Currie ebike energy consumption

[dnix71]

I bought a Walmart 24v ebike 'Curry Mongoose' a few years ago and was never happy with battery life. Thinking that it was the batteries or wiring I changed both several times with no real improvement. The current set of batts are UB 12350 Chinese made sla's usually installed on personal mobility scooters. I bought a pair "buy one get one free" at Radio Shack for $70.

The UB 12350 is 12v at 35 ah according to the label. The real nominal resting voltage is actually just above 13, since these are sealed, starved-electrolyte batts. If I fully charged the pair and full throttled the bike while stationary, the voltage would drop to about 24. The fuse is 40 amps, but I assumed -incorrectly- that the locked rotor amps was a lot less than this and wondered why the voltage sagged so much.

I hooked up a 130A Turnigy , recharged the batts and locked rotor tested again and was amazed to see 750 watts being pulled. The motor is only supposed to be rated 450 watts. In a road test today I pulled 925 watts peak power somewhere during a 19 mile round-trip ride to work and back. I have the week off, but rode to work today to get my paycheck.

The Turnigy readings were Begin: 27.14v; End: 24.36v. 44.58Ap; 925Wp; 20.33Vm; 19.499Ah; 439.2Wh

I didn't pedal much except at intersections. The bike was forced to carry my fat American @ss 9.5 miles out and back without being recharged. The trip took 2 hours including stops at Burger King for breakfast, work to pick up my check, the bank to deposit my check. A car trip would have taken an hour.

If I did have the money for lithium batteries, it would take at least 10c batts to be safe at that level of current draw.

The battery charger that came with the bike only comsumes 50 watts at the wall, so recharging from a round trip like this will take about 12 hours. There is a 4 amp version of this charger available from eBay. I think I need one.

[hiker]

my wife and i use to bike all over togeather--than she came down with arthritis..she missed riding a bike..so i picked up a  EBIKE  for her...she loves it..calls it her freedom bike..she weights less than a 100lbs..so the bike really gets out and goes..as far as the battery is concerned..ive never had a problem with that..i charge it back up after each use..she goes all over town with it..and never ran low on power,,,single battery...  all in all its been a real gas saver !

[mettleramiel]

Just a note about those batteries. Hold on to your receipt, I sell them where I work and they are absolute $#|+. You will be lucky if they last you 6 months, but don't count on it.

[taylorp035]

Hmm... 439 Wh would get me about 200 miles in the supermileage car... so your bike is 20x less efficient.  About the same weight.  The bike's air drag is going to be about 20-40 times worse and the tires are about 3x worse...  I bet if you pumped up the tires to somewhere around 80 psi (as long as the max recommended isn't like 40 psi), and swapped the Pb batteries for some cheap LiPos(~$175-200 for 450 Wh from a hobby website) I bet you could increase your range quite a bit.

[zap]

My Currie is the older USPD system with the Kollmorgen motor... It looks like this:


The way it appears in the image above... it weighs about 73lbs!  That's with a pair of 12v 12ah in the box situated in the triangle.
It's plenty heavy already and I've had a little over 40lbs in the panniers on more than a few rides (it turns into a wheelie machine with that much weight back there).
I can't imagine adding another 25lbs.  Especially on top of a rear rack or above the front wheel.

My hat is off to you dnix71!!!


As for range I really can't say.
I got the bike used and the batteries were already pretty sad.  I quickly replaced those with 5.2ah of NiCd which fit inside the original box.  That pack had decent range but I ended up frying one half of the pack
I replaced those with a used LifePo4 pack which didn't last long but was pretty nice when it was working.  The pack started bulging and I found some of the cells puffing

Unless I'm testing things, I always pedal.  I have a little under a 16 mile ride one way to church and I can usually average about 8-10 mph without turning the motor on.  It's easy to deplete the battery on the way home even using the throttle sparingly.

[dnix71]

My ebike has the brushless version of the Currie motor. I see brushed versions for sale on eBay, with the note that they have much more low end torque and use much less battery power. I suspect that's true. Brushless means no maintenance, but at a cost. There is some kind of gear reduction built-in behind the motor and more gear reduction from the back sprocket to the tire sprocket. Maybe Currie should have geared it down even more when using the brushless motor.

The rolling resistance of my bike is higher than stock because I replaced the front pnuematic rubber tube with a no-flat urethane tube. I also tried replacing the rear tube, but that made the rolling resistance way too much. I have been stranded with flats too often to go without at least one no-flat tire.

I don't consider battery weight to be that much of an issue. I could stand to lose a few pounds myself and easily lose enough to compensate for larger batteries.

[zap]

My ebike has the brushless version of the Currie motor. I see brushed versions for sale on eBay, with the note that they have much more low end torque and use much less battery power.

I'm not sure what you mean by less battery power.  IIRC and everything else being equal, a brushless will be 10-20% more efficient than a brushed motor.  I've never heard of them having more torque so that may be true.

After further research I believe I have the Mac-BMC version of the motor, not the Kollmorgen.
Although I never tested it enough to know for sure... I always guessed my bike used somewhere around 1ah/mile without any pedaling.  I'm glad you posted your numbers since it seems that's about what you're using.
Woody can do a little better, maybe because of the adjustable gearing?  The one 'no pedal' range test I did got 12 miles out of a 36v 10ah lithium pack.  Pedaling along with full throttle most of the time got me 18 miles averaging 17.2 mph.

It's funny you mentioned the no-flat tubes.
This season's first four rides (I'm a fair weather rider) resulted in four flat tires on two different bikes   The first two flats were only about a mile from home but then I got a pinch flat about 4 miles away and then another a little over 6 miles away
I've have more than 3K miles on my GT and have never had a puncture that the Slime didn't fix and I've put over a thousand on the Currie with the same results using Slime but the 'four for four' had me gun shy.
I considered the no-flat since I had them decades ago on my old 10-speed but reading some of the reviews on them helped me decide on some new thicker tubes... although I haven't added Slime... yet