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Old 03-23-14, 11:43 AM   #1
JustInTimePA
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Post Put together a nice e-bike but I messed up on the battery

Hi all. Looking for advice. I bought a 26" Mongoose bike and a 1000 watt front wheel conversion kit. Everything works great with one exception. I made the mistake of trying to save a few pennies by buying 4 12V-18AH Lead Acid batteries to provide power. They are rear rack mounted with the controller in a cloth pouch. It looked okay but at 50 pounds of battery, it was too unstable for me to ride it without risking my life! I crashed the thing twice before I finally gave up. Now it's collecting dust in my closet. Tried selling the lead acid batteries on Ebay for $100 + shipping but no luck.
Other than giving up on the idea of an Electric does anyone have some advice on where to go next? Ideally, from what I saw, a lighter battery, say 48 V 15-20 A/H LiPo battery pack mounted on a lower center of gravity would do the trick. Mounting it is a different story. It's the old story. I'm on a limited income and have no vehicle at the moment. Any help would be appreciated. Thanks..
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Old 03-23-14, 12:46 PM   #2
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Send us some pictures of the e-bike the way it looks now. Do you have the holes in the frame for a bicycle rack?
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Old 03-23-14, 04:46 PM   #3
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48v 8ah of Lipo would weigh about 2.2 Kg and easily power your kit for 20+ km, and your bicycle will still pedal like a bicycle instead of a drunk rhino .
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Old 03-23-14, 05:22 PM   #4
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Certainly a lighter battery pack would be preferable, but it's not clear to me why your current setup is so unstable. I frequently load my regular bicycle with 50 lbs. of groceries on the rear rack/panniers and have not had any stability issues. Is the rear rack securely attached and rigid enough to avoid swaying? And how are the batteries attached to the rack?
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Old 03-24-14, 10:19 AM   #5
JustInTimePA
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Thanks for the replies. The rear rack came with the kit but the support rods that attach to the rear wheel axels are not quite strong enough so they do tend to flex during a turn which makes the bike wobbly. Also the way I currently have the battery/Controller bag attached is with bungee cords which also aren't strong enough. One thing I didn't mention is that I have to carry the bike up a flight of stairs as I have no place to store it on ground level. (Apartment).
I took the bike out of storage today and I'll post pictures of my setup tomorrow. Again, thanks for the help.
P.S. "A Drunk Rhino" pretty much explains it..
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Old 03-24-14, 10:21 AM   #6
JustInTimePA
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Another question. Is an 48 v 8 ah really enough power for a 1000 watt bike? 2.2K and 20KM sounds okay.
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Old 03-25-14, 05:31 AM   #7
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50 pounds mounted up high on a rear rack will definitely cause handling problems. Converting your ebike to LiPo or LiFePO4 would be far better than lead acid in regards to stability, general performance, and possibly range (depending on the AH capacity).

If you can, post some more info on your E power system (brand/model, controller type, controller supported voltages, etc).
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Old 03-25-14, 10:44 AM   #8
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Don't forget the other expenses. Sure LiPo's great in terms of the amount of energy you get vs. the amount of weight in the battery, but it ain't cheap. I run 48v 10Ah Zippy LiPos I got from Hobby King. They cost about $200 plus shipping from HK. On top of that add another $200 from Progressive RC for a mid-range power supply and charger to make it all go. After the cost of andersen connectors to hook it all up, wiring, etc, etc. I was probably into it about $500. LiFePO4 from Ping at that voltage and rating is cheaper and safer. Same benjamins would bring you to 15Ah. Of course, LiFePO4 is heavier than LiPo, but nowhere near the tonnage you were toting with lead acid.
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Old 03-25-14, 11:07 AM   #9
JustInTimePA
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Thanks for the comments.. Here are a few photos of my setup. The manual I have for the conversion kit is weak on specs. but it looks exactly like this one I saw online. I paid for a 1000 watt motor and controller and I have to admit, it had great acceleration and speed the few times I rode it.
Here are what I believe the specs are:
Features:
  • 45 - 48 KM/H top speed
  • Provides you with a whole wheel with tire, not just the tire frame Takes less than hour to install
  • The kit includes motorized wheel, motor controller, speed throttle, power break lever, wire harness
  • Quiet and reliable brushless gearless hub motor
  • Motor specifications: 48v / 1000w / 470rpm
  • High motor efficiency: >80%
  • Motor diameter: 245mm
  • Drive system has no moving chains or gears, no friction, more efficient, less chance to break!
  • Brake shuts off motor automatically, saves energy, improves safety!
  • Thumb throttle with 3 LEDs indicator lights
  • Battery charger for charging lead-acid battery
  • Durable 600D Oxford cloth carrying bag along with a zippered main compartment for battery
Package Includes:
  • Powerful 1000W 48V brushless hub motor
  • 26" front wheel (the whole wheel with tire!)
  • Battery charger
  • 2 brake pullers
  • Electric controller
  • Thumb gear changer with battery power indicator
  • Battery power indicator
  • 2ea. handlebar grips
  • Rubber connecting harness (color will pick at random)
  • Battery not included
  • Special: Comes with upgraded battery carrying bag and end bracket for FREE
Battery Recommendation:
1. Electrokinetic cell battery ( Li, lead-acid, NiMH battery etc.) featured in nominal voltage 48v, nominal capacity not less than 17Ah is compatible with the motor.
2. Please note that the Battery Charger in the package is for lead-acid only and it will damage the battery if you use other types of battery
Hope this helps. It's looking more and more like I have to shell out for a LiPo or LiFePO4.
Thanks again..
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Old 03-25-14, 12:46 PM   #10
FMB42
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Electric e-bikes and e-bike conversions aren't cheap (especially when you start running LiFePO4 or Lipos). But then again, neither are gas conversions. However, the thing with electrics is that you can sometimes use one battery for several different e-bikes. I have a Direct Drive road setup and a "MTB" geared hub motor rig that use the same 36v LiFePO4 batt (sliding rack mounts make this an easy swap).
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Old 03-25-14, 02:30 PM   #11
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I can't tell from the picture but I didn't see any torque arm(s) nor are they shown in the list of items included. I think with 1000 watts on the front wheel, at least one and maybe one on each side would be a good idea.
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Old 03-25-14, 02:40 PM   #12
usnavystgc
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In my opinion, it is hardly enough. I have a 900 watt mid drive (pictured) that I use a 30ah pack on and it is sufficient for range but, cutting down to 8ah, that would honestly take me about five miles of all electric. I'm likely heavier than you. I attached another photo of my first ebike to give you another idea on how to mount the batteries. I hope it helps.


