Electric/hybrid question

I think the reason that rechargeables become less and less effective after a few years is probably because they are charged upto and beyond the 100% mark continuously. The electronics on these cars try to keep their batteries at around 80%.

I saw a website which showed the microscopic structures of rechargeables, and compared a new rechargeable with an old one. The difference seems to be in the buildup of some crystalline structures which act as barriers to chemical reactions. The site said that there are techniques available to breakup those structures and thus renew the batteries back to near original state.

Yousuf Khan

limiting the charge/discharge depth to just a few tens of percent kinda defeats the point using batteries doesn't it?

The simple answer is No. As an owner of an '04 Prius who follows a couple of Prius Yahoo Groups, I can tell you that the Toyota software keeps the high-voltage, or traction, battery at a state of charge (SOC) between 40% and 80%. Remember the car is *not* an electric car that is intended to go substantial distance on battery power alone. Rather the battery is a reservoir that in most situations is intended to be able to take in regenerated electricity (e.g. by braking) as well being able to supply energy for the electric motors to provide power when appropriate. When the traction battery reaches "full" charge, as in descending a long grade, the regenerative brake function cuts out and the car must rely on friction brakes alone. This doesn't happen in most normal driving but is an example of why the battery isn't intended to be kept at full charge.

I would stress that the Toyota hybrid design is an integrated approach wherein having the supplemental power from electric motors allows for the use of an smaller than normal internal combustion engine (ICE) that is optimized for efficient operation. Such operation is not possible for an ICE that has to provide start-up torque from a stop as well as power at hightway speeds.

Ed P '96 Outback

How long a grade does it have to be before the regenerative brakes fully recharge the batteries?

Yousuf Khan

I don't know. I live in Northern VA and my only personal experience on a big hill has been coming down Rt 211 from Skyline Drive to Sperryville and the battery did not max out. When some Prius owners were contemplating driving up and down Mt. Washington, the Prius chat group had all sorts of ideas about how best to deal with the situation. Certainly running the AC/heater, headlights, etc. expends some of the electricity and extends the time the brake regeneration takes to "fill" the battery. The car is equipped with a "B" mode wherein the ICE is spun to create engine braking.

Ed P

Our 2002 Prius "fills up" sometime shortly before we complete the 2700 ft descent from Flagstaff to Sedona, Arizona. I think the current model Prius has the same capacity, but allows higher regenerative braking rates so the hill could be steeper/faster and still not use the friction brakes.

Mike

For anyone interested in detailed discussion of hybrid cars, I recommend the Yahoo Groups Prius-2G and Prius_Technical_Stuff at

Ed P