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  1. #1
    RC Racer
    Join Date
    Mar 2009
    Posts
    110

    new to this need advice

    I am new to electric r/c. I think I want to get an electric because it seems like so much less work than my nitros. I am completely lost in the world of batteries and chargers. looking at getting a merv. i simply want someone to tell me what batteries i should get that will give me the longest run times and best performance. as well as what kind of charger that will get me back up and running the fastest. i read about needing to program chargers? that lost me as well. any input would be great!

  2. #2
    RC Turnbuckle Jr. JimmyNeutron's Avatar
    Join Date
    Oct 2009
    Location
    Alma, Michigan
    Posts
    12,290
    SPC will give you the longest run times. Run time comes from capacity... capacity is listed as mAh on a pack.
    http://spcracingbatteries.com/index....&product_id=54


    As far as which charger depends on your budget. Traxxas makes a very simple and basic charger linked to below:
    http://buy.traxxas.com/product_info....oducts_id=9821
    This charger just needs to be plugged in... no programming what so ever. The downsides are that it will take about 132 minutes to charge the above linked pack from LVC (when the ESC shuts off) to full and that it does not have any storage mode.

    This charger:
    http://buy.traxxas.com/product_info....oducts_id=5395
    Can charge the same pack in about 45 minutes at a standard 1C charge rate and about 20 minutes with a 2C charge rate... and it also has a storage feature. However, you will have to "program" the charger by selecting balance charge and giving it information about the battery. How to do so is explained in the manual of the charger.

    Both of the above chargers are great if you don't ever plan on running larger packs... once you start running 1/10th scale or larger the limitations of these chargers really start to make themselves apparent, but since you are just starting out and learning they make great stepping stones.




    I wrote this a while back... this is a lot more information that what you asked about, but having this information all in one spot is not such a bad idea. lol

    I apologize in advance for the length of this write up. Try not to get overwhelmed... just take it in bit by bit.
    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 hot... 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. However, LiPo's perform at their best once they are between 100F - 120F. (yet another reason to have a temperature gun)


    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 typed... could be wrong.

  3. #3
    RC Champion
    Join Date
    Sep 2011
    Location
    Iowa City, Iowa, USA
    Posts
    1,696
    I use a cellpro powerlab 6. Its great! 40 amps of charging power. 1000 watts. It'll charge a 5s at 40a. I got my power supply from Jimmie at a great price. My setup is a bit overkill but it is easy to use.

    lipo power!!!!!
    1:16 Slash VXL
    Stampede 4x4 3800kv
    Rustler VXL

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