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Old 03-25-14, 05:35 PM   #13
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I'm not trying to be a jerk, but your setup seems a bit off. Your fork is turned around the wrong way, and I've read that suspension forks can fail under the torque of the motor. Also, you have rear suspension which appears to interfere with the stable mounting of the rear rack (notice the top of the rack mounted to the "front triangle" and the bottom mounted to the "rear triangle"). Honestly, I think an older mountain bike with no suspension and a steel fork would be better suited for this conversion.
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Old 03-26-14, 09:07 AM   #14
JustInTimePA
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Thanks all for the observations and advice. I have to make a move quick so I can take advantage of the warmer weather. I hope that is soon but it snowed yesterday! This site is great.. Wish I had discovered it sooner.
TTFN.
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Old 03-26-14, 01:38 PM   #15
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Yeah, that rear suspension and rack combo = terrible handling even with a light battery on there ( and as noted above, the pivot point from the swingarm mounted rack is no good. )

regarding the battery question, 8ah of Lipo can easily cope with the 1000w controller. no problem there.... and for the range factor, 48v x 8ah = 384 wh ( watt hour ) , at 40 kph you can expect about 15 wh/km = 25 km

at 30 kph, 10wh/km is perfectly possible with very light pedaling for a range of 35+ kms

usnavystgc, if you burn thru 8 ah at 48v in 5 miles... 384 wh / 5 = 76 wh per mile ( 5 miles = 8 kms = 48 wh/km ) your brushed motor must be smoking hot at the end of a ride and horribly inefficient.

For example :
https://www.youtube.com/watch?v=hoVzQAQlPQ8

This is from 2010, my chopper has foot pegs, no pedals and no chain, going 60 kph, i averaged 30 wh/km
---

RC bike, mid-drive, 2 stage reduction, 50 + kph no pedaling 40 wh/km ( way less efficient, less speed, more energy used )
https://www.youtube.com/watch?v=RuNtnYdoxzE

---

BMX, 48v, hub motor, 25 wh/km going 50 kph , again, no pedaling.
https://www.youtube.com/watch?v=uUIBteWJv6s



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Old 03-26-14, 02:00 PM   #16
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Your front fork is backwards. That will lead to screwy handling even without the electric kit. I think your best bet is to strip the kit off. Fix the fork and then trade the bike for a hardtail or no-suspension mountain bike. Then re-mount the kit and see how it works.

My guess is that you'll be fine with a hardtail and properly setup bike even with the lead battery. Keep in mind the net cost of this is near zero, since you can even get a bike with trashed front wheel.
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Old 03-26-14, 02:22 PM   #17
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agreed.

And a good pair of widest tires you can fit ( avoid soft rubber knobies )..

I like Holy Rollers by kenda ( best i've used for ebikes yet ) or equivalent.. k-rad is ok but wears fast. Hookworms are also great long lasting tire.

A rigid with good tires is a better ride than pogo-stick-like-suspension on any tire.
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Old 03-28-14, 09:00 AM   #18
JustInTimePA
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Thanks for the tips. Looks like I can get lesser a/h LiPo battery and it would handle the distances I need to go. As far as the front fork being backwards. I didn't really notice it before, but after you guys comments, I looked at it and sure enough it is 180 degrees off. Brakes should be front of the fork. Good eye!
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Old 03-28-14, 09:42 AM   #19
JustInTimePA
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Wondering where you guys would recommend buying a LiPo battery. Hopefully not from Asia. (Due to the long shipping times)
Thanks
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Old 03-28-14, 09:55 AM   #20
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FWIW, HK appears to have 6s 5Ah 20C and 25C Zippy and Turnigy battery packs in their US Warehouse.
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Old 03-31-14, 07:46 AM   #21
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Thanks G1nko, I'll check it out..
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