2021 icon i40 with Roy pow lithium battery locks up

[trevorg7]

Is there a way to release the brake after a lock up event without removing/dismounting the brake from the motor?

Thanks in advance.

Trevor

Originally Posted by ATrain

What you experienced is the exact concern that I, and others, had with lithium packs and I'm sorry it happened to you, but in a weirdly good way you've proved our fear. I hope you're ok. Can you describe in more detail how you flipped? Did the tires lock and run you into a curb? Or did they lock and drag the cart sideways and flip? I'm curious if you were in a flat parking lot, would you have still flipped or was it locking tires and the road that caused it or turning the wheel?

It 100% is an issue and somebody (Roypow or ICON dealer most likely unless it came from factory) is liable. It's honestly absurd they're letting these carts go out when there's such a risk of what you experienced happening. I expect them to pull all lithium myself once one lawsuit happens. It's gross negligence IMO.

Lithium packs have a BMS (battery management system) that manages the lithium cells and makes sure they don't overheat, overcharge, etc.

If something happens that causes a BMS shutdown event, where it panics and cuts all power, this causes your "spring applied magnetic brake" to automatically engage and lock your tires up.

The way those brakes work is they're essentially a lock on the electric motor connected to an electromagnet. The lock has springs that try to push it closed. When the electromagnet receives power (42v @ 1.19amps per my calc) from the controller, it pulls the lock back against the springs and keeps it "unlocked" and your motor can operate. Here's a video how they work. When the electromagnet turns off or the battery gets cut, the springs push the lock and that's what happened to you.

There are various BMS "shutdown events". One example is if you have a FULLY charged battery and live on top of a hill and coast/drive down the hill with your foot off the brake, the motor essentially generates power via regenerative braking and it overcharges the already full batteries. This makes the BMS panic and cut off so you don't damage the lithium cells, so your magnetic brake engages. There are already reports of this happening where the cart just locks up down a hill.

If it's HOT outside, you've been driving the cart a long time, and there is not adequate ventilation/cooling of the lithium pack, the BMS might detect overheating of the cells and panic and shutoff. This would lock up your tires too. I'm curious if this is what happened to you?

Another example is perhaps if you run the lithium pack all the way dead it could happen.

Personally, I would have thought the momentum/weight of the cart at speed would break the magnetic brake, but apparently not! The magnetic brake on our carts is 46Nm...there's a bunch of math to determine what that can stop...tire friction, weight of the cart, cart speed, etc...but apparently it was able to stop your cart.

This thread has some discussion that covers what you experienced - https://buggiesgonewild.com/showthre...hlight=lithium

[ATrain]

Originally Posted by trevorg7

Is there a way to release the brake after a lock up event without removing/dismounting the brake from the motor?

Yes, just do the reverse of what I suggest in this post. You should be able to just tighten the 2 smaller hex-head screws and it prevents it from clamping down.

https://buggiesgonewild.com/showpost...69&postcount=5

[fixed4life]

Glad you are ok.

It is a seriously bad idea to run the EMB circuit through the BMS of a LiFePO4 battery, it is just plain dangerous. Not sure what access you would have in this particular battery, but it is a simple task (generally) to run the ground from the EMB circuit (isolate just that relay or do the entire chassis ground) to connect directly to the pack. If the BMS needs to intervene to stop an overcurrent issue, it needs to kill the motor, the rest of it is small beans.

[ATrain]

Originally Posted by fixed4life

Glad you are ok.

It is a seriously bad idea to run the EMB circuit through the BMS of a LiFePO4 battery, it is just plain dangerous. Not sure what access you would have in this particular battery, but it is a simple task (generally) to run the ground from the EMB circuit (isolate just that relay or do the entire chassis ground) to connect directly to the pack. If the BMS needs to intervene to stop an overcurrent issue, it needs to kill the motor, the rest of it is small beans.

The BMS is inside the pack I think. Is there a "pack" output and a BMS output?

I've never seen a RoyPow lithium pack up close but I had imagined there was just one output and the BMS determines if power flows or not?

[fixed4life]

Originally Posted by ATrain

The BMS is inside the pack I think. Is there a "pack" output and a BMS output?

I've never seen a RoyPow lithium pack up close but I had imagined there was just one output and the BMS determines if power flows or not?

I also do not have experience with RoyPow, but I am sure that there would only be a "post BMS" ground connection available outside the pack. Generally though, those batteries will have prismatic cells in 16s with threaded posts that are accessible once you open the lid, so bypassing it would not be too hard. That said, not sure about tamper prevention stickers, etc. that might void the warranty though.

I ended up building my own pack (16s, 4p) and I do not run a BMS at all on the load side. I use it solely for charging and balancing. The NEOS has a great set of configurable tools for managing overcurrent and low voltage situations (from a total voltage perspective at least) and that is honestly good enough for me.

[ATrain]

Originally Posted by fixed4life

I also do not have experience with RoyPow, but I am sure that there would only be a "post BMS" ground connection available outside the pack. Generally though, those batteries will have prismatic cells in 16s with threaded posts that are accessible once you open the lid, so bypassing it would not be too hard. That said, not sure about tamper prevention stickers, etc. that might void the warranty though.

I ended up building my own pack (16s, 4p) and I do not run a BMS at all on the load side. I use it solely for charging and balancing. The NEOS has a great set of configurable tools for managing overcurrent and low voltage situations (from a total voltage perspective at least) and that is honestly good enough for me.

