jbeebe
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Joined: Tue Jul 28, 2020 8:49 am
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Leaf Number: 300240

Regenerative Breaking and Break fluid

Tue Jul 28, 2020 8:57 am

I just bought my Leaf and had it inspected by the local Nissan dealership before sealing the deal.

Something that came up was that they recommended that I change my break fluid a little earlier than recommended because "regenerative breaking is a fluid heavy process." But isn't regen braking just reversing the polarity on the electric motors? Is there even ANY fluid involved in this process?

What I've found online confirms my suspicion that the service personnel were full of it, but I don't want to be wrong about it.

LeftieBiker
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Re: Regenerative Breaking and Break fluid

Tue Jul 28, 2020 2:58 pm

You are correct, and they are at best mistaken and at worst lying.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
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goldbrick
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Re: Regenerative Breaking and Break fluid

Tue Jul 28, 2020 3:02 pm

You're correct that regenerative braking is simply reversing the way the current flows. Nearly any electric motor can be turned into a generator by switching the electronics around so the mechanical energy is converted to electrical energy, rather than vice versa. The brake fluid has absolutely nothing to do with this and there is no heat generated at the wheel. etc.

Oilpan4
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Leaf Number: 004270

Re: Regenerative Breaking and Break fluid

Tue Jul 28, 2020 3:07 pm

Smells like the dealer trying to doop you.
At 80,000 miles my breaks are like new as far as wear.
Brake fluid is hydroscopic, which means it pulls in water like one of those "damp rid" dehumidifiers and needs to be changed every few years.
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Is going to get you.

jbeebe
Posts: 2
Joined: Tue Jul 28, 2020 8:49 am
Delivery Date: 28 Jun 2020
Leaf Number: 300240

Re: Regenerative Breaking and Break fluid

Tue Jul 28, 2020 3:32 pm

Thanks for the response! 🤙🏻

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Nubo
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Re: Regenerative Breaking and Break fluid

Wed Jul 29, 2020 12:00 am

Although regen is electrical, the car does need to "blend" the effect of both regenerative and friction braking. Thus the system is more complex than even a regular ABS equipped vehicle. Not that it wears out the fluid, but I've come around to the notion of 2-year flush intervals. Simply the expense of the braking components that could require replacement due to water/corrosion/contaminants dwarfs the expense of a fluid change by orders of magnitude.

Sure, you could get test equipment/strips, etc.. But really there is so little periodic maintenance that a 2-year flush seems the least bothersome and most certain method. And if you DIY it is very cheap insurance.
I noticed you're still working with polymers.

LeftieBiker
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Re: Regenerative Breaking and Break fluid

Wed Jul 29, 2020 1:04 am

There is a downside to that 'cheap insurance.' The person doing the flush can screw up and get water into the system where there was none before. I don't get automatic transmission flushes every two years 'just in case,' and I don't advise that anyone driving a Leaf normally, in a normal climate, get the brake flush any sooner than three or four years. Getting your car serviced is also rolling the dice on getting it damaged.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
BAFX OBDII Dongle
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

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Nubo
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Re: Regenerative Breaking and Break fluid

Wed Jul 29, 2020 3:33 pm

LeftieBiker wrote:
Wed Jul 29, 2020 1:04 am
There is a downside to that 'cheap insurance.' The person doing the flush can screw up and get water into the system where there was none before. I don't get automatic transmission flushes every two years 'just in case,' and I don't advise that anyone driving a Leaf normally, in a normal climate, get the brake slush any sooner than three or four years. Getting your car serviced is also rolling the dice on getting it damaged.
I imagine you mean getting air into the system. You'd really have to go out of your way to get water in the system. And the point is to get water out; as mentioned the fluid is hygroscopic.
I noticed you're still working with polymers.

LeftieBiker
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Re: Regenerative Breaking and Break fluid

Wed Jul 29, 2020 4:45 pm

Nubo wrote:
Wed Jul 29, 2020 3:33 pm
LeftieBiker wrote:
Wed Jul 29, 2020 1:04 am
There is a downside to that 'cheap insurance.' The person doing the flush can screw up and get water into the system where there was none before. I don't get automatic transmission flushes every two years 'just in case,' and I don't advise that anyone driving a Leaf normally, in a normal climate, get the brake flush any sooner than three or four years. Getting your car serviced is also rolling the dice on getting it damaged.
I imagine you mean getting air into the system. You'd really have to go out of your way to get water in the system. And the point is to get water out; as mentioned the fluid is hygroscopic.
Getting air in gets water in, in most climates.
Scarlet Ember 2018 Leaf SL W/ Pro Pilot
2009 Vectrix VX-1 W/18 Leaf modules, & 3 EZIP E-bicycles.
BAFX OBDII Dongle
PLEASE don't PM me with Leaf questions. Just post in the topic that seems most appropriate.

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Nubo
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Joined: Fri May 28, 2010 11:01 am
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Re: Regenerative Breaking and Break fluid

Wed Jul 29, 2020 5:20 pm

LeftieBiker wrote:
Wed Jul 29, 2020 4:45 pm
Nubo wrote:
Wed Jul 29, 2020 3:33 pm
LeftieBiker wrote:
Wed Jul 29, 2020 1:04 am
There is a downside to that 'cheap insurance.' The person doing the flush can screw up and get water into the system where there was none before. I don't get automatic transmission flushes every two years 'just in case,' and I don't advise that anyone driving a Leaf normally, in a normal climate, get the brake flush any sooner than three or four years. Getting your car serviced is also rolling the dice on getting it damaged.
I imagine you mean getting air into the system. You'd really have to go out of your way to get water in the system. And the point is to get water out; as mentioned the fluid is hygroscopic.
Getting air in gets water in, in most climates.
The fluid is always in contact with outside air because a vent mechanism is needed to equalize pressure in the reservoir as the brakes are depressed and released. That's how water slowly accumulates. The short period of time when the cap is off for refilling during flushing and bleeding isn't a concern. I was referring to air in the brake lines, which will degrade braking since it is compressible and is removed by bleeding.
I noticed you're still working with polymers.

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