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  1. #1

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    Charging multiple Lipos

    Hi all

    I am opening an outdoor rc car track here in Ireland to allow people to arrive and hire my cars ( 2 wd 1/10 slashes ) i am looking for the quickest and best way to recharge multiple lipos as possible.

    Can someone tell me what would be the best combo lipo/motor to use, and expected run times?

    The lipos, chargers and motors would need to be as reliable as possible.

    The titan motors in the 2 slashes i bought lasted 12 and 13, 7.2 batteries until they died within a day of each other with no more than running them on a flat 1" grass surface.

    All info greatfully accepted

    Thanks in advance

  2. #2
    Community Moderators Foxy's Avatar
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    RE: Charging multiple Lipos

    For RWD SC racing of 5 minute heats, you'll need batteries of at least 4000mAh at 25C in hard cases. These will give about 25 mins actual runtime I would expect, from full to cutoff.

    For charging I recommend you consider a few 4 way chargers (can charge 4 batteries at once), such as these...

    http://www.hobbyking.com/hobbyking/s...y_Charger.html

    This charger needs a DC power source, and depending how many batteries you will need to charge simultaneously, you need to consider your power requirements.

    Although a 2S battery is nominally 7.4v, when fully charged they are actually 8.4v, so that's the number you need to work with when considering charging requirements, since for at least the last 10 minutes of the charge, the voltage will be that high. Now you need to consider how quickly (therefore at how many amps) you want to charge the batteries. Since they will be loaners, I expect you will be going for maximum life charging methods? Getting the most cycles as is feasible, while still charging the batteries in a reasonable amount of time. In order to achieve this goal, I would say charge the batteries at 0.5C. 0.5C of a 4000mAh battery is only 2 amps, considering the charger will also have to balance the cells, lets make it 3 amps to get it within our 2 hour charge time. That should give you a nice easy charge that won't hurt the battery and will be finished in 2 hours, it also keeps your power requirements lower. So, let's take our example further, and consider how many batteries we will want to charge simultaneously...

    We know that for each battery, we will need 3A at 8.4v maximum, so thats 3*8.4=25.2Watts, lets say 25 just for ease of calculation. So your power supply needs to be capable of 25W per battery at a charging current of 3A.

    So, as you can probably imagine, if we want to charge 12 of these batteries in 2 hours, you will need (3 of those chargers obviously) 12*25W and 12*3A, so the power supply needs to push out minimum 300W at a steady 36A. Lets take into account other factors such as inefficiencies of the power supply, power the charger itself needs, and add another 10% for safety and we end up with 350W at about 40A. Of course if you then wanted to fast charge them at 6A (would be finished in less than an hour), you can double that again, 700-750W at 80A. I don't know what your plans are for a DC 12v source, but one capable of that kind of output will be expensive.

    Hope this helps and gave you insight into the math you need to consider while doing this.
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  3. #3
    Community Moderators Foxy's Avatar
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    RE: Charging multiple Lipos

    By the way, for motors, I would advise 3000-4000kv brushless motors. You'll also need a speed control to run brushless of course...

    This is a very reliable combo with good but not mad speed. 3000kv 13 turn, good speed for amateurs.

    http://www.hobbyhot.com/HOBBYWING-EZ...mbo-ME158.html
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  4. #4

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    RE: Charging multiple Lipos

    Ummm ok my heads boggerling.

    Wow that is very in depth thanks very much.

    was going to be using 240v mains supply to charge the batteries so i dont think getting power to the batteries would be a problem.

    If each battery gives 25 mins runtime i would need 2 batteries to cover an hour but it takes 2 hours to charge each battery so i would need 4 batteries per car i think ?

    What about motors? Are the titans usually that bad?

    Thanks again

  5. #5
    Community Moderators Foxy's Avatar
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    RE: Charging multiple Lipos

    Mains AC power is not compatible with DC batteries unfortunately. If you want to use mains power, then you will need either a charger with a built in AC/DC switching power supply, or a DC power supply that you can plug into the wall to use to power the chargers (real car batteries in parallel is another good source too, but then you need to have a means of charging them occasionally too).

