"mike" wrote in message
news
On 5/24/2017 6:49 AM, Jim Wilkins wrote:


Since I don't cycle my batteries daily I can afford to experiment
with
slow charging from the solar panels at a few percent of the
Amp-Hour
rating current. Rather than adding a current limiter which would
cut
into the already minimal voltage overhead of solar panels,

There are some nifty hall-effect sensors with almost zero drop.
Used one in a solar/wind system with a shunt regulator.
Wind generators don't like being unloaded by a series regulator.

http://www.ebay.com/itm/Bayite-DC-5-...-/361553795712

How stable is the zero reading? This is the best DC Hall effect
ammeter I've seen and its zero drifts by several mA per minute if held
still. When moved the Earth's magnetic field throws it way off.
https://www.eevblog.com/forum/testge...-uni-t-ut210e/

I built a homebrew power supply whose current limiter adjusts from
1mA to 0.4A. I use it to restore old electrolytic capacitors at
about
5mA and to desulfate free batteries that need to be hit with over
16V
to accept any current. For them the current needs a limiter to
avoid
pegging the ammeter as they recover. I've been using one such free
"dead" battery in my tractor for two years.

I'd like to hear more about your desulfation successes.
High voltage didn't help. Other crazy ideas I'd read about, like
AC at various frequencies to 'ring' the plates
and shake off sulfation, etc. Got absolutely nowhere.

http://batteryuniversity.com/learn/a..._to_prevent_it
I've fixed several "dead" U1R lawn tractor batteries and used them for
several years. The symptom was not accepting more than a few milliAmps
from a commercial charger, although the resting voltage seemed OK. The
fix was using the variable power supply to force 16V to 17V which
caused the current to very slowly increase and then the required
charging voltage to drop, an unstable condition that requires current
limiting, such as with a low end lab-type supply like these if you
can't rig up your own.
https://www.amazon.com/Dr-meter-PS-3.../dp/B00O8DJ8QC

After the battery had accepted enough charge to raise the electrolyte
level I checked specific gravity and found one or two low cells.
Charging at a current that didn't make the others bubble excessively,
around 0.5A, eventually brought up the low cells. The resurrected U1R
in the tractor now can put 150A into my HF carbon pile load tester.

I've read that salvaging batteries this way can take up to a week. I
saw progress with salvageable flooded batteries in a few hours but
haven't had much luck with AGMs.

The neighbors who give me these batteries know I can fix them, and
that they will need frequent attention afterwards. I have to top up
the charge at least monthly or their internal resistance will rise
again.

I don't know if the cause is literally lead sulfate recrystallization
or not but it's a handy suspect to blame. There's a theory that it's a
thin oxide barrier between the grid and the active material.
Whatever the cause, the effect is a very high internal resistance.
Automatic chargers see the voltage rise as though the battery was
fully charged and shut off. Some people have reported success using a
Harbor Freight manual charger on a Variac as the variable supply.
-jsw