CroBorg Super Commuter

[Alan B]

Under the Hood

66 volts 20 amp hours LiPo (HK Turnigy)
24 FET controller (Lyen)
HVC LVC boards (Methods)
LOTS of wires (HK wire, my own Hydraulic crimped main harness)(icecube made some of the parts for me)
Power Control/Throttle board (mine)
Room for (a little) more

I currently use 3 screws to hold the upper left hand cover, so it is not hard to get inside when needed.

There is some space in the lower compartment, but most of the space in the upper compartment is taken with wiring.

 

[Alan B]

A year or so ago I had an opportunity to lunch with a scientist who works on lithium batteries. We had a good discussion. Friday as I left work he was behind my 'Borg as we headed toward the lab's back gate. I took off gently, and then opened her up, then had to slow for a car, and finally accelerated again. When we arrived at the back gate he pulled alongside as we prepared to turn opposite directions and then he had questions for me. He was impressed by the bike.

His first question was what type of batteries, and the second was where I got the ebike. That's not so easy to answer.

I sent him an email after I got home and we will get together soon. He was very impressed by the acceleration and wants to know how fast it goes.

I'm sure we can exchange some good information. I'd like to learn a few things about lithium battery research, and he wants to know about ebikes.

Here he is in an interview on "The Future of Batteries": http://www.uctv.tv/shows/The-Future-of-Batteries-with-Venkat-Srinivasan-22552

The above discussion was pretty watered down for public understanding, but there is some good stuff there. I remember when they did that forum, I almost attended it but had time conflicts.

 

[hillzofvalp]

Make him get on ES and blog! That would be epic

 

[Alan B]

Today the upper gate is open so I'm back to the shorter route with less vertical (13.1 miles instead of 13.7), and it saved 10 degrees F on the motor temperature. Energy consumed was reduced by 5%.

I was also grilled by another lab employee who was impressed by the ebike.

I checked the power supply after charging, the warmest I found was 102F.

 

[hillzofvalp]

Wait.. What do you do at the lab?

 

[Alan B]

Accelerator Control Systems.

 

[hillzofvalp]

NukeE?

 

[Alan B]

We design, build and maintain the software and hardware (servers, networks, controls equipment, etc) for the control systems that operate a large machine (control hundreds of precision power supplies, motors, etc), accelerating electron beams to make light for many different types of research (45 beamlines taking different types of light simultaneously).

The light is different at each beamline, tailored to the science, but in many cases is millions of times brighter than the sun. Very concentrated over a small area. The light ranges from IR to hard X-Rays but the machine is optimized for the UV and soft X-Ray range.

http://www-ALS.lbl.gov The Advanced Light Source

Plus a few other projects.

 

[Alan B]

This morning I had a couple of electricians follow me into my building to ask questions about my Borg.

I handed out a couple more ebike "business" cards. (I'm not in the ebike business, but I had a card made with some info and link to my informational website).

It was a bit colder this morning, so I set the electric vest control on "high" instead of the usual "medium". There is one setting even higher, but high was enough, I've never used the highest setting. I may have to start wearing a warmer jacket. Still wearing a very light jacket over the vest, plus the neon windbreaker. It is nice to be able to just change the heat setting instead of having to add or peel off layers.

Passed a mile or more of cars this morning.

 

[whereswally606]

Here he is in an interview on "The Future of Batteries": http://www.uctv.tv/shows/The-Future-of-Batteries-with-Venkat-Srinivasan-22552

The above discussion was pretty watered down for public understanding, but there is some good stuff there. I remember when they did that forum, I almost attended it but had time conflicts.

Just wanted to highlight this post as I have just watched the whole hour video clip. There is definitely a lot of quality information packed into such a small show.

Thanks for posting this Alan
it may be worth reposting the link in the battery technology section so that it gets a bigger audience.
regards Andy

 

[hillzofvalp]

I wish he addressed more specifically whatit takes to damage a battery. Obviously not the right audience in video... But I would love to know how things like temperature, cut off voltages, and such will, when done in very short periods, will effect the life of a cell. So for example, ifi take it to 100% and then immediately bring it down to 80% in less than 5 minutes, how much more have a damaged the cell if i charged it to 100% and left it there for 2 hours, then discharged to 80%. The way I put it is very simplistic, but u can see what I'm getting at: it's hard to understand the true nature of battery health when the specification sheets give data for constant temperature use or constant DOD which is not a very good gauge all the time

 

[Alan B]

We might be able to get him to address some of these questions. I'll ask him if I get the opportunity.

