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OK, I found the thread that recommended using vaseline or grease to stop the corrosion. Sounds messy but I suppose it's doable. Now can anyone tell me why this is happening? Why doesn't it happen in my car, for example?

Thanks.

I'd agree except that this battery has a built in handle and was never carried by its terminal posts. Carrying batteries that way is the equivalent of lifting a dog by his ears - a horrible thing to do to a battery (and a dog). The only damage the posts have gotten from me is a bit of chewing from the many battery charger clips I've used on them. I use the battery to charge lipo packs for model airplanes - I've never actually used it in a car. You can see the hole in the side of the post near the base from all the corrosion. I see no electrolyte leakage, and the deposits are black in color and soft, like the lead of the post, not the usual white crusty stuff you see under the hood of your car. I will say that the corrosion has lessened somewhat since I began desulfating the battery, though maybe the good cleaning I gave it helped as much or more.

Thank you for these comments, NavyTrained. I have reduced my corrosion problem with a judicious cleaning and an application of a bit of vaseline jelly, and the corrosion of the post seems to have been arrested, but the negative battery clip is still picking up grayish gunk deposits. I'm not a chemist but it looks like some kind of galvanic corrosion is taking place as the clip's copper coating is being eaten away. Not sure yet if the steel underneath is also being eaten away. For all I know, however, the coating may not be copper at all but rather something that looks like copper. It's not flaking off and no green or white corrosion is evident anywhere. Maybe if I put on better quality clips this wouldn't be a problem?

As for progress in my battery's return to health, I confess I don't really know how to measure it to be sure. After a high-rate charge and the charger has dropped automatically to the trickle rate, the no-load voltage reads around 13.2V. This is up from 12.7V before desulfation bagan about two weeks ago. However, after a few days on trickle charge (with desulfator running) the no-load voltage drops to about 12.59V. I'm guessing this is because my charger's trickle current rate isn't quite enough to keep the battery topped off while the battery is feeding the desulfator at the same time? Is there an accurate way to measure a battery's improvement?

Hi Guys,

Well, it's been several weeks since I built my desulfator and I'm happy to report that it seems to be working well. Initially, however, I thought I had a problem where my battery would charge to steadily increasing voltage levels (now well past 14V) but it would drop gradually to about 12.6V after a few days, even with the charer left on. I found that this was caused by my charger as it apparently has no real trickle setting and gradually drops the charging current to 0.00A after it detects a full charge. The drop in voltage therefore reflects the current consumed by the pulser itself, which I have set at 0.70A AC. That's the setting that gives the highest pulse, around 36V into the battery, without overheating the diode, cap, and coils. I presume that my charger will eventually sense the drop in voltage and restart the charge but I've not let the battery voltage drop low enough to find out what that level is. This has not been a problem as I just reset the charger whenever I see the green light on and away she goes again at the high rate. A few hours later the charge will drop to zero again and the battery and pulser will be left alone to happily sing their duet together without benefit of the charger.

There are several improvements I'd like to make:

1. Adjust my charger so it puts out a true trickle current after a charge. I suspect I won't be able to do this without raising the pulser current past .70A, however. Anything beyond about .80A prevents the charger from completely turning off, that is, the charger stays in charge mode. This may not be a bad thing. I'll just have to watch the charger and pulser to make sure things don't overheat, or heatsink them if they do.

2. For my car, I want to add a relay with the coil going to the ignition switch and normally closed contacts going to the pulser so that when the ignition is on, the relay energizes, the contacts open and the circuit turns off. When the ignition is off the contacts close and the circuit turns on. For this to work without discharging a heavily sulfated battery by morning, however, a reliable low-voltage auto-shutdown circuit will be required.

3. Build a low-voltage auto-shutdown circuit so that the pulser won't discharge the battery past a prescribed level, say, 12.5V. I'm considering this design: http://electronicdesign.com/Articles/Index.cfm?ArticleID=6403, which has been mentioned before in this forum, though I don't know if anyone actually built it. One problem with this design is that the circuit only works up to 10V. Another is that I'm not sure it can tolerate repeated voltage spikes of around 50V without producing erratic operation. If it can't then I will either have to filter out the spikes or feed the output of this circuit to another FET which will power the pulser on thus isolating it from the low-voltage shutdown circuit. Can any of you help me answer the following questions:

a. How can I get the above low-voltage auto-shutdown circuit to shut off at 12.5V?

b. Have any of you built an automatic car battery circuit of the style I described, and how did you do it?

Many thanks for your inputs,
Kmpres