2021 icon i40 with Roy pow lithium battery locks up

[fixed4life]

Originally Posted by Pat911

You need to consider battery safety as well. Connecting the EMB prior to the BMS will mean that the EMB magnet cannot be disconnected to protect the battery from being over discharged. This needs to be considered when designing any solution to this problem as even a single incident of a cell getting below it’s threshold voltage will render it unsafe to use.

An acceptable solution would be for the BMS to cut power to the controller, allowing the cart to come to a gradual stop and then removing power to the EMB 30 seconds later. 30 seconds will give plenty of time for the cart to stop.

I do like the idea of a timer, that would absolutely be plenty time. That said, the EMB requires power to disengage, not to engage, so there should not be an excessive draw issue with wiring it pre-BMS as we were discussing here (not to mention, if you are going through the trouble of wiring in these relays, you will likely not forget to not charge the cart every few months).

I personally do not use a BMS at all on the load side of my battery and the EMB is the biggest reason. That said, I purposely built my pack (and all busbars, cables, etc) to handle 300A continuous, and since with the stock controller I zip along at 38-40 at 140A or less, so I am well within the safe zone. The neos controller also does a good job of managing low voltage situations (from a total voltage perspective) if you tune it correctly, and that is good enough for me. I understand and accept that I may loose a cell here and there (I run 16s 4p so a single dead cell would not ruin my day out), but those cells are $20-40 or so which is much cheaper than the associated expenses with flipping the cart and eating asphalt.

[Pat911]

Like you, I have a custom Lithium solution in my Club Car, and I don't pass discharge current through the BMS either. I only cut the keyswitch on a fault condition. I am not a layman end user though. I know all about the dangers of Lithium and how to avoid them. I therefore monitor my battery and am very aware if its condition.

There needs to be a laymans drop in solution for carts with an EMB as the current crop make the cart very dangerous to use. The only real solution is to make the manufacturers aware of the problem so that they can engineer a fix.

If this scenario was occurring to a full sized motor vehicle it would be recalled immediately.

[fixed4life]

Originally Posted by Pat911

Like you, I have a custom Lithium solution in my Club Car, and I don't pass discharge current through the BMS either. I only cut the keyswitch on a fault condition. I am not a layman end user though. I know all about the dangers of Lithium and how to avoid them. I therefore monitor my battery and am very aware if its condition.

There needs to be a laymans drop in solution for carts with an EMB as the current crop make the cart very dangerous to use. The only real solution is to make the manufacturers aware of the problem so that they can engineer a fix.

If this scenario was occurring to a full sized motor vehicle it would be recalled immediately.

I absolutely agree. Icon (as far as I know) does not install Lithium batteries in their carts, it is the dealers, and hobbyists that do it. Hopefully, if someone is the latter, they will take the time to understand that it can be a dangerous endeavor and learn how to avoid such perils. What concerns me most are the dealers and shops that are installing these in folks carts and just sending them on their way. This is where I imagine the biggest danger lies.

All of that said, there is a serious amount of merit to ATrain's idea to use an auxiliary battery and a relay or two to resolve this. 36v hoverboard batteries for example (10s @ 37v) come to mind as they are cheap as chips, have an internal BMS to manage charging voltage, and would energize the EMB for quite some time. I believe that the whole thing could be done though the run/tow switch connections by energizing the tow side (for a period of time as you suggest) in the event of a loss of continuity to the switch ground input (something that should never happen unless the battery was pulled or the BMS cut it).

[robertmII]

Atrain and Fixed,

This is outside of my level of understanding bur would gladly be willing to chip in to the development if one of you wants to take on the challenge.

I've got a lifted 6 passenger with the S51105P Roypow pack. This battery does a lot to limit the chance of shutoff. Higher continuous discharge, much higher max discharge for 30 sec and big resistor to blead off overcharge. It doesn't prevent some internal failure from shutting down the BMS though.

The most important people in my world ride in this cart so coming up with a way to prevent BMS shutdown induced lock up is a development project I will gladly support.

[dundeebarnbuggy]

Putting a normal [pedal] parking brake on the carts would be the the simple, safest, and reliable to the point of being damm near bulletproof, solution no?

[fixed4life]

Originally Posted by dundeebarnbuggy

Putting a normal [pedal] parking brake on the carts would be the the simple, safest, and reliable to the point of being damm near bulletproof, solution no?

Was not ignoring this suggestion, I just couldn't answer since I do not know if hardware exists to do something like this. The Icon has hydraulic disc brakes and the calipers are not parking brake compatible as far as I know.

If anyone has knowledge of the bits that could possibly get this done, I would certainly like to hear about it also.

[ATrain]

Originally Posted by dundeebarnbuggy

Putting a normal [pedal] parking brake on the carts would be the the simple, safest, and reliable to the point of being damm near bulletproof, solution no?

I don't think this can be easily done.

The EMB would have to be removed or those two screws tightened down (easy).

Then I don't think there's an off-the-shelf replacement pedal that would work with the disc brakes.

The real deal breaker I think is the EMB is critical to how the car drives and accommodates the accelerator delay.

Without the EMB, I remember if I was trying to make a right turn while on an incline, I'd have to keep my foot mashed on the brake and then use my other foot to press the accelerator and then release the brake once the motor engaged...otherwise I'd start rolling backwards then kind of lurch forward.

I think that type of delay behavior was mitigated by the controller releasing the EMB right when the motor engages/

[dundeebarnbuggy]

So your cart [without the electric brake] drives like any vehicle with a standard transmission, or any cart with mechanical brakes.

[Pat911]

Originally Posted by fixed4life

All of that said, there is a serious amount of merit to ATrain's idea to use an auxiliary battery and a relay or two to resolve this. 36v hoverboard batteries for example (10s @ 37v) come to mind as they are cheap as chips, have an internal BMS to manage charging voltage, and would energize the EMB for quite some time. I believe that the whole thing could be done though the run/tow switch connections by energizing the tow side (for a period of time as you suggest) in the event of a loss of continuity to the switch ground input (something that should never happen unless the battery was pulled or the BMS cut it).

I don't like this solution for a number of reasons, mainly because you're increasing the number of failure points and making charging more complex.

Firstly, if the second auxiliary lithium hoverboard battery is configured to always operate the EMB then what if it were to trip whilst the cart was in operation? we would have the same scenario as the OP.

Secondly, if the auxiliary battery was only called upon to operate the EMB if the main battery tripped, how do you know it is good if 99.99% of the time it just sits there doing nothing. Once again, you'd have the same scenario as the OP.

A solution I would implement would be to take a permanent, pre-BMS feed for the EMB with a timer to disconnect the EMB a preset time after the BMS trips. Having the battery power the EMB for less than a minute after the BMS trips will be perfectly safe, especially if conservative trip points are set in the BMS. The timer circuit could be very simple.

Another solution would be to utilise lead acid or GEL batteries for the EMB. Not as elegant as the timer solution though and creating charging issues.

Does anyone know the current draw of the EMB?

Cheers
Pat.

[ATrain]

Originally Posted by dundeebarnbuggy

So your cart [without the electric brake] drives like any vehicle with a standard transmission, or any cart with mechanical brakes.

Kind of, except I think the accelerator delay is the issue. You can't use one foot really to go from brake to accelerator to move the cart immediately. It'll just roll wherever it wants and then eventually the motor engages.

Gas carts, in my experience anyway, have variable transmissions and they don't start rolling backwards the second you take your foot off the brake either.

It's hard to explain, but it's easy to experience by just tightening the two screws on the EMB and driving the cart around a hilly area. It's just not usable in every scenario, which makes it not usable for me.