Roger, Thanks for the answer. The metric is what I made up as a way to compare the items on the website, but it takes into consideration what I have heard on this list. I (despite what folks might think from my constant poking about) actually prefer to follow advice I am given. The Enersys/Genesis cells look like a good bargain in #/lb and $/Ah and number and strength of recommendations.
*#1 13lb* $3.46/lb @ $45 17.2 Ah *$2.62/Ah* http://www.atbatt.com/genesis-np18-12-12v-172ah-sealed-lead-acid-battery-with-nb-terminal.asp?cr_brand=BB&cr_product=BP17-12#specifications On Thu, May 1, 2014 at 2:30 PM, Roger Stockton <rstock...@delta-q.com>wrote: > Michael Ross wrote: > > > When you say lead is the fuel - how does that work? I wouldn't have > > expected it unless it means the grids (my word for whatever they are > > called. plates?) are bigger... > > > > I guess you could make the grids heavier better life in severe > conditions. > > How do you know the extra weight is in grid area and not structure? > > > > Or do I have the wrong idea altogether? > > You have the right idea. Lead is the main active ingredient in the > battery, and it is quite dense, so it is a reasonable approximation to > state that the heavier a lead-acid battery, the greater its actual capacity > is likely to be. > > But, as you say, even if the battery is heavier, you don't know if the > extra weight means more active material (e.g. paste) or beefier grids (the > lead structure of the plates that supports the paste) or beefier internal > interconnections. > > Beefier grids or internal connections can both contribute to a more robust > or longer-lived battery, so this doesn't contradict the "heavier is better" > philosophy. > > I think David makes a good suggestion, which is to dig up specs on the > particular batteries you are considering and compare their capacities at > the discharge rate that you will operate them at. The 20hr rate is > meaningless for a mower that will likely deplete the batteries in about > 1hr, and different makes handle high rate discharge quite differently. > Also, as David notes, different manufacturers may state their battery's > rated capacity at different discharge rates; e.g. Hawker/Enersys often > states the rated capacity at the 10h rate while others may use the 20h rate. > > Note also that the weight metric really does not mean to shop by the best > $/lb value, but rather that for two batteries of the same physical size or > same rated capacity, the heavier of the two is likely to deliver greater > actual capacity and/or provide greater service life. > > One caveat I would offer is that I think especially for AGMs there is more > to the story than simply weight. With sealed batteries (AGM/gel), one of > the keys to long service life is avoiding venting since this corresponds to > (generally) irreversible loss of electrolyte. This is where a quality > brand can impact the outcome of your buying decision. The manufacturing > quality can affect the performance of the pressure relief valves that allow > the cells to vent in a controlled manner. It is not unusual for Chinese > AGMs with lower quality control to have vents that open at lower than > desirable pressures and/or open at pressures that vary from cell to cell. > > Good luck! ;^> > > Roger. > > _______________________________________________ > 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) > > -- Put this question to yourself: should I use everyone else to attain happiness, or should I help others gain happiness? *Dalai Lama * Tell me what it is you plan to do With your one wild and precious life? Mary Oliver, "The summer day." To invent, you need a good imagination and a pile of junk. Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. Ross (919) 550-2430 Land (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone (919) 631-1451 Cell (919) 513-0418 Desk michael.e.r...@gmail.com <michael.e.r...@gmail.com> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140501/9c5a53db/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)
