Help troubleshooting strange problem: yescom / LiPo

Hi guys,

Not sure what's going on but when connecting my battery pack throttle leds light up but won't give me any power to the motor.

Variables that could be the problem:

Cells in LiPo got a slightly heavier voltage charge (all balance) last night. All cells in my 3s2p 5s turnigy got charged 4.14 (highest cells are cell 1 at 4.15v) ... shouldnt be a problem because the controller has 63v caps...

Bike was transported to another location (but not leaning on the side that the motor connectors exit

When pack was plugged to bike today 2p was missing. Harness has connectors for 1p and 2p as connectors, 2nd connectors disconnected in transport. Woops. Still lit up the bike leds... but 5Ah of the 10Ah pack was missing.

All connections are set

Not sure where to go from here. Any help would be awesome. More details on my setup are in the thread in my sig.

Thanks in advance for any help!

More information:

When connecting my lipo pack to the ESC the plugs spark. I'm used to this as I haven't installed a precharge resistor yet.

On/off switch on the throttle with the leds works. Out, throttle off. In throttle on.

All connections are made to the ESC except brake connectors. Never been a problem though. (twist throttles and I'd be more concerned.)

All the Halls (green/blue/yellow and yellow connectors in the transparent green sleeves?) are all connected. When spinning the motor they will spark when in contact with eachother. Normal. I've heard about running these kits without the sensors connected. Disconnecting all three of these wires does not fix anything.

Motor hub turns freely without any resistance.

markw said:

On/off switch on the throttle with the leds works. Out, throttle off. In throttle on.

Click to expand...

It's just the opposite on all the yescom kits I've bought. In cuts power, Out for normal operation.

BTW, 3 5s packs in series is 15s, not 3s, by stating 3s2p 5s, you're just confusing the matter.

markw said:

All the Halls (green/blue/yellow and yellow connectors in the transparent green sleeves?) are all connected. When spinning the motor they will spark when in contact with eachother. Normal. I've heard about running these kits without the sensors connected. Disconnecting all three of these wires does not fix anything.

Click to expand...

If your hall wires are sparking when turning the motor, then they are shorted to their respective phase wires, which is an unlikely failure. I suspect what you are actually dealing with there are the actual phase wires themselves (there will be only three of htose, whereas your hall connector will usually have five in it). If those phase wires are disconnected then you will not get any motor movement because they are what creates that movement.

If those wires are in the wrong order they may also not work, unless you have a sensorless controller and/or a learning jumper wire, or an autosensing controller (like the Fusin 1000W one I have here that automatically looks for the right combination/direction everytime I throttle up).


Since some of the pack connections got disconnected in transport, the only thing I could say is to reverify all of your connections. It's obviously getting voltage at the battery/harness connection if it sparks during plugin, but that doesn't mean power is getting everywhere else.

Almost always these things are just simple connection problems, but sometimes it is a wire that's actually broken at the back of a contact pin, and tha't sharder to spot, especially if things are heatshrunk or sealed at the backs of teh connectors.

Hi guys!

After some tinkering I have found the problem. Basically the connecting contacts between the ESC and the battery pack have arc'd so much that the contacts are now somewhat compromised. This was discovered by applying slight throttle while plugging in the pack. At a certain point in the insertion the male end of the connector allowed and then halted power.

This was a very curious cause to me because the LEDs on the throttle sorta suggested to me that it wasn't a power delivery issue...

I took very fine sand paper and got a lot of the black nast off the contacts and now they work decently. I do feel that the current delivered may not be the same. Could just be me being superstitious and without a multimeter but I did start the day with 4.15v per cell and now it's down to 3.8v after not a lot of riding... under 5 miles of riding probably. I guess that's not that unheard of... can charred/compromised contacts decrease efficiency? Could also be wasted electricity from charging the caps in the controller several times.

As of now the contacts work still but system still seems weird. The red button on the throttle which use to operate correctly as an on/off switch now no longer functions correctly. Plug in battery while button is "on" position - test throttle, works fine. Button "off" button "on... test throttle... no dice. Strange...

