On 27 Feb 2016 at 8:56, Robert Bruninga via EV wrote: > only falling from about 13v down to about 11v (deep discharge)
Are you talking on load or open circuit? Normally 10.5v under load is considered flat for a 12v lead battery. Below that voltage, the risk of cell reversal.increases. Open circuit voltage is a pretty inaccurate SOC measure, but (again for 12v lead) 11.7v is considered flat, and 12.0v around 75% DOD. It's the loaded voltage that matters when you calculate Watt-hours. > so the average will be about 12v, times 100 = 1.2 kWh. As I said before, that's a reasonable approximation, but the actual Wh you can extract depends on the load. How accurate do you need to be? > But that 100 Ahrs is usually assessed at only a 25 amp draw. I don't know with what kind of battery that would be the case. Maybe some lithium batteries are rated that way? My experience with lithium batteries is limited, so I don't know. I do know that with a typical consumer grade (not industrial) lead deep cycle battery, the advertised amp-hour rating is almost always the 20 hour rate (C20), not the 4 hour rate (C4). Battery makers like the bigger number. I've even seen batteries for PV systems advertised at C100, for reasons I can't fathom. IIRC, industrial batteries are often rated at C6. For a 12v marine battery, the reserve capacity is measured at 25 amps. That's always going to be less than the C20 rating (unless you can find a marine battery C20 rated at >= 500 amp hours). As an example, the US Battery 27DC XC2 is C20 rated 105ah. Its RC is 205 minutes, or 3.4 hours. That gives it a 25a capacity of only 85ah. By Uve Rick's battery calculator, the 27DC XC2 would have a C4 of 87ah. I'm not sure whether this makes things clearer. :-\ 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 Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
