On 8 May 2018 at 17:17, Lawrence Rhodes via EV wrote: > Not interested in normal lead but lead/carbon. Is it more energy dense than > normal sealed batteries?
I don't know what you're responding to here. I didn't see anyone suggest that you should be or were interested in "normal lead," but I might have missed it. To try to answer your question as best I can: The only lead carbon battery I'm famiiliar with is the Firefly battery, originally developed about 15 years ago. IIRC Firefly began as a division of Caterpillar, was spun off, declared bankruptcy, and reorganized under the same name. Somehow I've gotten the impression that Firefly batteries are actually manufactured in India, but that might be wrong. In any case, it appears that the only current Firefly product is a group 31 marine battery. Their published specifications aren't directly comparable with Trojan's and US Battery's, but with Uve Rick's EVDL battery calculator I figured the Peukert exponent as 1.14 (quite decent) and the 1hr capacity as 80AH. A Trojan 30H marine battery has a Peukert of 1.24 and a calculated 1hr capacity of 72ah. A USBMC 31DCXC2 (what a model number!) has a rated 1hr capacity of 74ah. Since those two are close, I'll just compare the Firefly to the USBMC. If Firefly's claims can be believed, their battery stores about 8% more energy for the groiup 31 form factor. You asked about energy density (Wh/liter). With dimensions given for these batteries, we can calculate it. I'm still using the 1hr rate, as this is about the discharge level we use in EVs. The USBMC is 888Wh and 13.4 liters, for an energy density of 66.3Wh/L. The Firefly is 960Wh and 13.9 liters for -- again, if their specs are credible -- an energy density of 69.1Wh/L, about 4% more than USBMC's. You didn't ask about specific energy, but you might find the comparison interesting and useful. The USBMC weighs 29.7kg for a specific energy of 29.9Wh/kg. The Firefly is 33.5kg, for a specific energy of 28.7Wh/kg, about 4% less. The Firefly folks make rather impressive cycle life claims, 1000 cycles at 80% DOD and 3600 cycles at 50% DOD. I wasn't able to find any independent test corroborating those claims. Maybe Lee Hart will agree to test one for you if you buy it and have it sent to him! 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 Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
