On 17 Nov 2014 at 8:37, paul dove via EV wrote: > You all need to read the link I posted. > > It explains how to recondition Nickle based batteries. > > It also explains the failure mechanism and why this works.
I did read that page. It may be accurate - I'm not an electrochemist - but it reminds me of the woo-woo that lead battery pulse charging advocates use to explain why their chargers (like all other chargers!) temporarily improve battery capacity. That said, though I don't know about the physics of it, Saft for one does recommend re-conditioning their large flooded cells when they have declined in capacity. Note that I hyphenated "re-conditioning." Large NiCd cells and monoblocks, as used in some EVs, aircraft, and locomotives, are normally shipped uncharged. When they're installed, they require a procedure callled a commissioning or conditioning charge. (For the small cells you get in and for portable gadgets, this is done at the factory.) For this, Saft specifies a 14 hour 0.1C constant current charge. If you do the math, you see that this is essentially a 40% overcharge. (FWIW, Saft recommends a 20% overcharge on every normal charging cycle. This is for their non-recombinant open cells, not the MR blocks.) Re-conditioning is (duh) just repeating this conditioning process. Again going from Saft's instructions, the block or battery is discharged at a controlled low rate (Saft says 0.2C) to below 1.0 volts per cell (< 5v for a 6v nominal monoblock). Once flat, the battery is given a fresh conditioning charge. Saft says that for re-conditioning you can use 0.2C for 7 hours, instead of 0.1C for 14 hours, if you're short on time. One thing I should point out. "Re-conditioning" as the term is used in NiCd (and possibly NiMH) battery maintenance is not what many car folks think of as reconditioning. That is, what these guys are doing to a NiMH battery for $1000+ is not really similar to having a shop rebuild your ICEV's alternator. That rebuilt alternator will probably run about as long as a new one would, but your re-conditioned NiCd or NiMH battery almost certainly won't work as well or as long as a new one. "The Hybrid Shop" say that they replace under-performing blocks. I wonder whether they use new or used modules for replacements. I also wonder how well re-conditioning works with sealed cells, as opposed to open (flooded) ones. I own a Maha NiMH AA-cell charger that claims to do a re-conditioning cycle. I admit I haven't used that cycle frequently, but I have yet to see it significantly improve any of my older NiMH cells' capacity. Another little wrinkle here. IIRC, Toyota's onboard software carries out a form of re-conditioning and/or equalization automatically on their "hybrid" batteries when the computer senses a loss of capacity. I haven't heard that this kind of mini-re-conditioning is done automatically on the (small number of) true Toyota EVs such as the RAV4-EVs. Maybe someone else knows. As to whether Ford's software does such a quickie tweak, I don't know that either, but you might want to find out. If I'm not mistaken, for their early Escape "hybrid," Ford bought the design (and possibly the hardware) from Toyota. It was the design that Toyota had used in the first generation Prius, not the second generation. Hope this helps. David Roden - Akron, Ohio, USA EVDL Administrator = = = = = = = = = = = = = = = = = = = = = = = = = = = = = EVDL Information: http://www.evdl.org/help/ = = = = = = = = = = = = = = = = = = = = = = = = = = = = = Note: mail sent to "evpost" and "etpost" addresses will not reach me. To send a private message, please obtain my email address from the webpage http://www.evdl.org/help/ . = = = = = = = = = = = = = = = = = = = = = = = = = = = = = _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
