I have quite a few of extra Li-ion battery packs for either of my laptops problem that I am experiencing with some of those battery packs is that they cannot be recharged as they were not installed in laptop for months and so they won't take the charge. The batteries were perfectly fine before that, with about 90% of capacity left, measured by software that conditions those batteries and actual running time. it seems that once a li-ion battery pack is drained beyond certain voltage – the point of no return is reached, as those batteries will not take the charge, period. the main reason for this problem that I am experiencing is that some of the battery packs are seldom used, maybe once in 6 months or so and if I do not charge them periodically they begin to loose the charge rather quickly. Same thing happened with my li-ion camcorder battery, it did not want to take any charge because camcoder was not used for a while. I opened up the battery packs, and I measured the voltage directly and the batteries are for sure barely above zero volts, at most half a volt. I tried recharging those batteries via direct voltage to each cell, and yes I made sure that voltage and current are in safe levels (do not want any fires/explosions), yet I was unable to bring them back to life like I was able to resurrect most of the discharged ni-mh batteries. so, this made me think of how problematic it will be to have li-ion battery pack from a hybrid or electrical vehicle discharged, then left that pack in discharged state for a week or two? me thinks that it may take only a week or two to completely discharge below safe levels, therefore ruin li-ion the battery pack in an electric or a hybrid car that uses li-ion technology. what are your thoughts on this issue?
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?
thanks for your responses patsparks, i do not think it is a good idea to have engine start on its own. i can think of potential liability issues and, i do not think that a minute will suffice, engine may need lot more time to run to recharge the batteries if the level of charge goes too low and batteries are not taking the charge well, say due to temperature or other factors klodhopper, i think that you are addressing the same issues that i was thinking of yes, we need better storage device, or combination of 2 devices, like nanotech battery and a supercapacitor, something along the lines what Bill suggested I can see in my mind that supercapacitor can work really well with battery pack. supercapacitor can deliver large amount of power during acceleration, or at least starting off line, from say traffic light, and it can be recharged during regen braking or deceleration. battery can provide longer term energy delivery and together with capacitor overall performance could be improved. and, since you cannot overcharge capacitiors and there is no memory effect with capacitors -- there is no need for sophisticated circuitry. You can completely discharge capacitors, if needed, unlike battery packs. So, imagine a hybrid with battery pack, supercapacitor and super efficient ICE engine. I got the feeling that performance and fuel economy would improve substantially. If you give more "juice" to the traction motor via supercapacitor when car is accelerating, then ICE has to work less. What does that mean? well, if typical ICE is about 25% efficient and traction motor about 95% efficient you can easily picture that supercapacitor would help a lot during acceleration and because of overall increased efficiency ratio fuel economy and performance would be substantialy improved. I wonder if anyone has tried adding bank of supercapacitors to a hybrid? good articles on supercapacitors: What's the role of the Supercapacitor? Super Capacitors and Ultracapacitors - New Super Battery for Energy Storage
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.
those are some good points. yes, under normal conditions Li-ion battery may be kept at a safe level, but what about extreme conditions, like in sub zero temeratures? The li-ion battery pack can go from healthy to dead in mater of one freezing night, and once is dead it will stay dead. you could resurrect Ni-Mh or even Ni-Cad battery pack from "dead", as suggested, but i would like to know if anyone was able to resurrect Li-ion battery?
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.
