Battery never shows full charge??

[duraace]

Been driving Eco for a couple of days, and the battery has never shown 8 bars, only 7. Does this indicate a problem?

[drbrr]

We've had ours a little over a week and I think it only showed "full" once. I haven't had time (or inclination) to read the manual to see what that means.

[dmvp]

I've read this a few times in some another post, and supposedly the battery usually max's out at 80%, which is supposed to be best for the life of the battery. So it's designed for that. I've only seen mine at 7 as well, have a little over 600 miles, and will have owned it for a month tomorrow!

[1 mad scientist]

Originally Posted by duraace

Been driving Eco for a couple of days, and the battery has never shown 8 bars, only 7. Does this indicate a problem?

We have had our 2010 for 12 days. I noticed the battery never goes to full. If you think about what the traction battery is supposed to do, you don't want it to be full! The traction battery is an energy buffer. It accepts regen energy when stopping and being charged by the gas engine. The traction battery returns the stored energy during slow speed driving and acceleration.

What would happen if the battery is full and the system goes into regen mode? There would be no room left to store the recovered energy and it would be dissipated as heat, just like a conventional car! The computer needs to leave some reserve capacity in the traction battery to store the energy from the regen.

The hybrid drive can always store or use electrical energy if the traction battery stays somewhere between empty and full. The whole process is what makes the Prius different from electric and gas powered vehicles.

[duraace]

That makes sense. Thanks. I was wondering, because pictures of the battery in the manual shows it fully charged (i.e. 8 bars). It also warns, however, of the dangers of over charging, so 80% sounds good.

[fuzzy1]

In four weeks, I haven't yet seen 8 bars. I'm not expecting it until next week, when descending a couple 2000 vertical foot grades.

There are various threads here about the battery life vs. depth of charge cycle. These batteries dislike being full or empty, and frequent wide excursions produce poor life expectancy. Small cycles produce much better total lifetime energy throughput. Let the computer control the charge level without much interference from the driver.

[qbee42]

Originally Posted by 1 mad scientist

We have had our 2010 for 12 days. I noticed the battery never goes to full. If you think about what the traction battery is supposed to do, you don't want it to be full! The traction battery is an energy buffer. It accepts regen energy when stopping and being charged by the gas engine. The traction battery returns the stored energy during slow speed driving and acceleration.

What would happen if the battery is full and the system goes into regen mode? There would be no room left to store the recovered energy and it would be dissipated as heat, just like a conventional car! The computer needs to leave some reserve capacity in the traction battery to store the energy from the regen.

The hybrid drive can always store or use electrical energy if the traction battery stays somewhere between empty and full. The whole process is what makes the Prius different from electric and gas powered vehicles.

This is the correct answer.

Tom

[djasonw]

The battery graph which is computer controlled will stay within a range which optimizes the life of the hybrid traction battery. The only time you will see all bars lit (full green on gen ii) is if you're coming down a long hill which requires a great deal of braking. Even at that level, you're not at 100%. As previously mentioned, I think the computer will keep the battery at between 40 - 80 % during its life cycle so that it can last a LONG time. That's why it is crucial not to run out of gas which will drain the battery beyond its optimum low level. I know in gen ii it can go pretty low. I think gen iii has safeguards which prevent it from going below a certain point. Please correct me if I'm wrong. I wish my cell phone battery would last as long as these traction batteries!!!

[jim256]

Great post, probably should be a must read, the title says it all:

Understanding NiMH hypercycles (to prolong Prius HV battery life)

[stream]

My battery only went to 7 bars for the first week or 2, but now will go to 8 bars. I live in a hilly area (I'm at 750 feet, and routinely go down to sea level), and there's a 1 mile stretch I go down often where the battery gets fully charged half way down, since you need to use the brakes a lot.

When it wouldn't show 8 bars for the first week or 2, I was guessing it was being system limited to allow the battery pack to be conditioned before allowing a full charge. I recall reading in the owners manual that it takes a while for the battery to reach its full performance capacity (or words to that effect).