Emergency Release of Electric Hold Brake

[John CN]

I experienced a flat conventional Battery recently on my 21 plate Hybrid Yaris. It is a questionable issue as to why this came about, but the substative issue was that it seems that until I got a "Jump start" it was impossibe to release the brake hold system, leaving the vehicle utterly unmoveable in the meantime.  Whilst thankfully on that occassion not causing a real immediate issue, this cannot be a satsfactory situation.  How do you relase the brake hold system when there is no charge in the Battery?  

[Bper]

Hi John, whilst I don't own a hybrid I thought read that a mechanical release is available in case this event happens. Have you had a look in your owners manual to see if there is one.

[Cyker]

Just to be pedantic, it's not the brake hold but the EPB - Electronic Parking Brake; Is better to not mix up the two as the brake-hold uses the hydraulics while the EPB uses motor-driven screw clamps.

I don't know with the Yaris specifically, but in the past the only way to release EPBs is by supplying 12v power, either directly to them via  a power probe or via a jump-starter.

Some cars have a manual wind screw that requires the wheel to be taken off and the car jacked up but I don't think ours has one of those as I've only seen such a thing on some German cars...

 

[Bper]

6 minutes ago, Cyker said:

Just to be pedantic, it's not the brake hold but the EPB - Electronic Parking Brake; Is better to not mix up the two as the brake-hold uses the hydraulics while the EPB uses motor-driven screw clamps.

I don't know with the Yaris specifically, but in the past the only way to release EPBs is by supplying 12v power, either directly to them via  a power probe or via a jump-starter.

Some cars have a manual wind screw that requires the wheel to be taken off and the car jacked up but I don't think ours has one of those as I've only seen such a thing on some German cars...

 

Cyker, thanks for the information as I mentioned I do not YET😂 have a hybrid so its good to know. Now call me old fashioned but what is the point in having a system that if the Battery fails there is no way to release it except for supplying a 12v supply. How many people carry this around. Glad i have a manual handbrake.

[forkingabout]

1 hour ago, Bper said:

Hi John, whilst I don't own a hybrid I thought read that a mechanical release is available in case this event happens. Have you had a look in your owners manual to see if there is one.

Won't be a mechanical release as newer EPB like used on Toyota / Lexus products have the a electric motor on each rear caliper.

You would need to unplug the motor & apply 12 volts to it to release the caliper then repeat on the other side.

On the Toyota counter balance forklifts I look after with electric parking brakes we have a service tool that is basically a wiring loom with 2 connectors, plug in to each parking brake then apply the correct voltage ( 24 volt in that case ) in to the other end to release the parking brakes.

Wouldn't be surprised if the automotive side of Toyota had something similar.

[TonyHSD]

You need to feed the car 12v power from jump pack or smart charger to release parking brake, switch to N in some models and to unlock and open rear hatch. Modern cars relays on electric power for everything. 

[Cyker]

16 minutes ago, Bper said:

Cyker, thanks for the information as I mentioned I do not YET😂 have a hybrid so its good to know. Now call me old fashioned but what is the point in having a system that if the battery fails there is no way to release it except for supplying a 12v supply. How many people carry this around. Glad i have a manual handbrake.

That is why I'd also opt for a manual hand brake given a chance (And not just because you can't do handbrake turns with an EPB ) - You can't beat just having a simple mechanical linkage in an emergency!

I just feel a bit safer knowing that if all the electrics in the car suddenly shut off, I could still stop it with a manual handbrake, but then with the hybrid I'm giving up the manual gearbox too which I could also have used to slow the car down, but that's just how it is with modern cars, having a much higher reliance on the computers and electrics.

 

13 minutes ago, forkingabout said:

Won't be a mechanical release as newer EPB like used on Toyota / Lexus products have the a electric motor on each reach caliper.

You would need to unplug the motor & apply 12 volts to it to release the caliper then repeat on the other side.

On the Toyota counter balance forklifts I look after with electric parking brakes we have a service tool that is basically a wiring loom with 2 connectors, plug in to each parking brake then apply the correct voltage ( 24 volt in that case ) in to the other end to release the parking brakes.

Wouldn't be surprised if the automotive side of Toyota had something similar.

Wow that's neat having a dedicated tool - I think most garages just jam a 12v power probe onto the pins if they can't get the 12v system going, but usually they just connect one of those massive 12v jump packs to power the 12v system and use an ODB2 widget to put the EPB into service mode, which automatically unwinds them (And I assume recalibrates them after)

 

[Chas G]

A jammed on EPB was one of my fears either through flat 12v Battery or pads stuck to discs having parked a soaking wet car in the garage and left it for a week. Trying to sort things out with the car in the garage would be difficult because there is barely any room to work.

