Energy Dump?

(Not sure why this is in Audio & Electronics...)

Keep in mind that the battery meter on the MFD represents a relatively narrow window on the range the battery pack can be charged. The top of the meter represents about 80% of the HV pack's actual capacity; the bottom about 40%.

Why? Because the HSD is designed to try to keep the pack in roughly that range, to extend the pack's longevity. Full charges, and deep discharges, actually have a more detrimental effect on the battery's life cycle than just keeping the charge level somewhere in the middle.

So, when your meter appears to be 'topping out', you're not actually fully charged, physically; and when the meter 'bottoms out', you actually have a fair amount of slack.

The upshot is, in normal usage, it's actually going to be a pretty rare case that you're ever going to truly top out your battery!

 

I frequently drive down a long hill in which all the bars turn green way before reaching the end of the hill. The meter indicates that the battery is fully charged but continues to charge it. When reaching the bottom of the hill I can drive for a longer time before losing the first bar than I do when all bars turn green in another shorter hill.

Thus, mshappe is right. After al the bars turn green the battery is not yet fully charged.

 

Evan: I see all green bars two or three times a day, on the move and stopped at a light. I have not yet noticed the behaviors listed in 1 and 2.

 

Thanks for the explanation Evan! I thought that the engine turning was some kind of rare bug, but now it makes sense. I've experienced it a few times (very hill area). A full green battery wasn't uncommon in my semester.

 

furthur to Evan's #2, the engine runs at a faster speed to bring the MG1 speed down to a point were it's almost stopped and that decreases the output to the inverter/battery.

 

according to the tech specs a the battery indicator range is 70%-30%. so when the indicator says the battery is fully charged, it actually can take another 30%.

this is done because overcharging and undercharging the battery will greatly reduce the battery life. keeping the SOC in this range is the reason why this battery pack will last nearly 3 times longer than an average car battery.

iow, it aint the battery, its the computer controlling the charging circuit to the battery that is responsible for its long life. if the battery pack was treated like battery packs in laptops, etc. its life would be just as short as the laptop.

if you feel that you might be overcharging your batteries, turn on the headlights, crank the stereo, blast the air. it will all help burn off the charge. but unless the hill is huge, i wouldnt worry about it. the car's computer is set to guard against overcharge conditions.

 

Dave, don't the a/c, stereo, headlights, etc., run off the 12v system?
how do they draw power from the 200v+ battery?

it struck me that if the battery got too charged on a L O N G downhill stretch, say, from Donner's Pass to near Reno, couldn't MG1 and MG2 "buck" each other to consume energy, and perhaps pass that heat on to the radiator in front of the engine? i've wondered where heat from MG1 goes during a high-speed cruise. (or is it MG2... i keep forgetting)



ps. 47 mpg and round trip from Cupertino to Mendocino, plus some sightseeing there, ON ONE TANK! woweewoweewow! and handling on route 128 was super! loving this car more and more each day!

 

I experienced behavior 1 for the first time this morning. After going down a long hill and stopping at a red light, the ICE began turning on and off; it had done it three times before the light turned green. Thanks for pointing this out, Evan; I would have otherwise been afraid that something had gone very wrong.

 

Sometimes, it is almost impossible to prevent without major route changes. Here is my typical scenario that results in a 'full green':

1) Climb a 4% grade for 2 miles to a 1/3mile tunnel with a 2% dowgrade.

2) After the tunnel, coast down the freeway (at up to 70mph) 5% grade for 1.5 miles.

3) Brake to a stop on a long, almost level offramp to a traffic signal.

4) Coast down a 6 or 7% grade for 3 blocks.

At the end of this, I am almost always 'greened up'. If I lived in this neighborhood (the Rockridge district of Oakland, CA), that would be the normal final condition of the car when returning from work.

I actually proceed a few more miles to my home. I operate in stealth a good part of the distance, although one of my typical erands sends me up a 10 to 12% grade, giving the ICE a bit of a workout.

 

its situations like that where a larger power storage would come in handy.

the full charge indicator for the battery actually only represents a rather small range of charge. it is this range where the optimum life is achieved.

i think it would be nicer to have a battery pack that could say do 5-10 miles safely without the ICE. it could be used for short trips in town (these kill my mileage rating as i am positive i can exceed the EPA if not for these types of unavoidable trips and as the cold weather approaches i know my mileage will suffer even more)