Range issues

reikiman's picture

Recently I noticed some motorcycles w/ approx 100 lb battery packs are having the same range as I'm getting with the 220 lb pack on my Lectra. Namely 45 miles/hr and up to 10 miles range. Last weekend I showed the Lectra to a knowledgeable e-motorcycle builder and he thought I should be getting better range. So I'm wondering what's up with the range.

If I'm careful and don't hit the throttle real hard .. I can get 11-12 miles range. Hit the throttle hard, and the range is much less.

What I'm seeing on the ammeter is that cruising at 40 miles/hr consumes 100A current. This guy I talked with last week thought that was excessive, that the current should be much lower like 50A. And, I think y'all with the XM-2000 and other scooters are reporting approx 50A current for 40 miles/hr.

An interesting datum is the coast-down time as I reported earlier...

2004 Honda Rebel 250: 40->10 miles/hr takes approx 40 seconds

Lectra: 40->10 miles/hr takes approx 25-30 seconds

I also see this when I'm pushing the motorcycle around like when I'm backing out from being parked. It's a lot harder to push the Lectra around than the Rebel. So what this means is the Lectra has more rolling resistance. High rolling resistance should make the current draw higher to get the same speed.

Over the weekend I brought the bike into the garage and put it on the lift. This let me roll the wheels by hand. The rear wheel rolled pretty freely but the front wheel took a fair bit of effort. Hmm...

Just now I took it out for a spin to see if any part of the front wheel/axle/brake would get warm. The first time I stopped the front disc was pretty warm, but I'd been using it to stop quite a bit. I took it around the block a couple times, just using the rear brake for stopping. After that the disc was cool(er). Not sure what that proves.

I noticed the brake pad seems to be resting on the disc. But don't brake pads do that normally?

Another issue is the battery pack. I finally have the paktrakr running correctly. Until now I could only measure battery voltages after stopping and getting off and getting the meter out and measuring each battery individually. By the time I did that the batteries had time to recover their voltage, and I only ever saw the batteries having fairly even voltage. However I see now with the packtrakr the behavior while riding.

Battery #3 is much weaker than the others. Its voltage is dipping considerably during the ride and it runs out much earlier than the others.

This too is going to be affecting the range. Because the weak battery causes the other batteries to work harder.

Comments

andrew's picture

What are the specs of the bike? Did you put a vehicle page up anyplace?

A weak battery doesn't necessarily cause the other batteries to work harder. The current flow will be the same for all of the batteries, and this means the same for all of the cells in each battery. Usually a weak battery has a bad cell, and this is probably the case. When the charge in the cell drops to 0% SOC, than it adds a lot of resistance to the circuit, and this is why the battery power drastically reduces. Bypassing the battery with the bad cell at this point might get extra range.

The brakes seem normal. Check the tire pressure. Also check how freely the wheel rotates though the full 360 degrees. There may be a small amount of drag from the disc, but it should still rotate without much effort. It could be that the wheel bearings are overtightened if the pre-load is adjustable. Of course check the rear wheel too.

Another important thing is chain tightness. Chains should be loose for efficiency! And lubricate it well. If the chain is mounted in the stock fashion, and loosens/tightens when the shocks are depressed, than consider adding a custom tensioner like I have on my bike. It can be made with an idler sprocket, a bushing to hold it in place, and a spring. This way the chain can be kept loose with no risk of it coming off.

My 900 watt scooter was going kind of slow, even though it didn't seem like anything was bogging it down much. So, I adjusted the brakes, and that helped. But, I also loosened the chain. The rear sprocket was off center, and tightening/loosening the chain, so the chain would get pretty tight in cycles, and cause drag. And finally I pumped up the rear tire which was very hard to get to because the disc brake was in the way. After doing that, it was amazing how freely it glided down the road, and the coasting and top speed improved by a lot.

Check how the motor spins if the above doesn't lead to anything. Which motor are you using? Is it stock? The bearings could be bad, and adding some drag. The windings could also be shorting. Is the controller up to the task? Is it getting really hot? Could it be malfunctioning in any way, or not sending the proper waveform to the motor? How about the wiring? Any high-resistance points? Check every connection point.

Power should be considered when looking at current draw. If you are running the stock 24v setup, than 100 amps is completely normal in my mind to maintain speed. That's only 2400 watts into the motor/controller system which both have inefficiencies. A chain drive will not be as efficient as an in-wheel motor drive, so there will be losses in the drive system as well. And the stock Lectra motor was not a very efficient design, which would not be near as efficient as a brushless DC motor.

[url=/forum-topic/motorcycles-and-large-scooters/587-my-kz750-electric-motorcycle-project]KZ750 Motorcycle Conversion[/url]
[url=/forum-topic/motorcycles-and-large-scooters/588-fixing-my-chinese-scooter]900 watt scooter[/url]
Pic from http://www.electri

andrew's picture

I wanted to add that I do think your range is low. My bike in comparison has about 165 lbs of lead, and I can get about 10.5 miles range without much consideration to being careful. That's with two eteks and riding over 60 mph at some points, but about 45 average.

