Checking regenerative brakes

[verv]

Hey everyone, new to the forums here.

I've been working on a list of things to check for when buying a used EV, and I think a lot of it's pretty obvious once you're used to them, but I've been asked if there's any quick visual signs to look for that would be a red flag for problems with the regenerative braking system. The hypothetical example I was given was a car auction, where you're not going to get much time to check them out, but can potentially get really good deals. Any insight is appreciated.

Also if you have any other weird suggestions of similar things to check that aren't specific to a certain vehicle, just general "Look out for this" ideas, I'd be interested in that too.

 

[hobbit]

Regenerative capability may depend on how the vehicle's control
systems were designed. I.e. does it have fully blended braking, or
some compromise that gives some quantity of regen when feet
are off both pedals, etc.

One test is to perform a fairly hard but smoothly-applied stop from
a high-ish speed, preferably downhill to increase tne energy-capture
requirements, and then get out and feel the brake rotors. If they're
still cold after a successful slow/stop from a good clip, that's a
pretty clear indication that the braking energy went into the battery.

_H*

 

[electriceddy]

Regenerative capability may depend on how the vehicle's control
systems were designed. I.e. does it have fully blended braking, or
some compromise that gives some quantity of regen when feet
are off both pedals, etc.

One test is to perform a fairly hard but smoothly-applied stop from
a high-ish speed, preferably downhill to increase tne energy-capture
requirements, and then get out and feel the brake rotors. If they're
still cold after a successful slow/stop from a good clip, that's a
pretty clear indication that the braking energy went into the battery.

_H*

At an auction I doubt there is the chance of a test drive, you could however by observation check the rotors for minimum wear and the thick brake pads would indicate regen is working.
The biggest concern of course would be the condition of the battery pack itself, depending on the make/year/chemistry which may best be achieved by use of a dongle and app. You never know how the EV was treated eg: charging patterns , cycles and ambient temperatures depending on where the EV was located.

 

[bwilson4web]

and then get out and feel the brake rotors.

One caution, use an IR thermometer as some brakes (i.e., my Model 3) run with a little drag and reach temperatures of 140-180 F. Yes, I am looking for 'no drag' clips.

Bob Wilson

 

[verv]

Thanks guys, great stuff. To clarify the situation a bit I'm looking at the possibility of having to send employees to an auction and just telling them to buy any EVs they see that are great deals. Of course there are many things you can't quickly check for, and it's always a gamble to some degree, but I figured if I have a decent list of red flags even people who aren't very car savvy are going to have better odds. This hasn't actually come up yet, but I'm trying to be prepared, and it seemed like a fun project anyway.