Big spark connecting lyen 18 fet for first time

[electr0n]

So I'm trying to hook up my 18 fet lyen controller to my hs3540. I've only connected the 3 phase wires and 5 halls temporarily. I have the thin red wire directly connected to the positive wire. When I try to hook up my battery I get a big spark like there's a short. So I tried disconnecting the thin red wire from the positive and I still get a big spark when I try to connect the battery.

Any ideas? I hooked up my 12 fet from ebikes.ca without any issues and I had to figure out the hall and phase combos manually so I do have some experience doing this.

What would cause a big spark like that, a bad mosfet out of the box maybe? How should I proceed. Should I open it up and check the fets? How can I test the controller to make sure its working right? Could that thing be the cause of my spark?



I've opened up the controller. On the underside there is a single component. It looks like might be a diode or maybe a resistor and it looks damaged. Anyone know what it is?

 

[ohzee]

...

 

[electr0n]

That sucks to hear and I'm 99% certain I didn't do anything wrong. I had no trouble hooking up my 12 fet controller from ebikes.ca and it was not plug and play I had to figure out the hall and phase combos. I don't want to spend another $100 getting a controller repaired plus shipping if it wasn't my fault. Did lyen let you know which components were damaged?

 

[ohzee]

http://lyen.com/Pictures/Ohzee/

there's the pictures from my controller.

Lyen does awesome work and I am sure he knows more about controllers in his sleep then I will ever know.

 

[dnmun]

the spark is from the current surge as the input capacitors charge up. i find it hard to believe you never heard of this if you spent much time here before this. you really sent it back for repairs?

 

[ohzee]

Yea in my experience I had a short so if you just had a spark and no kff then were dealing with different things.

 

[electr0n]

With my two other controllers a small 6 or 9 fet (forget now) 20 amp and my 12 fet from ebikes.ca I get a relatively small spark and I know that's normal. I've even been running up to 88.8v. The spark on 44.4v is negligible on my 12 fet.

When I connect to the lyen 18 fet I got a major spark like a short. I was being cautious and only fully connected one battery lead and just touched the other for a brief moment and the huge spark startled me. I'm only testing at 44.4v so I was expecting very little sparking. The spark was enough to char my bullet connector pretty good and take a little chunk out of another wire on my 2nd attempt.

Could it be that the spark is bigger because the caps are bigger on the 18 fet and more current is flowing for the brief moment I'm connecting? I guess I'll give it another shot but I'm going to use a thin wire from a balance connector to connect to act as a fuse. I can't see anything damaged on the inside of my controller, nothing obvious. That single component on the underside is a resistor hidden under a sleeve that I thought might have been a damaged component.

 

[ohzee]

Yea sorry to mislead this sounds like expected behavior to myself.
removed my comments.

 

[Hyena]

It sounds more like inrush current to the caps to me. You're using pretty tiny power wires and assuming your running lipo from the voltages you quote if there really was a short they'd blow apart. A proper short on a lipo pack will vaporise some or all the connector - I've had 4mm bullets reduced to a melted stub. Just connect the other wire without hesitation and you'll probably find it's fine. If it's shorted then it's already stuffed so don't worry about it! If you're still scared put a resistor in line with the wire that's sparking to precharge the caps.

 

[electr0n]

All right I gave it another try. I soldered in a thin gauge wire between the positive battery connection to act as a fuse just in case. I jammed the plug in fast and still got a spark but nothing burned up to my relief. Gave the throttle a tiny twist and got a nasty sound so now I just have to figure out the phase and hall connections.

I feel like a bit of a heel for not realizing the big spark was ok. It's just quite a bit bigger than what I've experienced and reminded me of times when I've accidentally reversed polarity on my anderson connectors. I know some people are using resistors to help with the spark but in my experience with my setup it wasn't necessary but I can see how it would be desirable with this controller for sure.

Anyhow thanks for the help guys. I'll probably be back tomorrow with some controller programming questions. Looking forward to see if this controller fixes my stuttering problem around 60kph.

 

[dnmun]

the lyen controller has that draindown resistor on the input caps too so even if you use a precharge resistor to preload the caps, they can drain down before you swap the connection to the mains.

also that makes it impossible to keep the controller connected all the time unless you do the modification that alanB did when he removed that resistor from the controller.

 

[Jeremy Harris]

If you don't want the spark (and personally I hate the way that charge spark erodes connectors pretty fast) then the easy way around it is to fit a simple pre-charge switch. The very simple circuit below will do the job just fine, but there are probably better ways using soft switching if you want to get more adventurous (check my RFID switch thread for an example that works well).



