Lead Acid Battery Charging

The question wasn't answered but it looked to me that the intermediate voltages were being used.

I think that might have been me ;-)

-- "For a successful technology, reality must take precedence over public relations, for nature cannot be fooled." (Richard Feynman)

That wasn't what she drew.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

You're right. I was remembering that the arrows form the regulators were just that, not grounds.

connector on one end and solder it to the output of the 7805 ( positive terminal) and the ground of the battery.

solve the problem.

The 'real' solution is to design a custom battery charger - because that diode stuffs it up for off the self chargers. Normally the state of voltage tells a lot about the amount of charge but in this case there is an extra .7 that isn't taken into account.

As a suggestion you could replace it (IIRC D2) with a 1 amp 30 volt schottky diode (1N5818 or 1N5818 would be OK) - this will *reduce* the problem introduced by the diode.

But the best solution is to customize the charger (there is an ugly hack that might be possible - similar to using the diode to jack up the output voltage of the 7805)

Hi,

Will 1N5819R will work instead of 1N5818. The digikey link is given below

I have few 1N5819 already in stock. I have to place order for 1N5818.

Thanks

jess

Hi,

Will 1N5819R will work instead of 1N5818. The digikey link is given below

I have few 1N5819 already in stock. I have to place order for 1N5818.

***1N5817=20V, 1N5818=30V & 1N5819=40V.

Apart from those differences; all 3 are pretty much the same - The "R" suffix may be an artefact of their stock number, or posibly an encapsulation variant.

I am unable to understand that why a zener will work better than a diode

1N5818, etc are not zener, they are schottky.

Lower forward voltage than a junction diode, at the expense of (usually) higher leakage.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

I am unable to understand that why a zener will work better than a diode

***A zener is a diode with the difference that its doped in such a way as to have a closely defined by voltage, reverse leakage and a sharp knee curve in the reverse current - strictly speaking; anything less than 7V is a zener and anything over 7V is an avalanch diode.

***I've found by experiment that I can usually identify zeners with a DMM diode check range because they read almost exactly 0.7V, regular (for mains frequency) diodes usually come in between 0.55 & 0.65V, fast diodes usually have Vf down to about 0.4V. SB diodes are quite variable from as much as

0.4V for a small signal type, to as low as 0.1V for a thumping great metal stud rectifier.

***SB diodes with your application will give the lowest Vf loss, with a 12V SLA battery; any common SB diode will have adequate reverse voltage rating - provided there's no large inductors to produce back emf. SB diodes do have measurable reverse leakage, but that shouldn't be a problem.

1N5818, etc are not zener, they are schottky. ***Back in the days when I repaired monitors for a living, I found that some manufacturers used either a 1N5817 or a BYV10 20 SB diode to clamp the connection between the UC3842 & the MOSFET gate, it was fairly usual for the source current sensing resistor to fail O/C if the MOSFET punched through. The SB diodes were much better at failing S/C under such extreme conditions than a zener - sometimes they even protected the UC3842!