    The problem with chargers that include an AC/DC supply, is that the built in supplies do not deliver many amps You'd need many chargers and chargers which include AC/DC power supplies are also usually double the cost of ones without. Basically, for your purpose, by far the most sensible way to go is either a big bank of car batteries at the track wired in parallel, or a FAT DC power source. AC chargers are not going to be the ideal solution to the problem.

    For example, I have a nice dual charger, I can charge two batteries at once, to power it I have a 200W 24A DC power supply which plugs into the mains and my charger plugs into that. When I'm out in the field, of course I can charge off my car battery. My charger, as most good ones, can only accept 12v DC power, so plugging it directly into the wall is not an option. With this charger on this power supply, I can use up to 200W as long as I don't try to exceed 24A current delivery, I can charge 2 3S batteries simultaneously at 10A if I choose to. If I exceed either the 200W, OR the 24amps, I will have charger errors. If it had an AC built in supply, I would probably not be able to charge more than one battery at 10A or 2 batteries at 5A.

    What a lot of people do is use the 12v rail of server computer power supplies to provide power (as they are usually high wattage). As long as it provides 12v of DC it can be used, as long as it can do what you demand of it without exceeding the PSU's output in terms of Amps or Watts.

    If you need to cover an hour of running (I assume you are planning to charge for hire per hour?), I would suggest making them 5000mAh batteries at 25C, and simply giving a charged pair to each user. Two 'should' last an hour of near constant running, but most people do not run constantly, and will probably give you back at least one pack with a good charge still in it. As for charging time, you can fully charge a lipo in half an hour without danger of damaging it by charging at 10A (check that the battery says it can be charged at 2C), but it will reduce the number of useful cycles you will get out of that battery, and increase your power requirements for charging SIGNIFICANTLY!!
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  6. #6
    Community Moderators Foxy's Avatar
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    RE: Charging multiple Lipos

    Yes, Titans are bad. They're good when they work but they just don't last. Get the brushless combos I linked, you'll never have to worry about them, completely maintenance free and 100% reliable. If you go brushed motors, you will need to maintain them regularly, more trouble than its worth.
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  7. #7

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    RE: Charging multiple Lipos

    How about if i buy a car batery charger and connect that to the rc battery charger would that have enough amps and watts to charge plenty of lipos?

    I hope to have 15 slashes being used so i will need 15 of theTurnigy 4x6S 400W Lithium Polymer Battery Chargersyou sent me the link to all charging 45000mAh batteries at 25Ceach on an on going basis. That is at peak usage of course. so i could be charging 60 of those lipos at a time

    What you think is the best set up?

    Just dont want to waste money on one way and it to be wrong





  8. #8
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    RE: Charging multiple Lipos

    Hey Henry!  I think what you're doing is a great idea.  I'll be very interested to hear how it works out for you.  I'm curious tho. Are you doing this as part of a marketing plan for your hobby shop?  i.e. get folks interested in RC, then sell them cars/parts.  Or, are you just doing it for the fun of setting up a track and hoping to make a few bob renting out the cars?
    Just a schmoe....

  9. #9
    Community Moderators Foxy's Avatar
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    RE: Charging multiple Lipos

    A car battery charger does not deliver high current at all, not gonna work to power even 1 charger, let alone several.

    You plan to have 15 cars running pretty much full time...You're right you're gonna need 60 batteries, but I don't think you'll ever need the capacity to charge 60 batteries simultaneously, I would have thought that 30 charge stations would do it, all balance charging full time at 6A (my recommendation, as it gives you about a 50 min charge time per battery while trying to still get max life out of the batteries).

    So you'll need... at max capacity, 8 of those 4 way chargers (you'll have two spare charge ports), charging 30 8.4v batteries at 6A (50W*30=) is 1500W potential peak wattage and total current delivery required of (30*6A) 180A. LoL. Have you considered the electric bill for this?? lololol.

    So basically you need a 1600W 200A power supply if my math isn't letting me down, and allowing for a little slack. If you want to charge them faster than 50 mins, it goes up some more. Obviously if you really want 60 charge stations, it doubles.

