Motor works fine no-load, but jerks and cuts out with wheel on the ground.

[Gary Shannon]

Any idea what I should look for?

This is an AW 26" 48V 1000W front wheel from Amazon mounted on a Schwinn Meridian 3-wheeler. The unit is about a year old.

If I advance the throttle VERY VERY slowly it seems to work alright, but if I push the throttle at a normal, but gentle rate it bumps and jumps and then loses power.

With the front wheel off the ground, it works perfectly no matter how quickly I press the throttle. With the wheel on the ground I have to baby it to get up to cruising speed. Then it works fine while cruising, until the next time I release the throttle and press it again.

I thought it might have something to do with the controller getting a bogus "brake" signal and cutting power, but all the cabling looks fine from the brake levers.

 

[slomoshun]

Have you confirmed that the battery is healthy?

 

[harryS]

Really sounds like weak battery. It cannot deliver high currents any more. When called upon to do so via the throttle, the voltage from the battery sags so far that it triggers the low voltage alarms.

 

[Gary Shannon]

Have you confirmed that the battery is healthy?

Really sounds like weak battery. It cannot deliver high currents any more. When called upon to do so via the throttle, the voltage from the battery sags so far that it triggers the low voltage alarms.

That makes sense, but the battery is practically new 48V 20AH. I would hope it would last more than the 30 miles or so I've put on it so far. It's from an eBay seller with many hundreds of feedbacks, 100% positive.

Now that I think about it, there are three indicator lights on the throttle to indicate charge, and the "full" light blinks off when it stutters. That also sounds like battery sag.

I have an inline digital volt meter on the battery, but it's mounted on the cargo box and is behind me as I sit on the bike. I put it there to check battery charge before I go anywhere. I can crane my neck around and watch the voltage when I hit the throttle and see what happens. I'll report back in the morning on what I discover.

 

[Gary Shannon]

Have you confirmed that the battery is healthy?

Really sounds like weak battery. It cannot deliver high currents any more. When called upon to do so via the throttle, the voltage from the battery sags so far that it triggers the low voltage alarms.

Looks like you both got it right. I watched the voltage as I punched the throttle and it briefly drops from 54V to thirty something, and then when the motor cuts out it pops back up to 54V. That's really disappointing for such a new (and expensive) battery.

 

[slomoshun]

.... That's really disappointing for such a new (and expensive) battery.

Check the charger output.