"Leon Fisk" wrote in message
news
On Thu, 15 Dec 2016 08:46:53 -0500
"Jim Wilkins" wrote:

snip
my tractor has
had a series of cheap U1R batteries others had discarded.

These lithium batteries caught my eye last spring:

https://www.amazon.com/Lithium-Phosp...dp/B00O4FLQN2/

The price is very interesting, compared to $1000 for some of the
others on that page. How do you keep your regulator output from
exceeding 10A, or limit the under-hood temperature to 140F?


I've had pretty good luck with the lawn tractor battery but the
motorcycle battery has always been troublesome. Real lucky to get 5
years from one, usually less. Stored inside, water topped off with
distilled, regularly charged with a smart desulphating charger... If
one
of those lithium replacements would last around 10 years it would be
worth it.

You tried any of the Lithium Iron Phosphate batteries yet?

--
Leon Fisk
Grand Rapids MI/Zone 5b
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I was the battery tech at Segway and Zoll Medical, and once a chemist
who experienced a Lithium Aluminum Hydride fire in a fume hood.

Lithiums are great while they work, as long as you observe the many
restrictions on them. When they deteriorate there's no way I know to
salvage them. The ones I tested had a supposedly guaranteed lifetime
of at least 3 years but my experience has been that it varied from
less than one year to possibly as much as 15.

Commercial Lithium packs have built-in supervisory circuits like this
to limit their charge and discharge voltages, balance the individual
cells and hopefully protect them from igniting:
http://www.ti.com/lit/ds/slus039/slus039.pdf

It's possible to use the batteries without a control circuit but you
need to watch them carefully. At Segway we charged individual
evaluation samples with either a model airplane charger or a voltage
and current controlled lab power supply. One battery isn't as bad as a
string of them since unlike other battery types they have no good
inherent way to divert excess current once fully charged, so without
an external balancing circuit an unequal cell may allow others to
overcharge before the pack reaches its "full" voltage.

The "Gas Gauge" circuit integrates and records charge and discharge
currents on the assumption that charging is 100% efficient. It needs
an initial calibration to determine the actual Coulomb capacity of the
pack, and recalibration as the pack ages. That's why a laptop may shut
off at 40% indicated remaining capacity.

Which "smart, desulfating charger" did you use? Opinions vary on their
effectiveness. Pulsing makes sense from the circuit designer's
perspective because it cheaply forces current with higher voltage
while limiting current and heating, but I'm not so sure it does what
they claim inside the battery. The DC overvoltage desulfation method
I use can run away if the current isn't limited by either circuitry or
using a small solar panel as the source.

--jsw