Charge long or often?

Is this a good practice to avoid the last minutes of charging which are actually used to balance the charge between cells ?
Usually I'm either charging for 1 hour ( L2 charger with 2 hours until full charge from empty ) or I will leave it to fully charge.

 

Thanks.....I've been trying to figure out that little battery meter that reads 31% in the pic. I could never get that meter to read anything (it's either 100% or 0%) - sounds like I just need to change the HSI EV gauge to %

 

Refer to the manual page 228.

 

It won't matter one way or the other. And I've never heard of any balancing taking place at the end of charging. If that was the case, I'm sure it would have come up in one of the Weber Auto videos about the Prime. It just slows down near the end to keep the battery cool. 100% on the display is still only 84% in the battery. Don't overthink it.

 

Good stuff! Today I took a 70 mile drive after a full charge. Ran out the 31 EV miles available at departure then auto switched to hybrid mode. Near the end of the trip I took a pic of the display - attached. It didn't give me any reading for the EV battery - probably because I was in hybrid mode when the pic was taken.

Thanks for the manual page reference! It says one of the three settings can read "blank", and I was drained and not in EV mode so it makes sense what I'm seeing in my pic. Good to know that that particular battery meter is only measuring the EV battery remaining power.

 

Yup! That's how the display should look when you've run out of EV range. No percent and no miles. Now it's a regular hybrid -- except that a regular Prius might let you put it in EV mode for a little bit under the right conditions but the Prime, once EV range is depleted, just beeps at you if you hit the EV button.

 

If you look enough of the situations, you will notice that traction battery % and GOM EV range miles will not always have the same combination. 100% SoC maybe 31miles one day and 28miles the next day, this applies to all of SoC%, but when it approaches 0%(--%) the range also will approach 0 miles (--.-miles). The estimation of the EV range is always accurate when the EV SoC is depleted. At any other time, it is just an estimation.

 

True dat! As the GOM remaining miles estimate approaches zero, it'll get closer to being accurate because there's less distance for changes in power use to affect accuracy. But it won't be perfect until it's at zero. There have been several times where my GOM has estimated 0.1 miles left and I nursed 0.3-0.4 miles out of the battery. And, if you driving 50-60 mph with 0.1 miles left on the GOM and stop at a traffic light, the GOM might show 0.5 or more when you get stopped. Of course, that 0.5 will disappear in a hurry when the light turns green.

 

In a way, GOM is like a watch with broken hands that never move. That watch is more accurate than a watch 5 min off. The latter is NEVER accurate, but the stopped watch is accurate at least twice a day.

 

It seems like it might be doing something special for the last few minutes where it's sitting at about 800W. The battery doesn't get particularly hot when charging, so I don't expect it to suddenly get hot going from 83 to 84%. I don't think it slows down for temperature reasons.

 

I'm not suggesting that it does get hot, but the Prius isn't the only one that tapers off near the end of the charge and I suspect that at least one reason for it is to prevent it from getting warmer than it should. It can't be balancing because that would need the battery to go to a true 100% SOC and stay there. However, since it's only going to 84%, I don't think it should get very warm anyway, so I'm not really sure about it either way.

 

This is almost exactly what I do.
I have a very short commute to work (under 3 miles each way). Rarely do I go too many other places, and when I do, I usually know ahead of time. I set my departure time for 9:00am, but I really leave around 7:40am or so. I may have a SOC of ~80% (it fluctuates). This is actually good for a couple of days. When it starts to get low (~25% or so), I'll plug it in at night.
Obviously, I'll modify this if I know I have to go to another work location, or drive out of the area, but it's rare, and I usually know ahead of time.
If my SOC will get low, I'll just go into HV mode, which will keep it constant. I really don't like to have the battery hit either extreme (even though 0% and 100% aren't the real 0% and 100%...I'm just giving a little extra buffer: I really intend to keep this car for 10+ years and don't want a battery replacement).
I've had the car for 4 months, and I just filled it up last week for the first time (only ~4 gallons, and I still wasn't on empty), so any HV usage will aid in the fight against stale gas.

I guess I'm applying the logic of cell phone charging: If a charge of 0-100% is considered one charge cycle, then a 25-75% charge, by comparison, is much less than 1/2 of a cycle, because I'm not hitting either extreme.

 

You're right that you don't want to charge a Li-ion battery to 100% and that the Prius won't let you do that. (84% is the actual charge when it says 100%.)

But keeping it between 25-50% vs 25-75% (for the sake of using nice round numbers) won't make any difference. Each charge/discharge at 25-50% is 1/4 of a full cycle. Each 25-75% charge/discharge is 1/2 of a cycle. Doing two 25-50s is the same portion of one full cycle as a single 25-75 cycle. If you stay anywhere in Toyota's charging limits (and there's no way to go beyond them anyway) you'll not put extra wear on the battery.

I frequently let mine sit overnight with 65% or so showing after driving home from work. It still takes the same kWh to charge from fully depleted as it did when I got it over 1/1/2 years and 24,000 miles ago. Clock is now reading 45,000 miles and, as far as I can tell, it still acts like a new car.

Doing those kinds of exercises to keep the battery in the middle of its charge range sure won't hurt, but I'm sure Toyota didn't intend for customers to have to jump through hoops like that. I'm sure they meant the cars to just be driven.