Figuring out what batteries I will need for a new purchase

Discussion in 'Electronics & Electrics' started by OPM881, Apr 20, 2012.

  1. OPM881

    OPM881 Member

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    ----EDIT-----
    Update on page 2

    So recently I have decided that I need a way to go get my car from the uni bar near my place after I leave it there after drinking. A mate recently was talking to me about electric skateboards and I figured "Hey, that doesnt sound like a bad idea" so decided to do some research and get one. I found one in the states that I wanted, but it was going to cost $400 and with a $1100 car bill on the way I couldnt afford it. However, I stumbled across one of the same design, but a different brand from what I can tell, and uses a 150watt motor. I am thinking of replacing this motor, but that really just depends on what kind of speed I can get with it. If it goes fast enough, and lasts long enough, then I wont bother just yet. Anyway, the problem with my recent purchase is that it doesnt have the batteries for the board. They are the only part missing. Having a look around, other boards using a 150w motor seem to be using 2*5amp 24volt batteries. My question is, how can I(when I get the board) determine what size of battery would be best to use?
     
    Last edited: Aug 13, 2012
  2. mittons

    mittons Member

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    any chance of a linky ?

    to confirm specs and what batt type
     
  3. aXis

    aXis Member

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    Usually the motors are rated for a particular maximum voltage. Pick any battery you like up to that maximum, or if you go over that voltage then just dont go full throttle on the speed controller.

    My RC aircraft motor (300 size so about the size of a film canister) does about 25A at 14V, so over 350W @ 18000RPM. Other similar motors will do higher torque at lower RPM for a similar power level. It is trivially cheap and easy to buy the speed controllers and LiPo batteries for them.

    RC car motors and speed controllers will be a better option though, slightly more expensive but they have better heatsinking as you generally dont get the same airflow over them.
     
  4. Paronga

    Paronga Member

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    did it never occur to you to take public transport or some such?
    sober people hurt the selfs skate boarding without a motor....
     
  5. Dingostolemyghz

    Dingostolemyghz Member

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    150W is pretty poxy.
    A more powerful way to propel the skateboard would be to remove one foot from the board, place on the ground and push.
     
  6. Hive

    Hive Member

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    :thumbup:

    Best option would be a nice big fat LiPo pack.
     
  7. aXis

    aXis Member

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    The electric scooters are about that and it's not too bad. Even better, 2 x 150W motors, each with a small pinion gear on to the left and right rear skateboard wheels. Or quad drive!

    You can get dial control servo testers, plug one of those into a brusheless speed controller and you'd have a handheld throttle.
     
  8. xc351

    xc351 Member

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    will prolly still be illegal to drive/ride drunk people get done on push bikes all teh time.

    look at a crusin cooler i hav eone with the the cooler wagen (extra esky) i had decals made up (professionally) to say the motor is 200w maxium limit. how ever i now run the 500w 24v motor on 36v with 3 x 24a/h baterys.

    it goes great and can do 5km trips to work with its trailer full of beer easy as. mainly gets used aus day doing laps of the strand or to mates bbq 2km from my place
     
  9. OPM881

    OPM881 Member

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    http://www.ebay.com.au/itm/33071504...NX:IT&_trksid=p3984.m1497.l2649#ht_722wt_1348
    Thats the one I got, which I am pretty sure is simply a different branded one of these:
    http://www.ebay.com.au/itm/Skateboa...ltDomain_0&hash=item3a6fc2272c#ht_3295wt_1348
    I have emailed the guys of that second one asking what battery setup they use but they havent replied yet(due to time difference I think).

    Now, first, normally I can get a ride to my place from someone who lives about 20 mins away from the uni(I live 5 by car), but getting to my car the next morning its either walk, or pay the $2.20 to get a bus, if it rocks up, which run once an hour and are never on time.

    @xc351 - I would be sober when using it, would be using it to get to my car the next morning.

    As for using a normal skateboard or public transport, where is the fun in that?

    Anyway, onto questions.
    @aXis - would this be on the motor anywhere? Like on a sticker or engraved or something?
     
  10. aXis

    aXis Member

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    Usually, however the nameplate value is usually the typical maximum "rating", not the absolute maximum. There should be some sort of identifier though and you might be able to look up it's specs online.

    It's a bit like overclocking really. In the end, most low voltage motor ratings are really just with respect to heat. As long as the motor windings stays cool enough they can take much higher than typical voltages / currents. Push it too far and they melt.
     
  11. SLATYE

    SLATYE SLATYE, not SLAYTE

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    It'd be good to find out what the 'normal' batteries were. If they're anything other than LiPo, using the standard charger with LiPo batteries is a recipe for a nice lithium fire and/or explosion.

    The sensored ones are also much better for high-torque, low-RPM thing (like starting on a skateboard). Definitely worth having a car one on this rather than a plane one.
     
  12. noboundaries-au

    noboundaries-au Member

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    Indeed, most likely Sealed Lead Acid.

    LiPo's have a lot of grunt, but an SLA has both grunt and capacity (and are reasonably cheap). Id recomment using them, and Ive not seen an electric scooter (young people or old people type, NOT powered by SLAs)
     
  13. OPM881

    OPM881 Member

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    Yea, well the guys in the states that sell the same sorta board emailed me back(they didnt really answer my questions, but they did help slightly) saying they use 2x12v lead acid batteries. They didnt tell me the amps or if it is wired serial or parallel or anything else really, but still, better than nothing.
     
  14. aXis

    aXis Member

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    LiPo's will beat an SLA on both current and capacity. Take a common 7Ah SLA for example - you could easily fit 4 x 20C 4S1P 5000mAh batteries in the same package, for a grand total of 20AH @ 14.8V, with the ability to sustain a 400A constant load. Problem is it would cost about $120 versus $30 for an SLA.

    That said, even a single 5000mAH pack would be a reasonable solution at $30, and quite compact. Or 4 x smaller (and much cheaper) 2200's or 2600's for a long thin pack under the skateboard - you could even use one per motor to simplify the wiring.

    Personally I recon you could make a kickass motorised skateboard with LiPo and RC car parts.
     
    Last edited: Apr 23, 2012
  15. TERRA Operative

    TERRA Operative Member

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    check out hobbyking for cheap lipo batteries and chargers. You might even find a motor (although they're probably too small for a skateboard).
     
  16. aXis

    aXis Member

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    I did the math and you can easily use $25 car motors from hobbyking :)

    Pretty typical ratings is 3 cells LiPo (11.1V), max 20 - 25Amps. If you do the math that's around 220 to 270W max power. Strap on four of those bad boys and you could have up to a 1kW skateboard - even taking into account transmission efficiency you're over 1 horsepower.
     
  17. Phido

    Phido Member

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    Im actually working on making my own electric scooter, board thing.

    I got some 200w scooter motors for ~$20. I figured 2 x 200w = 400w would be fine for a scooter or skateboard given you usually give them a bit of a flick with the foot to get them started. That 400w is to just keeping you going.

    http://www.oatleyelectronics.com/

    was going to use SLA batteries. Jaycar has a wide assortment of odd shaped 6v and 12 v SLA batteries (some 30mm thin!). Given how heavy a person is the difference between Li and SLA is not going to be much.

    Im over 120kg and over 6'6 so using a kids scooter scares me. I can build something to take my weight and also have some cooler features, integrated lighting (indicators, brakes, headlights, maybe a pic controller estimating range, speed etc).

    Unfortunately I haven't had much time to work on it. I've got the parts sitting in a box.
     
  18. Renza

    Renza Member

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    You might want to note that an electric assisted bicycle must have a motor under 200w to be road legal in Australia. I assume that the same would apply for scooters
     
  19. Phido

    Phido Member

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    This is not for on road use. Just getting around big private sites etc.
    One of the main reasons for double rear wheel is to increase load carrying capacity. I could in theory never hook up the other motor so it would remain under 200w.

    The problem is most cops don't know how to rate an electric motor, basically what ever the motor claims it to be.

    Generally people don't really care about electric bikes. They are quiet, people don't hoon around on them all day and they are generally used by much older people.

    2 stroke conversions in the suburbs will get you pulled up. Esp if you take the same route every day and floor it everywhere early in the morning.
     
  20. OPM881

    OPM881 Member

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    Massive bump time!
    Ok, used 2x 12V 9AH batteries, and it seemed to work fine, however I have come to an issue where for some reason the batteries were not charging. Went and got a stand alone 12V SLA battery charger and it says they are charged as well. I have taken the motor off its frame, the whole thing is still hooked up however, and I am currently in the process of running the batteries down some.

    Ok, so, after I ran the motor for roughly 1-2 mins, the batteries did state that they were not charged fully and so I hooked them up to the stand alone charger, and it charged them in a matter of mins. I have hooked the whole skateboard system back up and am now running the motor. It really isnt running as fast as it should be(I am basing this off the sound it is making, not the same as it used to), even though both batteries are supposedly full. This begs the question, could the controller board be stuffed? The brains of the whole unit?
     

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