To avoid this I always disable the EPB before I park in the garage if the car is wet. I have a jump pack etc and I leave the wheels straight as the steering lock will be on.

Thankfully a friend said just ring him if there is a problem and he will just drag the car out of the garage with his truck so I can get it transported to a scrap yard.

[dash]

Don’t forget that the transmission is also locked with a pawl until you can move the lever out of P position 

[MikeSh]

2 hours ago, Bper said:

what is the point in having a system that if the battery fails there is no way to release it except for supplying a 12v supply.

What's the point of releasing it if you can't start it? 

Seriously, the first thing to do if the electrics are dead isn't releasing the parking brake.

2 hours ago, Cyker said:

if all the electrics in the car suddenly shut off, I could still stop it with a manual handbrake,

You could try using the footbrake. Even without power assist it'll be better than a handbrake. 

2 hours ago, Cyker said:

having a much higher reliance on the computers and electrics.

Airliners* have been fly-by-wire, so totally dependent on those, for decades.

( * Except the 737 which is a 60's design with improvements. But even that seems to be worse than the modern stuff ... )

[Cyker]

2 hours ago, MikeSh said:

What's the point of releasing it if you can't start it? 

Seriously, the first thing to do if the electrics are dead isn't releasing the parking brake.

The obvious answer is to allow it to be pushed out of harms way or to tow it - They thought of it with the P mode pawl, as there is an interlock switch to allow it to be disengaged, but that won't release the EPB.

 

2 hours ago, MikeSh said:

You could try using the footbrake. Even without power assist it'll be better than a handbrake. 

I'm not sure it would in our cars - Don't forget they are Brake-By-Wire and although it does have a fail-over mode, IIRC that looses all brake boost assistance - Trying to stop a car on the hydraulic brakes with no brake booster requires an incredible amount of force!

A handbrake with the mechanical advantage of the lever would likely be better in that scenario, or even help as you could use both!

These are all worst-case scenarios though, and unlikely to happen, but still worth contemplating and definitely not dismissing...!

 

2 hours ago, MikeSh said:

Airliners* have been fly-by-wire, so totally dependent on those, for decades.

For large aircraft that is true, but they have triple redundancy and a mechanical backup with two pilots to put in the required force; I don't think the cars have any redundancy and only an unassisted backup on the hydraulic brakes for a single driver to supply all the force...

It's one of the reasons I was very against Toyota's steer-by-wire idea, as that doesn't even have the mechanical backup!

[forkingabout]

39 minutes ago, Cyker said:

It's one of the reasons I was very against Toyota's steer-by-wire idea, as that doesn't even have the mechanical backup!

Hopefully the automotive side have asked the forklift side about steer by wire as they have used it for at least 30 years now.

I've never ( 18+ years & counting fixing them ) seen a BT / Toyota steer by wire system fail & cause an accident.

Extremely rarely I've seen the system has detect a fault but it will always fail safe, stops traction & won't release the parking brake.

 

[Cyker]

I'm sure the systems are very reliable but forklifts have a much easier life - they don't need to go at 70mph or over pot-hole ridden wastelands or cope with large temperature swings or being exposed to acidic salty water, snow, gravel, clods of dirt, wasp and midge swarms, cats, rats and bats, etc. (Less so the latter but I'm a sucker for rhymes...   )

I much prefer mechanical systems as they give me consistent and useful feedback - The Yaris is the first car I've driven with brake-by-wire and it's given me several squeaky bum moments already as, contrary to what I was led to believe, the force-feedback has very little bearing on the amount of braking force applied and it's something I still haven't gotten used to.

Given how little feedback modern electric powersteering already gives - I have a lot of difficulty telling what the front wheels of my Mk4 are doing compared to my Mk1 - I can only imagine steer-by-wire feedback will be non-existent to misleading.

The problem is the people developing these systems don't seem to understand and just downplay its importance so I'm not optimistic.

[Dick_Dastardly]

I tried to roll mine forward yesterday after parking in a supermarket and realising I was a good foot short of where I should be.