My precharge resistor is in the mail and will be installed very soon. In the mean time I'll try to keep these contacts clean. Would dielectric grease work with this application? Or would the arc from the connection just vaporize it?

@wesnewell 15s! Thank you for the correction... I'm still new and my terminology is not solid yet. Also a big thank you for all of your documentation and sharing of information related to yescom kits/lipo/more. I can safely say that your confidence in these motors steered me to buying one!

@amberwolf Thank you! I went through all the connectors and... y'know, in the end your post is pretty much dead on. Simple connection problem in the end. I overlooked this possibility because it hadn't impeded me from riding until today.

Yescom advertises their kit as being able to be used sensorless and with sensor I think?

Thank you ES!

Motors will run either way, but I don't know if they've started shipping controllers that will work both ways. Earlier versions were all sensor only.

wesnewell said:

Motors will run either way, but I don't know if they've started shipping controllers that will work both ways. Earlier versions were all sensor only.

Click to expand...

Just checked and they claim on their site, in actually decent english, that their controllers are sensored/sensorless now.

With our controller if the components break down, it'll switch into non-hall effect mode, the motor will still be working.

Click to expand...

though the "if components break down" seems to be a bit more inclusive than it should be. What happens if I get a flat tire, is it going to start running sensor less?

Back at home now. Recharged pack. Plug -spark- throttle... nothing.

Tried (very fine paper) sanding down the contact ends, cleaned them with cotton swab/alcohol, dried. Retried connection, nothing.

Tested throttle while wiggling plug ends... when in the last bit of travel current is strong enough to proc the motor to turn.

Aside from some of the gold plate missing on these bullet connectors they don't seem all too bruised. I have new contacts on the way and when they arrive I'll surely install them with my resistor.

For reference purposes though, are there any ways to restore these plug ends until new ones arrive? Are there ways to preserve them? Surely there are others who have dealt with scorched ends or others who chose not to implement resistor plugs.

I see on the wiki that from battery to controller 4mm bullets are not listed on the types of connectors used between battery and controller. Perhaps this is why it's not recommended and why manufacturers don't use them?

I've been using the same 4mm bullets for at least 3 years on mine with at least 1000 connects and they still look good as new. I do use a precharge resistor though. It makes all the difference when there isn't a spark when you connect them.

I don't think your battery connectors are the issue. Otherwise you wouldn't have had lights on your throttle. It would take some seriously badly corroded discharge connectors to give you that problem. I think you have a broken wire or badly crimped connector somewhere else, such as the signal wire on your throttle. I'd do some careful wiggling and checking until you find it.

Hello friends!

After carefully inspecting and going through all of your wonderful suggestions I found myself back to square one. I then moved back to my initial post that listed variables that had occurred between its operating/inop state. One that bothered me immensely was that I had moved the voltage up on my charger to 4.14v. I did this more for the health of my batteries than anything, after giving them a good discharge on the bike I wanted to give them a slightly more robust charge. I did this carefully because I had read in @wesnewell's "What you need to know about yescomusa kits" post...

wesnewell said:

500W kits come with 12 fet controller. 1000W kits come with 15 fet controller. 63V caps and 68-75V fets. So 63V max power.

Click to expand...

...so I knew that I was treading dangerously close to max voltage. I use two instruments to measure cell voltage and after charging they nailed it pretty well to 4.15v per cell x 15s = 62.25v - perfect! But maybe not?

Today I remeasured voltages on my packs... still 4.15v. Again... the throttle lights would illuminate, but nothing would turn the motor. I followed my first suspicion... I discharged the batteries back to what I had been using them at 4.10v x 15 = 61.5v. Plugged my pack back into the bike and whammo! It's working!

I will test things out, reset the harness, and move some stuff around to make sure it's not some whack connection that just happens to be in a functioning position, but I'm pretty sure that it was my controller refusing the overall pack voltage after trying my luck with a robust charge. I'll report in with results soon!

Very interesting. If you want to be able to bump your voltage, you might consider replacing the yescomusa controller with a lyen controller.

Or since you're running 15s, raise the lvc from the default 42V, to 52V, where it should be for 15s lipo. That alone may raise the HVC where you could charge fully to 63V. I don't think the older controllers even had a HVC.