How to charge batteries to their max?

I actually saw my battery full charge on my week old 2005 Prius. I was on a LONG 500 mile round trip when I hit a mountain grade. Of course going up the sucker wasn't good for my MPG but downhill was awesome and while it was coasting down the grade by battery was charging as well. About 3/4 of the way down I noticed full green and was grinning!

So either go down a nice mountain grade or you can probably slowly charge it up by staying on a flat road?

 

No, the computers protect against that if at all possible.

Why would you want to force the car to do something that would have a negative effect on both mileage and battery life?

 

I've only had my Prius for little over a week but the SOC seems to hang right at 6 bars.
Very seldom higher or lower.
If the SOC drops to 5, it quickly goes back to 6 and after a 30 mile highway drive, and a 1/4 mile coast to the off ramp, it just hits 7 bars but quickly drops back to 6.
I've actually had cases where I am coasting then the display goes to what looks like the 'Ready' mode.
Car is moving, SOC at 6 bars but no charging and no output from motor or ICE.
All arrows to and from ICE, Motor and Battery are blacked out.
So I have to say the newer models are set to maintain a somewhat constant charge level at 6 bars.

 

That is what you would expect to see if you drive in essentially flat terrain, such as South Jersey

 

Trust me - the battery SOC will fluctuate over the entire usable range if required. My commute used to take me over a large hill (or small mountain, depending on your perspective) every day. I'd typically see SOC go from 5 to 2 (rarely one bar) to full and back again during each commute.

In order to maximize the life of the battery, the Prius won't do this unless absolutely necessary. Keep in mind that the sole source of energy in our Hybrid system is the gas engine.

 

I have had a 100% charge about three times now. (Bought Prius 24 Dec.) A 7000 foot drop does it nicely.

 

A few times, I've seen a full battery driving around town.

On a trip up north with plenty of mountains to roll down, I saw it plenty of times...

 

Toyota says the SOC is controlled between 40-80% to prolong battery life. Therefore, I guess 8 bars represent 80% and 0 bars 40%. That's only a guess though!