit snuggly. This results in a loose connection and causes alot of cogging. All you need to do for that is to stretch the motor bullet connectors with a phillps head screw drives and it would fit much more snuggly into the ESC and eliminate all cogging. Also if you know how to solder, shorten the motor wires for a much cleaner setup.

    For batteries I'd suggest you don't go with Traxxas batteries. There's nothing with them it's just that they're kind of overpriced and come with terrible ID connectors. My reccomendations are: Gens Ace, SPC, SMC, Zip.py (some other hobby king batteries), and Venom lipo batteries. I know Venom lipos are kinda overpriced too, but if you can find them for cheap on Amazon, I'd suggest getting them cause they also come with an excellent warranty service.

  16. #16
    RC Competitor
    Join Date
    Apr 2017
    Posts
    81
    Thanks for all your help with this. I did some looking, and found a gens ace that is meant for the mini models, it is 50c, 2s, and it comes standard with the traxxas plug. My only question is what is balancing supposed to do? It also came with a balance plug, but I am not sure what that is for. I have never ran a lipo before, so please excuse my lack of knowledge.

    Thanks!

  17. #17
    RC Champion
    Join Date
    May 2002
    Location
    Midvale Utah
    Posts
    1,773
    Any battery pack is composed of individual cells, either in Series, parallel, or both. A typical 2 cell pack is 2 cells in Series (that's why you will often see lipos described as being 2s or 3s, the s stands for series, a 3s2p pack is a pack made using 6 cells, it's basically two 3 cell packs in parallel. When you run two 2 cell packs in these trucks, you are running 2s2p)

    So typically, with a 6 cell NIMH pack, you charge in series, through the discharge port. Since the cells all have slightly different internal resistance, this results in some cells being slightly over charged. With NIMH, that's not a problem, as they can handle it and just release the extra as heat.
    Lipos on the other hand cannot hand being over charged. A slight overcharge will damage the cells, reducing capacity and increasing internal resistance (C rating is based off internal resistance, Lower​ IR means higher C rating). They will also release the extra power as heat, which can lead to a thermal runaway, the battery gets hotter and hotter, expanding till it pops and bursts into flame, not good....

    So the best way to charge a lipo is by charging each cell individually, to make sure no cell goes over 4.2v, which is what the balance plug is for. Depending on the charger, it can charge entirely through the balance plug, or charge through the discharge plug while using the balance plug to monitor each cell and keep them in balance by discharging the highest voltage cell through the balance plug while continuing to charge through the discharge plug
    Dacaur

  18. #18
    RC Competitor
    Join Date
    Apr 2017
    Posts
    81
    Thanks for the clarification. Here is the battery that I was thinking of getting: https://www.rcplanet.com/gens-ace-22...jkmGU_mdI2W_Ah

    Will this work well, because it has a balance plug?

    Thanks!

  19. #19
    RC Turnbuckle Jr. Petertje60's Avatar
    Join Date
    Jan 2011
    Location
    Rotterdam, Netherlands
    Posts
    8,617
    All lipos from 2S and higher have a balance plug. That battery will work fine.
    Nobody is born with experience

  20. #20
    RC Competitor
    Join Date
    Apr 2017
    Posts
    81
    Thanks for replying. So, I would charge it off of the balance plug, and run it off of the trx plug , right? Also, are all balance plugs universal, or can they be different?


    Thanks!

  21. #21
    RC Turnbuckle Jr.
    Join Date
    Dec 2004
    Location
    PA
    Posts
    4,083
    Quote Originally Posted by dacaur View Post
    Any battery pack is composed of individual cells, either in Series, parallel, or both. A typical 2 cell pack is 2 cells in Series (that's why you will often see lipos described as being 2s or 3s, the s stands for series, a 3s2p pack is a pack made using 6 cells, it's basically two 3 cell packs in parallel. When you run two 2 cell packs in these trucks, you are running 2s2p)

    So typically, with a 6 cell NIMH pack, you charge in series, through the discharge port. Since the cells all have slightly different internal resistance, this results in some cells being slightly over charged. With NIMH, that's not a problem, as they can handle it and just release the extra as heat.

    Lipos on the other hand cannot hand being over charged. A slight overcharge will damage the cells, reducing capacity and increasing internal resistance (C rating is based off internal resistance, Lower​ IR means higher C rating). They will also release the extra power as heat, which can lead to a thermal runaway, the battery gets hotter and hotter, expanding till it pops and bursts into flame, not good....

    So the best way to charge a lipo is by charging each cell individually, to make sure no cell goes over 4.2v, which is what the balance plug is for. Depending on the charger, it can charge entirely through the balance plug, or charge through the discharge plug while using the balance plug to monitor each cell and keep them in balance by discharging the highest voltage cell through the balance plug while continuing to charge through the discharge plug
    Actully you have part of this post backwards.

    Nimh absolutely cannot handle being over-charged. Also, they do not like to be over-discharged. Either will permanently damaged the cells. Nimh cells are much more fragile than most people think. Which is one of the reasons Nimh has earned the reputation of losing power slowly as the pack is run down; people tend to over-charge or over-discharge them on a regular basis. Good (new) Nimh cells hold voltage very well under load, but damaged, over-charged or over-discharged, Nimh cells suffer terribly under load.

    Even though I do not recommend doing so, many Lithium-based cells can handle minimal over-charging with no problem. However much like Nimh, over-discharging a LiPo cell causes serious and irreversible damage.


    Edit: For the OP - Listen to Peterje60. He knows what he is talking about!
    Last edited by Jakey; 05-26-2017 at 10:15 AM.

  22. #22
    RC Competitor
    Join Date
    Apr 2017
    Posts
    81
    Is that what a lipo alarm is for?

    Thanks!

  23. #23
    RC Turnbuckle Jr.
    Join Date
    Dec 2004
    Location
    PA
    Posts
    4,083
    You mean a Low Voltage Alarm, right?

    A Low Voltage Alarm is another tool to use to help avoid over discharging your LiPo packs and yes they are worth every penny. Try to find one that is adjustable and set it to 3.4 volts per cell. No lower!! Then stop the RC vehicle when you hear the alarm beeping continuously. Do not pass go, do not keep driving a few more seconds. STOP!
    Last edited by Jakey; 05-26-2017 at 11:27 AM.

  24. #24
    RC Competitor
    Join Date
    Apr 2017
    Posts
    81
    Any alarms that you would recommend?

    Thanks!

  25. #25
    RC Turnbuckle Jr.
    Join Date
    Dec 2004
    Location
    PA
    Posts
    4,083
    You can find them readily on Ebay. Just do a search for Low Voltage Alarms. You should be able to find them for under $5.

  26. #26
    RC Competitor
    Join Date
    Apr 2017
    Posts
    81
    Ok, I looked at the imax b6, and i found it for $15. Is this a good deal? And will it work with the gens ace battery linked above?

    Thanks!
    Last edited by MiniSummit50Mph; 05-26-2017 at 01:24 PM.

  27. #27
    RC Turnbuckle Jr. Petertje60's Avatar
    Join Date
    Jan 2011
    Location
    Rotterdam, Netherlands
    Posts
    8,617
    Sounds like a good deal. It will charge the GensAce Lipo. Just check if the Imax is the version that has the power supply built in (the AC version). If it hasn't, then you need an external power supply.
    Nobody is born with experience

  28. #28
    RC Champion
    Join Date
    May 2002
    Location
    Midvale Utah
    Posts
    1,773
    I use a laptop power supply for my Imax b6.
    Dacaur

Posting Permissions

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