Battery

Don't have a pic, but it can be done, most often after an extended period of regeneration -- i.e., coming down a long hill.

Having said that, I wouldn't worry if you don't see it. The car's computer aims for an optimal state of charge of 60%, which is 6 blue bars. This allows a little headroom for any upcoming periods of extended regeneration. As soon as it creeps up much above 60%, at the next opportunity the car draws a little more from the battery than it might otherwise.

 

Drive in Winnipeg city traffic at -40 with no winter front. The ICE will constantly run and the battery SOC will be all green.

Otherwise, the Prius is smart enough to keep the battery SOC within a fairly narrow and comfortable range. Remember that purple is *not* "empty" and all green is *not* "full.

The battery SOC will typically represent a state of charge on the NiMH traction battery of 40-80%

 

I think mine has only been full(8 bars) once. It was after I force charged the battery to see what behavior the car would exhibit. I have been at 7 bars a half dozen or so times.

 

I see a full battery indicator quite often. Of course, that tends to happen when your choice is either up hill or down. I'm usually looking where I'm going, but I'll see what I can do about a picture.

 

usually I see 8 full bars when it showed 7 bars before and I take a downhill slope in "B" mode for a mile or two

How far have you guys been able to drive without the engine coming on? my record is about .9 miles

frosh

 

My record is 35.56 km (22.1 miles) on downhill.

Ken@Japan

 

u can force charge it by putting it in drive, pressing firmly on brake, then pressing gas alll the way until it charges the battery to the top.

not sure if any damage occurs with this.

 

Yes, when you run out of gas and you continue to drive on it, it can get quite low, which risks damaging it. Therefore, don't run out, or if you do, park it!

Under normal driving, the computer also keeps it from getting too low. Percent state of charge in the low 40s is the typical low limit; zero bars is still 40%. The lower it gets, the more the engine will be given preference for power -- and to recharge the battery.

 

there is another way to discharge the battery. I've gotten it down to just 2 bars by driving over 100 mph for an extended period of time. When you need a lot of speed the electric and gas engines both kick in. Theoretically you could drain the battery this way, but you'd need a long empty stretch of road.

 

No, you cannot drain the battery that way. The charge will go to the minimum level that you saw and then stay there. In that condition only engine power is available until the car recharges the battery in normal operation.

 

While there are lots of people who think you can fully discharge the traction battery, for example, by running out of gas, this is just not true. You -CAN- take it down to about 30% charge (so lower than the "normal" minimum of 40%), but the car then shuts down and will not let you take it any further. Taking it to 30% -may- be more risky than 40%, but not much more.

The danger is - fully discharging the lowest capacity cell (or cells) in the battery. If you did this and continued to draw power from the battery, those cells would be reverse charging, which can be death for NiMH cells. Which is why Toyota only runs the battery as low as they do.

 

Again, we saw 18%.
http://priuschat.com/forums/prius-technical-discussion/41778-battery.html#post545883

Ken@Japan

 

When fully discharging a set of batteries in series, the weakest cells will discharge first and then be subject to reverse charging. But this simply converts these weakest cells into hydrolysis cells, generating H_{2} and O_{2} gas.

Built-in to our NiMH battery modules are catalysts that try to convert these gasses back into water but they get hot and that leads to over pressure and out-gassing. Once enough water is lost, the electrolyte level gets lower and lower and the cell loses more capacity.

Bob Wilson

 

While what you say is true Bob, you can also get "whiskers" of nickel growing and they will short out the cell. I've seen this a lot in the handheld radio batteries I'm most familiar with. Their charge/discharge systems are not very advanced and allow cells to reach zero charge often. Once shorted out, it's VERY difficult to "blow" the short, and, even if you do, it grows back very quickly, as that cell will continue to fully drain first and reverse charge. I've seen the "repaired" cell (I blew the short with a high current pulse) short again on the next discharge cycle.

Thanks Ken for enlightening me on the exact number re max discharge allowed by the system.

 

What do the colors of the battery icon mean, (blue/green)? Is blue the state of charge and amount and green the rate of re-charging?
I can drive my new 05 (new to me) appx. 5 miles, then the battery goes to green (shows 7-8 bars) for 10 or more miles, maybe longer, before it returns to blue (show 6-7 bars), stays blue for a short while, 5 miles or so, then back to green, Is this normal?
Thanks
Ed

 

No, it's all based on the SOC. 7-8 bars is green, 3-6 is blue, 1-2 is purple. When you have green, it's because the battery is nearly maxed out (as much as Toyota programmed the computer to allow it).

What you're experiencing is entirely dependent on your driving circumstances. The car wants to be in the blue, but will allow some deviation depending on how and where you are driving. Since you're battery seems to go up after about 5 miles of driving, either you are doing a lot of downhill driving, or it's cold out (<50 degrees F), or some other reason to be running the ICE a lot. The car also wants to keep the coolant at an ideal temp for emissions purposes, and will run the ICE more to warm itself when you first start it. If you're running the heater, that pulls away more heat (as I've found here in Minnesota), and the car tries to save some of that energy by charging the battery more than normal.

Back in LA, I would get 8 bars anytime I came home from the Valley or farther north. I lived near the bottom of the mountains separating the Valley from West LA, and parked two floors down in an underground garage. Once you hit 8 bars and you're still going downhill, the engine kicks on to slow you down, even if you're not in B.

 

Interesting. I knew the NiCD batteries had that problem and using a surge charge to burn-out the needles was necessary. I was under the impression the NiMH batteries were resistant to this problem.

FYI, one of the two 'failed' battery modules 'healed' itself when charged with my MRC 989. I was using .1C charge rate, 700 ma., which seems a bit weak to burnout whiskers. This is the cell assembly I'll use for my first experiments.

Chat at you later,
Bob Wilson

 

I figure why take any chances at all, especially considering the cost of a failed traction battery. I'm thinking of those who seem to chronically run outof gas, as if trying to prove some point. If a Prius runs out of gas, stop, and call for assistance

As far as low SOC, what happens in N? I was under the impression that defeated the built in battery protection