decisions, decisions...

[pedelectro]

ok, so i have a bike, it is a 1996 cannodale killer v 500, front rock shocks, i found it, probably stolen, but in rough shape... i brought it home and swapped out a few parts, put on new tires with slime tubes and a seatpost rack... looks great, is not great to ride... i have a surly lht that i love... so this guy goes whirring by me a month or so ago, and i thought, was he on an electric bike? so i get on the internet, and here i am, completely fascinated by this not so new, but developing, field... and i want to electrify my bike... so, here is what i am looking at... crystalyte 3540, apm, brakes, the ususal kit, but here is where i am stuck... do i 1. get a lipo or a limn battery, and 2. do i get a 48, 60, or 72 volt battery and matching controller? i can't help but think i will kick myself if i undersize my ride, but i can get a 48v20ah limn battery for about the same as 72v15ah lipo that weighs twice as much... please let me know your thoughts, i have read many posts looking for a good rule of thumb here, i really will be using this to get out and go for bike trail touring...

 

[dogman dan]

The battery decision is the hardest for most of us. You pick your motor and controller, then choose a battery voltage and size that can provide the amps the controller needs, plus some extra.

So for example, a common 20 amps controller will not be a good match for a battery that provides 20 amps max. One that can provide 20 amps comfortably is what you need, like 30 amps continuous or more on the spec sheet. Look for the c rate of the battery. If it's 2c, then 10 ah can provide enough for a 15 ah controller. In other words, the max c rate is not what you should be using all the time. More like half that.

You sound torn between a reasonable bike for what you say you will do, and a desire to have an illegal homemade motorcycle. Do both of course, but I suggest you make your first bike closer to legal, with a 48v 20-30 amps controller. It will still be quite fast for a bike, and should do your touring needs unless you mean dirt single track trail riding.

If you get into off road trail riding, expect to spend a lot of money, break or melt stuff from time to time, and need more c rate in your battery. You can start with 48v, and then switch to a 72v controller later. If you start with a good strong battery, it can become part of your 72v battery later when you want to go 40 mph. Something weak and cheap will be used up by then.

 

[pedelectro]

thanks for your insight... yes, the dilemma is how illegal to make my electric bike... i admit it... i also admit that i enjoy biking and i would like to be pedaling, or moving my legs! this motor-cycle thing fascinates me, and perhaps the 'stealth' aspect of it as well... but my question is what type 48v20ah battery with the 4840 controller should i get, the lipo or limn or is there another type that has the weight /size ratio that works better? or one that as you say i can upgrade?

 

[dogman dan]

Like a lot of new guys, you may be confusing amps and amp hours. Amps is a rate of flow, Amp hours is a quantity, like a gallon. 1 ah is enough to have one amp flow for one hour. Or like this, one amp flowing out of a battery takes an hour to use up one amp hour.

It will take a strong battery to run a 40 amps controller. But 48v 20 ah is very heavy and bulky to carry on a bike. 48v 15 ah of the typical lifepo4 is good for a 20 25 amps controller, but it will fail running a big 40 amps one. Batteries hate being used at their maximum amps rate.

RC lipo is very strong, but I consider it safe only for those with experience, or those who really study and can avoid costly mistakes. Like burn the house down. The progression I went through might be best for many. I started with 48v 15 ah of lifepo4, then went to stronger controllers and RC batteries only after gaining a great deal of knowledge reading this forum for a some time.

If you really want to pedal along, then 48v 20 amps might take you faster than your can gear the bike for. Few mountain bikes are geared for even 30 mph.

 

[pedelectro]

thanks dogman... that brings me to my other point, does the apm, or another such device, actually determine what wattage goes to the controller/motor, so if i want to run at 16-40watts i can set that on the apm? that is why i thought having a higher rated controller would be more versatile than a lower one... i may be misinformed

 

[dogman dan]

APM? Is that a dashboard display thing?. The newer kits are coming with a dashboard, usually with an on off switch, a crude battery meter, speedo and odometer, and often 3-5 speed settings. The multi speed settings often don't limit amps per se, but limit speed so that cruise amps are much lower on the slow settings.

