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Thread: New To Lipo!!

  1. #1
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    Talking New To Lipo!!

    Hey, I'm new to lipos, I was wondering why do you have to discharge your lipo battery. How do you do it? What is a good lipo charger under $40? Why do you need to balance your cells?

    Just give me an overall idea about lipos.

    Thankyou!

  2. #2
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    Yeah i was wondering about how long like the 8000 mah ones lasts 5000 etc. and would the ez peak 4 amp fast charge work for lipos or would you have to get the 6 amp fast one. Im thinking about getting one and i want a long lasting battery and what charger it needs and how long it takes to charge. Plz help

  3. #3
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    Hey there, well to your first question personally i never discharged my lipos. I'm not sure what others have to say but i did that with 3 different lipos for 6 months and never had bad luck. Second question, your lipo charger will have an option for discharging, the charger I use is the Thunder AC6 which can be found at Hobby Partz for like $45 and its been great for me, charges NIMH and lipos. And for balancing I have no idea why you do but for me i balance every single charge I have heard rumors about lipos blowing up because the cells were unbalanced better safe than sorry... hope this helps buddy!

    @littlejoe the mah level is how long the battery last... and i recommend the Thunder AC6 charger, it has never let me down. The nice thing about this charger is you can balance and charge your lipo at the same time! And you will be fine with a 5000mah battery, the run time all depends on how you drive just buy like 2 or 3, 5000mah batteries and you will be good to go!
    Last edited by cooleocool; 01-03-2012 at 07:20 PM. Reason: post merge
    Use less brakes

  4. #4
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    Well what should I buy if I only am getting one battery and how quick does the ac charger take to charge

    O and 2 or 3s lipo which one sorry about the 2 sections
    Last edited by cooleocool; 01-03-2012 at 07:21 PM. Reason: post merge

  5. #5
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    I have a 3s 5000mah lipo. I was wondering if this charger will work with it?
    http://www.ebay.com/itm/Traxxas-2-3-...item43ac4b1c16
    How do Balance Chargers work?(I dont mind if it take 6-10 hours to charge)
    Is it safe?
    Will it mess up my Battery?

  6. #6
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    You should mind if it takes 6-10 hours to charge or balance I charge/balance 2 6000mAh 2S LiPo's at the same time on my charger and it takes about 32 minutes, and will go even faster as soon as I get 24V going rather than just my 1 12V.

    mAh shouldn't be explained as how long your battery lasts, but instead the actual capacity of the battery. Depending on many factors, you can determine roughly how many mAh your truck might use per minute, and you can guess as to how long a certain capacity battery will last you. Obviously one that holds 6000mAh has a higher capacity than a 5000mAh battery. Often times, they weigh more (not always, or if its 4 grams, who cares!) so that is a factor you should consider.

    Each cell in a lithium polymer battery will be 3.6V, so a 2S is 7.4V and a 3S is 11.1V etc. For example, a 2S you should have your low-voltage-cutoff stop at 6.0V or more. If your cells are not balanced you could end up with 3.2V in one cell and 2.8V in another (bad). So keeping them "balanced" so that when you reach your cut off, both (or more) of your cells are close in voltage) will keep your battery lasting longer. It's for the health of your battery, which to me translates to my wallet

    Balancing the battery shouldnt add too much more time to the total time to charge/balance, as long as they arent too out of sync.
    Losi TEN-SCTE | Tekin RX8 | Tekin Pro4 4600

  7. #7
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    Thanks, That helped alot, but can you tell me about that charger that i mentioned above on the link? If that charger isn't any good, which one is best for $40 or less?

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  9. #9
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    There are a few things that you need to know about electricity and the LiPo battery formulation to get the most out of your packs, and to use them safely. First is that any battery will have a working voltage range , discharge ratings and capacity. The voltage range of each cell in a LiPo pack is 3v to 4.2v, if they are charged or discharged outside of this range the cells can become permanently damaged, other types like NiCd and NiMH can be discharged down to practically nothing or charged higher than their peak voltage without damage.

    Capacity is rated by amps per hour, a 5 amp hour battery can ideally supply 5 amps for 1 hour or an equivalent discharge like 10 amps in 30 minutes or 2.5 amps over 2 hours. Often for RC packs they rate packs in milliamps, 1,000mA=1A, so a 5000mA pack is a 5A or 5 amp/hour pack. This capacity or C rating also dictates charging and discharge ratings, a 5 amp hour pack with a 20C discharge rating can be discharged at 20 times it's capacity or 100 amps in 5 minutes. If it has a 1C charge rating then you can charge up to the capacity, 5 amps taking an hour for a 5 amp hour battery, a 3C charge rating would be 15A and could ideally be charged in 20 minutes. When a LiPo pack is discharged, it can release a huge ammount of electricity, and it's internal resistance and geometry affect the discharge rating and heat buildup, when a pack is discharged close to it's max rating, it heats up and the output voltage lowers, this is why higher discharge ratings for a given motor/ESC setup can keep packs cooler, and give better performance as voltage drops less under load.