Tried putting it into neutral to just roll it forward but it wouldn't let me remove the EPB until I'd shut the door, enabled Ready mode, and put my seatbelt on. 🤔

I really miss a manual gearbox sometimes 😅

[Cyker]

I did something similar a few weeks ago but didn't have to put it in Ready mode again because I'd forgotten to switch it off  

 

[bathtub tom]

I've been blocked in a parking space by some silly sod who had a flat Battery and couldn't release their EPB as result. Scraped an othewise perfect alloy trying to manoeuvre out!

[MikeSh]

4 hours ago, Cyker said:

and a mechanical backup with two pilots to put in the required force

With the exception of the 737, and possibly some older Boeings, no they don't. They are pure electro-hydraulic. (There are 'only' three hydraulic systems, but 4 or 5 power sources and 5 flight control computers.)

But only two engines ... 🤔

4 hours ago, Cyker said:

Trying to stop a car on the hydraulic brakes with no brake booster requires an incredible amount of force!

I know. I've occasionally rolled a car out of the garage, which goes onto a downslope, without turning it on and been alarmed by the difference of having no assistance. But it did stop.

[Hadrian1]

17 hours ago, John CN said:

I experienced a flat conventional battery recently on my 21 plate Hybrid Yaris. It is a questionable issue as to why this came about,

It doesn't  take a lot to flatten the 12v Battery.  Mine went flat while I was sitting in the car waiting for my wife.  I was playing around with the Android Auto and the radio, and had been doing mostly short journeys in the winter.  I had to call out Green Flag.

I now carry a 12v power pack.

[Cyker]

7 hours ago, MikeSh said:

I know. I've occasionally rolled a car out of the garage, which goes onto a downslope, without turning it on and been alarmed by the difference of having no assistance. But it did stop.

Ha, same!  That's why I know a handbrake works a a LOT more effectively - I thought I was going to roll into the road because the hydraulic braking was so weak but panic-yanked on the handbrake and it stopped immediately!

I don't think it will ever be a situation I'll be in with the hybrid as I don't even know how I could roll it off-power like I could in my old manual cars!  

It does make you appreciate how much force a vacuum brake booster supplies - I don't know how people stopped their cars before it was invented...! (Or did everything just use all drums before that??)

[bathtub tom]

2 hours ago, Cyker said:

It does make you appreciate how much force a vacuum brake booster supplies - I don't know how people stopped their cars before it was invented...! (Or did everything just use all drums before that??)

I've had two cars with discs (no self-servo effect) and no servo. '60s Vitesse and Panda. Braking was no problem and much lighter than an old LandRover on all drums. We've all become too used to over-assistance, particularly steering.

[Chas G]

23 hours ago, Cyker said:

The Yaris is the first car I've driven with brake-by-wire and it's given me several squeaky bum moments already as, contrary to what I was led to believe, the force-feedback has very little bearing on the amount of braking force applied and it's something I still haven't gotten used to.

The first car I drove that had brake-by-wire was a 1934 MG PA.

It had a cable to the drum brake on each wheel and no syncromesh on the gearbox.

Really quite frightening because whether it stopped in a straight line depended on the tension of each cable.

[bathtub tom]

I recall sorting the brakes on my brother's sit-up-and-beg Ford, shortly before his driving test. Straightened the brake rods and replaced the clevis pins. Examiner stated "the brakes on these aren't normally that good".

[Gren]

I have a 1971 Austin, when I want to brake, I need to plan ahead, e.g. 2pm next Tuesday

[Sharnie70]

On 5/4/2024 at 9:48 PM, Dick_Dastardly said:

I tried to roll mine forward yesterday after parking in a supermarket and realising I was a good foot short of where I should be.

Tried putting it into neutral to just roll it forward but it wouldn't let me remove the EPB until I'd shut the door, enabled Ready mode, and put my seatbelt on. 🤔

I really miss a manual gearbox sometimes 😅

On Saturday I reversed into a parking space at the shopping centre and did what I used to do in my petrol car - put my foot on the brake and opened the door to see if I was within the lines. The car was just about screaming at me to put it into park. Lesson learnt 🥱. 

[Cyker]

2 hours ago, Gren said:

I have a 1971 Austin, when I want to brake, I need to plan ahead, e.g. 2pm next Tuesday

Funnily enough that sounds like the accelerator on my first car!  

 

1 hour ago, Sharnie70 said:

On Saturday I reversed into a parking space at the shopping centre and did what I used to do in my petrol car - put my foot on the brake and opened the door to see if I was within the lines. The car was just about screaming at me to put it into park. Lesson learnt 🥱. 

The car does feel like it comes with a highly-strung R2D2 robot with PTSD built-in sometimes...