So you still get full controller amps on a start, or steep hill, but can hold full throttle and not go faster than you want. That's good, because holding 1/3 throttle is pretty hard to learn. You tend to creep faster and faster, ending up riding using your power faster.

 

[pedelectro]

crystalyte sells an active power management (apm) device/display... here is the link to the owners manual... http://www.crystalyte.com/APMDisplay_Owners_Manual_V2.pdf
you can set parameters for your system directly from the device, like the cycleanalyst... the one thing you can do there is set the maximum current level you want sent to the controller, so you can run at lower current to save 'fuel'... but i think i would prefer to have a controller that could handle more if i needed/wanted to use it, because i think the motor that i want can handle the higher wattage potential of a 40a controller... i really am asking what the tradeoffs are with some of these batteries/packs with weight to efficiency, i am leaning toward the larger lipo4's as they seem better designed for this type of use than the smaller multi-packs that require a more sophisticated bms... almost there....

 

[dogman dan]

For 40 amps, you tend to want a high c rate battery, 5c or better, 30c even more better. The problem is that with less expensive lifepo4 that is only 2c, you need to have at least 20 ah of it to produce 40 amps.

Then there is an additional problem, a battery still hates to be used at it's max rate. So for a 40 amps controller, you might need 30 amp hours of 2c lifepo4 to run it without wearing out the battery prematurely.

So say you get 48v 30 ah of cheaper lifepo4, Now your battery weighs about 30 pounds, and is the size of a small suitcase. How the hell do you carry that? For this reason, a much more powerful battery is desired. A 10 pound battery the size of a lunchbox can be much nicer to carry. But it needs to be strong to put out 40-60 amps in a 10 ah size.

10 ah at 1c discharge rate is 10 amps, 2c is 20 amps, and so on. 10c to 20c discharge rate batteries are ideal for 40 amps, unless you have a cargo bike that rides nice with 30 or more pounds of battery on board.

 

[pedelectro]

you bring up a good point, i think i can easily get by without the 40a controller, the 25 or 30 would be sufficient, and be less likely to cause problems... thanks!

 

[pedelectro]

here is the battery i was looking at, looks like it has a good rating...

http://www.all-battery.com/datasheet/30078_datasheet.pdf

 

[dogman dan]

My computer is unable to show the font used on the spec sheet.

What do they claim the discharge rate is? They look superficially like the headway cells, that claim 5c. So 2-3 c discharges are ok with those.

15 ah size, 2c would get you 30 amps. 30 amps is all you need for most bike uses.

 

[pedelectro]

max. discharge rate 10c (45A)... low v cutoff 2v... they are very much like headway, are those batteries not good to use for my situation?

 

[dogman dan]

Should work good then.

 

[dannyboyohyeah]

Dogman always has solid advice. I tend to be conservative where speed is concerned. Maybe it's because I've got so much metal in me, holding me together. A crash at speed, and I'd explode like Humpty Dumpty. Anything over 30mph wigs me out anymore. I like 55volts. It gets me to 30...but if either traffic or road conditions warrent more caution, I slow er down, to 20 or so, which is fast in traffic to me. A 3spd switch is very helpful, not just in limiting speed, but maybe more importantly, to conserve battery so you can go farther. Your confidence on a bike and your athletic abilities, your alertness, should be factors in choosing the speed you travel at, more than just what you imagine you wish for. There's nothing like a test-ride on a variety of ebikes, set at different voltages, to help you understand the reality of what you want. From 48v to 72v and to feel it in traffic. If that is possible for you to accomplish, I'd recommend it. Takes a great deal of guesswork out've where you are headed. Best of luck with your new enthusiasm and build~!

 

[pedelectro]

thanks, yeah i suppose i really do not need to go real fast, i have ridden on the stock bikes and they are fun, but lack the oomph that a 48-60v 1000w bike will have... i keep thinking that there is going to be a miracle battery out there that meets all the criteria, but it looks like the lifepo4's are it, just on the heavy, not sla heavy, but heavy side...

