Re: Unsmoothed car battery charger - is it crap?

I keep one just for that purpose & then connect the new fangled smart charger soon as the batt can take it. From experience though, if connecting a totally flat batt get ready to switch off the old charger before the needle goes off the scale followed by a big bang as the bridge rectifier decides its had enough!!

My ancient one has a series resistor to limit the current - and has both mains and DC fuses.

The one I built in the '60s has a Variac to set the charging current, ot float voltage.

I'm the OP. Oddly enough when I used my old charger on the almost flat low maintenance battery, the ammeter needle hardly moved at all.

After a few minutes the needle was about midway on the scale where it more or less stayed for a few hours.

What was happening? Didn't see any great rush of current as you might have once had!

PHOTOS: front =

That sounds like a classic symptom of the battery being badly sulphated.

Lead-acid batteries run on... well, lead and (sulphuric) acid. The electrochemical reaction which produces current, is one in which the lead reacts with the acid. converting the lead to lead sulphate. When you re-charge the battery, the reaction is reversed... the lead sulphate is broken up into lead (metallic) and sulphate ion, which goes back into the electrolyte to once again form sulphuric acid.

The lead sulphate which is formed during discharge has a couple of different crystal forms. The initial deposition of sulphate isn't too difficult to dissolve... but it converts spontaneously to a different crystal form which is hard, difficult to dissolve, and forms an effective insulator.

I think that's what happened to your battery. When you initially tried to recharge it, the plates were covered with a uniform layer of lead sulphate, and were thus well insulated from one another. Very little current could flow. After a few minutes, the relatively high voltage from the old-style charger managed to break down some of the sulphate layer, allowing an increase in the current flow.

There are techniques and devices on the market which are intended to reverse the sulphation of batteries. They usually involve some form of high-voltage pulse charging, sometimes using an inductive "tank" circuit to create very short radio-frequency pulses. This is supposed to break down the insoluble sulphate crystals. Some people swear by these devices, other people swear that they're useless.

Deep-discharging most car batteries (low-maintenance or otherwise) is usually said to be very bad for them. The extensive conversion of lead to lead sulphate (and then back again) damages the structure of the lead plates, and the plates begin to crumble and disintegrate, greatly shortening the battery's lifetime.

I can't remember for how long i have known that deep cycling was bas for lead-acid batteries, it is nice to have some insight into the damage process.

I remember buying an AC Delco battery years ago - and it had a three year unconditional warranty if used on a car, but only one if used in a golf buggy, etc.

I have resurected some batteries that have sit around that initially soak very little input current. I have left it go for a week sometimes. I need to try that with some old gel cells I have. After overcharging them, they partially clear up the sulfation. I mostly use deep discharge batteries in the truck. They seem to hold up better after complete discharge, while the truck sits for long periods. The thicker plates seem to last longer. I keep thinking of hooking up that solar cell charger but never have yet.

greg

clear

They do hold up better, you can still kill them, but deep cycle batteries tend to have solid plates which are much more resistant to damage from sulfation, they do however have a much lower capacity to begin with due to the lower surface area vs the porous plates.

Actually the capicity is similar, it's the peak current that you compromise on.

soak very

to try

partially clear

It is more a matter of degree rather than a sharp distinction from what i have been able to find of the details.

how do you deal with mains fluctuations?

How do you do it with any battery charger? Hint: You don't. It would require the AC line to be well out of tolerance, either high or low before the charging current would change more than a few percent. That is what a transformer does. I used a 24 volt 15 amp transformer after the variac. That reduces the change in line voltage by a factor of 5 to 1. The variac raises it to around 7 to one at the five amp charge rate I use most of the time, so the line voltage would have to go up to 128.4 for a 1% rise in the transformer's secondary voltage. The change in charging current is quite small.

If the battery is quite low, or dying I have a garage type charger that will start most car engines, even with no battery in the vehicle. It has no adjustments, other than a mechanical timer to set the charge time.

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LOL...you have no idea what you are talking about.

TMT

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