    There are some special considerations needed to use LiPo packs in order to keep them from going under 3v or over 4.2v per cell, and to make them last a long time. First is that you need a low voltage cutoff, this will reduce power output from the ESC or cut power entirely when the pack is drained, and the voltage gets near 3V per cell. This also requires some form of cell detection, usually by reading the voltage when the pack is plugged in. If an ESC like the VXL cut output at 6V for 2S packs, without detecting cell count it would drain a 3S pack past the point of damage. A charger has to be made specifically for LiPos, instead of other types of battery chargers that sense resistance as a pack nears a full charge, a LiPo charger has to detect voltage as the pack will keep charging past the 4.2V peak if it isn't controlled, and the pack will overheat and possibly explode. The purpose of balancing cells is that all cells have slightly different internal resistances and going by the collective serial voltage can leave one cell above 4.2v while charging, or if an unbalanced 2 cell pack is run to a "safe" 6v cutoff, one cell ould be at 3.2v and the other at a damaging 2.8v. This is done one of two ways, either a charger charges each cell individually through the balance lead or the charger applies a draw to a cell at higher voltage while charging through the main power wires. The first solution limits the charge rate to only an amp or two at most, being the balance wires are very small, and this can take several hours to charge a large pack, this is the problem with the ebay charger linked above. The second method is better, it allows high charge rates, and has a mode that can drain batteries for storage.

    LiPos lose some voltage in storage, and if stored at full capacity can end up losing capacity in the long run, storing at about 1/2 capacity or 3.8v per cell can help make them last longer, most computerized chargers have a storage mode that will charge or discharge a pack to 3.8v if you won't be using it for a couple weeks or more. Ideally you want a charger that can charge packs at their full charge rating, most are limited by wattage, but advertised in amperage. Something like the popular Thunder AC6 is advertized as a 5 amp charger, but it is atually a 50 watt charger, a 2s pack charging to 8.4V can be charged at the full 5 amps, but a 3s pack being charged to 12.6v will be limited to about 4 amps. If you have 5Ah packs that can be charged at 3C or 15 amps then a 150 or 200 watt charger can charge it at the max rating. If you have a few packs and don't care if it takes an hour to charge packs then something like the AC6 is fine. There are plenty of similar chargers for cheap that work well, you might have to solder a connector to the charging leads or get an adapter for it to work though.

  10. #10
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    How long does a thunder ac6 take to charge a 5000 mah lipo.

    Or anyone else

  11. #11
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    it will take under an hour

  12. #12
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    it can charge at 5 amps/50 watts, so a drained 2 call can charge in a little more than an hour, and balance up in 5 to 20 minutes more around 90 minutes, a half drained pack can be fully charged in about 45 min. On a 3 cell pack it can only charge around 4 amps before it hits the 50 watt limit of the charger.

  13. #13
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    If you're looking for some additional info, This page helped me a ton in understanding lipos a little better. I'm still waiting on my first truck so I'm not purporting to actually know anything, mind you.

    www.rchelicopterfun.com/rc-lipo-batteries.html

  14. #14
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    Sweet thanks do you think I should get the Traxxas 6 amp fast one or thunder ac6 charger

  15. #15
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    Thunder Ac6

  16. #16
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    Okay but what's better on the thunder ac6 than on the Traxxas 6 amp fast one one

  17. #17
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    Quote Originally Posted by littlejoe View Post
    Okay but what's better on the thunder ac6 than on the Traxxas 6 amp fast one one
    The price is the biggest difference. The Traxxas is an 80W charge / 10w discharge, nice looking charger with traxxas connectors included, so no soldering, ac and dc power sources are nice too. The AC6 is a 50w charge / 5w discharge, the programming language is a little different, but outside of the lower output, case and better support of the traxxas charger there isn't much difference. The thunder AC680 dual power matches the traxxas unit's output. I have a couple dc only T680s and they work good for the price, just got a skycharger 6200 and it is 200 w /25w, more than double the charge rate of the traxxas/AC680 and 4 times the AC6. It can charge a 5000mah pack at 2C and with a simple parallel harness can charge 2 packs at 1C, only problem is that it hits the 10 amp limit before the 200w limit on the 2 and 3 cell packs I run in cars, but for 4-6S aircraft packs or by charging serial it can put out it's full power. Those don't have a/c inputs though, no big deal for me, I have a big DC field power supply that I can plug in at home too.

  18. #18
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    I just got the Thunder AC6 today and like it. It charges my Gens ace 5000 mah 2s in about 90 minutes.

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