Re: Battery Cycle Life/Cost - Real Word Wisdom

[Seth <sethea@mediaone.net>]

If you aren't driving, you should be charging PbA batteries, even if it
is on float charge. This is hard to do, but given the choice of charging
or not, always charge. With an EV, it is unlikely you will ever have
enough batteries to never go below a 20% DOD.

-Seth

"M.C. Appleby" wrote:
> 
> Is my thinking incorrect that batteries consistantly discharged 20% (80% of
> their max charge remains) that are consistantly then recharged will dimisish
> in capacity?  Would a battery at 80% of full charge be damaged sitting one
> night?  Maybe this begs my question for my "coming along conversion" &
> battery education.   All I have been reading indicates lead has a strong
> battery memory for shallow charging and eventually these short
> discharge/charge cycles will kill a pack and/or render amp/hours to far
> below rated levels.  I believe I have planned a pack (T-105's) that will
> typically be discharged 60 - 70% on daily driving, but I felt that on a 5
> mile trip to the store and back I would not plan a recharge, but wait to get
> more miles the next day.  Your belief is my wait will damage lead batteries
> and I should hook up to charge.
> 
> ----- Original Message -----
> From: "Seth" <sethea@mediaone.net>
> To: <ev@listproc.sjsu.edu>
> Sent: Sunday, January 27, 2002 7:37 AM
> Subject: Re: Battery Cycle Life/Cost
> 
> > Doing this is very bad for the PbA batteries.
> >
> > Deeper discrages and leaving them less than fully charged, even for a
> > day, are two great ways to kill PbA batteries faster.
> >
> > -Seth
> >
> >
> > "M.C. Appleby" wrote:
> > >
> > > You have your trip energy consumption down to a science.   Presuming
> your
> > > trips are daily (back to back) - why would you not recharge every two
> days
> > > or possibly every three days?  It sounds like even every two days you
> would
> > > only be at 50% SOC, but you would have doubled your cycles.
> > >
> > > ----- Original Message -----
> > > From: "Mike Chancey" <evtinker@evalbum.com>
> > > To: <ev@listproc.sjsu.edu>
> > > Sent: Saturday, January 26, 2002 10:12 PM
> > > Subject: Battery Cycle Life/Cost
> > >
> > > > Hi folks,
> > > >
> > > > I have been wrestling with long term battery life issues,  trying to
> come
> > > > up with an affordable way to get my Civic back into regular daily
> commuter
> > > > use.  Unfortunately, all I am really discovering is this was the kind
> of
> > > > analysis I probably should have done before building the car in the
> first
> > > > place.  Here is what I came up with:
> > > >
> > > > My commute is roughly 25 miles round trip, but charging is usually
> > > > available at work.  On weekends I probably put about 20 miles on each
> day,
> > > > mostly in little 5 or 10 mile hops, so we are looking at about 165
> miles
> > > > per week, or about 8580 miles per year.  Assuming I recharge once at
> work
> > > > and once at home every workday, and at least two charges per day on
> > > > weekends, that is about 728 cycles per year.  Considering the current
> > > power
> > > > consumption of my Civic, roughly 350 watt hours/ mile due to hills and
> > > > heater use, the 12.5 miles of each workday commute leg uses about 28%
> of a
> > > > charge.  So, the battery pack is asked to deliver about 728 cycles at
> 28%
> > > > depth of discharge.  The question is, how many cycles can I expect the
> > > > batteries to deliver before failure?
> > > >
> > > > Currently, I have the Civic equipped with a set of 13 used Dynasty
> group
> > > 31
> > > > AGMs (12 volt 100AH).  Due to numerous failures, I have discovered a
> $20
> > > > used battery probably really isn't cheap after all.  Before I even
> > > consider
> > > > investing in 13 new ones though, I feel it might be wise to look at
> the
> > > > chances of them lasting 1 year under my service demands.  I suspect
> there
> > > > is little chance of getting a year out of them at all.  If they did
> last 1
> > > > year, at roughly $1700 a set, my 8600 miles is going to cost about 20
> > > cents
> > > > per mile just for battery replacement cost.  Ouch.  Another
> alternative
> > > > must be found.
> > > >
> > > > It just might be possible to rebuild the Civic to use 18 8-volt Trojan
> > > > T-875 flooded batteries, though this would really ruin some of the
> car's
> > > > best features.  Now we are looking at a battery cost of about $1200
> per
> > > > set, but due to the greater capacity, the cycle depth would only be
> about
> > > > 20%.  For those who have used the T-875, what is the likely cycle life
> at
> > > > 20% discharge?  I am guessing it might be possible to get at least 2
> years
> > > > out of them at this shallow cycle, 1456 cycles, or maybe that is too
> > > > optimistic.  If they would last that long, then the battery cost would
> be
> > > > down to about 7 cents per mile, quite a bit more reasonable.
> > > >
> > > > Taking this further, dropping down to 18 T-105s would make for pretty
> lame
> > > > performance, (from 156 volts to 108) but that would increase capacity
> and
> > > > reduce the cycle depth still further, to around 18%.  Battery pack
> cost
> > > > would drop to about $900, or 10 cents per mile for 1 year of life, 5
> cents
> > > > per mile if they last for 2 years of service.
> > > >
> > > > At this point we are getting so far away from the existing conversion
> I
> > > > would probably be better off to buy/build/trade for an EV designed for
> > > > these more cost effective battery choices.  A 120-144 volt, T-105
> equipped
> > > > pickup would probably be a more appropriate choice for this commute I
> > > guess.
> > > >
> > > > So, what kind of words of wisdom can you folks share with me?  Is
> there a
> > > > better alternative?
> > > >
> > > > Thanks,
> > > >
> > > > Mike Chancey,
> > > > '88 Civic EV
> > > > Kansas City, Missouri
> > > > EV List Photo Album at: http://evalbum.com
> > > > My Electric Car at: http://www.geocities.com/electric_honda
> > > > Mid-America EAA chapter at: http://maeaa.org
> > > > Join the EV List at: http://www.madkatz.com/ev/evlist.html
> > > >
> > > >
> > > >
> >
> >
> >