Braking to a red light

[sshaw10]

I've read some conflicting info regarding braking into a red light. One post said above 7 MPH, provided the brakes are not applied "hard", the regen system is used to slow the car and the pads are not engaged. Below 7 MPH or when applied hard the pads are used. If this is correct, if I know I have to stop at a red light and nobody is behind me and I can lightly ride the brakes wouldn't that be best for recharging the battery and if this is true it seems would lead to very long lasting brake pads?

[a64pilot]

I think you have it nailed. I try to start coasting so early that I don't have to brake, but of course for many reasons, it's not always possible, then your way comes into effect. I theorize it's better to slowly charge and discharge the battery as opposed to big loads, which if I'm correct leads further importance to your method.

[qbee42]

With the Gen III Prius, the cutoff speed for regenerative braking has been lowered, so it works even below 7 mph, although obviously the amount of available regen drops at low speeds.

For best efficiency, you don't want to brake at all. Try to anticipate the red light and coast. Failing that, brake at a moderate level, as that seems to produce fairly efficient battery recharging without invoking friction brakes.

Tom

[Mr. Bill]

Hey - I also use the shifter 'b' brake mode to assist in recharging - down shift to the dynamic braking mode also provides a wonderful way to recharge the battery without pressing the brake pads - try it.

Cool feature

Mr.Bill

[TonyPSchaefer]

Unfortunately, this is not the best use of the B mode. In fact, Shifting to B spins up the ICE.

[Mike Dimmick]

'Recharging the battery' is never necessary. The computer's target is 60% State of Charge, and it will burn extra fuel to get back there. It's rather like your toilet cistern, with a ball valve controlling the flow of water - if the tank is empty, the valve opens to refill it from the water supply, and the valve opens wider the further down the tank goes. If overfull, you can drain some without opening the valve and consuming water from the supply.

The car will leave the engine off if power demand is low, below a certain speed limit where it has to run the engine to prevent overspeed on the motors. This does allow the 'tank' to drain a bit, but the further it drains, the lower power demand you can get away with before it restarts the engine.

Because of the shape of the engine's efficiency curve, it can sometimes be more efficient to run the engine a little faster, to provide the road demand and charge the battery, than to just run the engine alone. Most of the battery charge comes from normal cruising, not from regen braking. Regen is a bonus, but the car doesn't account for any regen at all. You don't capture a great deal of energy from any one stop.

[reagd]

Originally Posted by TonyPSchaefer

Unfortunately, this is not the best use of the B mode. In fact, Shifting to B spins up the ICE.

+1. Yeah. I keep B mode as much as I can.

[philobeddoe]

Originally Posted by reagd

+1. Yeah. I keep B mode as much as I can.

why?

[fuzzy1]

I've read some conflicting info regarding braking into a red light. One post said above 7 MPH, provided the brakes are not applied "hard", the regen system is used to slow the car and the pads are not engaged. ...

A previous discussion did not come to a consensus, but I have to claim that braking has to be moderate or even light, depending on speed, to prevent pad engagement. Regen braking power is limited by the battery current limit, and common street braking rates that people are accustomed to on their non-hybrids very easily exceed this limit.

I try to make sure the the 2010's HSI display does not peg the recharge bar, whenever possible. It takes significant advance planning and change of habits to achieve this. And the accuracy of this display has not been confirmed.

[patsparks]

Originally Posted by Mr. Bill

Hey - I also use the shifter 'b' brake mode to assist in recharging - down shift to the dynamic braking mode also provides a wonderful way to recharge the battery without pressing the brake pads - try it.

Cool feature

Mr.Bill

Sorry, but B mode wastes energy.

The OP has the right idea.
Drive like your brakes are stuffed. Don't brake if you can coast to a stop, brake as long and light as you can if you have to brake. Best of all, time traffic lights so you don't have to stop at all.