Huh? Plenty wrong with your assumptions. > $6k of golf cart batteries is about 60 of them; that's around 80 KWH of storage! Who on earth needs that much for a home.
My solar panels produce typically 60 to 70 kWH every sunny day. If I do not use every bit of it every day, then I am wasting my solar investment right? Hence, I sell it to the grid every day and buy it back when I need it at no net cost.. If I had to store it in batteries (at your proposed 10% daily depth of discharge) then I would need 600 kWh of batteries or $60K investment (and replace it every 10 years). Again, batteries MAKE NO ECONOMICAL SENSE WHATSOEVER compared to grid-tie. BUT... BUT, if utilities began paying the homeowner the same TEN-TIMES PEAK rates they have to pay for power during summer peaks, then of course, batteries coiuld make some economical sense. They don't have to handle the full working load of my solar array, but only enough to meet those instantaneoud peak value periods... Bob -----Original Message----- From: EV [mailto:[email protected]] On Behalf Of Lee Hart via EV Sent: Friday, May 01, 2015 7:02 PM To: Electric Vehicle Discussion List Subject: Re: [EVDL] Tesla plugs into new market with home battery system (backup foolishness) Robert Bruninga via EV wrote: >> A quality GC2 golf cart battery (Trojan, US Battery, etc.) is 220-240 >> amphours at the 20-hour rate, and costs $75-$150. They are good for >> 5-10 years, and 600-1200 discharges to 50% or so state of charge. > > No, not BOTH. One or the other. 5-10 years just sitting there doing > nothing but waiting for the grid to go out (4 hours a year around here)... Correct. They are "used up" once they have accumulated 600-1200 cycles, *or* are 5-10 years old. > OR they barely will last 2 years in daily solar-off-grid use (and > note, you are only getting 50% of their capacity just to last that long)... That would be the case if you discharge them 50% or so every day. But 50% is an excessively deep discharge if you're going to use them every day. For daily use, you would limit your depth of discharge to just 10% or so. Then they would still last for their calendary life; 5-10 years. Note that life is a function of depth of discharge for *all* types of batteries. If you expect them to last, the shallower the discharge, the better. You'd also murder a lithium pack in a few years, if you deeply discharged it every day. If you really have a situation that requires daily deep discharges, you probably have to use the old Edison nickel-iron cells. Aside from quality or abuse, they are the only type with an indefinite cycle life. (There are 100-year-old Edison cells still in use). > Yes, may as well just throw $6k in the trash every few years since you > never use them. The cost of the electricity for the 4 hours average > outage per year is only about 80 cents. (1 kW for 4 hours). Amazing > how many people will spend $6k for that 80 cent problem. I see a pretty heavy thumb on the scale here, Bob. :-) $6k of golf cart batteries is about 60 of them; that's around 80 KWH of storage! Who on earth needs that much for a home. You have to select the size and type of battery according to the application. Some will be best served with lead-acid, some nickel-iron, others lithium etc. Some applications aren't appropriate for batteries of any type. If all you have to cover is 4 hours of outage per year, then dumb old lead-acids are going to be the cheapest by far. Like I said, they will die of old age before you wear them out. -- Don't worry about people stealing your ideas. If your ideas are any good, you'll have to ram them down people's throats. -- Howard Aiken -- Lee Hart, 814 8th Ave N, Sartell MN 56377, www.sunrise-ev.com _______________________________________________ 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) _______________________________________________ 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)
