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dangers in converting your bike to an eBike for the first time

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dangers in converting your bike to an eBike for the first time

Old 07-03-09, 05:53 PM
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dangers in converting your bike to an eBike for the first time

Hi

a friend of mine wants to convert both our bicycles into electric ones NOT with a pre-made electric kit.
meaning buying the parts separately (motor, batteries, extra chains and cranks etc.)
I know very little about all this, he however has been reading a lot about it on the web, seeing a lot of pictures and video of kits and electric bicycles...

my question is:
is it dangerous to let him convert my bicycle and for me to ride it afterwards ?
what are the dangers ? what's the worst that can happen ?
I've heard of batteries exploding and burning
cranks failing and letting the motor swirl the peddles like crazy breaking legs


btw, we can't use electric kits that are on the web because it is illegal to import them to our country (it IS however legal to use them here) but don't let me get into that because it only makes less and less sense
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Old 07-04-09, 07:03 AM
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Originally Posted by gentler400
my question is:
1. is it dangerous to let him convert my bicycle and for me to ride it afterwards ?
2. what are the dangers ? what's the worst that can happen ?
3. I've heard of batteries exploding and burning
4. cranks failing and letting the motor swirl the peddles like crazy breaking legs
1. if you are going to do it, do it yourself, don't let your friend do it for you else, you wont know what to repair if you get stranded in the middle of a street far away from home.
Hauling a heavy bike by foot is no fun.

2. There isn't any real danger, you'll always have your normal bike breaks, the worse that can happen is that the battery or circuit board gets fried, and you'll have to haul the super heavy bike back home on your own.

3. this might happen only if you ever get a cheap build, and did not build the battery properly with the circuit protector, and it Only happens when it's recharging at home, not when you are riding.

4. this is non sense the majority of the electric upgrades are blushless hub motor - translation a regular bike wheel that replaces your old wheel, with a magnetic motor inside.

you still use your normal bike crank and chain, if there's no power your motor will stop right away.

so there's no chain wiping around if your chain ever breaks or whatever, it's not a GAS motorcycle.

you still have to pedal your bike, you can not just push a button an expect the bike to move on its own.

well it can but that type of build sucks.
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Old 07-06-09, 03:32 PM
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I've heard of batteries exploding and burning
1 - always use a fuse (or a circuit breaker) to protect your battery
2 - LiFePo4 and non-lithium batteries will not explode or burn, as long as you don't short-circuit them (use a fuse!) and use the correct type of charger. (always use a 24 volt LIFEPO4 charger for 24 volt LIFEPO4 battery pack, use a 36 volt SLA charger for 36 volt SLA battery pack, etc).
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Likewise, if you don't design your system to drive the cranks with a motor, you won't have to worry about the cranks hitting your legs.
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Old 07-07-09, 08:20 AM
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Originally Posted by cerewa
1 - always use a fuse (or a circuit breaker) to protect your battery
2 - LiFePo4 and non-lithium batteries will not explode or burn, as long as you don't short-circuit them (use a fuse!) and use the correct type of charger. (always use a 24 volt LIFEPO4 charger for 24 volt LIFEPO4 battery pack, use a 36 volt SLA charger for 36 volt SLA battery pack, etc).
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Likewise, if you don't design your system to drive the cranks with a motor, you won't have to worry about the cranks hitting your legs.
even with lithium batteries, the risk of the batteries exploding/burning is just during the charging time, not while you ride and drain power from them, right ?
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Old 07-07-09, 10:48 AM
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In my experience, doing this even from a kit can be dangerous. I would imagine doing it from scratch would be even more so. I ride a mountain bike with a front hub motor, and I never feel completely at ease while riding it. I've heard/seen so many stories of people snapping forks, breaking chains, getting something caught in spokes, having wires short out, motors freezing up wheels, etc, that this isn't something you want to do if you're not an extremely cautious and patient hobbyist who has a significant interest in trouble shooting.
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Old 07-07-09, 09:24 PM
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The good answers have already been given.

I'm an ebiker here from another forum.

Some just want to kit-convert the cheapest safe way:
that might be SLA batteries and a cheap front hub motor.