One thing you might want to do is find the lecture on lithium batteries that was posted on ES some time back. I think it was an MIT lecturer, someone much like Venkat. He talked about a lot of these mechanisms and the chemistry and simplified versions of what goes on, but with a lot more detail than the above video. It was a lecture for a group of students building electric vehicles.

Essentially the electrolyte side reactions are proportional to the voltage and the temperature. So you want low volage and low temperature for long battery life. The amount of time spent at full voltage and high temperature ages the battery quickly. So 5 minutes at full voltage doesn't matter much, but days at full voltage is not good. High temperature is similar. Both together can age a battery very quickly.

So best to keep batteries cool at 50% charge state and then fully charge right before use and warm to their favorite temperature, which is about the same as humans find comfortable.

 

[hillzofvalp]

SO in effect, charging to 100% every time but only being at 100% for 15 minutes (then to 90% after first 10% of traveling) is pretty much the same damage to the pack as charging to 90% and leaving it there for hours? If so.. that's awesome. I wish that I could develop some smarts into my charger for my motorcycle so that it goes up to 3.45-3.5V/cell at the optimum time (2 hours before I use the bike).

The thermal management I'm using in my motorcycle is not optimum for this particular chemistry (A123 M1). THe PCM changes phase at around 55C or 131F, effectively limiting the temperature of the cells to this figure. However, now I have a better way of looking at it... The cells are allowed to get up to low resistance region in higher temperature, but they are allowed to cool just as easily and evenly. This should in theory mean a little bit more capacity while riding, and assuming they cool evenly and quickly enough after each ride, basically the same cycle life as if they were kept say under 35C (which is the recommended temperature according to my supplier)

 

[Alan B]

I agree that we need a smart charger that will take the pack to some level like 70% and stop, and then at the latest time do the final charging to 100% so it completes right before we need it. Optimally it might have several hold points that one could program.

I do this a little by deferring charging. Start later and charge slower at night, and on a weekend don't charge for a day or two if the capacity is not needed. Defer charging until Sunday night, for example.

But ultimately I look forward to buying a new pack with better features and capabilities in a year or two so not sure that a pack that lasts 3,000+ cycles is all that important or desirable on the ebike, but on a vehicle that's a different story.

edit - differentiate ebike from vehicle

 

[icecube57]

Wish you could send commands remotely to the Icharger from the computer

 

[Alan B]

Yesterday on my way down through the twisty road in the park I had to slow down while following a motorcycle.

That doesn't happen every day. It has happened once before.

Not that I'm going all that fast, (maybe 30 downhill with a tailwind), but these curves are twisty and some riders are tenative.

The weather is quite nice these days. A bit cool in the morning, very nice in the afternoon. I've been running the vest on medium in the morning, using about 1 amp hour during the 40 minute ride.

I dialed down the charging current to the 4.2AH 13V LiFePO4 battery I use for the vest. Now I'm charging it at 1 amp, and the fans don't come on in either the charger or the power supply. So charging is totally quiet since there are no fans in the 1KW main charging setup. Charging takes an hour and a half or so. It is mostly done in one hour if I needed to cut it short.

 

[hillzofvalp]

Wish you could send commands remotely to the Icharger from the computer

it's probably doable. bluetooth modules are easily installed on the hyperion (in place of USB to serial connection) allowing you to use ECDS to control remotely.

 

[Alan B]

Special Treat yesterday

I thought this week was going to be a clean sweep of ebike commuting, but between a tooth gone bad and the need to bring in my camera and big lens I only made 3 days. Here's a couple of the pics I snapped:

Space Shuttle's Final Flight

Seen from Lawrence Berkeley National Lab

Nikon D7000 w 70-300mm

 

[docnjoj]

Wow Alan! Those are wonderful!
otherDoc

 

[Alan B]

Thanks Doc.

Skies were a bit gray, we had a great view though. At 300mm it was a large fraction of the frame, looks like over half the width. Those middle shots are not cropped much. I realized later I didn't set up the camera quite optimally, they could have been even better. I let Picasa adjust the color so they are not quite matched. The real color looked closer to the first one, but the bluer ones look better.

 

[Cicada]

wooo, nice catch, great!

 

[Alan B]

Range Anxiety

Today I answered the age old question - can I make the round trip to work without charging.

