Help! First e-Bike conversion - works but keeps cutting out at PAS level 5 or when using throttle

[John3mary]

Like the title says, I bought a rear wheel e-bike conversion kit, installed it. I amusing my own home build LiOn battery pack from recycled 18650s. The battery is not the problem, it has plenty of capacity (14s5p). This kit has PAS level 1 thru 5. 1 thru 4 work well, when I select level 5 it stops working and then I lost all power and the LCD goes dead. All I have to do is remove power, unplug from the controller leads that go to the battery, then reconnect and I have power again. If I try to use the throttle, same thing it starts to move and then it dies, remove power, resets something I guess, reconnect power and LCD comes back on again. If I stick to PAS 1-4 no problem, works great.

I am wondering if when it tries to draw a certain amount of power it cuts out because the battery or the wiring cannot provide the level of current it needs. That is my guess. The wire I used for my battery to the controller is size 12, the controller leads that use maybe, kind of small I think.

Has anyone experienced this type of behavior? Any thoughts on troubleshooting steps or solutions?

Thanks,

John

 

[Benjahmin]

In pas 5 or on throttle the controller is trying to provide maximum current (depends on the rating of your controller). From your description it sounds like the battery is not capable of delivering this current, therefore the voltage drops and the bms cuts out on low voltage to protect the battery.
Best way to prove it is to have a voltmeter connected to the battery when you use pas5. Should see the voltage sag severely just before cutoff.
This is the problem with using recycled 18650's, their state of health will be variable at best.
The solution is to have a battery whose known maximum current delivering capacity is around 1.5 times that of the maximum current rating of the controller.

 

[Nealh]

Battery can't supply the current demand and is sagging badly.
Old/used cells not 100% matched capacity or IR wise only needs one or two bad cells to tip LVC once sag is induced.

To make any more comments we need to know more details.
Cell spec used and BMS rating ?
Buss material & size used in the series connections ?

If the Buss material isn't spec'd for the current demand, it can't deliver the current load. More current will be lost to heat instead of power delivery.
12awg should be ok as rated for 45a minimum.

In general the the current can deliver about 50% of the current but not the 100% PAS 5/ throttle demands.

 

[vfr400]

The problem is that your battery cannot provide the current that the controller demands.

What is the maximum current written on the controller's label?
What is the continuus current that the BMS allows?

Assuming that you have compatible controller and BMS, recycled cells are a complete waste of time for an ebike unless you know their history and usage. If they were originally discarded because they were worn out, they become very saggy,. Did you do the essential capacity test and/or internal resistance test for the individual cells before assembling them to the batery?

 

[John3mary]

The problem is that your battery cannot provide the current that the controller demands.

What is the maximum current written on the controller's label?
What is the continuus current that the BMS allows?

Assuming that you have compatible controller and BMS, recycled cells are a complete waste of time for an ebike unless you know their history and usage. If they were originally discarded because they were worn out, they become very saggy,. Did you do the essential capacity test and/or internal resistance test for the individual cells before assembling them to the batery?

All excellent comments and observations, thank you.

All the batteries were tested for capacity and then I used a Repacker site on the Internet to enter all my batteries capacities and then created each 5p pack to match the others, very close within a few mAh for each 5p. The controller is model KT48ZWSRL-LCD, Rated at 13A, it also says on the label is has a Max current of 26 +/- 2A. My BMS says Maximum rated discharge current: 30 A. The internal resistance was not recorded on each of my batteries, I know some are 30 mR and some are 125 mR according to my LiitoKala Lii-500 charger.

I will put a volt meter on the battery to see if I can see the drop in voltage when using the throttle or PAS 5. I will also check my connections since I think the connection from the controller to the battery could be improved as well as the temporary cable to the battery is 7 feet long ( I was carrying it in my backpack), that could be shortened to about 6 -12" when mounted on the bike frame.

Thanks for everyone's help.

John

 

[Nealh]

Voltage drop will be about 0.6 - 0.7v for 7 feet, 1 ft wold be about 0.09v.
125mr is high so those high cells will draw the pack down irrelevant of capacity equalisation.

 

[vfr400]

you have a 26 amp controller and a 5P battery, which means approx 5 amps per cell. That's much too much for recycled ones. Exactly which cells are they?