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Thread: lipo?

  1. #1
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    lipo?

    I hope this is right place for this thread, I am buying a 1/16 summit Friday and I have ran a 1/16 on stock batteries but I am thinking of going lipo for it. My problem is my nephew got me back into RC and I have been out of it for several years. That being said I know nothing about lipo so whats a good pack for my new summit jr and what charger do I need without breaking the bank? Also can someone in plain terms explain the balancing and such for me and anything else I need to know about when it comes to lipo? Your help will be greatly appreciated!

  2. #2
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    If you are going to stick to 1/16th size packs this charger is SAFE and decently affordable:
    http://traxxas.com/products/parts/ch...ipo2s3scharger

    I recommend getting a 2500mAh 2S pack (or two) from SPC.
    http://www.specpointbatteries.com/in...?productID=107

    With the above charger and battery, you can expect the following charge times:
    From LVC to full: about 140 minutes
    From storage to full: about 70 minutes

    With two of the batteries ran in parallel, you can expect roughly 1.5 hour run times.


    My next post is going to cover some LiPo basics.
    Whatever it is I just said... I could be wrong.

  3. #3
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    I wrote this a while back... but most of it applies here too:

    I apologize in advance for the length of this write up. However, I feel that it is important to have as much factual LiPo information as possible and to have it all in one location.
    That being said...

    LiPo 101
    now in session


    Rules
    1) NEVER discharge below 3v/cell
    2) NEVER charge above 4.2v/cell
    3) NEVER puncture your pack
    4) NEVER short out your pack
    5) NEVER use a pack that has puffed
    6) NEVER charge unattended
    7) NEVER charge at a higher C rate than recommended
    8) NEVER use a pack that has been over charged/discharged
    9) ALWAYS check cell voltage before connecting your pack to anything
    10) ALWAYS keep your LiPo pack well balanced

    To calculate the charge rate of your pack
    mAh x charge C rate / 1000 = charge amps
    For example:
    A 2200mah 20-40C pack that states a 2C charge rate.
    2,200 x 2 / 1000 = 4.4
    This battery pack can be charged at 4.4 amps.
    - Please note that if no charge C rate is stated, 1C is standard.

    To calculate the constant discharge rate of your pack
    mAh x minimum discharge C rate / 1,000 = available amps
    For example:
    The same 2200mah 20-40C pack.
    2,200 x 20 / 1000 = 44
    This battery pack can consistently provide up to 44 amps.

    To calculate the peak/burst discharge rate of your pack
    mAh x maximum discharge C rate / 1,000 = available amps
    For example:
    Again, the same 2200mah 20-40C pack.
    2,200 x 40 / 1000 = 88
    This battery pack can provide a peak discharge rate of up to 88 amps.
    Peak rates are limited in time... unfortunately, this amount of time does not have an industry standard. This is how a lot of inflated discharge ratings can be claimed. In my experience, honest retailers/manufactures of packs will list the constant discharge rating along with the burst discharge rating and not only the burst rating.

    Ratings
    When setting up your power system for your RC, make sure that the lower discharge C rate matches or beats the continuous amperage rating of the ESC. I try to beat it by at least 10%. This practice will provide you the most out of your system and it will also keep your batteries from working too hard. A LiPo should NEVER be warm... during use or charging. If it is, you are abusing the pack. Also, the less your pack has to work the longer it will last.


    Parallel
    Running two LiPo's in parallel will double run time and also your available amperage... which is handy for high demand systems. Some misinformation I have read about the discharge C rating of packs in parallel is that the rating of the pack doubles. This is not the case. The C-rating of a battery pack is a fixed parameter of that pack; well actually it is the cells within the pack that have the C rating. Connecting two packs in parallel does not change either pack as they still have the same specifications, however it does create a battery "system" with twice the effective C rating. The packs are the same, but the parallel system is now theoretically capable of discharging at twice the Amp rate. This is much like the cumulative capacity available when connecting two packs in parallel.
    The packs ran in parallel MUST be of the same cell count and should be the same age, capacity, and brand.

