garsh
Posts: 1173
Joined: Sat Feb 12, 2011 5:27 am
Delivery Date: 05 Apr 2012
Location: Pittsburgh PA

Braking idea: dynamic braking

Mon Mar 04, 2013 3:35 am

If, like me, you often need to charge to 100% for your trips, then you too probably hate how the regenerative braking is much weaker or non-existent at those battery levels. It got me thinking about my days working for General Electric on diesel-electric locomotives. These things use their massive electric motors to slow down just like electric cars, but they don't have batteries in which to store the generated power. This system is generally known as dynamic braking.

Basically, they dump all that electricity into a big resistive heater. So that got me thinking - could we ("we" as in, "electric car designers", not we as in car owners & tinkerers) add a resistor grid to electric cars to act as a place to shunt generated electricity when the batteries are too full or too cold to accept the current? The main benefit would be that "regenerative braking" would always feel the same, so no surprises for the user. A secondary benefit would be less wear on the brakepads. Resistors shouldn't be expensive, but the electronics & controls for deciding where to shunt the generated electricity could be. And then there's the question of how to control & dispose of the heat that would be generated.

I'm guessing that the complexity just isn't worth the cost, but wondered what other people thought of the idea.
2012 Black SV, bought 2012-04-04, sold 2019-05-10. 7 bars, 101,850 miles.
Current rides: 2018 Tesla Model 3 Performance, 2018 Chevrolet Volt LT

BEVeedom
Posts: 31
Joined: Tue Oct 23, 2012 12:23 am
Delivery Date: 16 Oct 2012
Leaf Number: 021754

Re: Braking idea: dynamic braking

Mon Mar 04, 2013 4:34 am

That is an interesting thought and I know just what you mean about the fully charged car having no regen braking force. I like to drive in "D" and switch to "eco" when coming to a light, sorta like a compression brake on a big rig or downshifting a manual car. Resistors would be cheap. Maybe the heat could aid the HVAC system in winter on the first few stops. Or, switch to an Absorber type A/C that uses surplus heat and lithium bromide instead of the "heat of compression" type found on typical A/C compressors.

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