Safe's Electric Bike Project #001

[Link]

Nope. The Doc Wattson doesn't lie, and it says I was drawing exactly the controller's limit: 31.25A. Granted it also said that this 48V pack was sagging down as low as 30V before they were dead. Yeesh.

So these were new batteries right? That's another possibility, that maybe when new they work the best and then decline. Do you have the battery manufacturers name? I'd like to research this battery and check with their technical documents. My big 38Ah batteries were the "cheapo specials" and probably the bottom of the line as far as quality. It does suggest the better SLA cells might matter... especially when dealing with micro sizes. (Sub 12Ah is "micro" in my book)

The big cells allow enough room between power "needed" and power "available" so as to work for a long time without any problem.

Really? New cells work BETTER than when they're old? HOLY CRAP!

Though I don't think they're that new. They're the ones I ripped out of my electric skateboards, which were probably sitting in a warehouse for quite some time. I had put them through a few charge cycles myself.

Two of them are "Enduring" brand, the other two were kind of hard to read. The logo is clear, but I can't tell if it says "Eco" or "Eoo". Interesting to note that this pair of batteries is rated at 4.5Ah at the 10 hour rate.

 

[safe]

Fellow missourian here too. What part of the state are you? Im dead central.

I'm in the "Northland" above Kansas City... right on the edge where the city and suburbs start to slip into the country. So I can get to nice roads in about a mile.

 

[D-Man]

Safe, what kind of chargers are you using? How many are you using to charge 48 volts? Just wondering how the old batts charge with new ones given that they have the same capacity even though they are different sizes.

 

[safe]

Safe, what kind of chargers are you using? How many are you using to charge 48 volts? Just wondering how the old batts charge with new ones given that they have the same capacity even though they are different sizes.

I use a Victor four stage SLA charger. Desulfate, Charge, Taper, Trickle. It's a regular 12 volt charger that can go up to 10 amps. So I just disconnect the Dean Connectors and plug the charger in as parallel.

 

[safe]

Downsizing

I'm in the process of downsizing my batteries from the older 38 Ah size to the 18 Ah size and this will require the creation of a new insert that will hold the smaller batteries in the larger cube. So a little fiddling around is in order.

The new configuration will be four 18Ah SLA batteries running at 48 volts and 40 amps... that is unless I feel like trying out my 100 amp controller... we will see. The 100 amp 48 volt controller is supposed to go on #002 as it is going to the fastest bike of all of them.

So I'm going from about 86 lbs of batteries to about 52 lbs of batteries... a savings in weight of about 34 lbs, so this will seem a lot lighter afterwards. Less range, but what it will do it will do really fast.

 

[Lessss]

CARGO!!!!

Instead of chopping it all up how about leaving the extra space as cargo storage?

 

[Link]

Why would you need a new insert? Two normal-sized 18Ahs (1/2 U1s) are almost exactly the same size as the 35Ah U1s you were using.

 

[safe]

Two 18 Ah cells do indeed fit into the space of one 38 Ah cell and I could leave one open for cargo space... at least one MIGHT try something like that if they were unaware of what a "stressed member" frame design is about. In a "stressed member" frame design the battery is supposed to assist the frame from flexing... it's actually supposed to add stiffness. This is in part why such a relatively light weight frame has been able to withstand the speeds and forces that it has because it's a unit that works together.

So I have no choice... I really cannot leave a cell space completely open. Instead I'll be placing two cells into the front location and then one in the each of the back two. Then I'll get most of the structural support that I had before.

Pictures will follow eventually...

The frame will not be "chopped", I'm simply adding a little tray that will allow the back two batteries to be centered in their cubes. It's like adding an adaptor, the frame will still be able to run 38 Ah afterwards if I wanted to switch back for any reason.

 

[johnrobholmes]

I would be amazed if that frame flexed very much even without the batteries. The only point I can see for weakness is the rear arm. You have the main frame trussed up pretty well.

 

[safe]

I would be amazed if that frame flexed very much even without the batteries. The only point I can see for weakness is the rear arm. You have the main frame trussed up pretty well.

It's been very solid... but why take a chance? If the batteries can be used to stiffen the frame as a stressed member why not take adavantage of that feature? The bike will also be 34 lbs lighter so that's less weight to worry about. But you are right, it might not matter and in theory that extra space could be converted into cargo space. But cargo space on a racebike? It would just give off the wrong impression visually. :wink:

 

[Miles]

It would just give off the wrong impression visually. :wink:

Just make a storage box out of a battery casing :wink:

 

[safe]

55 mph

A new record top speed for my first bike. (downhill)


I've replaced the last of the heavy 38 Ah cells and have built the little battery trays to make the smaller 18 Ah cells fit nicely. It's been two days of fabrication to get this done... I'm pretty tired. :|

The lighter weight and the fact that I now have four new batteries (well two of them have about 500 miles on them) means that I'm able to go faster EVERYWHERE and it's kind of impressive. That 34 lbs really makes a big difference on the hills and now I can pull taller gears in places I never imagined. The bike has again been transformed.

