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  1. #1
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    Question Handling of LiPo batteries

    Hi everyone,

    M new so please show patience even if my question seemed dumb for you guys here.
    My dealer from who i bought my car told me to be careful as the LiPo battery is a bomb.. keep it in refrigerator and keep it cold or else it can blow...
    Please tell me as if keeping it in fridge necessary? or what can cause a blast? I have kept them in LiPo Safe bag... even i charge them while keeping them in the bag...

    I would appreciate any tips from the experience of you guys... thanks.

  2. #2
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    You don't need to keep them in the refrigerator.

    They only become dangerous if charged improperly or over discharged. You should always be in the nearby vicinity so you can quickly stop charging if a problem arises.

    As long as you use a balancing LiPo charger and make sure the number of cells and amp charge rate are set properly, there should be no problem. i.e. if the pack is 3000 mAh you can charge at 3amps. If 5000 mAh you can charge at 5amps -- this is the 1C charging rate which is basically calculated by taking the number of mAh and dividing by 1000 to get number of amps to charge at.

    Storage temperatures are typically between 40-80 degrees F.

    Allow batteries to return to ambient temperature before charging. Typical charging temperature range is between 40-110 F. Do not let the battery get above 110 during charging (doesn't happen if the charger is set properly and you haven't previously damaged the battery.

    When operating, never allow battery temp to exceed 143F. Above that temperature and you get a fire that cannot be put out with water -- need to let it burn in an open non flammable area or smother with lots of sand. Use a temp gun to monitor your car until you are comfortable knowing the safe operating limits for your RC.

    Never puncture Lipo. If in a bad crash, disconnect lipo and observe it in a fire safe area for 30 minutes to make sure it doesn't puff or burn. If it's okay, charge as normal. If it puff, dispose safely per instructions that came with the battery.

    You can do searches on the web about lipo fires and explosions. These only happen because someone is purposely charging the battery incorrectly and trying to get it to burn or explode. If you charge it properly using the proper equipment and settings, then the risk of fire and explosion is very small.

  3. #3
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    Thanks a lot Dementor...
    your reply certainly cleared a lot lot of stuff in my mind. Just a few question that arise from your reply, if you could help me by answering them as well. i will appreciate.

    - You said that while operating, the battery temp shouldn't exceed 143 F. The last time i ran my xo1 for around 15-20 mins (not continuously) and when i took the car in hands to remove the batteries, the batteries were extremely hot. this was the first time i noted that batteries have become so hot. i immediately sat in car and put the batteries in front of AC. in your experience, what you say that is it normal for batteries become this hot when the car was not over run or used roughly? and after this putting them in front of AC to cool off more quickly, is it a good step?

    normally when you run your RC, do the batteries become hot or no? or should i check whether there is something wrong with either car or batteries.

  4. #4
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    Hot to the touch means very little... a thermometer is a must-have tool in my book.

    The RC I have that abuses the packs the most (highest amp draw) is my MT4... packs come out of that at around 100-120F depending on ambient temps, running conditions, ect.. All of my other RC's the packs come out no more than ambient.
    Whatever it is I just said... I could be wrong.

  5. #5
    Marshal ksb51rl's Avatar
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    If your packs are hitting more than 120*F then they are being overdrawn.
    "The general rule is if you can't comfortably hold a LiPo pack tightly in your hand after using it, it's way too hot."
    Alt-248 on the number pad =

  6. #6
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    I was thinking the same thing, K... but didn't want to cut down D's post without knowing for sure.

    Those temps are also why I am saving up for better packs!
    Whatever it is I just said... I could be wrong.

  7. #7
    Marshal ksb51rl's Avatar
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    Quote Originally Posted by Jimmie Neutron View Post
    I was thinking the same thing, K... but didn't want to cut down D's post without knowing for sure.

    Those temps are also why I am saving up for better packs!
    I realize that was a bit abrupt, but 143*F is far beyond what I consider safe.
    In my experience, a LiPo within 10*F of ambient is a happy LiPo.
    Alt-248 on the number pad =

  8. #8
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    if lipos are getting too hot what is the best way to get them to a safe temp? Gearing, higher C rating?

