Lost Bigtime Battery Studies

[BillBlake]

<snip>

A good reference for charging L-16 batteries is a Sandia National Labs report (year 2000) titled

“PV Hybrid Battery Tests on L-16 Batteries.”

Website: www.sandia(DOT)gov/pv.
.................................................. ..................................................

That info above came from the Legendary Morningstar Corporation.

Page 51, 9.3 (L-16 Cells). TriStar Installation and Operation Manual.

How could a Government and Industry funded Study about 4 Brands of L-16 Batteries

just disappear off the face of the earth? One source saw it and says basically it was a landmark study.

Supposedly they talked about how to get twice as many Cycles (compared to average) among other things.

http://www.morningstarcorp(DOT)com/en/su...nual.04.EN.pdf

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Batteries and PV Systems

By: Don Loweburg

http://www.advancedpowerproducts(DOT)com/batteriesandpv.php

http://homepower(DOT)com/view/?file=HP89_pg120_IPP

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<Snip>

June 2007 Response to a Blog.

By: Bill Kaszeta

Photovoltaic Resources Int'l Tempe Arizona USA

Response:

These charge 12 Trojan L6 batteries via a Trace C40 charge controller. (Wired in a 24V configuration)

I assume you have L-16 batteries. You should be aware of the following. Sandia National Laboratories

published the following interesting document on charging a flooded lead-acid battery for use in PV systems.

Author(s) Sandia National Laboratories, Albuquerque, NM Hund, Thomas D.

Title Quarterly highlights of Sandia's photovoltaics program :

PV hybrid battery tests on L-16 batteries. Volume 4, 2000. Report Number SAND2001-3521P

Classification Unclassified Unlimited Release Imprint October 2001. Description 8 p. Notes

< snip>

< snip> However when I try to link to the above electronic version, I find that a username and password are

required even though the classification

is "Unclassified Unlimited Release".

Perhaps if enough people request the document they will make it available on-line. The printed report says

that copies can be requested from

With difficulty (the front page is in red and has a red watermark) I have scanned the summary:

Summary While the L- 16 is a very good candidate for use in PV Systems, results of the PV Hybrid Test Procedure
indicate several ways that the L- 16′s performance can be enhanced.

The first set of test results were obtained with 12 volt batteries (that is, two L16′s in series).

The puipose of this test procedure was to characterize charging profiles in a generic PY hybrid cycle.

Results show that the L-16 battery can quickly lose as much as 48% of its initial available capacity

if the regulation voltage is too low, the time at regulation is too short, and the time
between the finish-charges is too long.

The data in this report suggest the following:

(1) L-16 regulation voltage in PV hybrids should be well above 2.40 vpc (14.40 volts) and may need

to be as high as 2.55 vpc or higher (15.3 volts for a 12 volt battery) depending on how the battery is charged.

(2) L-16 finish-charge time in PV hybrids should be at least 3 hours and may need to be longer depending on

the time between finish-charges.

(3) The maximum interval between L-16 finish-charges should be about one week.

(4) Results vary significantly for different manufacturers.

The 12-volt testing was followed by 48-volt battery string tests that demonstrate how weak or low capacity

cells will function within the 24-ce11 string. Further, results show the need for proper charge control and

regular inspections.

This test identified a low capacity cell that was forced into reversal on discharge.

A cell in reversal wlll eventually be damaged and require replacement Additionally, the 48-volt battery

string test provides information on how specific gravity measurements, monoblock

(a monoblock is the smallest packaged battery size – three cells or six volts in the case of an L-16 battery)

voltages, can he used to track battery health. Implementation of these procedures can help ensure that the

L-16 will achieve its maximum cycle-life and thus minimum life-cycle cost. ========== end of scan ==========

Anyone using L-16 batteries in PV or hybrid systems should read this report. Hopefully, it will be available

on the web.

Other suggestions:

1. If you can, measure the short circuit current and open circuit voltage of each series string of 2 modules.

Look for differences.

2. Look for loose connections in the junction boxes.

3. Has anything grown and shadowed the array? Even a small part of the modules?

Bill Kaszeta Photovoltaic Resources Int'l Tempe Arizona USA

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As of 2011, ten to eleven years after the fact - these 4 references above were about the end of the line -
on the Internet for hundreds if not thousands of people searching in vain.

The badboy finally turned up in 2012. The links were disabled but I suspect that you may get a hint . 

Concorde told me that they heard of the studies but who knows what happened to them.
They did some studies that had a similar outcome.

A few conversations with the brass at the Legendary ODYSSEY® Batteries Division of EnerSys Energy Products Inc.
and I heard a similar story but got a lot more details on THEIR latest AGM studies.
Naturally the numbers were a bit different but the principals for longer life cycles were very similar.

