2021 icon i40 with Roy pow lithium battery locks up

[Franklpaz]

I have 2021 Icon i40 with the Roy pow lithium battery. Last weekend I was driving home from a round of golf and all the wheels locked up when I was going about 25mph. The wheels locking up caused the cart to flip and for me to be ejected. Once I got off the ground a couple passerby’s help me flip it back over, but the wheels were still locked and the cart would not roll. We tried the switch under the seat and it still wouldn’t roll. The cart was on a full charge from the previous night and was driven a total of ~15 miles that day before the accident. I have no idea how or why this would happen, I’m just happy my young children weren’t with me. The icon store is being very unhelpful in this situation and just keeps saying “it probably ran out of battery”. I would never have purchased this if it is really supposed to lock up the wheels at 25mph if the battery runs dead because I often ride with my children. Since the cart is only 4 months old, it should be under warranty, but I think the store is giving me the run around to cover themselves. Any advice or knowledge of this happening would be greatly appreciated. Thanks.

[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]

The solution to this is complicated because the nature of the 2 devices. The magnetic brake wants to lock without power and the lithium pack wants to cut power in a panic. They are at odds with each other.

I'm not an electrical engineer, but I have an above average understanding of electronics. My layman's idea/approach is essentially a small backup battery and a logic circuit. I was eventually going to try and prototype something ghetto and then hand it to an EE and say "make this a real thing the way it should be."

When there is no power to the cart, the magnetic brake doesn't know if it's because you turned the key off or the BMS shutdown suddenly. That's where we need logic.

Coincidentally I was thinking about this on Monday so I've had 1 day to imagine something. For my ghetto prototype I was going to get one of those power banks people charge their phones with. It would need to be pass-through, where it can charge & distribute power simultaneously, and I'd hook it up to a buck converter. It would also have to be sufficient to engage the electromagnet.

The idea would be to hook it directly to the magnetic brake with a few relays for the logic so that when:

• Key is on + Battery Power = No power from backup battery
• Key is off = No power from backup battery
• Key is on + no battery power = POWER from backup battery to magnetic brake, preventing your scenario. The idea being when a shutdown event happens but your key is still on, your cart would just roll. You could still apply the physical brake and when the battery bank eventually died or the key was turned off, the brake would engage.

I think this would solve it. My initial concerns are:

• How fast does the magnetic brake close vs how fast could the relay switch power?
• How fast do those pass-through lithium packs take to turn "on" when power is requested? Some of them take a couple seconds
• How do you verify the backup battery is fully charged and working? It would need a status indicator on your dash

For a "final" product I would probably not use one of those power banks, but instead a small 12v lead acid battery used in e-bikes or something. Combined with a charger, buck converter, etc. Something super simple.

[Franklpaz]

Thanks for the response, I don’t know enough about these things. It happened on a flat road driving in a straight line. I got up to about ~20ish mph and the wheels locked. I’m assuming since I was driving in front left seat and golf bag on back left that once the wheels locked it cause the cart to lean one way ever so slightly which caught the edge of the front tire and violently flipped it on its side. I had no indication that the battery was low, so I’m not sure that was it. Like I said it had ~15 miles on the full charge. I’m assuming icon knows about these problems and is scared of a lawsuit and doesn’t want to acknowledge the problem. I’m just more worried about my kids riding in the cart in the future. How is this ever prevented from happening again?

[ATrain]

What was the outside temperature?

Do you think things (cart/battery/motor) got really hot?

Are you a heavy person?

Were you going up/down hills before your flat, 25mph drive?

What size/model is your RoyPow pack?

How far/long had you been driving the cart that day?

How long after you took it off the charger did this happen?

[IWalker]

I would think all the logic you would need is RPM>0 lock function disabled.

Of course the simple mechanical solution should be a torque break away safety value on the electro brake. Kind of like the parking prawl in an automatic trans will just tick away at speed.

Sympathy for the OP. Super crazy and destructive thing to happen on a new cart

[ATrain]

Originally Posted by IWalker

I would think all the logic you would need is RPM>0 lock function disabled.
Of course the simple mechanical solution should be a torque break away safety value on the brake. Kind of like the parking prawl in an automatic trans.

Measuring RPM > 0 from the controller requires the controller has power, which it wouldn't with a BMS shutdown.

I'm sure the motor has an RPM sensor (binary hall effect sensor?), but offhand I don't know how to find that data. Even if I did, it would be pure circuit design stuff plus ultimately still needing an aux battery.

My key logic vs your RPM logic really wouldn't make much of a difference...just deciding when the brake should not be applied.

Mechanical solution would work, but you're talking re-engineering the cart and the brake already on it.

My idea, I think, is more practical and could be easily applied to existing carts. I'm thinking a wiring harness, dual relay enclosure, small aux lead acid battery, aux battery level gauge, special automotive wire connections, and instructions and then it's solved.

[Franklpaz]

The outside temp was 65-70F

I'm not sure (outside of normal driving) if it overheated, wouldn't make sense for it to be hot

200lb guy

no hills whatsoever where I live

Paperwork says 51V / 105aH

cart drove about 15 total miles and was "on" for about 6 hours during that time

this happened about 8 hours after it was taken off the charger

[Franklpaz]

update: Icon store said initially that the battery was dead when they got it (2 1/2 days after the accident without it being charged again). Now they are saying that the battery is telling them that I never fully charged it the day prior to accident (even though it was on charger for 12+ hours prior to me taking it out that morning and it said it was fully charged. They say they are sending it to Roy Pow for a diagnostic, but I have a hard time believing that they are going to be honest with me. They are taking zero responsibility. They told me to file a claim with my insurance company. Not sure where to go from here. All I know is it wasn't my fault the cart locked and flipped.

[Pat911]

A cart that locks the brakes without power should never be converted to lithium. Lithium will cut all power on a fault condition to protect the cells, in this case injuring or possibly even killing the carts riders in the process.

I'm unfamiliar with the Icon. Can the magnetic brake be disabled? Are there mechanical brakes on this cart?