I'm guessing your batteries weigh 50 lbs each?

[url=/forum-topic/motorcycles-and-large-scooters/587-my-kz750-electric-motorcycle-project]KZ750 Motorcycle Conversion[/url]
[url=/forum-topic/motorcycles-and-large-scooters/588-fixing-my-chinese-scooter]900 watt scooter[/url]
Pic from http://www.electri

reikiman's picture

What are the specs of the bike? Did you put a vehicle page up anyplace?

This is my Lectra motorcycle -- 60v system, controller is 72v alltrax 400A max, and the motor is an Advanced DC A89

Another important thing is chain tightness. Chains should be loose for efficiency!

Hmm, when I broke the chain a couple months ago and then replaced the chain, the chain ended up very tight. It had to be ether very tight or so loose it would fall off. I'll have to look into adjusting the rear wheel to let the chain loosen a bit.

The motor is on the swing arm so does not slacken as you go over bumps.

And the stock Lectra motor was not a very efficient design, which would not be near as efficient as a brushless DC motor.

My Lectra is not stock (as I said above).

I haven't thought about feeling the controller to see if it's getting hot.

- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
- Electrified Electra To

reikiman's picture

I'm guessing your batteries weigh 50 lbs each?

The pack is 5 pairs of these: http://www.batteryweb.com/powersonic12vsla-detail-PS-12260%20F2.htm

10 batteries total, in 5 pairs.

Voltage: 12 V
AH: 26 AH
Terminal: F2
Weight: 18.7 Lbs
Length: 6.55
Width: 6.9
Height: 4.95

So, uh, 187 lbs of lead. Or thereabouts.

Okay, so there is another extenuating consideration.

I bought the pack in Oct 2006 but didn't get the bike running until a year later. I kept charging them regularly (like, once a month) ... but it's well known that batteries are badly affected if they sit half charged.

- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
- Electrified Electra To

andrew's picture

Ok... sorry I'm lazy. I went through your blog to get up to date. I see your main blog about it My Lectra project and the previous owner EV album page.

I bought the pack in Oct 2006 but didn't get the bike running until a year later. I kept charging them regularly (like, once a month) ... but it's well known that batteries are badly affected if they sit half charged.

Lol. I had the same problem with my bike. I was excited about doing my bike. I thought I could buy all the parts and have it together in a month. I kept charging the batteries every month at least. The batteries should be ok under this treatment, as long as they don't sit at very high temperature. In fact, it's best to keep them as cold as possible for storage. And charging them often should keep them good for years according to specs, but I don't know if their cycling life degrades with time which it probably does.

Yea, I think my batteries are kind of weak, and I already had one go. I'm using a sort of not as bad replacement that I bought initially as a spar (I should of warrantied it now that I think of it). I'll see how this works when I get finished with the recent upgrades, but I'm not too hopeful.

Anyway, I would adjust the chain just so it's not loose enough to fall off. With a small amount of movement required for tensioning, then an elastomeric chain tensoner as a complete unit can be bought from Grainger (or maybe another industrial supplier). This didn't work for me because the change in slack is very large, and happens every time I pull back on the throttle.

What's the top speed? Do you still have the 54/12 sprocket setup?

[url=/forum-topic/motorcycles-and-large-scooters/587-my-kz750-electric-motorcycle-project]KZ750 Motorcycle Conversion[/url]
[url=/forum-topic/motorcycles-and-large-scooters/588-fixing-my-chinese-scooter]900 watt scooter[/url]
Pic from http://www.electri

reikiman's picture

At the SF EVA meeting today I had a chance to show the Lectra to Lawrence. He's the guy I bought it from. He was really impressed by what I'd done with the bike, it rides better than when he had it. Probably switching to 60v from the 48v he'd run it at made a lot of difference.

Anyway I asked him to take a look at the front wheel. He agreed it wasn't right and thought something in the brake was binding. We ended up taking it to a motorcycle shop that he knew about, a real hole in the wall. Gosh what a scene.. at first this guy brings out a large orange plastic mallet and starts banging on the brake. That loosened it up a bit but when we operated the brakes it started binding up again.

They looked at it more deeply and started talking about shims and whatnot which I didn't fully follow, and I ended up leaving the Lectra at that shop. It should be ready by next weekend. Assuming they can straighten out the front wheel issue then the Lectra should run a lot better.. Lawrence thought double the range and a few miles/hr speed.

- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
- Electrified Electra To

pchilds's picture

Congratulations, soon your bike will well.

Philip
2011 Nissan Leaf SL

the range depend on motor efficiency and transmission loss and loading weight...

XM2000 and XM3000 is hub motor drive directly.....no transmission loss and 92% high efficiency

XM3500 consume only 46A at 80km/H speed ....

Torque is very important too ....which will reduce the seconds of accelerating when big AMP output.....only 6 seconds for my VK2008 to reach 80km/H top speed

Bigger capacity with heavy will reduce range too...that's why XM3500 use Lithium battery instead of Lead acid EfunD.... only 600dollars price difference ,but more range and more flexible ,less dangerous

Professional tester use AMP meter while riding


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