    There may be some kind of industrial or whatever charging unit available that I don't know about. Given the number of units you are planning to do it with, you should definitely look into it before buying 8 chargers and a 2000W 300A 12v supply (lol), but what you want to do can be achieved this way. You may find cheaper 4 way chargers if you look around too, I'll keep my eye out, but these turnigy ones are very good for the money, I think they'd be a good choice.

    Consider the alternative...30 $50 AC chargers limited to 5A charging (70 minute balance charge for a 5000mAh battery).
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    RE: Charging multiple Lipos

    Hi Rob

    It will be a track with a hobby shop as well, if i make wages i be happy

    Foxy , you have been a great help but have you any idea where i could get such a unit that will run off mains to give me enough power to run2000W 300A 12v to charge my lipos

    The charging unit that came with my slashes can charge 2 batteries ( not lipos ) and it plugs into the mains electricity.

    Lots of questions i know, hope its ok.

  11. #11
    Community Moderators Foxy's Avatar
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    RE: Charging multiple Lipos

    At how many amps can your AC charger charge two packs simultaneously? Just curious, if its up to the task, and its cheap enough, buying 15 of those might be a better answer, but it needs to be able to work at 12A all day, which not all AC chargers could do I don't think.

    I'd say use one of these for every charger...cheapest answer really and they are more than adequate.

    http://www.hobbyking.com/hobbyking/s...35A_350W_.html

    Tally it up, 8 chargers at 120 bucks and 8 power supplies at 33 bucks (1240), plus delivery and tax, lets say another 250? You're at the same price now as if you'd just bought 30 AC chargers in the first place, however, those chargers with these power supplies will be a lot better than a $50 charger with an AC supply built in. Now throw in the motors and escs, 80*15 plus delivery and tax, lets say another 1400, you're looking at about 1855 quid for a complete brushless motor and lipo charging setup for 15 cars, which isn't actually that bad at all. Batteries are about 25 bucks each for what you want to do, here's a good and cheap one, keeping all your shopping in one place... http://www.hobbyking.com/hobbyking/s...case_pack.html

    So 60*24, another 1600 bucks delivered, now you're looking at about 2.8 grand in sterling for good quality reliable stuff that exceeds your requirements of it (first rule of RC durability) and all you need are the cars.

    If you're going to go ahead with orders of this size, make sure you contact hobbyking first, they'll give you a good additional discount for this kind of volume I'm sure.
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  12. #12
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    RE: Charging multiple Lipos

    http://www.rc-monster.com/forum/showthread.php?t=27554
    I use that to power my chargers. The power supply can put out 47 Amps @12Volts
    I figured it out I can run 5-6 cheap $20 chargers on that one at once. I use it currently for 2.

    Foxy I had a similar power supply to that from hobby king it blew out in 5 minutes, and was rated for 2X more than I was using They might sell decent batteries, and chargers. But I will not trust their AC-DC power supplies after that one. I then went to normal PC power supplies,and found the 12v rails weren't able to deliver the power usage out then finally ended up at that sucker I linked
    With great speed comes greater repair bills.
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  13. #13
    Community Moderators Foxy's Avatar
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    RE: Charging multiple Lipos

    Can't help thinking you were just unlucky, but anyway, there are myriad power supplies available.
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  14. #14
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    RE: Charging multiple Lipos

    ORIGINAL: Foxy

    Can't help thinking you were just unlucky, but anyway, there are myriad power supplies available.
    well in the one I bought within one month after I ordered it (took a month to come via slow post) there were 30 negative reviews all saying the same thing(read the reviews AFTER mine burned) so I doubt it was me alone. It was a new product at the time I ordered it and 2 months later they removed it and replaced it with one that looked exactly the same (diff name) and that had a pile of negatives within 2-3 months stating the same issues. I took it apart the soldering on it was so half assed it wasn't even remotely funny. The 5V fan was connected to a 12V rail which cause the fan to burn up, and the voltage regulators to burn up VERY shortly after(which the one review said and I couldn't believe till I opened it up)...
    With great speed comes greater repair bills.
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    RE: Charging multiple Lipos

    Thanks for all the feedback and opinions.

    Anyone any idea if these cars are hired out on an ongoing daily basis how long the motors will last? For example is there a stat for how many hours various motors will run for? or does anyone have any idea?

