Power and torque reduction when PHEV's battery is drained?

[YurkshireLad]

I'm trying to educate myself on PHEVs compared to hybrids. If a PHEV's battery drains while driving, it'll continue at a lower efficiency. Though some, like the Kona seem to still offer decent fuel economy for longer drives. Once the battery is drained, how does that affect the power and torque from the drivetrain? Is it significantly reduced?

I drive in some hilly areas and a huge drop in power could be an issue on the highway. I seem to recall the Toyota Hybrid I owned many years ago had that same problem. Once the battery was drained, the available power was much lower and was an issue in hilly areas. Thanks

 

[bwilson4web]

A former Prius owner, 2003, 2010, 2017, and BMW i3-REx, 2014, 2017, I have some experience to share:

• Reduce speed to avoid draining the battery - use the battery as an energy buffer that gets charged descending hills and braking. Then drawn upon to climb or accelerate while engine stays at optimum thermal dynamic efficiency.

Instead of either/or operation of the engine and battery, use them to complement each other. Keep the ICE running at peak efficiency using the battery SOC to fill in the deficits or save energy normally wasted by braking.

Bob Wilson

 

[insightman]

I'm trying to educate myself on PHEVs compared to hybrids. If a PHEV's battery drains while driving, it'll continue at a lower efficiency. Though some, like the Kona seem to still offer decent fuel economy for longer drives. Once the battery is drained, how does that affect the power and torque from the drivetrain? Is it significantly reduced?

I drive in some hilly areas and a huge drop in power could be an issue on the highway. I seem to recall the Toyota Hybrid I owned many years ago had that same problem. Once the battery was drained, the available power was much lower and was an issue in hilly areas. Thanks

In the case of my Honda Clarity PHEV, it's very rare to have it go down to a single bar of charge in it's charge gauge. If I continue driving in EV mode, when the charge gauge reaches two bars, The Clarity switches to HV mode, preserving the remaining charge for use as a buffer. It can still achieve an average of 42 mpg in that situation, just as if I had manually selected HV mode earlier to preserve the remaining charge at a higher level.