Scooter has no "pulling power"

[TjorvenV]

Hi all,

I have a 1200W 60V electric scooter which was left in the wild world of rain, plants and lonelyness for a couple of years. It had 5 12V 22Ah AGM batteries which were dead. I tried to charge them but they did not hold any charge.

I decided to make myself a Lithium Ion battery pack. It is a 16s7p battery made with Panasonic NCR18650PF cells (3.6V 2900mAh 10A). The battery pack is connected to a BMS from aliexpress. I used pure nickel strips (0.15 x 6mm) which where 4 times spot welded on every battery pole. I used 7 strips for every series connection. The internet shows me that it could handle at least 4.7A per strip and 7A per strip was possible. On both ends of the pack I took one long stretch of 2.5mm copper wire which I soldered in between the cells on the nickel strip with a big soldering iron to reduce the time exposed to heat. Immediatly blowed cold air on it to cool after it flowed like I wanted. All the cell groups had the same voltage.

I tried the scooter with the new battery pack, but still the same result. It isn't strong enough to just ride me on a small uphill. The battery meter (which I think is just a voltmeter) went all the way in red when accelerating. I guess the red zone is less than 20%, but for lead acid voltages. It hit 30km/h max while it supposed to go 50km/h. I charged it to 67.2V and nothing changed except that the voltage doesn't drop that hard.

I opened up the controller to check for maybe burned mosfets or something. And I found that 1 of the 3 shunts is missing. I swapped it out with the 36V-72V 3000W bluetooth controller from Lunacycle. I had to solder the old connectors on it to connect it to the scooter but everything was straight forward. The controller connected to bluetooth and saved the settings like it should. I had to swap 2 phase wires for it to work properly, but still no progress. It still does 35km/h and has no pulling power.

I opened up one side of the hub motor (and broke a bolt ) but nothing seems burned or had a smell. I measured between single phases and the motor cover, but no connection so that was not the problem. The motor moves smoothly even when the cables are disconnected. It does cog when I connect 2 phases like it should.

I found some specs online:
https://m.globalsources.com/si/AS/Zhejiang-Haoren/6008837963258/pdtl/electric-scooter/1031106928.htm

Has anyone had kind of like this situation? Or can someone help me?

 

[larsb]

I guess you can readout the current in the app? ( check how much you're getting.)
After a long time outside i'd suspect all original connectors are destroyed. I'd switch all of them.

Do a max run, up a hill and check power reading:

-If it's low like 1000-1500W then it could be poor connections someplace, stopping current flow.

-It could also be throttle voltage not high enough to give full throttle (if the hall throttle or magnet is damaged/corroded or connectors are poor) What is throttle voltage max you can get?

-If power is 3000w or close to that then you have power to motor - then motor is not running well if you don't get ooomph

If there's enough power to the motor but no acceleration:
-it could be the motor magnets are toasted or corroded

-It could also be that hall sensors not corresponding to the phase connections on the new controller.

In those cases motor will get hot during riding caused by the poor efficiency.

A film with noload acceleration of motor (wheel in the air) from zero to max rpm, both slow acceleration and fastest possible throttle would give a lot of useful info. What speed do you get in this test @ what voltage and what current at max rpm?

 

[dogman dan]

What gets hot? That's your reason. hot battery or wires, its that. hot motor, its that, wires to the motor, particularly at the plug, its that.

Any stutter on it on the hill at all? one phase wire making bad contact, at the plug usually, can result in the thing running smooth no load, but no power under load because one phase cant get any watts. Essentially, its running on two wires, and coasting on the third. If its bad enough, it will stutter as well, on the heaviest load only.

 

[fechter]

It might be good to try measuring the battery voltage while under load. If the battery indicator is going into the red with a freshly charged pack, it seems the pack is sagging a lot under load.

Ideally you want to measure the current. Not easy unless you have a meter made to do that.

The comments about heat are good. If you are pulling enough current to make a good pack sag but not getting strong acceleration, then something is likely to be getting really hot somewhere. It might take a minute of trying before you can tell what it is. Go for a run, stop and immediately feel the motor, controller, and battery looking for hot spots.

 

[TjorvenV]

I will renew the phase wire connectors so they make proper connection and then I am going to do the testing you guys advise me. I have a 35A amp meter which I hope I don't destroy and a multimeter for the voltage. The app shows battery voltage but I think no current. I will be checking that also.

I tested the motor with a cheap LYEN e bike tester. The LED's of the phases light up when I turn the wheel fast (but doesn't mean the connection is good I guess) but the tester shows nothing when the hall sensor plug is plugged in. I tested them with a 9V battery on the red and black wire and a 10K ohms resistor in series with an amp meter from the red wire to every signal wire one at a time. They all gave 0.3mA when I waved a magnet above them.