Four 18 Ah SLA's seems a nice "sweet spot" as far as a configuration goes. Any more than that and the weight becomes so much that parts want to break, but now it's so light I can actually lift it up. Only 52 lbs of batteries means that the whole bike is now down to a little over 100 lbs.

 

[D-Man]

Where did you buy those batteries at?

 

[safe]

Where did you buy those batteries at?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=190152225431

Price for Two - US $48.95

Shipping costs: US $24.95

They've got "pep" right now because they are new... we will see how long they last now that I'm pulling 2.2C everywhere.

 

[safe]

First Full Test Ride

Trip Length - 10.49 miles
Trip Time - 21.09 minutes (1269 seconds)

(10.49 / 1269) * 3600 = 29.76 mph average.

Not bad... :|

I wasn't sure of the range, but it seems that 10 miles is okay. The final voltages came to around 11.8 volts each. Despite two being slightly older they seem to be working about equally. (no wear noticeable on the older cells based on final voltage)

 

[safe]

Second Full Test Ride (Using ACL)

Trip Length - 10.62 miles
Trip Time - 20.24 minutes (1224 seconds)

(10.62 / 1224) * 3600 = 31.23 mph average.

Now before you all get too excited... on this ride I knew that with ACL I could always run the bike with full throttle without having to worry about either heat, efficiency or range, so I was going faster than usual this time. It's possible to beat this average speed using the regular controller too, since ACL (Armature Current Limiting) is simply a "filter" of unwise throttle settings for multiple speed electric bikes.

That said...

Hot damn... I set a new average speed record for the bike and while using ACL!

Basically my first gear is a little high for this and any time I drop below 20 mph it's really slow to get back on the powerband, but once above 30 mph the bike works great. With a different gearing setup that allowed for the shift that ACL requires it would be much better. My bike is geared too tall to use this fully.

How It Feels

The bike's powerband feels totally different. Instead of the "vague" wide powerband that gives no real feedback about what gear to be in and what rpm to run at, the ACL circuit makes it PERFECTLY CLEAR what gear is the right choice. No more wondering "is this the right gear?"

So (and I hate to say: "I told you so, but I must") the bike performed the same timed course and did well. In fact, the motor ended up a little cooler and the batteries drained just a little less (ending voltage was 12.1 rather than the previous 11.8 ) so the bike simply performed more efficiently.

All my "blabbering" about ACL has been proven to not be bullshit after all.

Hard to imagine huh? :wink:

 

[TylerDurden]

All my "blabbering" about ACL has been proven to not be bullshit after all.

Actually safe is still making claims & assertions... "proof" requires validation (data, 3rd parties, duplication, etc.)

 

[D-Man]

I don't get how this ACL makes it "perfectly clear" to you when to shift. So what do you do; just constantly turn the knob back and forth while driving or something. Its only your second run on the new batteries and they really haven't broken in yet also.

 

[AussieJester]

Where did you buy those batteries at?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=190152225431

Price for Two - US $48.95

So annoying when i see prices like this, is going to cost me around 80 bucks each for a decent quality 18ah sla PLUS delivery if I get them off ebay :: sigh :: :-(

 

[dirty_d]

while i don't think "ACL" is a bad idea as long as the limit isn't too low (id use the motors max continuous current). i cant see how it would really make shifting any easier, the gear you should be in should be directly related to the speed you are going. you would always want the motor to be running as close to the rpm that it puts out the max power at to get the quickest acceleration. tahts from a performance standpoint, but from an efficiency standpoint you want it to just be running at the highest possible rpms(just short of no-load, it wont get to the no-load area where the efficiency drops since there IS a load). you could just calculate out for each gear where the right rpm would be to switch to the next, then work that out to mph. then you can just shift from looking at the speedometer. or you could do something awesome like make a circuit that watches your speed and beeps or something when its time to shift.

safe, have you worked out how you are going to have different speeds for the motor on your other bikes while still being able to pedal? i was thinking that it might be possible to just run the motor through the derailer like on this bike, but flip the pedals around so the chainring is on the other side and attach a singlespeed freewheel to the other side of the hub somehow. that wouldn't be without issues though as i don't really see an easy way to attach a freewheel to the other side of the hub, and the pedals will be turning the wrong way, so they are being loosened instead of tightened.

 

[safe]

So annoying when i see prices like this, is going to cost me around 80 bucks each for a decent quality 18ah sla PLUS delivery if I get them off ebay :: sigh :: :-(

I paid $73.90 for two 18Ah SLA batteries.

So that means $36.95 each. (delivered)

(but I guess to ship to Australia it would cost a bundle... you would need to find a local supplier)

 

[safe]

ACL... i cant see how it would really make shifting any easier, the gear you should be in should be directly related to the speed you are going. you would always want the motor to be running as close to the rpm that it puts out the max power at to get the quickest acceleration. tahts from a performance standpoint, but from an efficiency standpoint you want it to just be running at the highest possible rpms.

