David Nelson wrote:
With LiFePO4 cells all you need is a charger which can terminate on two
values: target voltage followed by target minimum current. Nothing else is
needed.
That's the simplest way to do it. And, it works equally well for lead-acids.
The trouble with such a simple charging algorithm is that the charge
rate is slow, and you don't get maximum life. Sometimes that is
important to people; other times it isn't.
The more complicated charging algorithms are used to improve on charging
rate and battery life. With lead-acid, this usually means adding an
equalization step, a minimum charging current at the beginning of a
charge cycle, reduced charging current when above the gassing threshold,
temperature compensation of the charging voltage, and other factors.
With lithiums, this usually means individual cell monitoring, strictly
limited maximum voltage, temperature compensation, and amphour counting.
I suspect there will turn out to be more factors, but lithiums are so
new, and so little testing has been done that we don't know what they
are yet.
Let's face it; battery charging is a murky science. The field is awash
with bad advice, old wives (mechanics) tales, anecdotal stories, and
"experts" who never measure anything. It's hard to find factual evidence
and real test data!
Advice from people on this list is often better than the average website
"authoritative sources". They are actually *using* the batteries in EVs
(where it counts), and they *measure* things! They don't always get
*all* the measurements we'd like; but it's a start!
Just beware of applying a special-case to the general case. Each person
typically tests one battery, one way. So, he really doesn't know if the
results apply to other situations, and other batteries. Differences of
opinion are often the result of different test methods.
If possible, we should strive to include enough details so others can
tell if what we did in our tests applies to their situation.
--
There are few industries with more BS than the battery industry.
Elon Musk
--
Lee A. Hart, http://www.sunrise-ev.com/LeesEVs.htm
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