Thank you David, this should help, I'm just starting to "get" the terminology and sometimes when they talk about power and energy I scratch my head and think I will never understand it.
----- Original Message ----- From: "David Roden (Akron OH USA)" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Sunday, September 22, 2002 10:58 PM Subject: Using the correct terminology (was Re: New battery technology?) > On 21 Sep 2002 at 2:45, someone wrote: > > > According to the site, the current issue is energy density - at > > 25kW/kg. They have some research that gets to 35kW/kg, but expect that > > they would need to get to 50kW/kg to be viable for consumer EVs. > > If you mean 25 Kilowatt hours per kilogram (kWh/kg) specific energy, that > would be a sensational figure! Or perhaps you really do mean kW/kg -- a > measure of specific POWER -- also extraordinarily high, as typical golf car > batteries can comfortably deliver around 100 W/kg (not kW). > > State of the art in lead acid is around 35watt hours (NOT KILO-watt hours) > per kg, nicad 55 is Wh/kg. Some advanced chemistries run 80+ Wh/kg. There > is NOTHING I know of in the kilowatt hours per kg, except maybe some liquid > fuels. > > Not to bash this poster or anyone else, but what's going on here is some > plain vanilla carelessness in nomenclature. > > On this list I frequently read kW (kilowatts, a measure of POWER) where the > posters mean kWh (kilowatt-hours, a measure of ENERGY). Recently there was > an exchange in which two people, both of whom are well educated, highly > experienced with EVs, and definitely know better, wrote kW instead of kWh. > > In this case, the post quoted above probably meant Wh (watt hours) instead > of kWh (kilowatt hours). > > Then there are the posts that refer to batteries as cells. Great heavens, > it's bad enough that Energizer and the others call flashlight cells > "batteries." This misuse is so entrenched that it's futile to fight it. > However, misuse of the terms in EV power systems is fortunately not yet > established and I see no reason not to try to correct it. > > For the record, the smallest electrical unit of a battery is a cell (2 volts > is nominal potential in lead acid, 1.2 volts in most alkaline chemistries > such as nicad and NiMH). > > The next smallest unit, a group of cells, is a battery or a module > (sometimes called monoblock, especially in alkaline chemistries). There is > some flexibility in expression at this level: > > 2v lead cell * 6 => 12v battery * 12 => 144v pack > > 2v lead cell * 6 => 12v module * 12 => 144v battery > > 1.2v nickel cell * 5 => 6v monoblock * 24 => 144v battery > > I know I seem like a fussy old nag, but it doesn't take much to get the > terminology right. With that little bit of extra effort, we'll all know > instantly what you're talking about without having to deduce it from the > context. Thus clarity will be much enhanced. > > Thanks for putting up with my rant. > > > = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > Want to unsubscribe, stop the EV list mail while you're on vacation, or > switch to digest mode? See http://www.evdl.org/help/ > = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > David Roden - Akron, Ohio, USA > 1991 Solectria Force 144vac > 1991 Ford Escort Green/EV 128vdc > 1970 GE Elec-trak E15 36vdc > 1974 Avco New Idea rider 36vdc > = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > Thou shalt not send me any thing which says unto thee, "send this to all > thou knowest." Neither shalt thou send me any spam, lest I smite thee. > = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = > www.lasvegasev.com Richard Furniss Las Vegas, NV 1986 Mazda EX-7 192v 1981 Lectra Centauri 108v 3 Wheel Trail Master 12v Board Member, www.lveva.org Las Vegas Electric Vehicle Association
