Unsmoothed car battery charger - is it crap?

The only time I've ever seen a battery damaged by overcharging was when the voltage regulator failed on a friend's car in a way that the output was much higher than it should be, and it boiled almost all the water out.

I was very close to that once I reckon, with a motorcycle battery, when I neglected to remove the vent plug before charging. The whole case was bulging ominously by the time I noticed.

Every low maintenance wet battery I've seen has a vent to stop this happening. Often with a plastic tube attached to vent the fumes out of harm's way. Genuine SLA have a vent too - but no 'vent plug'

In article , Dave Plowman (News) writes

This was a small (easy to overcharge and froth) basic liquid lead/acid battery, a Yuasa YB3L, IIRC. All cells breathe to a vent at the side, then a plastic tube downwards. When it is supplied wet, this vent is plugged for obvious reasons, and it is easy to forget to remove it before the initial trickle charge I used to give them.

That is not the style, action, or purpose of an equalizing charge. No bubbling is involved in anything i have found on equalizing charging.

"JosephKK"

The bubbling is mainly released hydrogen. This results in an unwanted excess of sulfate ions. You should be able to figure it out from there.

Interesting - thanks. I've seen articles posted which assert that the equalizing and de-stratification does involve some amount of gassing... and now that I look, I see other references which either don't mention gassing during equalization charge or which state that a proper equalizing charge should be prolonged, slow, and should definitely _not_ cause gassing.

Every wet battery I've ever seen starts producing the odd gas bubble some time before its fully charged.

Indeed. Used to get lots of bubbles from the fork lift truck batteries where I worked. So much that the insurers refused to let them be charged inside the building.

Each battery weighed two tonnes, so I suppose it was to be expected.

Chris

Yes - explosions in battery charging rooms in garages etc were very common.

That is not the style, action, or purpose of an equalizing charge. No bubbling is involved in anything i have found on equalizing charging.

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Beg to differ. Equalizing charge is typically charge at the voltage limit that will *not* produce gassing until current drops to a low value (often 20 or 30 hour rating). Then hold current and let voltage rise above the gassing limit. Because voltage is above gassing limit, gassing occurs. Hold current until voltage stops rising for about 1/2 hour and terminate the charge.

Cheap store-bought chargers will simply have two voltage settings, 'float' and 'equalizer'. But 'equalizer' done with this constant-voltage type unit doesn't do as good a job as the method I described above.

The gassing does promote mixing, but the primary thing is to charge all cells until voltage stops rising. Then you can be sure that all sulphates have been converted back to acid in the electrolyte. Has to be done at a low current to avoid excessive heating and water loss.

daestrom

Try charging submarine batteries. About 128 individual 'cells', each one weighing over several ton. Finishing rate was 200 A, the 3-hour discharge rate was 1750A. And being on a submarine, you had to recirculate the H2 generated and send it to a 'burner'.

When doing an equalizing charge at the finishing rate, the gas evolved was almost perfect 2H2 + 1O2 (electrolysis of H2O). Boat's O2 content would rise with the H2 content (until the 'burner' could catch up with the battery).

daestrom

The bubbling is mainly released hydrogen. This results in an unwanted excess of sulfate ions. You should be able to figure it out from there.

Not on the finishing rate of an equalizer. Then the gas is almost perfect

Been there, and qualified charging electrician to do that.

daestrom

OTOH look at the practices, procedures, and policies in Telco battery rooms.

In article , JosephKK writes

Really? I was in a Tesco battery area the other day and noticed nothing special.

You missed it, they had a special on AAA's couple weeks ago.

In article , Redwood writes

I've never seen a lead/acid AAA battery.

Were the cells charged individually, or did they just do several at once at a fixed rate?

I've wondered before if there's any sense in trying to charge car battery cells individually, but I suspect it's just not possible without dedicated terminals for each cell. (sometimes it's useful with an ailing battery to stick probes down through the cell covers and see what's going on with individual cells)

How long is a piece of string? With a crude transformer/rectifier one, depends on the transformer design. And the type of rectifier. And the device measuring the voltage. ;-) What matters is the voltage under load.

These days silicon diodes. Suitably heatsinked.