Using the charging timer

Page 93 of the Owner's Manual states:

I've read that storing the battery in a fully charged state reduces battery life/capacity more quickly than in a non-fully charged state, which is what I think this refers to.Another PriusChatter said that the issue was letting the batteries cool before charging. However, the "charge ... immediately before starting" seems to indicate the issue the keeping the battery fully charged.

Anyhow, I'm not going to worry about it too much. I plan to use the timer function when charging overnight or when I know I won't be driving soon, but will charge immediately if I need will be driving soon or if I'm unsure.

 

LiPo (LiIon etc,)batteries of all kinds generally don't like to be fully charged and then left sitting *for long periods of time*. In the ideal world you would fully charge them and then use them.
So Toyota included a feature that allows the option to allow this. The additional benefit of a timer is to take advantage of lower electrice rates at off peak, late night hours, if that applys to you.
A Pip that is a daily driver doesn't really need to worry about deterioration associated with overcharged storage situation.
A good example is a car left at the airport on charger for a week, something like that.

And LiPo batteries tend to cool down more quickly when charged right after use.
At least the ones in my 3D Heli do.

 

On one of the following pages, it has a list of guidelines for prolonging the life of your battery (I just read this last night too). One of them is something to the effect of letting the battery rest after use and try to only charge up immediately prior to use.

So ideally, after I get home and I dont plan to use the car anymore that day. I would set the timer to start charging at 5AM since I leave the house at about 8AM (giving it the 3 hours to fully charge - at 120v - right before I leave).

But these are just guidelines. There are many threads and opinions here on how to treat your battery. My personal opinion is I will do what I can to prolong the life of the battery. But I certainly dont plan to change my lifestyle to religiously follow the guidelines either.

What the dealer should have told you regarding the timer is that it CAN be used to help prolong the life of the battery by delaying your charging to "better" time ("better" for the battery and also better for your electricity bill if you have special time-of-use rates). But it has nothing to do with overcharging.

 

The Plug-In Prius has two batteries. One is the 12v battery for accessories located under the hood. The other is the traction battery which is a single Li-Ion battery consisting of 4 modules in series. The confusion about multiple batteries comes from the fact that the pre-production Prius had the standard NiMH battery that the hatchback Prius has plus it had two Li-Ion batteries. The production Plug-In Prius has a single Li-Ion traction battery described above.

 

Not sure if this was mentioned already but there are 2 charging timers:

One is to start at a certain time - ie midnight, to maybe take advantage of off-peak electrical rate.

The other is to Finish by a certain time - i assume that it'll do the math to start charging by a certain time so that it can finish by the time you set. So if you say finish by 7:00AM then it may start by 4AM if fully discharged so that it finishes by 7.

Some of the other messages mentioned already that it is believed to be better to charge the battery just before you need it and not leave it fully charged for long periods of time.

 

Yep. The traction battery is what gets charged by 1) external AC charging, 2) ICE (internal combustion engine), and 3) regeneration by applying the brakes.

 

I was also confused by this. One only sets one of these timers, either the "start at" or "finish by" timer. It's NOT a "start here and finish then" range! This is explained in section "1-2. Charging" in the owner's manual.

 

Haven't picked up my car yet, but from what I have read here, it looks like it would be best to pick the "finish" time. That way it would only charge long enough to top off the battery,(or fully charge if needed) and it would be freshly charged when I am ready to leave. Is that correct?

 

yes.