The problem most people are seeing is the high quiescent drain. IMO, this started with the Prius with the smart-key option. It was exacerbated with the introduction of telematics, which means there's a cell modem always on in your car now. Most modern cars now have both. So if you drive every day, and long enough to get your absorption phase completed, likely not going to be much of a problem, but if your car isn't used as often, you are in trouble.
Ultracaps (or any capacitors) have a linear Dv/dt plot, which means voltage falls immediately on discharge. This means to get the capacity anywhere CLOSE to what you get with lead-acid, you'd need a ludicrously large cap array. On Tue, Apr 20, 2021 at 8:36 PM George Tyler via EV <[email protected]> wrote: > The leaf battery behaves much like the 12V Prius battery in my experience. > They both seem to fail earlier than they should, but when should they fail? > That is "opinion". The failure mode is different, probably because they > don't fail by not turning a started motor? So you don't know capacity is > almost zero. > I don't think a lithium is good for this application. To get > voltages that are close enough you have to use LiPo4 litiums, with a very > flat discharge curve. This means that the charging voltage is not optimal, > although they do work in this application in ice cars with 14.7V charging. > 4 > cells at 13V is 3.25/cell, that's totally flat for these batteries! 14.7V > in > an ICE is 3.675V per cell which is about right. Temperature compensation > for > a lead acid may be way off. How about a supercap "battery", much less > critical. Seeing that we don't notice the leaf battery losing capacity > until > it's dead, maybe we don't actually need much capacity? > GWT > > -----Original Message----- > From: EV On Behalf Of Lee Hart via EV > Sent: Wednesday, 21 April 2021 2:14 pm > To: Lawrence Rhodes via EV <[email protected]> > Cc: Lee Hart <[email protected]> > Subject: Re: [EVDL] From my nissan leaf .com: Why the Leaf 12v system > undercharges the 12v battery. > > Lawrence Rhodes via EV wrote: > > https://mynissanleaf.com/viewtopic.php?t=22752 According to these guys > > a lead battery is not what a Leaf needs. Seems a lithium of some sort > > would do great. Another site said the DC/DC converter can put out as > > much as 120amps. The brakes and other systems that run on the 12v > > system might need a boost if the battery fails and braking is very > > important. After finding out that the lead battery is under charged I > > suspect an undercharged lithium battery might fair much better and for > > longer. Lawrence Rhodes > > I don't "buy" it, Lawrence. Too many of his comments are just opinions; not > facts. Just a few glaring points: > > - A 12v battery *will* reach full charge at 13.0v; it just takes a long > time > (like a week or so). > - He ignores temperature compensation. The Leaf does temperature compensate > its charging. > - He ignores aging. The older the battery, the lower its basic charging > voltage. > - 14.4v will easily fully charge a 12v battery. Remember, if it's holding > the battery at around 13.0v, it's already close to full; so it takes very > little time at 14.4v to finish the job. > > Lee > > _______________________________________________ > Address messages to [email protected] > No other addresses in TO and CC fields > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > ARCHIVE: http://www.evdl.org/archive/ > LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20210420/bc2bc0ee/attachment.html> _______________________________________________ Address messages to [email protected] No other addresses in TO and CC fields UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub ARCHIVE: http://www.evdl.org/archive/ LIST INFO: http://lists.evdl.org/listinfo.cgi/ev-evdl.org
