Check this charger out; it is user adjustable: http://endless-sphere.com/forums/viewtopic.php?f=14&t=29096
Available also from bmsbattery.com On Jan 28, 2013, at 5:44 PM, Lee Hart <[email protected]> wrote: > On 1/28/2013 4:54 PM, Chuck Hursch wrote: >> I think the Elcon gets set up with IUI for floodies, with perhaps even a >> fourth-stage trickle charge. > > The final xxI in an IUI charge cycle is generally for equalization. After the > battery is nominally "full", it keeps charging at some low current until some > cutoff condition is satisfied. It might be for a fixed time (1-2 hours), or > until a particular voltage is reached, or some other condition. But this > final xxI stage should in no case last more than a couple hours. > > A lead-acid battery should never be trickle charged. It is bound to > overcharge it. "Trickle charge" means continuing to charge at some low > current forever, regardless of what the battery voltage is. > > It's acceptable to end a lead-acid charge cycle with a constant *voltage* > step (i.e. a "float" voltage). > >> Knowing how Greg McCrea set up my K2 after >> he did the one repair back in 2006, it's going to be IUI. I think >> US Battery once upon a time recommended IU, but it now seems to be IUI. >> I'm not at all clear if there's an advantage one way or the other. >> Third-stage `I' may give you more assurance of getting the amp-hours >> into the pack. > > I don't think the particular algorithm used is all that critical. The > important thing is to charge until it is full, and then shut off. Failing to > fully charge, or going well past fully charged, is going to shorten the life > of the pack. > > Occasionally not fully recharging (such as opportunity charging) is OK. > Occasionally overcharging (equalization) is also OK. The problems come when > you *chronically* undercharge or overcharge. > >>> I've had the best luck with chargers that use some form of dv/dt or >>> di/dt algorithm... you could *add* something to the charger to >>> produce this behavior. It could detect the old battery's "full" >>> point, and just shut off the charger early. > >> Yeah, maybe that's what has to happen. Something to watch the dV. > > Some people think this requires computers and complexity, but it doesn't. A > simple "add on" scheme is just a DC meter in series with a big electrolytic > capacitor. As long as the voltage keeps rising, the meter reads a positive > voltage. Set up your circuit to turn off the charger when the meter falls to > zero. > > 50 years ago, they would have used a real analog meter, with a tiny switch > contact operated by the pointer. Today's equivalent would be a MOSFET > transistor, with a 10v zener diode from gate to source (to clamp the voltage > between -0.6v and +10v). Also put a high-value resistor or potentiometer (1 > megohm or so) from gate to source. Use the drain to operate a relay coil, > wired so the relay drops out when the gate voltage falls too low to keep the > MOSFET on. > > Then, connect a big capacitor and diode in series from your pack to the > MOSFET gate and source. As long as the voltage is rising, the capacitor > couples the rise to the gate of the MOSFET. The gate stays on, so the relay > is on. When the voltage stops rising, the capacitor current falls to zero, > and the MOSFET and relay turn off, stopping the charger. > > As I recall, Lester's dv/dt chargers shut off when the rate of change of > voltage is less than 0.005v per cell per 15 minutes. On a 120v (60-cell) > pack, that would be 0.3v in 15 minutes. If the gate resistor is 10 megohms, > and the MOSFET turns off at Vgt=1 volt, then the series capacitor needed is: > > dv/dt = 0.3v/15min = 0.02v/1min = 0.000333v/sec = 333uV/sec > i = v/r = 1v / 10megohms = 0.1uA > > For a capacitor, i = C dv/dt, so > C = i / (dv/dt) = 0.1uA / 333uV = 0.0003 farads = 300uF > > This is a significant amount of capacitance, so it will be an electrolytic. > Use a good one, with a voltage rating well above your pack voltage. It will > still leak current, which is why the resistor across the MOSFET gate-source > should be adjustable. > >> However, an aging battery is probably going to be dumped in the bulk >> charge stage, 13A to nothing in a heartbeat. > > It's hard to say. An old battery has a lower end-of charge voltage, so the > charger may remain in bulk charge mode until some internal timer shuts it > off. Or, the old battery may also have higher internal resistance, so the > voltage rises too *high*, and the charger shuts off before it's actually full. > > -- > First they ignore you; then they mock you; then they fight you; then you win. > -- Mahatma Gandhi > -- > Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm > _______________________________________________ > 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) > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20130128/8d152ca5/attachment.htm> _______________________________________________ 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)