There were also other references to other 'Longer Life' Lead Acid Battery studies on the Internet.

This is the end of Part One. Next we will fast forward to this years developments.

Without information like this (and more) it would have been impossible to have formulated

'The Ni-Fe Theory of Battery-tivity'   

Bill Blake   

[bob g]

somewhere in my collection i have several sandia reports relating to battery studies done by them. as far as i am concerned they are gospel in my opinion.

the only parting i have with them is the use of voltage as an indication of battery condition.  voltage tells you very little in my opinion.

a battery that has lost capacity can still be charged to the point that the voltage looks good and fully charged but the reality is quite different.

many folks get into trouble with this one, and i think it is pushed by the controller industry because it is about the only parameter that they can reliably monitor and work with.

a much more reliable indicator of battery condition is the old specific gravity test.

a battery that has been charged and shows 12.8 volts or so, appears to be fully charged but may well have a low specific gravity. the low specific gravity is caused in this case by sulfation that has been allowed to harden to the point that it does not return to the electrolyte under normal charging and will require equalization as sandia alludes to.

having said that, "if" one were to keep good records, do the 3 hour top off, and periodic equalization (which is monitored by the specific gravity) then it can be assumed that voltage might be a fair indicator of cell condition...

not many folks get into the weeds deep enough to keep this sort of records or do the proper charging as set out by the oem manufacture of the batteries, until they either murder their first set or if they purchase very expensive banks of batteries that hurt like hell when they turned over the cash.

because one ought to be doing the equalization periodically, and ought to be checking the specific gravity while doing so, and one should be keeping a log on each cell, then why not add a line to the log and check the specific gravity a bit more often until such time that the bank is well understood.

even then, about the time you think you understand your bank it will age, with age everything starts to change, as does the specific gravity, top off times and frequency and time of equalization.

so?

in my opinion, get a good hydrometer, learn how to use it, then use it, and keep a log on each cell, for the life of the bank.

getting back to sandia, they have done efficiency testing and published several papers explaining why it is not desirable to fully charge the battery every cycle.  very informative reading and it works.

bob g

[BillBlake]

Hello bob g,

How do I find out what Sandia Reports have already been posted here?
When 'Sandia Report' was typed into the search bar all that came up was you and me.
That seems impossible. There is at least one other Sandia Report that is a Cornerstone of the
Theory that I would like to discuss here someday once the groundwork is laid out. I agree with much
of what you say but wonder about not bringing the batteries up all the way when you have the chance.
Assuming that your going to charge them anyway.

One huge Battery outfit that has always stood strong and stood alone doesn't like charging the batteries
at all unless You HAVE TO. They want their big monsters run down to 80% DOD all the time - tonight is fine. :-)
They claim that Any Charge is counted as a Cycle even if it's a Little 'Lunchtime Battery Pick-me-up'
so they don't want to hear it.
Just run them down real good for a day or two (or whatever) and don't mess with their program is how they Likes it.
Also how they guaranteed it the last I checked over a year ago. They might have to go in the Legendary Class
someday. Maybe not. Time will tell. I'll check them out again before saying anymore about that deal.
Thanks.

Bill Blake

[dnix71]

The Sandia study simply found what everyone else should have already known.

If you discharge any series of cells too deep, one of them gets reversed and then the whole string is hosed.

That's why there are battery management modules on every cell in well made tool power packs. The Tesla has 6800 or so AA NiMH's and every one has a chip that monitors charge and discharge and is programmed to prevent over charge or charge reversal during discharge.

The obvious problem with monitoring a series string of 6v batteries is that each "monoblock" has 3 cells, so the best you can do is watch each monoblock for voltage sag. That's why the Telcos used to use 2v monoblocks. You can watch each one and if one gets too low, it can be automatically disconnected if wired with relays to allow for that. You also must have some way to shed load as monoblocks are disconnected to protect them. A power drill will simply run slower and with less torque as the battery fades, but some appliances won't tolerate that.

If you have four 6-volt batteries in series and you have even one weak cell inside any one monoblock, that is the real limit of the whole string (weak link in a chain, literally).

Deficit charging in a 4 x 6 string is pretty hard to avoid unless you keep the size of the string small enough to trickle charge for 4 hours at absorption rates. But the smaller the string the more likely you are to over discharge if you aren't careful.

Simple answer is lots and lots of PV. So much PV that it is rarely used to capacity. With my bank, 7 batteries works much better than 8, because they get fully charged almost every day even in marginal weather. I have 800 watts of name plate PV, but in real life don't get more than about 1/2 that even for short periods. PV has gotten cheaper lately. Buy as much solar as you can afford, skimp on battery size if you have to.