Here's a post with pictures of someone's. The last picture shows the terminals. https://buggiesgonewild.com/showpost...55&postcount=3

It looks like one would need to just unscrew the top plate to access and yes they should be prismatic cells like you said. I remember reading that at one point.

Why would you run the EMB ground to the battery ground though? I'd think you'd run the EMB positive to the pack bypassing the BMS? And wouldn't that prevent the EMB from ever engaging?

[fixed4life]

Originally Posted by ATrain

Here's a post with pictures of someone's. The last picture shows the terminals. https://buggiesgonewild.com/showpost...55&postcount=3

It looks like one would need to just unscrew the top plate to access and yes they should be prismatic cells like you said. I remember reading that at one point.

Why would you run the EMB ground to the battery ground though? I'd think you'd run the EMB positive to the pack bypassing the BMS? And wouldn't that prevent the EMB from ever engaging?

Seems about right. Looks like that one might not even have any tamper evident seal type label (or at least not on the outside).

Inside, you will find that the BMS is inline with, and cuts power via the ground not the positive.

Like this:

[ATrain]

Ah I see what you're saying now. In layman's terms, when the BMS cuts power, it's basically pulling the negative terminal off the pack. And you're suggesting connecting the EMB somewhere inline where I pictured below so that it will remain powered in the event of a BMS issue. Right?



Doesn't that make the EMB always on?

It seems like the best solution would be just hooking only the motor and charger somehow but keeping power to the controller. So when the BMS shuts down the primary load (motor) is disconnected.

[fixed4life]

Originally Posted by ATrain

Ah I see what you're saying now. In layman's terms, when the BMS cuts power, it's basically pulling the negative terminal off the pack. And you're suggesting connecting the EMB somewhere inline where I pictured below so that it will remain powered in the event of a BMS issue. Right?



Doesn't that make the EMB always on?

It seems like the best solution would be just hooking only the motor and charger somehow but keeping power to the controller. So when the BMS shuts down the primary load (motor) is disconnected.

Yes, it cuts the ground.

My initial thought was to isolate that circuit so only the ground to the relay / run/tow switch bypassed the BMS (as pictured in red), or to bypass the entire chassis wiring as you suggest since the load is still relatively small (shown in blue). So, not wiring the EMB to be constantly on, but providing an uninterruptible ground to the circuit one way or another. Trouble is, the more I look at this, the more it looks like the signal to the relay from the controller will still drop if the BMS cuts power to the the big cables as the controller ground will drop.



I plan to work on mine this weekend in sort of the opposite fashion (I would like to get my chassis wiring (sans the EMB of course) on my BMS because the Daly Smart bluetooth functionality only activates when it detects load or charging) so, I will confirm that is the case.

Otherwise, I think there are two ways around it for sure.

1 - Parking brake switch. Not as convenient for sure as the auto brake feature, but as long as you wire it to a pre-BMS ground, it would be an easy way to solve the problem (I would use a relay for good measure). The right switch, wouldn't even look too bad.


2 - Auxiliary relay. One that works in some set of conditions. So, if you say move the chassis wiring to be pre-BMS, you could have a relay wired so that if the power is on to the chassis the EMB is off. Or, if you added a speed sensor to the mix, it would be possible to simply not allow the EMB to engage if the cart is moving, but that one would require a bit of extra hardware.

[ATrain]

Originally Posted by fixed4life

Yes, it cuts the ground.

My initial thought was to isolate that circuit so only the ground to the relay / run/tow switch bypassed the BMS (as pictured in red), or to bypass the entire chassis wiring as you suggest since the load is still relatively small (shown in blue). So, not wiring the EMB to be constantly on, but providing an uninterruptible ground to the circuit one way or another. Trouble is, the more I look at this, the more it looks like the signal to the relay from the controller will still drop if the BMS cuts power to the the big cables as the controller ground will drop.



I plan to work on mine this weekend in sort of the opposite fashion (I would like to get my chassis wiring (sans the EMB of course) on my BMS because the Daly Smart bluetooth functionality only activates when it detects load or charging) so, I will confirm that is the case.

Otherwise, I think there are two ways around it for sure.

1 - Parking brake switch. Not as convenient for sure as the auto brake feature, but as long as you wire it to a pre-BMS ground, it would be an easy way to solve the problem (I would use a relay for good measure). The right switch, wouldn't even look too bad.


2 - Auxiliary relay. One that works in some set of conditions. So, if you say move the chassis wiring to be pre-BMS, you could have a relay wired so that if the power is on to the chassis the EMB is off. Or, if you added a speed sensor to the mix, it would be possible to simply not allow the EMB to engage if the cart is moving, but that one would require a bit of extra hardware.

Your #2 sounds like what I was thinking from the beginning, except your suggestion avoids an auxiliary power supply all together. I haven't worked with lithium enough so I was unaware you could bypass the BMS.

I'd actually do 2 relays for redundancy and have them with basic logic where the keyswitch on + BMS off = EMB off. Otherwise, EMB = on, except the BMS/controller would work as normal turning the EMB on/off as needed.

That way, in the event of a BMS event, the loss of power keeps the EMB on. Essentially turning the keyswitch into an auxiliary tow switch.