  9. #9
    RC Turnbuckle Jr. Jimmie Neutron's Avatar
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    Probably gearing... but if you like the speed get higher rated packs. They are warming because too many amps are being pulled from them.

    Getting higher rated packs is not as easy as it seems due to their not being an industry standard. Two companies can claim that the same pack has two very different C ratings and quite a few brands don't do any testing what so ever and just trust the factory's claimed rating.
    Whatever it is I just said... I could be wrong.

  10. #10
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    I started NiMHs and was originally very afraid of getting LiPos because of the liability and warning stuff provided by anyone making and selling em as well as all the youtube videos showing explosions and fires when doing dangerous things, so I did a lot of research trying to find the most common storage voltage ranges, temperature operating ranges and conditions to minimize the chance of LiPo fire.

    The temp ranges I posted are derived based on information obtained from Traxxas and Venom battery package inserts, battery university info, and information I was able to find perusing multiple RC truck, boat, flight, heli, forums.

    I use an IR temperature unit to measure temperatures, but it can fail. I built an aluminum heat sink for my boat when I was running NiMHs and the IR sensor couldn't read the temperature. I also keep logs of vehicle operation (conditions, motor/esc/battery temperatures, and run times) in order to determine safe run times, conditions, and end points to minimize risk of Lipo fire and maximize lipo cycle life.

    The rule about holding for 5 second doesn't work if one has diabetic neuropathy and can't feel or one is relatively tolerant of heat. Use a temperature gun.

    So where do my vehicles run:

    My UL-1 Hydroplane can drive a 40c 2S Lipo to 134F on a 7-8 min aggressive acceleration start and stop runs, but maintains 120s on WOT or 3/4 throttle continuously. Boats are harder on batteries. So to keep in safe operating parameters, I run at 3/4 to WOT continuously for 6-8 minutes. If I do the start and stop acceleration stop that really draws current, then I run for 2 minutes, let the boat sit and cool down for 2 minutes, and repeat the cycle for a total of 8 minutes of operation. I stop well above LVC.

    On my ERBE, Slash, and Summit, my 2S and 3S all stay in the 90s. Very good. I run til I'm down to storage voltage well above the 3.2-3.5 v/cell LVC.

    -------------------

    GN or someone here I think posts the following

    Motor ~ 180/190*F (82/88*C) maximum, ideally 140/160*F (60/71*C), temps can be 10*F higher inside the motor
    ESC ~ pretty much same temps / Fan comes on @ 150*F (65*C)
    Lipo's ~ 140*F (60*C) max, ideally 100/120*F (38/49*C).........


    v/cell 2S 3S
    4.20v = 100% 8.4v 12.6v
    4.03v = 76% 12.09v
    3.86v = 52% 11.58v
    3.83v = 42% 7.6v 11.49v storage level
    3.79v = 30% 11.37v
    3.70v = 11% 11.1v
    3.60v = 0% 10.8v

    -------------------

    So this is what I operate my Lipos by to keep as safe as I think I can get:

    1. Store between 40 and 80F in a fire safe box in Lipo storage bag. Storage bags are probably really rated for no more than 3000 mAh. I use 5000 mAh. Storage box is not locked but has a belt around it so the thing can vent in the event of fire.

    2. Charge on a ceramic tile away from flammables. Check and double check charger settings before starting and monitor for 1 minute before leaving the immediate charge vicinity. Never let charge temp exceed 110F; My charge temps stay at ambient range and don't heat up.

    3. Never store fully charged from more than 24 hours. I try to use the battery ASAP to get it between 40-90% of capacity, even for storage. Why?

    a. Maximum recharge life on any lipo is achieved by avoiding charging to 100% regularly and discharging below 40%. Something like 1000+ recharges doing this vs 300 recharges when doing the max charge discharge thing

    b. Full charge kept in prolonged unattended storage may stress the battery to the point it may puff and become dangerous

    4. I will use batteries multiple times for runs at different times and only recharge the battery once I get down to 40% storage capacity (7.6v on 2S, 11.5v on 3S). Never go below 40% because this starts to strain the battery to the point it starts to heat up (overdrawn).

