reliability of Lithium-ion batteries in hybrid cars.

Would an easy way to overcome this be that the engine could fire up automatically for a minute if the charge started to fall below an accepted level? I know it is a waste of fuel but better than a waste of batteries.
One minute run time in a closed garage shouldn't be an issue.

 

I'm in no way a "guru" on this subject, but in my opinion, from what I've seen as far as what you are experiencing, is exactly what I've experienced with Li-on through the years, it doesn't recover well from "total discharge". Hopefully the car manufacturers haven't considered this when they are designing in their "programmed obsolesence" as they usually do in their production schemes.

We have another problem with Li-on in below zero weather. Li-on does not fare well in very cold climates. Below zero temperature seriously impairs it's battery capacity, or ability to provide it's full discharge capacity at lower temps, not only taking into consideration the mechanical efficiency it has to overcome at that temperature. With that in mind, maybe we should consider keeping the snowmobile handy in winter?

NIMH, on the other hand doesn't have the same "loss curve" that Li-on has, and with EBH's (Engine Block Heaters), etc., still perform respectfully at those temps, and don't seem to acquire a "sulfation" type refusal to take a charge (like a lead-acid and Li-on type does) when fully discharged for any given period of time. Panasonic has done very well, I think, in designing a mass production battery with a little less weight than a lead-acid system, that fulfills the need for rapid charge/discharge rates needed for the hybrid industry.

I think that we are all still looking for a good electrical storage device...battery or whatever for the future though. The problem exists that we can produce energy in many ways, but we do not have the storage media to store it and use it later. I'm sure that later on, we will even refer to NIMH as an "archaic" storage media.

 

What we really need is to get the chemistry out of the picture. Perhaps carbon nanotube super capacitors?

 

These problems are not unique to Lithium Ion. I use NiMH rechargeable batteries instead of disposable alkaline, and they usually last about three years. If one sits for a while without having been charged they rarely come back, so they get recycled. Temperature is a problem for NiMH too as evidenced by the Prius' behavior below freezing. It doesn't use the battery until it warms up. (Very frustrating!)

I agree that the ultimate solution would be non-chemical storage.

 

You can safely fully discharge or allow to fully discharge either a NiCd or a NiMH cell. They WILL fully come back. I have and can demonstrate this to anyone who doesn't believe me. The only exception is if you discharge a pack fully with a load and one (or more) cells discharge first, they will reverse charge if you continue, and THAT will destroy them. If you allow them to self discharge this is not a problem.

You cannot fully discharge a "rechargeable alkaline" or a rechargeable lithium (LiIon) cell/battery or allow them to self discharge on the shelf. They chemically self destruct (no fire or anything, they just become paperweights). For this reason, most LiIon cells have a built-in chip that disconnects them from discharge at a certain voltage. This doesn't help if they are being self discharged (all cells of any chemistry self discharge, some faster than others).

In a hybrid car, I doubt this self discharge would be a problem with a LiIon battery. It takes more than 6 months to self discharge a LiIon cell beyond recovery. If you're leaving your car for that long you really don't need a car. Take a taxi.

 

I had the same initial reaction about Li-ion batteries for hybrids... from experience laptop batteries are awful after 1-2 years, and that's in a nice controlled environment.

After a bit of research/reading, I learned that Li-ion for hybrids would be a different kind. Li-ion batteries in hybrid would be Lithium iron phosphate whereas the batties in laptops are most likely lithium cobalt oxide batteries.

Here's some interesting reading:



Lithium iron phosphate battery - Wikipedia, the free encyclopedia

 

One more thing to consider is battery management. You know the SOC of your Prius NiMH is well controlled. I think a Prius with Li-Ion/LiFep/LiFeS would have at least as good battery management.

 

I think the future will be in supercapacitors, with LFP and it's cousins being only a rest stop on the battery freeway. There is a lot more of a push for better batteries now than just a few years ago and I only see it accelerating. Batteries are now money-makers with growing applications due to the growing green movement. There is a LOT more interest in developing an EV now. An EV is now seen as a profit making pot of gold. Ten years ago it was a forced burden to be undermined and destroyed.

And I credit the success of the Prius with the growing interest in EV.