I bought a stripped down (just frame w/ tires&motor) Currie J3 bike on eBay cheap. Looked like it had been crashed, everything removed but the above. So I rebuilt it with new Currie controller, etc and tested it. When I turn the throttle the wheel goes around but the voltmeter drops from 110% Charge to 20% charge. Out on the street it just looses all power and stalls - peddles only get it going. Does anyone have any idea whats going on? If it is a fault in the brushless motor I wouldn't have the slightest clue how to fix it.

sounds like a dead battery

As I mention, initially the battery pack (new, 36v) measures at 110%, i.e, 39.7V.
When throttle on the bike is activated, the voltmeter on the bike drops to 20%.

you didnt say it was a new battery
what current is it drawing when the motor is turned on at full throttle?
what is the rating of the motor (watts)

a) Old Currie motor.
b) New battery. What is its Ah? SLA?
c) New Currie controller.

If ((b) and (c) are new and Ok,
then (a) is NG => old motor is no good.

Yeah, Battery and controller are new. I have no idea what condition in the motor would cause the bike voltmeter to drop to 20% when activated and return to 110% when the throttle is let go. It's like all the warp speed power vanishes into a black hole and then returns to haunt me. BTW, the batteries are (3) 12V12ah in series. The new controller was purchased from a Currie dealer.

To test at no-load (when the drive wheel is off ground):
a) What is the no-load speed at full throttle? Also read the voltmeter.
b) What is the no-load speed at 1/4 throttle? Also read the voltmeter.

To road test on flat:
c) What is the max speed at full throttle? Can it reach 20-25 km/h?
d) What is the speed at 1/4 throttle? Can the ebike move slowly?

Estimate the speed if you do not have a speedometer.

The 24 V Curries have a battery cuttoff when the battery is 2/3 discharged because deep cycling lead acid batteries beyond that point does a lot of damage with sulfonation. My guess is the 36V battery systems have the same protection in them.

After you see the cuttout, try backing the throttle way back and see if it continues. If so, you've probably hit the voltage cuttout and see if that confirms the diagnosis.



My suspicion is the problem lies directly with the batteries (defective batteries) or indirectly (bad charger that never got the batteries properly charged).

Also, read the voltage on the battery pack and on the individual batteries. You might have a bad cell or one of the batteries is not charged itself- since you charge the cells in series, if you get one undercharged, it keeps the whole pack low.

If you have a 12V charger, charge the cells up once seperately so that you get all 3 12V batteries in your pack properly charged.

Response to "The7":

Response to "The 7":
The throttle is the one that came with the bike and, as such, is suspect I guess. It is a twist - motorcycle style - throttle. It has about a 90* range of throw. In a No Load situation there is no response for about the first 30-40*, at 45* (half throttle) the rear wheel is moving very slowly and the bike voltmeter has decreased form a nominal 100% to about 60%. At 90* - full throttle - the wheel is going very rapidly and will apparently go forever even though the voltmeter at this point has declined to about 40%. When I let go of the throttle and it returns to the neutral position the bike voltmeter returns to the 100% "full" reading.

This is from memory from a couple of weeks ago when I decided to set it aside before I was tempted to take a sledge hammer to it. I took it down to the apartment parking lot which has perhaps a 2 or 3% grade. The bike just labored to get up the grade at about 4-5 mph, at the most. The voltmeter behaved as described above, dropping down into the 30-40% range. I took it back upstairs and recheck the wiring (the same controller is used for two 36V brushless Currie bikes with different features - I confirmed that the bike wouldn't work wired any other way). The next day I took it down for a street test. I ran the bike for about four blocks at about 5mph before it lost all power and would respond to peddle only. At this point I recall the bike voltmeter was down at the yellow <40% zone, closer to the 20% reading I think. Once more when I let up on the throttle completely the meter returned to 100% "full". I don't think I tried the throttle again, I just peddled home, took it up in the elevator and stashed it in my bedroom and hid my hammer from myself.

Reply to MEB:

I've measured the batteries with my hand held multimeter and get readings that roughly match the bike voltmeter readings so I don't thing there is anything wrong with the batteries. The charger I bought is a new soniel ( supposed to be a topnotch unit) and it appears to be working properly. Each individual battery measures as it should (no faulty - dead cells). It all adds up properly that the battery is OK as is the charger. I'm pretty convinced it is the throttle (slight chance) or the motor itself. The puzzling things are the voltage drop when in use with instant recovery when not in use and the fact that it will apparenlt go forever in a "no load" situation but has no "drive" in a load situation. It's like the amps vanish in a "load" situation.

Check the batteries with a amp meter and voltage meter with a auto headlight with the high beam element on as well see how many amps it draws untill your battery voltage drops to cuttoff. and time it to see how good your batteries work.

This shows that the no-load current at 1/2 throttle is too high so that the voltage drop is too much.
This fault could be due to an bad motor.

"At 90* - full throttle - the wheel is going very rapidly and will apparently go forever even though the voltmeter at this point has declined to about 40%"

Too high current again. Faulty motor! The no-load current at full throttle is usually less than 2A. This low current will not cause any significant volt drop. The voltmeter should stay close to 100%

Your road test was also pointing to a sign of faulty motor.

Currie usually use geared hub motors with free-wheeling. Even with an sticky motor, you still could pedal it with easy.

