What do you think of this wheel and battery kit?

[deetoau]

hi,

long time e-bike wannabe, taking the plunge to get some parts together and assemble a bike.

What do you guys think of these kits from ebay?

48V 20Ah, AU$387 [cheap nasty? is the charger going to damage the batteries?]
http://www.ebay.com.au/itm/2013-48v-20ah-LiFePO4-Battery-5A-Charger-BMS-For-Ebike-Powerful-Sea-7-8-Weeks-/130923064982?pt=AU_Electronics_Batteries_Chargers&hash=item1e7b9f6e96&_uhb=1

48V 1000W rear wheel [cheap nasty? - will the controller prevent over discharging the battery?]
http://cgi.ebay.com.au/ws/eBayISAPI.dll?ViewItem&item=111198095220&fromMakeTrack=true&ssPageName=VIP:watchlink:top:en

I've previously read of the problems with high power wheels transferring power to the bicycle frame safely. Recall seeing some kits that include brace arm brackets for more secure mounting of the wheel to the frame.

I've seen various battery problems in different forums, overdischarging cells within battery packs seems to be the main cause of premature battery pack failure. I suspect the cheaper battery chargers will not have the features to prevent over charging (either over voltage or overcurrent) and the cheaper battery packs may not have features to prevent over discharging individual cells. [do the better battery packs have features to prevent over discharging individual cells?]

finally : is there really much difference between the amp.hour discharge rate cycle between LiFePO4 batteries?

 

[dogman dan]

First and foremost, do some measurements and figure out if you can possibly carry a 22 pound chunk of battery that size and shape. Put it on your rear rack, and your bike will handle pretty darn horrible. It will be ridable, but not very nice. Much better to carry the battery inside the bike frames front triangle space.

I often recommend the 15 ah size in 48v, because this size often fits in the triangle area of traditional bikes and cruisers. 48v 15 ah is also enough for 20 miles range hauling ass. Plenty for most.

As for the kit, can you find one without the cheap crappy horn and light? I like a motor kit simple as possible. Last thing you need as a newb is more plugs that could be the problem why your bike won't run.

Nothing wrong with the motor type, I just would prefer one with just a throttle, and no other crap the circuit has to go through for the thing to operate.

Back to the battery, that is indeed a low quality battery, and charger. But mostly the problems people have is related to trying to save money by buying a battery too small. In the lowest priced lifepo4, 10 ah would be too small to reliably run that size bike for years. But a 15 ah should be big enough. If possible, try to find out what exactly you get with the controller. A 20 or 25 amps controller will be ideal for that battery in 15 ah size. A 30 amps controller would be a bit harder on it, but can be used with care.

Whatever size you buy, then there remains a bit of a matter of luck. Sometimes a cell just fails early, and there you are. It happens to even the best vendors. The battery you link to appears to be a pouch cell pack, so that is known to have a better reliability than the cheaper round cell packs. But in the end, you do have to rely some on luck. Then, if unlucky, the ebay guy is unlikely to be very helpful.

Re the charger. Very doubtfull it would damage the battery. But it looks like a type known to be unlikely to last very long. But you never know, I have a few cheapies that have run for many years. If the charger dies, it can be real good to have a second one in hand already. EM3ev has a nice line of chargers IMO, but another super cheap 2 amp one will do to get you through till you can order another. Two chargers is smart, even the best eventually wear out..

 

[wesnewell]

Motor kit looks like the same one I've been using for over 10,000 miles and close to 3 years. Basically a GM 901 clone. But I didn't get a light with mine. I'd say it's as good as any. I don't use lifepo4 batteries though. Some have given good recommendations for sunthing here.

 

[dogman dan]

Nothing wrong with the motor or controller. Bound to be quite reliable. It's just that cheese on the handlebars I object to myself.

I don't know how that light is wired, but a kit I had with the similar light and keyswitch had the battery wire running up the frame to the handlebars, through the cheapo switch at full amps, then back to the controller. In total, it was about 6 feet of additional too thin wire that 100% of the motors power was running through.

I thought it was an incredibly poor design. Maybe this is different, if it's just a low amps wire to the keyswitch, in circuit with a separate red wire that just powers up the controller, then it will be fine. If that is the case, then the switch won't fry right away. Well, fine unless the extra plugs don't make contact, or the switch flakes out from just being a cheap one.

It should be quite simple, to remove any of that crap if it bothers you. I assure you the light will only be bright enough to ride in the daytime. I just prefer a much simpler wiring, cleaner looking, and less to go wrong in the wet. For lights, I want a good bright one, since that morning I hit a pedestrian wearing all black walking in the bike lane.

I didn't notice that the battery vendor was sunthing. he's got a fairly good reputation with us here. The charger is cheap, but it won't ruin the battery. Get a second better charger, and keep the original one for a spare. Again, 48v 20 ah is very hard to carry on most bikes.