    Series
    Running two LiPo's in series will double voltage, therefore nearly doubling the speed of your RC. Capacity remains the same. The two packs ran in series MUST have the same capacity and discharge rate. Also, they should be of the same age and brand.
    Be prepared to gear down when increasing voltage on your power system.

    Charging
    There are many charging options out there... it can get really confusing really fast. The best advise I can give is to get the absolute best charger you can afford and to ask before you purchase. Your charge system is the backbone of your electric RC hobby, treat it as such. RC's will come and go, but your charge system will remain.

    The following features are what I consider to be the absolute bare minimum for a charger... balance charging and a storage charge/discharge feature. If the charger cannot perform these tasks, look for another charger. If you are going to be charging multiple LiPo's at the same time or 10th scale or larger packs, I recommend getting a charger that is capable of at least 10 amps or more. Also, ANY half-decent charger can charge multiple LiPo's at a time. It does not require a dual or multi-charger to perform such a task. It only requires the right support equipment... such as a ParaBoard, which I use.

    Storage
    Storage voltage is 3.85v/cell. This voltage is the only voltage that is not super critical for LiPo. Anywhere between 3.5-4v/cell is considered to be acceptable for storage.
    I suggest putting a full pack to storage voltage if it is not going to be used within 30 hours or so. The longer a pack is at full capacity, the shorter its lifespan will be.
    I also suggest bringing a pack up to storage voltage after a run. When a LiPo's voltage lowers to a certain point, they begin to loose their voltage quickly. I would hate to see you loose a pack (or more) due to not charging up within a few hours after a run.
    For long term storage; I bring my packs to storage voltage, seal them in an airtight container, and stick them in the refrigerator. As I type this, I have had my "speed" set of 3S packs in the fridge for over 8 months at storage voltage... I check them monthly and they are still at 3.85v/cell. Almost makes me regret buying them. lol

    Making your LiPo's last
    I will just give an example of how much a small change in how a pack is taken care of can dramatically change how the pack behaves.
    Two identical packs were both charged and discharged in the exact same matter.... except one pack was charged to 4.20v/cell and the other to 4.10v/cell. This was done in a very controlled environment... NOT in an RC.
    After 500 cycles, the pack that was charged to 4.20v/cell had reached its life expectancy... it would not take more than 65% of its original capacity; meaning the LiPo was no longer able to be used safely.
    The pack that was charged to 4.10v/cell was still at 70% capacity after 1,000 cycles... so the .10v/cell difference more than doubled the life expectancy.



    Here is what I have done...
    this information might help with your decision

    I use inexpensive batteries.
    I have found them to be very reliable, extremely cost effective, and they have been proven to be under-rated; usually providing more mAh and a higher discharge C rate than stated on the pack. SPC is a great brand that under promises and over delivers. There are others that claim extreme discharge ratings that are simply impossible with the technology that is available.

    I use an iCharger 206B.
    When I purchased the charger, I thought I would never use all 20 amps of its capability. Well, now I rarely charge at anything less than 20 amps lol. I have even considered selling it to get more amperage! I have performed hundreds of charge cycles with this charger and it handles the task without a single issue.
    I highly recommend any charger in the iCharger line.

    I built my own power supply.
    I have ~$30 into my 24v 75a 1800watt power supply.
    Sounds complicated, but it really is not that difficult. If you go this route, you are going to want a server power supply as they do not drop voltage when you are pulling amperage like a standard ATX PC power supply.
    You can also purchase these pre-built at a very reasonable price.

    I hope this information helps!!

    Here are some links to some more:
    http://traxxas.com/forums/showthread...rger-vs-cooker
    http://traxxas.com/forums/showthread...charging-setup
    http://traxxas.com/forums/showthread...ply-Conversion
    Whatever it is I just said... I could be wrong.

  4. #4
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    Thanks Jimmie thats some really good info, i like the pack and the price and run times from them so what other choices do I have as far as shortening my charge time or is that about normal for most chargers? How do I know what my storage volts are when I plan on storing them? Thanks again for your help

  5. #5
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    There are a LOT of chargers out there for around $50-100 that I personally do not trust. LiPo is not something to fool around with... a charger that abuses your pack is just as dangerous as puncturing it.

