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
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