Battery on prius vs pip

New York State is a "CARB State," meaning that the Lithium Ion battery carries a 150,000 mile, ten-year warranty. After that, I don't know...

But if your friend is insistent, ask him if he can explain how the chemical differences between lithium ion and nickel metal hydride batteries affect longevity in favor of the NiMh chemistry. Most likely, he'll tell you that he doesn't know, "he heard it," and then you can thank him for giving you car purchase advice based on a bunch of BS he made up.

I'll be really honest with you -- I don't know how long lithium ion batteries last in cars, I just know the warranty for New Yorkers is 10 years/150,000 miles.

 

I feel that the honest truth is that we don't know for certain, because lithium ion in cars is very new. So to be honest with you, there is risk. But there is a lot we know:

It's not a big giant battery, it's over a hundred small batteries. The failed batteries are rebuilt, not discarded.

Lithium ion lasts longest if it stays depleted. I charge my car once a day. When I come home at night, I push a button on the dash which causes the car to time it's charge to complete at 7 am. Then, I don't use the HV/EV button, I just drive and deplete the battery first. So my batteries are in a depleted state about 22 hours each day. I don't get religious about this. The car has sat for days with a full charge a few times. I'm not a slave to the car, I just follow simple habits without getting upset when I don't follow them, because sometimes life happens.

 

It is a bit more complicated than that.

For charging, the important thing is the amps going in/the amp capacity of the battery.
The leaf has a 24 kwh battery pack, the PiP has a 4.4 kwh battery pack.
Everything else being equal, you can charge the leaf with 6 times as much current as the PiP and have the same battery life.
That is one reason the leaf can be bought with the high power dc charger. That is also why tesla will have a 100 kw charger for their model S, as it has a really big battery.

In addition, the charging algorithm is important for battery life. This is why people measure the temperature of the battery while charging.

In addition, how much you charge the battery is important for battery life. With many li-ion batteries, charging them to 80-90 % will make them last longer than 100% charging.

In addition, the battery chemistry is critical to battery life.

As far as I know, only the tesla has been built in commercial quantities with li-ion batteries.
So except for them, nobody really knows how the batteries will degrade over time.

 

The hybrid doesn't allow deep discharges, which is what shortens the life of rechargeable batteries.

There isn't any protective mechanism to prevent that on your cordless tools. They cannot just fire up an engine to continue operating; instead, the battery gets stressed.

After all, think about how often people ignore low indicators... using their phone until the very last moment of electricity is squeezed out. That just plain won't happen with a regular or plug-in hybrid, since the system automatically controls that for you.

 

The Nissan Leaf uses Li-Ion. I think Volt does as well. But those cars use different approaches, with the Volt having an active liquid cooling system. The Prius approach is to use a small pack to supplement an efficient car. They don't charge the battery beyond 85% and it doesn't deplete beyond 15%. The all-electric cars can't remain depleted most of the time, the way my Prius does -- my PiP battery is in a happy, long-life depleted state 22 hours a day.

 

This is important to remember. Deep discharges reduce lifetime of Li-Ion chemistries more than others. Lead-acid can survive this type of duty much better.

Ni-Cad battery chemistry had what was known as "memory effect". The battery capacity would settle at some point if you discharge the battery continuously to that point. That's why it was recommended that you periodically discharge Ni-Cad completely to "wipe out" that memory point although that was an imperfect solution. NiMH still had some memory effect but not as much as Ni-Cad.

Li-Ion is completely different. It has no memory effect that would cause a false capacity if partially discharged. What limits the life of Li-Ion battery chemistry, among other things, is deep discharge. That's why it is better to keep this chemistry type charged than let it discharge to nothing.

In addition, even the most basic Li-Ion batteries have circuitry inside them that controls the charging of the cells as well as protection algorithms since lithium is a hazardous material. I would imagine the charge-discharge controls on a Li-Ion battery powered automobile are pretty sophisticated and the logic is written to optimize a number of factors including long life.

 

The PiP does that for you. But beyond that, everything I've read, including the manual, advises to keep the batteries depleted and cool as much as possible to maximize their longevity. If you disagree, I'd like to know. I'm not a chemist, myself.

 

I don't believe the PiP will let you deplete, or charge, the Li-Ion battery low enough, or high enough, to impact it's lifespan. It is something like a 4.4kwh battery, of which the user is allowed to use 3kwh.

 

I was speaking about Li-Ion battery chemistry in general. As a rule of thumb it's better to keep them charged than allow them to discharge to a very low level.

Applying Li-Ion technology to the Prius is much more complicated as the engineers had to accommodate a variety of factors. In the previous Prius models the NiMH batteries were only allowed to discharge and be charged within a certain range of the cells true full capacity. This kept the cells lifespan as long as possible although I would imagine there were other benefits as well. I don't know enough about the Plug-in Prius to know if it is the same but my guess is there something similar going on.

 

Page 93 of the Owner's Manual:
Capacity reduction of the hybrid battery
By observing the following precautions, battery charge decline can be suppressed:

• Avoid parking the vehicle in areas with a high temperature under direct sunlight when the hybrid battery (traction battery) is fully charged
• Leave a low level of charge in the hybrid battery (traction battery) when leaving the vehicle undriven for a long period of time
• Use the charging timer function as much as possible in order to fully charge the hybrid battery (traction battery) immediately before starting off.

 

Curious ... Did they use the same verbage regarding the NiMH traction battery in the regular Prius models? (not the charging timer function obviously)

 

No, the state of charge of the standard hybrid battery isn't effectively under owner control.

 

i suppose it might help not to park it in hot sun, although, it is different battery chemistry.

 

The NiMH battery SoC range is more limited. The max is only around 65% SoC, so it isn't possible to leave it charged as high as the Plug-in battery which goes up to somewhere around 80-85%.