"Jim Wilkins" wrote in message
...
On Oct 12, 8:35 pm, "RogerN" wrote:
"James Waldby" wrote in message

. ..




Smart chargers are based on a chip that have the lead acid charge/
decay curves telling it how to act. I suspect it monitors the voltage
of the battery and if that info is faulty then the charger works
erractically.
jiw

The 2A rating on a lead acid battery charger is more like 2A for a
discharged battery and lower current depending on the state of charge,
quite
different than a 2A constant current charger.

RogerN
/
/The "2A" range on my 2/10/50A Schumacher starts at 4 - 5A and
/decreases as the battery comes up; it passed smoothly through 2A but
/didn't stay there, IIRC at cutoff the current was less than 1A.
/
/An LM317 adjustable regulator IC is enough to make a decent trickle
/charger. Adjust the pot that sets it to the end voltage, the device
/limits the current to 1.25A max, then it falls off as the battery
/nears the set point. You could print the temperature compensation
/chart and tape it to the box.
/
/This is a commercial version with voltage and current meters:
/http://www.testequipmentdepot.com/lascar/dataloggers/psu130.htm#00034606?ref=gbase
/The one-turn voltage adjustment is tricky but good enough for lead-
/acids, though you'll need a separate voltmeter with more resolution
/
/jsw

That would be interesting, I could send a higher DC voltage to the vehicle
and have the voltage regulator on board. It would be neat if I could get
temperature compensation close with a PT100 RTD or similar, I guess I'd just
have to calculate the temperature coefficient of the platinum
versus -0.022V/deg C for the battery. Anyway, if I could get the circuit
right, I could power it a couple of hours a day and keep the battery topped
off. I would think that would do at least as good as an automotive
alternator/regulator does.

RogerN