General wisdom, and I've learned the hard way: Front motors must, must, be on steel, not alloy forks.

A torque arm is a nearly vital necessity for any ebike of any real power;
even in an accident, the D axle shaft can spread apart steel dropout lips, and wind up the cord,
breaking vital wires.

Torque arm all ebikes? As a general rule, this is best.

Rear motors offer advantages of certain sorts.
Front motors also have their good points, especially for bike-speed ebikes (not over 20mph).

Ebikes are fun and they can be very neatly done by the home builder.

They can, with the new and safe LiFePo4 batteries (heavier than Lipo), take you clear across town and back,
and you just add your 150W or whatever, however, whenever you like.

Someday here I may tell about my very special "Stealth Cruiser" conversion, nearly finished now.
It will be a ride, all right, and =no front brake=

Only angels tread where fools dare to ride (no front brake).
I live in flat territory, no hills, no need to ever panic stop.
I know how to make a coaster brake, brake pretty good.
But I will not reccomend such a stunt for others: danger!
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Old 07-07-09, 09:30 PM
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Red face

I would say a lot more, easily, by referencing interested parties to a non-commericial, ebike-only forum, to specific thread/s only.

But, I have read the rules. Traffic is not to be diverted from this place, even for good intentions.

Ergo, I cannot cite specific links and hereby now ask that Admin review my recent posting record, and remove said links to a thread, elsewhere, that I authored.

I did not read the sticky guideline in time. MY fault, not the forums' fault.

I do not intend to make "waves" here. But I do promote ebiking for all, young and buff, or old and knocking at the knees:

every biker can become Lance Armstrong for the day.

And what is wrong with that?
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Old 07-09-09, 12:18 PM
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+1 on all the good info given so far! Especially re: bike & kit selection. I see in your original post that you mention extra chains & cranks - this implies, to me, that your friend may be planning to do one of the many chain driven conversions available.

If safety is a concern, you would do well to research hub motor kits - specifically, brushless, direct drive hub motor kits. Further, I would suggest you read as much as you can stand about these products as, sadly, there are many truly sub-par products on the market & it would be easy for the uneducated consumer to waste money or have a bad experience. Thankfully, you've found a good forum with many educated & experienced members, so pull up a chair & get your read on!
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Old 07-09-09, 03:40 PM
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Originally Posted by cerewa
2 - LiFePo4 and non-lithium batteries will not explode or burn, as long as you don't short-circuit them (use a fuse!) and use the correct type of charger. (always use a 24 volt LIFEPO4 charger for 24 volt LIFEPO4 battery pack, use a 36 volt SLA charger for 36 volt SLA battery pack, etc).
thanks for the info so far.
forget what I posted about the stupid chain...that's won't happen the way i'm building it...
My only concern left is about the batteries.
I still didn't get an answer to whether the risk of the batteries exploding/burning is just during charging time (even with lithium batteries, regardless of using a fuse) ? anyone ?
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Old 07-10-09, 07:31 AM
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There is an important distinction to be made between Lithium Polymer (LiPo) and Lithium Iron Phosphate (LiFePO4).

LiPo batteries have the highest energy density of any commonly available battery type, but are also relatively volatile making them a fairly poor choice for an e-Bike conversion. They are the batteries you've heard of having issues with charge/discharge, blowing up, etc.

LiFePO4 are more stable, much less likely have to 'thermal runaway' issues, charge more quickly & will handle many more charge cycles than LiPo batteries. Though their energy density is a bit lower, it is still much better than older technologies (NiCd, NiMh, SLA). If you're goal is to build an excellent electric bike, most folks will agree, put your money into a GOOD LiFePO4 pack, from a trusted manufacturer, with a good BMS. Oops - should probably clarify: the BMS (battery management system) is a small computer that monitors the cells in a pack & ensures that they are evenly charged, prevents over-charge/discharge, etc. One last consideration is that not all LiFePO4 packs are created equal - be sure to know if the pack you get is round cells (cheaper, lower Ah, lower safe discharge rates) or prismatic cells which allow for more Ah & generally imply a better pack.
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