You see, I forgot to charge last night...

I've been using about 8-9 am hours going home, and about 12-13 amp hours going to work. Which is a round trip total of 20-22 amp hours out of 20.

Going home last night I used about 8 amp hours. So in theory I had about 12 amp hours left, but that has never been verified, and even the calibration of my CA has never been accurately tested.

This morning as I picked up my helmet I realized that I forgot to charge the bike last night.

So the question was - take the suv (can't do that as it is going in the shop today), take another ebike (could do that, but no rack on the recumbent, and the mountain bike is buried behind other stuff), or hyper-mile and see what I could do...

So I left the motor off as I went down my street (slight downhill), and switched into speed I. All the way to work I kept the speed down to about 15-17, pedaled most of the time, and used regen when I could to keep from wasting energy on downhill speeds above 15 mph.

I arrived at work with these CA stats:

26.2 miles (total round trip)
16.6 amp hours (of 20 rated, never verified)
1175 watt hours
44.0 watt hours per mile
2.1% regen
17.1 amp hours forward
0.35 ah regen
-37 amps min (regen)
77 amps max
18.9 mph average (my home bound trip was not slow, so this skewed the average higher)
1 hour 23 min (for both trips)
947 miles on the odometer (two more commute days to 1,000 miles)
66.7 volts at end after a few minutes rest (LVC is about 63 volts)

The charger is on now, so we'll get another reading on amp hours from that soon. The balance looks good after an hour of charging.

For all you folks with light ebikes this may seem like poor efficiency, but remember this is a 110 pound ebike with full suspension and fat moped tires, it takes a bit more energy to move it.

As we already know, slowing down helps efficiency a LOT. Pedaling a lot helps some too, but slowing down is even more helpful.

This is one case where the Cycle Analyst allowed me to make this trip safely and gave me the information so that I could plan and know what I needed to do, and helped protect my batteries. Folks often ask if the CA is worth the cost. My answer is, if the CA saves your battery pack ONCE, it has paid for itself several times over. Riding without a CA is like driving with no gas gauge, speedometer or odometer. In other words, like driving with no instruments. There are other ways to get speed, voltage, current and wattage, but integrated amp hours over multiple on-off cycles is not so common.

This is one time a powerful charger at home would have been useful. I could have taken 30 minutes and put 6 amp hours back with my 12 amp bulk charging system that I use at work. I could even charge as part of my morning ritual instead of charging the night before. Just might have to get another set of those LED power supplies soon...

I'll sleep well tonite.

 

[hjns]

very nice!

44Wh/mile is around 27Wh/km. If I commute fast with many accelerations (80A peak), I get 30Wh/km. If I take it slowly, I get below 20Wh/km. As your bike is probably much heavier than mine (around 30kg incl battery), 27Wh/km does sound like quite an achievement!

You may want to calibrate your CA....

 

[Alan B]

I do need to more accurately calibrate my CA. It is roughly calibrated, but I don't trust it yet. This is a V3 beta with early firmware and the wh seems to jump around, not sure why.

The watts-up says 15.8 amp hours, so that's nice, but it reads slightly low that I know of. But in any case the CA is probably reading a bit high so the wh/mi figures would also be high.

Just to be clear, that 44 wh/mile is from the round trip, and the first half was fast and not very efficient with 600 feet of UP, so the inbound trip this morning was probably more like 40 wh/mile, and that includes 1200 feet of climbing.

Let's see if the numbers make sense here.

16.6 - 8.7 = 8.6 ah inbound at 68 volts so 537 watt hours / 13.1 miles = 41 watt hours per mile. My inbound trips are usually 50-59 wh/mile. So this was a bit better.

Working from memory on the 8.7 amp hour reading this morning, I didn't write it down. Amazingly that means the trip in used about the same as yesterday's trip home.

Just checked balance while still charging and it was 4.16/4.17 on each cell. There was one cell flipping occasionally from 4.16 to 4.15.

 

[Alan B]

Calibration

So today the battery was charged, and I didn't have to slow down or pedal so much on the way in.

But the calibration between the CA and the charge cycle on the Watts Up continues to baffle. I adjusted it a few times, but they bounce around . Usually the CA reads higher (more amp-hours) than the watts-up. Today they are 12.2 for the watts up and 12.0 for the cycle analyst. I know the watts up reads slightly low on voltage and current, so that is just about perfect agreement. They haven't agreed that well in the past. Something's not consistent.