Disconnect the battery pack, turn the drive wheel directly forward by hand. Then turn it backward.
Turning forward, the motor will not turn due to free-wheeling. The drag should be very low.
Turning backward, the motor will turn. The drag should be slightly higher.

Compare the forces required to do forward turning and backward turning.

Try to take a reading on each individual battery whilst loaded ie at 1\2 throttle (wheel off the ground).
A bad battery will often show correct voltage at no load and may even look as if it is charging correctly but under load the bad battery will sag severely making identifying the culprit easy.
If the above is ok or you prefer to do thing the other way round, check the current draw in the above situation (don't know the older Curries but do the newer ones) the amps should be fairly low with out a load my assorted motors vary quite a bit but should be well under 5amps probaly closer to 1 or 2.
If that reading is to high current wise put the amp meter in ciruit between the controller and motor and recheck still high motor is dodgy lower the controller is the culprit.

The quick and dirty way to do the above is give it a large amount of throttle for say 30 seconds and see whats hot, if the controller and motor are cold still its the batteries, if one or the other is hot it is the culprit.
The amount of current required to cause the voltage drop you are describing will generate enough heat for you to smell the faulty part frying in 30 seconds.
My money is on a dud battery, it's not uncommon in SLA's.

"The7"wrote:
"Currie usually use geared hub motors"

Just for clarification, mine is one of their big hub motor models - brushless.
Well, at this point I suppose it won't do any harm to take the thing apart and find out if I can see anything that I can recognize as being amiss (don't have much faith in my ability to do that though).

Geared hub motor could be brushed or brushless.
Does your motor have free-wheeling?
Had you tried to do the forward and backward test?

The7:
OK, just so we are talking about the same animal, here is a link to the Currie site as well as a small photo:

https://www.currietech.com/html/mongo...nMainProd.html

Scroll down to the J3 and click on Large Photo" to see item. Mine has all the plastic bits stripped off, and no front basket .

As the hub motor only has a single sprocket/gear attaching the peddles to the motor, it behaves as follows:
It can't "freewheel" anytime as the motor is an integral part of the wheel. By hand, forward turn (peddles are disengaged) is easier than rear turn (peddles are engaged). Turning the wheel by peddles, forward of course turns the wheel; reverse the peddles and the wheel is disengaged.


GeeBee:

I did the quick and dirty and ran the thing with no load for one minute - nothing was hot. So, from this you think the new batteries are bad? As I said above, each battery alone measures correctly, and they sum up correctly on my voltmeter. They also give approximately the correct readings on the cheap voltmeter on the bike.

GeeBee,
OK dude, I have a couple of spare !2v SLAs here so I'll take apart the battery pack and try swapping out the batteries but that's a HUGE pain in the a**.
Likely I won't get to it until early next week. I'll get back to you.

Yes, we are talking about the same animal.

The site says: "Exclsuive DC Brushless Geared Hub Motor".

There is an motor inside the outer hub.
The outer hub is connected to the rim/tire (drive wheel) via spokes.
The outer hub is always turning with the same rpm as the drive wheel.
The motor is connected to the outer hub through an internal gear (usually planetary gear) such that the the outer hub will have a lower rpm than that of the motor.
Most designs add an internal free-wheel inside the hub such the motor will only drive the hub.

Thus if you turn the hub forward, the motor inside will not turn at all due to the internal free-wheel.
If turn the hub backward, the motor will also turn backwad with faster rpm.
You cannot see the motor and the internal gear (and the internal free-wheel) unless you open up the hub.

To "The7"
I would say Turning the wheel fwd by hand is only low resistance when compared to the opposite when the peddles are engaged. The Fwd turn has quite a bit of resistance.

Check how many total amp hours you get from your batteries by hooking up a auto head light as I suggested. Try to get something to draw about 10 ah until you see a major voltage sag. That will tell the story about the batteries.If they are week that large amp sucking Hub motor will give you the problem you have.

In view of your results the battery is close to being the only possible culprit, assuming you were measuring the voltage drop at the batteries (in your earlier testing) to eliminate the wiring having a bad connection between where you measured and the battery pack?

The voltage measurements on the individual batteries and the batteries in series were taken at the battery terminals with my multimeter. The voltage readings involving the motor operation were taken from a combo Voltmeter/headlight/horn that gets its signal through the controller.

To GeeBee:
Well, I have 5 SLA's on hand - the primary three and two alternates. I hooked up the two alternates and one of the primaries, then the two alternates and another primary - an both cases I got the same voltage drop when using the throttle (no load). I have no hope that presenting the batteries with a load would change prior results. Thanks for your help anyway - it eliminated one possibility.

To "The7":
Well, at this point it is a junker so I might as well take the motor apart and see if I can recognize anything as "wrong". Do you have any idea what I might be looking for?
Thanks,
Dennis

Could you first check the cabling from the motor and identify their coloring?
Usually there are 3 thick wires for the 3-phase windings; and
5 thin wires for the Hall sensors.

I'd check the plug things on the battery terminals, my guess is these are the culprits. You can tighten them down by taking them off the batteries and squeezing them lightly with pliers. They should fit tight on the battery terminals. Same kinda deal could be going on with the fuse holder, or other contacts between battery & controller. While you're at it check for rust in the contacts, or anything else obviously amiss. Oh and, you did use something like 14-12 AWG cable or thicker, right?