Battery only switch

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Sep 16, 2004
Vista, CA
Current gas/electric hybrids have a long warranty on batteries. The system keeps batteries operating in their sweet spot, charge wise and this will contribute to a very long life with few problems. Do you think the battery only operation switch is left off in the US because batteries would be deep cycled and will not live nearly as long, even though they could be charged up overnight at home?
makes sense. Also, if a battery costs $1000, and survives 500 deep cycles, with a 30 mile range on each cycle, that's 6.7 cents per mile, not including the cost of the charger or electricity.

Don't forget the primary mission of the battery array in a hybrid. It's more of an energy "buffer" than a sustained store of power. The array in a Prius, for example, will take you only a couple miles tops, when run in the "sweet spot" to which you refer, which in the Prius is actually a range of 40-80% SOC (state of charge). Even without the switch, you can induce such a run by driving at a steady state at roughly 35 mph or so on flat land. So, with the current array in the Prius, which is roughly the size of a medium suit case, even if you could plug in and even if you could defeat the ECU's sophisticated gas-electric balancing "plan," you might manage to go only a tad more than five miles on a totally full, 100% SOC array.

Why bother?

The genius in the current crop of hybrids is not in the total "volume" of electric energy storage, rather, it's the ECU's ability to optimally "recover" energy that you'd normally throw away every time you brake, decelerate, or both. Even before you can feel the "negative G" of deceleraton, the motor-generators are already pumping "juice" back into the array. Next time you step on the "gas" you get to use that energy again. You don't need a big array to do this, and you don't get one. Plugging in and EV-only switches don't really help, and therefore, we don't have them.
ekpolk, you're right. Hybrids could be called a buffer against poor driving habits, too. Today a Prius driver beat me to every stop light on my trip to Home Depot. My driving was so bad that every time I got to the next light it had just turned green. I could not even hit the brakes. I just had to keep pushing on. The Prius driver was so good that he would pass me up again, and agin, every time from a dead stop. It happened five time. Those Prius cars are tough to beat when you're driving a 22 year old Civic. He was cheating, though. He had two motors and I have only one. I rolled down my window, and sure enough when we pulled into Home Depot, I could not hear the engine running. The reason I could hear so well? I turned off my engine, too, and coasted into the parking lot, just like he did. I coasted all the way to a stop without using my brakes. I wanted all my energy back, sort of like a Prius. I've decided to have a contest with myself. I'm going to try coasting with the engine off, when I can, and see if I get better mileage.
Are other people doing that, too? I quickly learned not to shut down the engine while making a turn in a parking lot, with power steering.
The Prius driver has another trick up his sleve too: the electric side kicks in 295 lb-ft of torque. No, that's not a typo. It's all available from 0-1200 rpms. Result: the car is very, very quick off the line, and in short bursts. Of course, when you "add up" the rest of the driveline's characteristics, you get performance similar to an I-4 auto trans Camry.

PS and AC are electric driven (off the traction battery, incidentally), so gas engine state is totally irrelevant to their operation.
The conspiracy theorists say the EPA was confused by the battery only button; how could they judge pollution by the internal combustion section if the car was parked in a different state of charge than it departed?

Naturally it makes sense that the electricity probably came from a cleaner/ more scrubbed source... but the EPA doesn't make sense.

I would buy the battery preservation argument too though.
epolk, the gas and electric motors make a good combination, electric gets max torque and stall speed and the gas motor get is best will spinning much faster. I've been wondering if you could build your own hybrid and manually control the mix. I'll bet someone is doing it.

Originally posted by LarryL:
epolk, the gas and electric motors make a good combination, electric gets max torque and stall speed and the gas motor get is best will spinning much faster. I've been wondering if you could build your own hybrid and manually control the mix. I'll bet someone is doing it.

I'll bet many of them are doing it to their Prii. I've already dug deep into the internet Prius info, and it's amazing what some pioneers, experimenters, and well, just plain crackpots are doing with the Prius. Unfortunately, mine has to get me to work every day, or I'd probably be tweaking it some myself. From my observations so far, the ECU is very good at evaluating the battery's current SOC, and balancing the gas-electric mix optimally depending upon what you're trying to do. One of the truly strange aspects of life in a Prius is that it does not always react the same way to the same set of circumstances. In short, the more juice there is in the array, the more the ECU will rely upon torque from the motor-generators vs. power from the ICE.

The most interesting mods that I've seen (my perspective mind you) are the parallel battery set ups. You could do one of these that would eat up most of your cargo compartment, and add a lot of weight. Done right, and in conjunction with one of the plug-in mods, you could really tip the balance toward the electric side, and boost mileage considerably. Of course, a lot of folks seem to forget that the plug-in isn't free either - you pay the utility company for that energy instead of Exxon, Shell, or Citgo. I hasten to add also that such tinkering isn't for the faint hearted or the ignorant. One could do a lot of damage messing up such a mod. . .
Its interesting here to note that at the 15cents per kwhr we pay, gas is cheaper to burn than electric from PECO
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