    Also it is very wet here in Ireland so the cars will be getting soaked with rain etc, will the brushless motors be ok in the wet?

    Thanks in advance

  16. #16
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    RE: Charging multiple Lipos

    Hey bud i have a seen a lipo charger that charger 10 batteries 1A-20A i think its a 1000watt.  It had power supply for USA and Europe with a switch on the back to switch from 110 to 240 volts.  It was $1500.  This was at my local hobby store this guys has money so he buys wierd expensive things.  just get a charger like that.  His charges only take 10-20mins per battery with a 5000Mah Lipo,  Its crazy fast  but i dont fast charge my batteries.

    As for Titan they sux it was cost you more money to keep replacing them, instead get a Tacon Motor they are brushless and awesome i have 2 of them and the work great, but i mostly use Castle Creation but they would be more expensive to replace and plus i would not rent out them motors to newbies.

    thats my thought if you want the name of the charger let me know ill ask my Hobby shop owner
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    RE: Charging multiple Lipos

    any multi charger such as the hitec x4 sold in your country would already have the 240 volt plug.

  18. #18
    Community Moderators Foxy's Avatar
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    RE: Charging multiple Lipos


    ORIGINAL: zman5000

    any multi charger such as the hitec x4 sold in your country would already have the 240 volt plug.
    Need to know how many watts the power supply can support and how many simultaneous amps. It wouldn't be much good for this guy's use if it only allowed 4 batteries to be charged at 2A each.
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  19. #19
    Community Moderators Foxy's Avatar
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    RE: Charging multiple Lipos


    ORIGINAL: Henryslash

    Thanks for all the feedback and opinions.

    Anyone any idea if these cars are hired out on an ongoing daily basis how long the motors will last? For example is there a stat for how many hours various motors will run for? or does anyone have any idea?

    Also it is very wet here in Ireland so the cars will be getting soaked with rain etc, will the brushless motors be ok in the wet?

    Thanks in advance [img][/img]*
    The titan motors won't last more than a few runs. The brushless ones will last a long time, and usually have sealed cans (semi waterproof), the ESCs you may need to take some additional waterproofing steps.
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  20. #20

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    RE: Charging multiple Lipos

    OK so i have ordered 2 of the brushless motors and escs, 4 of the lipos batteries and one of the chargers Foxy recommended along with the power supply Syco sent me a link to...just have to wait until they arrive and i get to use them

    Do any of you know any tracks that have websites who hire out rc cars?



  21. #21
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    RE: Charging multiple Lipos


    ORIGINAL: Henryslash

    OK so i have ordered 2 of the brushless motors and escs, 4 of the lipos batteries and one of the chargers Foxy recommended along with the power supply Syco sent me a link to...just have to wait until they arrive and i get to use them

    Do any of you know any tracks that have websites who hire out rc cars?

    What Motor and esc did you buy and lipos just wondering.

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    RE: Charging multiple Lipos

    I ordered 4 of theseZIPPY Flightmax 5200mAh 2S2P 30C hardcase pack one of theseTurnigy 4x6S 400W Lithium Polymer Battery Chargers
    and one of these which arrived today
    http://www.rc-monster.com/forum/showthread.php?t=27554plus 2 of the brushless motors and escs foxy recommended which as we speak have just left Hong Kong

  23. #23
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    RE: Charging multiple Lipos


    ORIGINAL: Henryslash
    Do any of you know any tracks that have websites who hire out rc cars?

    Not that I'VE ever heard about. It's getting hard just to find a track! The nearest one to me, Iheard, just closed. The only one left is over an hour away. Good thing I've got ten acres to run on!

    Just a schmoe....

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    RE: Charging multiple Lipos

    Hi all

    I got my power supply i went with a HP 12.5V 47A and was wondering if someone could tell me how many of the 4 way chargers i could connectto it? Maybe Foxy has an idea?

    Thanks


  25. #25
    Community Moderators Foxy's Avatar
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    RE: Charging multiple Lipos

    4 batteries at 6A charge=24A. You will struggle to power 2, but it may be possible. If you give the power supply a hard time though, it may not last long. I'd recommend one of those for EACH charger, at least then you have the option to fast charge (4 batteries at 10A) sometimes.
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