With this circuit what you do is connect the connector or switch at the top (the one in series with the resistor) first, then connect the connector or switch at the bottom maybe 1 second or so later to connect full power. There won't be any appreciable sparks and your connectors/switches will have a happier time (and longer life). The way it works is that the precharge connection has a resistor to limit the inrush current, so reducing or eliminating the spark. The capacitors still charge OK. When the main power connection is made a second or so (or any time) later the capacitors are already charged and so there's no spark.

 

[The Mighty Volt]

@OP

From my limited experience, you didn't damage anything.

Imagine the battery pack as being an area of high potential, and the capacitors in the controller as being areas of low potential.

When you connect the controller and the battery, there is a "surge" from the area of of high potential to the area of low potential.

The capacitors fill very quickly in an unregulated fashion and that's the noise you hear, its like a loud crack and can, as Jeremy pointed out, do tangible damage to not just the connectors but also internal components, especially over time.

If you have difficulty with the schematic which Jeremy laid out, then simply follow the more illustrative method as laid down by ES member Zenid in his blog:

http://zenid10.wordpress.com/2011/02/20/adding-a-controller-pre-charge-switch/

Its an excellent step-by-step guide and I recommend it fully.

 

[electr0n]

Thank you for all the replies. My controller is fine. No harm caused. The spark is significant and I will have to eventually do something about that. Lyen said the capacitors are much larger in the 18 fet vs the 12 fet so that is why the spark is bigger. That resistor in the switch looks easy enough to do so I will probably try something like that once I get a switch. Appreciate the explanation

For now I'm excited to get my bike out for a ride. I'm just now trying to flash the controller. The default profile for the lyen 18 fet is set to only 30 battery amps and 80 phase amps. However I read a post from methods:

"There is DC current and Phase current. The numbers you see in the software are based on a LARGER shunt resistance value. When you cut the shunt resistance value in half you are effectively tricking the controller. When you are running 100A the controller thinks it is only 50A. That being the case, we have understand the relationship between the actual current and the programmed current.

The shunt values range from around 220uOhms to 240uOhms. This will put some variance in the numbers. As a rule of thumb, the controller is going to run about double the current you set up. If you want a DC current of 60A I would suggest that you start by setting the DC current in the software to 30A."

So I suppose I should leave it at the default settings if I want to run 60 amps battery current? That's 30 amps battery, 80 phase. I also reduced block time to 0.1 for now. Any other settings I need to change?

 

[RichiePA]

Hey I really like the look of this a simple way of pre charging so I'm going to nick it at stick it on my bike but have the precharge switch as a push button switch (non toggling) so I can just push it and hold while I flip the main switch.

Even simple electronics like this can make my brain hurt so I have a few questions
is a 100Ohm 1W resistor beefy enough to do the job on my 72V15Ahr pack would a 5W resistor be better?
what sort of rise time would you expect, I know you'd need to know the exact capacitance to work it out propperly but I'm not sure what that would be on my 12 fet 72V 45A crystalyte controller but a guestimate time would be good, i.e. do I need to push the resistor switch for less than a second before flipping the main switch or would it take a few seconds?
would the precharge circuit need beefy 10AWG wiring or would you get away with thinnner wires.

If you don't want the spark (and personally I hate the way that charge spark erodes connectors pretty fast) then the easy way around it is to fit a simple pre-charge switch. The very simple circuit below will do the job just fine, but there are probably better ways using soft switching if you want to get more adventurous (check my RFID switch thread for an example that works well).



With this circuit what you do is connect the connector or switch at the top (the one in series with the resistor) first, then connect the connector or switch at the bottom maybe 1 second or so later to connect full power. There won't be any appreciable sparks and your connectors/switches will have a happier time (and longer life). The way it works is that the precharge connection has a resistor to limit the inrush current, so reducing or eliminating the spark. The capacitors still charge OK. When the main power connection is made a second or so (or any time) later the capacitors are already charged and so there's no spark.

 

[HighTekBikes]

You want the momentary position to connect the resistor to the center connector, so double check with an ohm meter.

You should have an inline fuse (battery or controller side) on the plus wire for safety reasons. These are available at your local auto parts store.

 

[Jeremy Harris]

Why bother with the momentary switch?

Seems a way to make a really simple thing complex and subject to user error to me. Switching the resistor permanently, then shorting it, is foolproof, whereas the momentary switch relies on the user switching back quickly, especially with the newer versions of the Xiechang (like the ones Lyen sells) that have a built in discharge resistor.