...safe, have you worked out how you are going to have different speeds for the motor on your other bikes while still being able to pedal?

First the gearing question... on Project #002 I'll have an internally geared 8-speed rear hub by Sturmey Archer. Direct chain to the rear wheel... (no frills) On Project #003 I'll run the chain from the motor to the rear wheel and then loop around the front pedaling sprocket too, so three sprockets for one chain, plus a 7-speed rear derailler.

More About ACL

Before you will have any ability to comprehend how ACL benefits multiple speed gearing you need to HAVE multiple speed gearing attached to your motor.

So that's step one.

Once you have the gearing mated up with the motor then you begin to realize how ACL makes performance riding easier.


Lurch, Surge, EV Grin

No matter what colorful phrase you want to give it the stock electric motor has a very strange way of delivering it's power. Without a controller at all (unlimited) the torque is highest at lower rpms and yet the efficiency is positively terrible and the horsepower is also terrible down there. Even with a controller that limits the current, the strange way that the PWM gives added torque in areas where the motor is "bogged down" (low horsepower) causes the rider to be confused. He "feels" something like:

"Wow, I feel torque, I feel an EV Grin, I feel a surge, I feel a lurch... this must be the RIGHT thing to do."

...and yet our rational minds can study a chart and realize that the maximum horsepower is actually occurring in a completely different place in the powerband. The best horsepower is actually somewhere OTHER than what feels right.

It actually shouldn't have been that much of a surprise that I set a new average speed record the first time out using ACL because for the first time I was TRULY hitting the peaks perfectly rather than trying to "torque my way through it" as is what feels natural.

The core message of ACL is:

"What 'feels right' using a standard controller is not actually what "is right' because the low level torque 'tricks' you into using the wrong part of the powerband."

ACL cannot give you anything that the motor doesn't already have, but it does allow you to ride better. As I've said elsewhere ACL attached to multiple speed gears is a REFINEMENT for the rider experience. If you haven't had the rider experience you would never comprehend it.

ACL helps to make a good rider better.

The Need For Low Gears

What this teaches me about my previous riding behavior was that I was always pulling a gear that was too tall. The ACL powerband gives what is the "ideal" riding style because it forces you to do the "right" thing rather than the "wrong" thing. What it makes me realize is that my bike as it is now is geared waaaay too high. If I could shift the gearing down so that my first gear would rev out to about 20 mph rather than 30 mph then I would be in great shape. The Project #002 and #003 will do just that and first gear will be about 20 mph at peak power.

 

[safe]

Passed 4,100 miles today...

 

[safe]

Back To The Stock Controller

I switched back to the stock controller (no ACL) and it was amazing how quickly I reverted back to the "short shifting" behavior I had before. Even though rationally I know that running a gear that is too tall is a bad idea for all kinds of reasons the low end torque invites you to do it. However, I did check the speedometer more often and then calibrated backwards in my head what gear would be more appropriate.

There is this longer ride that goes through a back road (very pretty ride) and it has the steepest hillclimb in the area. I wanted to see how it might do and I managed to carry 20 mph all the way up it, so I was (after conferring with my spreadsheet) still able to carry enough speed to make it up while only resorting to a 67% efficiency rating. That's pretty good. Drop to 16 mph and you are down to 60%. Drop to 12 mph and you are down into the 52% efficiency range... and that means 825 watts of heat in the motor, over three times the rated load. At 20 mph it's only 500 watts of heat, about double the rated load. I still really need lower gears whether in ACL mode or standard, but there's no easy way given my setup. :|

 

[safe]

Passed 32 mph Average Speed

Trip Length - 10.42 miles
Trip Time - 19.29 minutes (1169 seconds)

(10.42 / 1169) * 3600 = 32.09 mph average.

I was going as fast as I could using the standard controller scheme. Having learned to rev out the motor with ACL I "remembered" and did not run the bike in too tall a gear. Add in the 0-20 mph advantage that the low end torque gives and it makes it faster getting up to speed. If I had another one or two lower gears I could go ACL all the time, or simply shift my existing gear ratios down a few notches, but as it is the 0-20 mph with a first gear that peaks at 30 mph is simply too tall. ACL is just not going to work on this bike with gearing this tall.

All that said... that's a new average speed record for the bike for a distance over ten miles... I suspect that's about it though because I was riding flat out the whole way. The only way to do better would be on a track without hills, turns, and stops... a velodrome.

My top speed was 53 mph on the downhill and there are about four or five sections where I'm going above 45 mph for a short time. True flat land speed is around 38-42 mph, but it's actually hard to find "true" flat land here in Missouri. All the roads near my house are on small hills that often are rolling. So I'll maybe crest a hill at 25 mph and then hit 46 mph at the bottom before slowing to 25 mph again. (shifting about every three or four seconds by the way)

It does make me wonder where I might take the bike for a true "velodrome" like straightaway. Right now it's like I'm on a road course, but for average speed testing you need something more wide open. Hmmmm...