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  1. #1
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    motor cutting out

    the kit i put together has problem where the motor only stays on for a second or two and then cuts off, or if i use only partial throttle approximately 1/4 it might stay on for 4 or 5 seconds then cut off. this problem dose not happen when the wheel is off the ground. the only thing i can think it might be is the batteries not putting out enough amperage but i have been assured that they should be able to.

    i bought a 1000 watt electric bike kitt off ebay heres the link to the kit
    http://cgi.ebay.com.au/ws/eBayISAPI....m=350233496441

    for the batteries i done something slightly dodgy but i think it should be able to be made to work.
    i got 3 li-po 14.8v 4000mah batteries off of ebay and wired them up in series heres the link.
    http://cgi.ebay.com/ws/eBayISAPI.dll...EOIBSA:US:1123

    sorry about any spelling mistakes i'm sure theres lots
    can some one please help.
    Last edited by shift; 10-21-09 at 03:30 AM.

  2. #2
    Member toyotaboy's Avatar
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    I have the 800watt version of that. Always check your voltage first. Not sure if lipo batteries would work or not (in theory they should be the best thing to use since yours is 10c continous, or 10 times the rated amperage), which in your case would be 40amps. Most people don't use lipo because they're even a little more pricey than lithium-ion (but even lighter).

    That kit only requires 2-3 amps since it's 3-phase AC, so it's not an amperage problem. I would question whether the controller is working properly. If it's working off the ground, there is no load, and therefore the controller just runs freely. When you have load (weight), the controller has to do some math to figure out what position it's in.

    One thing I have to ask, you do have the 5-pin connector besides the 3-wire motor leads hooked up right? That's the sensor leads that lets the controller know position.
    I ride the asphalt, one mile at a time

  3. #3
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    i will have another look at the 5 pin connector and make sure its getting a good connection but i know its connected in the right way, thanks for the battery info.

  4. #4
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    Normally LiPo's use a BMS (battery management system) to protect the cells. If the motor is drawing too much current, it could cause the power to cutout. Since this occurs when you use the bike (under load), but it doesn't occur with the wheel is lifted off the ground, I'm guessing the battery's BMS can't handle the amp draw under load... that's why it's cutting out...

    If this is the case, you'll need another battery with higher rated BMS... or you'll have to bypass the BMS... which could damage the battery...

  5. #5
    eBiker alfonsopilato's Avatar
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    I agree with ecowheelz, and this because I've experienced this myself.

    BTW this sounds very similar to this recent post: Bike cutting out - Help please!!
    .. same symptoms, under load the system shuts down. If you read this post, you will see responses inline with those of ecowheez.

  6. #6
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    i only have a limited knowledge of this gear but as for the bms idea these are the batteries ive purchased http://cgi.ebay.com/ws/eBayISAPI.dll...EOIBSA:US:1123
    they wouldnt come with a bms installed would they?
    and i checked out the other post about this simular problem i was thinking it might be the controller as was metioned in the other post any thoughts?

  7. #7
    Senior Member nwmtnbkr's Avatar
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    I would agree with the others--it's probably the battery, those aren't very good specs (wiring in series you may have doubled your voltage, but your AH remains the same, those are only 4 AH batteries). There's a discussion on another forum about the cost of LIFEPO4s and whether the cost will fall. The interesting thing is that one vendor is offering Thunder Sky cells at $1.10 per AH (plus a 10 per cent Customs fee). That's got me seriously considering buying 8 20AH cells to build a battery pack for my 24V system. The BMS will be additional and I'll probably buy the 8-cell, 40A BMS that Battery Space sells.

  8. #8
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    would this problem be fixed buy doubling the AH

  9. #9
    Senior Member nwmtnbkr's Avatar
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    Truthfully, I think you'd want a minimum of 10AH for an e-bike. With LIFEPO4s it's not just a matter of stringing up low-powered battery packs in series and getting power. Unlike SLAs, the LIFEPO4 battery packs are constructed with a safety feature--a computerized card that will manage power discharge and charging called the "Battery Management System" or "BMS." Before purchasing LIFEPO4 packs, you need to know the specs on your controller, especially the maximum discharge rate. What kind of BMS do those tiny RC batteries have? That may be part of the problem, too. The BMS in these packs probably has very low maximum discharge rate. When people that have e-bikes with controllers that can demand 35A when the throttle is opened up buy a low AH LIFEPO4 battery with a BMS designed for lower power demands they quickly become unhappy. The BMS will do its job and cut off the battery to protect it if the controller is demanding more power than the maximum discharge rate allowed by the BMS. I'm not sure stringing more of these low-powered packs will help you. You might try to resell the packs you bought to an RC hobbyist, but you'll not get what you paid for them. Otherwise, you may have to disassemble the packs, get more individuals cells a BMS with power ratings consistent with your controller and build a completely new pack.

    Elite Power Solutions has a good sale on 12V 20AH LIFEPO4s--$128 each. http://elitepowersolutions.com/produ...products_id=74
    These are comprised of 4-cell prismatic Thunder Sky LIFEPO4 batteries and don't have a BMS so you'd want to add a BMS. You can take the cells out of the gray plastic case they come in if you want to put them in a customized container. If you aren't in a rush, you can call EV Components and special order the same 20AH Thunder Sky prismatic cells for a slightly lower price ($1.10 an AH plus a 10% customs fee; I'm seriously considering that option to build a 24V pack since the total cost will be $193.60 plus shipping). The special orders to Thunder Sky only go out once a month so there's a 6-8 week wait from the time you place the order until EV Components receives the cells from the factory. http://www.evcomponents.com/ Again, you'll need to get a BMS to add to the battery pack you build, which means you need to know the specs on your controller.

    Good luck.
    Last edited by nwmtnbkr; 10-25-09 at 01:23 PM.

  10. #10
    Senior Member misslexi's Avatar
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    The BMS with RC batteries is in the charger generally, if at all. These packs have outrageous C discharge rates. The problem is they are power dense rather than energy dense so you'll need to package a lot of them together in order have sufficient energy stored. It's possible they offer too much of what eBikes don't need in return for a high price and the added complexity of deployment.

  11. #11
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    4AH? Holy cow - that's not nearly enough capacity to supply most eBikes for even a short distance. Most Li's should be 20AH to deliver enough start-up and full power current.

    Nilar builds some very interesting NiMh choices - these aren't your usual NiMh batteries either. I've been sour on NiMh for years but these have got me revisiting the chemistry.

    http://www.nilar.com/

    I heard about some newer lead-acid designs that aren't your grand dad's lead batteries?

    Lipoe is cool but you gotta be a good, decent, safe tech to mess around with that and my experience is 20% cell failure rate even under ideal conditions. Moral is - if you're gonna build your own LiP packs buy 20% extra cells and be prepared to troubleshoot battery problems.

  12. #12
    Senior Member nwmtnbkr's Avatar
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    Broadway Joe,

    I think LIFEPO4 technology has improved some. I wouldn't buy LIFEPO4's directly from a foreign vendor. The sources I listed are US companies and they warranty the cells they sell so you shouldn't need to order extra cells. Where people experience issues with LIFEPO4s is with the BMS. Early versions of BMS were mere problematic. There still are potential issues, but there are more choices available now. One problem is that you do need to know the power specs on your controller to get the appropriate BMS. Otherwise, your battery pack may shut down constantly.

  13. #13
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    nwmtnbkr - I hear you buddy! It's definitely getting better out there and you pointed out some great resources.

    Frankly, I haven't been following battery stuff too closely - still running my own personal mixture of Lith, lead and Nickel across several platforms - really tempted to try those Nilar packs or maybe a Thunder Sky Lipoe4 - the price seems righteous enough compared to only a year ago?

    But still - this OP needs to get a larger pack and probably tailor a BMS to their controller fer sure...



  14. #14
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    sorry about the bold - never been too keen typing...

  15. #15
    Senior Member nwmtnbkr's Avatar
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    No problem. I looked at the link you posted on Nilar, but that seemed geared toward custom, OEM orders. Is there a retail source for Nilar packs that you're aware of other than Colorado Advanced Battery, which seems to only offer a 48V Nilar pack for e-bikes. My system is 24V and I'd prefer to get a 24V pack rather than having to upgrade my controller and throttle to accommodate more volts. I've been happy with NIMH for other applications in the past.

    Edited--I take it back Colorado Advanced Battery offers 2 24V Nilar batteries--a 10AH and a 20AH. The prices aren't too bad, either. Here's a link for anyone interested. http://www.coloradoadvancedbattery.c...b-n-24v20a.htm
    Last edited by nwmtnbkr; 10-29-09 at 07:19 PM.

  16. #16
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    Quote Originally Posted by nwmtnbkr View Post
    Edited--I take it back Colorado Advanced Battery offers 2 24V Nilar batteries--a 10AH and a 20AH. The prices aren't too bad, either. Here's a link for anyone interested. http://www.coloradoadvancedbattery.c...b-n-24v20a.htm
    I'm under the impression these NiMh batteries are similar to the NiMh chemistry that Toyota uses. Far, far better at delivering high current than the NiMh F-cell packs that I've used in the past. I also like the Nilar dimensions - they come in what seems to be a useful size for replacing 12V - 10-12AH SLA's? 'Looks like they might fit nicely in those Battery brackets/mounts Electric Rider offers?

    But, I also like what I see from Thunder Sky in the LiPOE chemiistry - sure has come a long way in a short time...

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