 

[kfong]

My solution was to use a delay and allow Fets to power up the circuit. It keeps it simple as well as allow for other useful functions. No more sparks, or having to remember to precharge.

 

[Gow864]

Why use a switch at all? My resistor is permanently connected across my main switch. Yes, it means that the controller is on all the time, I mean on as in having an electrical feed to it. It's not enough to make the controller run though. It could be a problem if I were to leave the bike unused for a while, it would probably drain the battery, but, as I use my bike daily it's not a problem.

Gow.

PS: I have held my resistor between the batt + and controller + for a few seconds (I can feel the resistor get warm), I can then remove the resistor and connect the + leads with no spark at all.

 

[HighTekBikes]

What happens if the switch is left on the resistor position? It either drains the battery or worse, they try to run the motor in that position. If something simple works for you, great. I have to take the average user into consideration. My circuit works perfectly with all controllers.

 

[wesnewell]

I have my resistor permanently wired in parallel with the + 8mm bullet connector to the battery. Plug in controller side. then plug in the 8mm connector. Reverse procedure to disconnect. Simple. Easy. No switch to break. Mine works with all controllers too.

 

[Jeremy Harris]

What happens if the switch is left on the resistor position? It either drains the battery or worse, they try to run the motor in that position. If something simple works for you, great. I have to take the average user into consideration. My circuit works perfectly with all controllers.

If you're quick enough it does, not if you're not. Those controllers with drain down resistors (like the one in question here) need the power to be switched fairly quickly after precharge with this momentary arrangement, else the capacitors discharge again.

Why use a switch at all? My resistor is permanently connected across my main switch. Yes, it means that the controller is on all the time, I mean on as in having an electrical feed to it. It's not enough to make the controller run though. It could be a problem if I were to leave the bike unused for a while, it would probably drain the battery, but, as I use my bike daily it's not a problem.

Gow.

PS: I have held my resistor between the batt + and controller + for a few seconds (I can feel the resistor get warm), I can then remove the resistor and connect the + leads with no spark at all.

The problem with leaving the controller on (at least for controllers like this one with a drain down resistor) is that they do draw current all the time.

My solution was to use a delay and allow Fets to power up the circuit. It keeps it simple as well as allow for other useful functions. No more sparks, or having to remember to precharge.

FWIW I now use a simple slow-start FET power switch too, which completely removes the need for any high current switching and gets back to just a simple on-off switch. It's a bit more complex, but is pretty much bomb-proof in terms of being simple to use. The only thing I found was the need to use several FETs in parallel to get the Rdson down to the same sort of resistance as a conventional switch. In my case that meant using four paralleled 4110s to get a reasonably low voltage drop (I get around 30 mV drop across my switch FETs at 30A, which is OK, I think).

 

[Hyena]

controllers with drain down resistors (like the one in question here) need the power to be switched fairly quickly after precharge with this momentary arrangement, else the capacitors discharge again.

Do you know the reasoning behind fitting these drain down resistors Jeremy ?
I was surprised to use a controller recently that apparently didn't have this fitted because after turning off the controller with the controller power switch and then removing the battery to recharge, it didn't spark at all when reconnecting. I'd become so used to seeing that zap on connnection that I though I had a loose wire or dud controller at first! (it'd been several hours) It was an infineon type too, just a different model I guess.

 

[Jeremy Harris]

controllers with drain down resistors (like the one in question here) need the power to be switched fairly quickly after precharge with this momentary arrangement, else the capacitors discharge again.

Do you know the reasoning behind fitting these drain down resistors Jeremy ?
I was surprised to use a controller recently that apparently didn't have this fitted because after turning off the controller with the controller power switch and then removing the battery to recharge, it didn't spark at all when reconnecting. I'd become so used to seeing that zap on connnection that I though I had a loose wire or dud controller at first! (it'd been several hours) It was an infineon type too, just a different model I guess.

Just a safety thing, really, to remove stored energy from within the controller when it's disconnected. As some have found when taking controllers apart, those without discharge resistors (some of the Xiechang/Infineons, for example) can easily short the board to the case as you slide it out, blowing the controller (I think methods was one of the first to discover this, with the 18 FET Xiechang controllers I believe). It also prevents the risk of getting a big spark if the controller leads are accidentally shorted after it's been disconnected from the battery. The capacitors can hold a charge for a fair time if they don't have a discharge resistor, so best to drain them down if possible.

I'm not sure when the Xiechang controllers started being fitted with discharge resistors, or whether it's just something Ed Lyen adds to the versions he sells.