    My charger system as described in the end of post #3 can safely charge BOTH of the 2500's...
    from LVC to full in about 20 minutes at a 2C charge rate
    from storage to full in about 10 minutes at a 2C charge rate
    about double those times for a 1C charge rate

    You can get the exact same charge times from the following:
    10 amp iCharger 106 - $90ish shipped ($35 more for the 20 amp 206)
    TRX ParaBoard - $17ish shipped
    Power Supply - $53 shipped

    Now, I realize that this charge system is quite a bit more than the one I linked to in post #2... but this system has features like storage, brushed motor break in, charging multiple chemistries, and 10 amps of charging power. And it does all of these very safely.

    With the charger in post #2, you would have to constantly monitor and time your charges to manually stop the charge at 3.85v/cell. With either iCharger, you simply use the "storage charge" mode and it does it automatically.
    Whatever it is I just said... I could be wrong.

  6. #6
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    ok so I'm thinking that 206 be good since I could charge lipos for my vxl pede too, and much better charge times I can spend the cash for that, sounds like a good set up with the SPC packs. Whats the TRX paraboard and power supply for? Sorry for all the ?'s but I appreciate your time Jimmie thanks.

  7. #7
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    Asking questions is better than jumping into something and regretting it later on... usually cheaper too. lol

    Here are some links to the 206 and the TRX ParaBoard.
    Be sure to check your PM's.

    http://www.progressiverc.com/icharger-206b.html
    http://www.progressiverc.com/paralle...h-traxxas.html

    The ParaBoard allows you to charge up to 6 same cell count LiPo's that are of a similar charge level at the same time. The power supply is to power the DC only charger... pretty much all high end chargers are DC only.

    The good thing about getting a higher end charge system up front:
    It will probably be the only one you will need to buy.
    Last edited by Jimmie Neutron; 01-30-2013 at 10:08 PM.
    Whatever it is I just said... I could be wrong.

  8. #8
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    Gotcha so the 206 is a dc charger and I need the power supply for it and the paraboard let's me hook up to six of those spc packs at one time and charge them at the same time....I am liking this at up already thanks Jimmie of I thank I'd any other question I'll be back lol

  9. #9
    RC Turnbuckle Jr. mike-susieq1's Avatar
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    Timber211: ill be getting the same setup 206b+paraboard mentioned i have a power supply already waiting for it for sometime now. I decided to get that charger setup because of these guys Jimmie, Pave, Ksb and many others from talking to them and seeing how good the charging setups are and how bad some junk chargers are doing to my lipos.
    I can tell you you wont regret the purchase if you do buy Progressiverc is a good company for warranty support or questions about the charger after you buy and many here like Jimmie can help as well perhaps
    DEU 8:18 ESV

  10. #10
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    I agree mike these guys are a knowledgable on this stuff and I trust what they are saying and in a few weeks it will be my next purchase for sure. I like having the support of the traxxas and their forums one reason I always have stuck with traxxas. Thanks for the help I will check out progressiverc for sure!

  11. #11
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    Subbed! This is great reference material!
    / 16

  12. #12
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    K till I get my lipo set up going, just making sure my charger is ok for the stock battery, its lowest charge amp is 1.5 is that ok or do I need one at 1 amp?

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    Should be ok. Someone can correct me, but I think 1/1000 amp per mah is proper. So 2 amps for 2000 mah.
    / 16

  14. #14
    RC Turnbuckle Jr. jamann's Avatar
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    The para board is nice.well made,good size traces on the circuit board.
    The one thing I recommend is some balance lead extensions.the balance leads on batts are pretty short makes your life easier.a pic to illustrate

    Without the extensions

    Just more crammed and awkward on the wires




    Sent using lipo power
    Mountains cant stop me
    they have tried

  15. #15
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    Nice set up Jamann thanks for the pictures and thanks jrmbtr for the reply.

  16. #16
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    I didn't think of the extensions...
    Whatever it is I just said... I could be wrong.

  17. #17
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    I have 6 extensions on the way! I have the same board and way to tight without it!

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