    4. 143F is the absolute maximum Lipo temp above which there is very high risk of fire or explosion.
    For trucks, I actually keep operating temperatures in 80-110F (110F is the maximum safe charge temperature).
    For my boats I'll push it at 130F but it gets dangerously close to the 143F danger limit.
    I agree with the 10F above ambient rule

    5. To avoid heating up the batteries, one has to avoid situations which draw more current than the battery can provide. The C ratings provided by the manufacturers aren't always accurate, so one needs to monitor temperatures and if the temperatures are up, then one either needs to back off on run times or get a higher capacity battery with higher C rating.

    I run 5000 mAh 40C which give me long enough run times without heating up on my trucks. On my boats, the batteries can't supply enough current to keep up with the motor and ESC under certain conditions and end up heating up to the 120-130F range which is what should really be considered the maximum safe operating temperature in order to give a 10-15% safety buffer before getting to 143F. This means I probably need to run a better battery from a different manufacturer or something like 5000 mAh 50-60C from the same manufacturer. If I go with a different manufacturer, I still have to monitor the temps to determine the safe operating range. Can't compare C rating between manufacturers, but can get an idea of the the manufacturer is doing by assessing operating characteristics of their different C ratings.

    Your XO-1 needs lots of current so you really need a higher C rated battery than what you are using. Taking the battery and trying to cool it with the AC in your car runs the risk of starting a fire in your car if the thing puffs while you are trying to cool it. If you get a hot battery put it in a safe area and monitor for 30 minutes. Once you hit that critical temperature above 143 or it puffs you can't do anything to stop the reaction from proceeding ... never leave a hot battery in your car under any circumstances.

    Lots of starts and stops and rapid accelerations draw lots of current stressing the battery resulting in heating up the battery.

    I think what I have posted are generally accepted safe starting points and limits. Monitor your temps and as you learn, determine how far you want to push the envelope to balance safety vs performance. Push to the limit (as one does in racing) and run the risk of catastrophe.

    This is my experience. YMMV. Best wishes.

  11. #11
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    Thank you.

  12. #12
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    Dementor: Million thanks for such a detailed reply.... !!

  13. #13
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    One more thing

    Be very careful if you do you're own wiring. Shorting a Lipo can cause a thermal runaway resulting in very hot fire.

    Case in point, I stuck an 18v NiMH battery in my jacket pocket not realizing I had a penny in it. Unfortunately, the penny shorted the terminals resulting in super heating and melting the penny and partly burning my jacket. Fortunately no thermal runaway, but imaging had this been a LiPo ... probably 750F unstoppable fire. Good idea to put some kind of plastic cap over the terminals.

    A Lipo fire cannot be put out in water. If mine ever catch fire from a boat run, I'll let it burn in the pond so nothing else catches fire. On land, it has to be smothered with sand.

    Had I known all this information before hand, I would have just gone straight to LiPo and saved the money on NiMHs. Problem is, sometimes one has to have actual 1st hand experience (with or without a mentor) to get comfortable with the concepts espoused by various people and entities on the net or in books. And there is always the question of how much can I trust what the other person is saying. One can read about how to fly an RC airplane or helicopter or how to drive a car, but that vicarious experience is not the same as actively learning by seeing and doing. Simulators can give one practice on what to do but there is nothing on the line in a simulator compared to real risk when you actually try to do something.

    Having said that, my method of researching is to look at lots of sources. Truth over time. The more that independent resources seem to be saying the same thing, the higher the likelihood the information is on the right track. I used the most common denominators to determine the optimum operating ranges I posted above. The ranges may change as more data is discovered, but these are the best I could identify at this time.

    Have fun. Be safe.

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