Sunrunner 24v bike repair

[KirstinS]

I'm trying to help out a local ebiker wth this , it transpires, unusual bike.

It is 24v system , the battery is a mere 5ah in a handlebar mounted box. Crucially it is Lifepo4

The controller is mounted in a box by the front fork it has an integrated led light.

The motor has some markings and I gather is Taiwan made . Presumably brushless at this stage.

First question then - anyone recognise this motor ?

Second - could a flat Lifepo4 show 25.5v? The led show empty. I just wonder if Lifepo4 can appear like the old prismatic lithium when knackered ? Ie show a decent voltage and seem charged but drop to nought as soon as a load is applied ?

I've asked her to leave pack on charge for 12hours and I'll go back tomorrow with a 22.2v Lipo fully charged to test further

Photo to follow

 

[flecc]

I'm trying to help out a local ebiker wth this , it transpires, unusual bike.

It is 24v system , the battery is a mere 5ah in a handlebar mounted box. Crucially it is Lifepo4

The controller is mounted in a box by the front fork it has an integrated led light.

The motor has some markings and I gather is Taiwan made . Presumably brushless at this stage.

First question then - anyone recognise this motor ?

Second - could a flat Lifepo4 show 25.5v? The led show empty. I just wonder if Lifepo4 can appear like the old prismatic lithium when knackered ? Ie show a decent voltage and seem charged but drop to nought as soon as a load is applied ?

I've asked her to leave pack on charge for 12hours and I'll go back tomorrow with a 22.2v Lipo fully charged to test further

Photo to follow

Before I even see the photo I'm guessing it's a Sun e-bike, originally marketed as Sun rather than Sunrunner. They used the Tongxin Nano motor in this model with the handlebar mounted battery box and left fork mounted controller. This is the motor with roller drive instead of internal gears.

It's not unusual for a battery to show high voltage but the voltage collapse under any load if one or more cells are dud.
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[anotherkiwi]

From ES

"Most likely the long term storage without disconnecting the bms or recharging the battery regularly has led to the bms discharging one or two cells. The BMS runs on less than pack voltage, and over a few months can discharge the cells it runs on.

You will need to acess the battery before the bms, and get voltmeter readings on each cell. Usually you can do that by unplugging the bms, and then probing at the plug contacts. Move the probes down the row, getting a voltage on each of the cells.

Likely you will have to replace the dead cells to fix it. But you can try to use a cell phone power supply to bring the low cells up, if they are not at zero. Once up to 3v or so, the bms may then allow the battery to charge."

 

[KirstinS]

From ES

"Most likely the long term storage without disconnecting the bms or recharging the battery regularly has led to the bms discharging one or two cells. The BMS runs on less than pack voltage, and over a few months can discharge the cells it runs on.

You will need to acess the battery before the bms, and get voltmeter readings on each cell. Usually you can do that by unplugging the bms, and then probing at the plug contacts. Move the probes down the row, getting a voltage on each of the cells.

Likely you will have to replace the dead cells to fix it. But you can try to use a cell phone power supply to bring the low cells up, if they are not at zero. Once up to 3v or so, the bms may then allow the battery to charge."

I recognise that phrasing, it's d8veh I'll bet !

Ok, well I'll plug my Lipo in as a first test and see if it's just duff battery

Thanks all

 

[KirstinS]

 

[KirstinS]

Have to say it seems too big for a tongxin, no ?

 

[KirstinS]

 

[flecc]

Have to say it seems too big for a tongxin, no ?

That's the bike I meant ok, but not the same motor. It was a Tongxin Nano in the one I saw reviewed, arranged to be quite low powered due to that tiny battery. They must have fitted another motor at some time and I've no idea what that one is.

P.S. Just did some searching and it seems these came in different versions. There was also a 3.5 Ah battery option apparently, which seems even more odd.
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[anotherkiwi]

Can I say it?

OMG!