Fw: L-16s Like Higher Voltages [RE-wrenches]

[Allan Sindelar]

Wrenches,
I forwarded the L-16 comments to Sandia. Below is the author's response.
Allan @PosEn

----- Original Message -----
From: "Hund, Thomas" <tdhund at sandia.gov>


> Allan,
>
> Thanks for the E-mail!
> It seems that the battery quarterly got some discussion going.
>
> Before I get started, I want to say that lead-acid batteries are much more
> complex and difficult to use than most people realize. The best that I can
> hope for in my work is to provide general recommendations for PV systems
> which are better than nothing, at the same time realizing that some
> batteries/battery-applications will not fit the general rule.  I can
> appreciate why the lead-acid battery industry after over 100 years of
> manufacturing these devices still has problems defining how to charge
their
> batteries. The battery industry likes well defined battery applications
that
> are well controlled. PV systems are neither well defined and/or
controlled.
>
> I must apologize for not including temperature in the quarterly. The
> batteries were tested in air (no water bath) at 25C. The 25C is industry
> standard for regulation voltage and capacity measurements. Not using a
water
> bath allows the batteries to naturally heat up on charge, usually 2 to
10C.
> No temperature compensated regulation voltage. The batteries did cool to
25C
> in about 12h or less. The heating is important because the batteries will
> heat up in PV systems and it improves charge effectiveness, thus results,
> especially for equalization.
>
> I thought most of the comments were good, but I do think that one point
was
> misinterpreted.
> That was the equalization charge. I restated the comment below:
>
> "David Palumbo, Independent Power & Light" wrote:
> > >
> > > >2. The report's conclusion that its necessary to EQ at 15.3 v
> (2.55v/cell)
> > > >for up to 20 hours on a regular basis ( weekly or less) is totally
> > > >impractical offgrid. They mentioned using a generator to do this, but
> that
> > > >would totally negate any  environmental or cost benefits from going
> solar
> > > >in the first place.
>
> The report conclusions #4 and #5 indicated that I used a 12 hr
equalization
> in #4 for a 12V battery and a 20 hr equalization in #5 for a 48V battery.
> The intent of this part of the conclusions was to emphasize what the
battery
> industry would consider a real equalization charge. I do agree with the
> comments that its not practical!  The point that got lost was how
important
> it is to do the finish-charge for 3 to 6 hr at least once per week. The
> discussion in the quarterly on PV system equalization should help clarify
> the confusion between finish-charge and equalization.
>
> As for identifying battery manufacturers, its something I would like to do
> and sometimes we can do it when the results are positive. If the results
are
> negative we don't publish the names of the manufacturers to prevent upset
> manufacturers and potential legal problems. Since we are government
funded,
> our goal is to help the PV industry improve product performance and
> reliability, not cause manufacturers to lose business.
>
> Tom

> ----- Original Message -----

To the Sandia folks,
I have been forwarding responses to the recent Sandia Highlights on battery
charging. If you care to reply, I would be happy to post your reply to the
RE-Wrenches list.
Yours,
Allan Sindelar

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