 

[dogman dan]

It would seem to me, that you are about to start out on to that slippery slope many of us have. The ebike grin will take possession of your mind, and take all your money for a year or so. The best advice I can give is to not try to make one bike do everything. Build at least two bikes eventually.

The very basic commuter setup is able to do a lot really, and doesn't generally have to go 40 mph. A 30 mph or near 30 mph 48v setup can be done with a fairly cheap battery if the controller is under 30 amps. Build that first, learn a bit about how it all goes together, how to install torque arms, etc. This bike can do the basic needs of getting to work or school, and can also do long fun rides on the weekend. With some fat cruiser tires, it can even still do easy trail riding, or long weekend rambles. It won't be a no fun bike just because it doesn't do 40 mph, or climb a wall. It will still get up 10% grades miles long. This is the bike you choose for rides that might be longer than 10 miles.


Then build your hot rod which will need to run on very powerful batteries, usually the RC lipo. These take much care, and even then could burn the house down, but they are the battery of choice for a hot bike.

That bike might be for dirt only, or be a street rod. But either way, it's a hooligan build strictly from your entertainment budget. Street and dirt is tough, because the dirt tires are costly and wear out so fast on pavement. Street tires will make you crash riding trails. To keep the weight down this bike is short range, but still able to do a 30 min blast that is super fun.

 

[pedelectro]

ok, i hear you... i have cut back considerably on my ambitions, settled for a 48v system, will let you know how it handles...thanks again...

 

[pedelectro]

well i am back... i have on order the battery, motor with rim, controller etc... thanks for all the input here and all the extra-curricular reading on the blog, i am not alone!
i have decided to go with the 60v battery set and the hs3540 clyte motor, with clyte 6040 controller, and clyte apm... i like the way the parts connect together, and i really do not want to mess with wiring options! i have also ordered a pair of custom boxes for the batteries, and i will send pictures as things arrive and i begin the build...

 

[pedelectro]

here is the before picture...

 

[pedelectro]

wired up, waiting for battery boxes... tested things out, have recorded 57mph, plenty of power, the hs3540 is d'bomb, the crystalyte apm makes setup a snap... will send pictures, need to reduce size...

 

[pedelectro]

ok, got a quick gerry rigged platform to put the batteries on and wrapped it all with tape and rain pants, it is rainy and cold, but i could care less... took a 15 mile ride with speeds up to 40mph... what a blast, i was 13 again! i live in d.c. and i rode to the lincoln memorial and past the capitol... just nudging the throttle most of the time, but when the tourists moved aside i was flying! still have plenty of charge... can't wait to get out again! still cannot get a photo less than 512kb... any hints, even email is 870...

 

[pedelectro]

ok i got a reduced photo, here it is... 60 v hs3540, top speed 40 mph, handles great, fun to ride...

 

[pedelectro]

forgot to note that i also increased the front sprocket from 42 teeth to 48 teeth, the maximum for that crank, just so i can pedal some times... :lol:

 

[dogman dan]

Nice boxes, but what do they weigh with the battery in them? I've bent some seatposts, and had to ride home with no seat, and the battery and seat tucked under one arm when one broke off. You need to put some kind of brace on that rack, either back to the seatpost tube, or to the axle.

I'll grant that it might handle OK, but I don't believe it handles great, unless the battery weight is under 10 pounds. You need to put your battery in the middle for it to come close to handling great. You might not notice the difference though, street riding. You would notice it on a twisty race track, or mountain trail.

Have fun on it, and stay out of the ER.

 

[Ghost (bike)rider]

I would fit a rear rack, attach the controller to the centre and but the battery in a pannier.

This will lower the centre of gravity and remove the risk of a bent seat post.

Are the brakes up to the job? Tried them in the wet? No reply in a week means "no" and "yes" in that order due to broken limbs :lol: