Accumulator charge rate?

[Boom]

What is a safe charge rate for an Exide CZG6? The bit of the label with the details is missing.

I don't suppose anyone has a scan of the labels for me too?

Thanks

[Peter.N.]

If this is a 'standard' 2 volt radio accumulator we used to charge them at about 1 amp.

Peter

[Boom]

Thanks Peter. There is a bit of the label left and I can see 'charge' and '5 amp' but that seemed a lot to me. I wondered if there might be a '.' missing in front of the 5? Did they use decimal points in those days?

[AVO_VCM163]

The last digit in this range is usually the Ampere-Hour Capacity divided by 10.

The charging rate recommended is typically 1/10 to 1/20 of the AH figure.
Hence 5A would be probably be the correct maximum rate for this cell.

Roy

P.S. The decimal point predated the accumulator by a long-long time !!

[Peter.N.]

50 -100 ah ?

[Boom]

Originally Posted by AVO_VCM163

P.S. The decimal point predated the accumulator by a long-long time !!

Lol - Yes I know but I was probably expecting to see 1/2 Amp. I really wasn't about at the time and when I was at school in the 50s the teachers were forever trying to drum fractions into me. Something they never succeeded in.

[murphyv310]

Hi.
I would go with Peter here and charge at 1 amp, the voltage should be monitored and the cell voltage should rise to 2.2v, this voltage should remain stable and the cell should liberate gas after 30mins to a couple of hours, this depends on the AH capacity of the cell. A brand new cell will often rise to 2.4 or 2.5v. The correct check though is the specific gravity.
I feed any cells from a stable 2.2v per cell supply with current limiting (a resistor) and leave the 2.2v on the cell until the cell gasses freely.

[Dave757]

Originally Posted by Boom

Yes I know but I was probably expecting to see 1/2 Amp. I really wasn't about at the time and when I was at school in the 50s the teachers were forever trying to drum fractions into me. Something they never succeeded in.

Hi Dave

My Exide DTG accumulator is also missing parts of the label, but
it has 'Charge at half ampere' cast onto the glass. I understand
the capacity of this cell is 20Ah.

Kind regards

Dave G0ELJ

[Boom]

Thanks for the guidance. I've had it powering the Melody Maker tonight after a couple of hours charge at 2A. The voltage is a little low at 1.9V off charge but I've got it on an Alum electrolyte and not at all sure if there should be a difference than with H2SO4. I'll give it a long charge and see what happens.

[Boom]

After a full night on charge at 1A the voltage still isn't above 1.8 but a lash up shows the cell is easily capable of taking 5A from a supply.

I flushed it out with baking soda and refilled with H2SO4 but the same. It holds a charge but not enough volts.

Here's a picture of the plates. There is still some brown muck on the white separators although the grey plates look useable. Is the brown muck likely to be the problem? The only way I can see of totally ridding the cell of it is to take the top off and manually pick it off and I haven't a clue how to get the tar off.

Any ideas? Thanks

[McMurdo]

Ive just come across my 1933 practical wireless accumulator charging tables and it says a rule of thumb is 1/10th of Ah capacity as AVO Roy has said.

[Boom]

Thanks Kevin. That would give 6 Amps for 10 hours or 3 Amps for 20 hours for this 60AH. It's going to take a while for my little 1A PSU to do the job fully. As I say I missed this era but I seem to recall my old man saying that a customer had to leave their second accumulator with the charging source for 48 hours which is a bit mystifying. How many chargers would a shop have needed to keep their customers happy and the equipment can't have been cheap?

Sorry. This looks as though I'm talking to myself. I'm not, I'm only mumbling lol...

Well with nothing to lose I went for the kill. I picked away the tar and managed to get the top cover off.

I then found that the plates/insulators are actually jammed inside a channel in a 'pack' and that they wouldn't budge! With the top cover off though I managed to get a thin piece of metal in next to the brown muck and started
scraping away.

After an hour I had managed to clean off half of one strip so had another look to see if it was possible to get the cell pack out in one go. This time it was and the whole lot slid out to give me full access to the plate edges
and after a short while nearly all of the sludge was cut levered or washed out.

For cheapness mainly but I really can't see why not I rinsed the lot off with warm water from the kettle interspersed with dipping in a baking soda solution. Very small bits of insulator were starting to show in the rinse so I decided not to push my luck too far and started putting it all back together.

An old soldering iron melted all of the saved tar bits back into the lid channel and the cell was filled back up with the H2SO4. (I haven't forgotten the Alum experiment but am getting mixed up trying to play two projects together with not much of a clue what I am doing with either so I decided to stick to H2SO4.)

To be honest I really wasn't expecting the cleanup to result in anything better but after the battery had been on a 1A charge for half an hour it was obvious that it was different. The voltage was now well over 2 volts and stayed there even after turning the PSU off! Previously the volts wouldn't go over 1.9 and were sometimes down to 1.7. With the cell off charge and after 20 minutes it is still 2.1 volts. I'll have to wait and see now...

I can't emphasise the safety aspect enough of playing with these things just in case I am giving anyone ideas. Everyone was barred from the kitchen while this went on. The whole operation was completed in an hour.

A picture of the cell and another of the plate assembly attached.

[AVO_VCM163]

There are two different aspects here.
The original question was what was the safe charging rate for a particular accumulator - the CZG6.
In its original state it had a capacity of 60AH so the normal maximum safe charging rate would have been 1/10 or 6AH - nominally rounded down to 5A. This would have been the rate used when taken to your local garage. They would connect a number in series and just take them off when seen to be gassing profusely.

The other aspect is how to deal practically with an old specimen!
Even with the correct electrolyte this would have lost considerable capacity due to plate degradation as seen in the pictures. So on this account the maximum charging rate should be much lower.
I find the easiest and safest way to charge all unknown cells and batteries is to use a voltage and current regulated DC power supply and monitor the cell voltage.
Set the voltage without the cell connected to the fully charged voltage (2.2 for lead acid), and gradually raise the current to a maximum of 1/10 AH capacity but start at 1/50. Assuming that current flows, watch the voltage. In a good cell this will slowly rise but remain below the fully charged value for a long time until fully charged. The time to reach full voltage multiplied by the current will probably be about twice the AH capacity.

Often no current will flow when starting the procedure because the cell has a high resistance. In this case set the current limit to 1/50 AH rate and slowly raise the voltage until current starts to flow. With a NiCd cell this may require 20V or more. The cell voltage should then slowly FALL towards the fully charged voltage. This can sometimes reactivate very poor cells but they will often only achieve a fraction of their original capacity.

Coming back to the Lead-acid cell. Some have reported success in improving the plates by adding AC to the charging current. I have tried this but with no success.

Do check the specific gravity of the acid when charged a fully as possible. A weak acid will severely restrict capacity and not be helpful to the plates.

Also ensure that any sludge has been removed and that the plates have been thoroughly purged of any chemicals introduced - this requires many hours of water flushing followed by soaking and changing in distilled water to removed tap water contaminants.

Happy charging!
Roy

P.S. Started to write/post before seeing your last! Great to see the experimental approach!

[Parkford]

Found this just a wee bit late but the info may still be of use to others. I have at the school several of the Exide CZG6 which have their labels intact!

The amount of information is wonderful. As follows:

Capacity 60Ah at 20 hour rate
Charge at 5 Amperes

INSTRUCTIONS
FIRST CHARGE - Fill to 'acid-level' line with sulphuric acid 1.250 specific gravity. Stand for 12 hours. Add sufficient acid to restore to original level. Charge as described for recharge, but for 48 hours minimum. The cell is then ready for service.

RECHARGE whenever specific gravity falls to 1.100 or voltage falls during discharge to 1.8. Even though these values are not reached, charge every two months. Charge at the current givenabove until specific gravity rises to approx. 1.250 and remains steady for 3 hours.

GENERAL - Maintain the level with pure water (preferably distilled or de-ionised). Keep terminals clean and coated with petroleum jelly. eg 'Vaseline'


Given the style and content of the above label, I'd say my ones were made in the 60s - relatively recent!

Hope this may be of help to someone else.

Bob Stewart

[Peter.N.]

Ot having seen a picture of it I was assuming it was the two thick plate type that I used to charge in my youth, that does look quite a high capacity affair. The brown area should be the positive plates but they look as though they are separating a bit.

Peter

[G6Tanuki]

Having been involved with the vast banks of lead-acid batteries used as backups for telephone exchanges, the usual rule was to charge at C/10 for 16C Hours.

So a hypothetical battery with a C of 1 amp-hour would be charged at 100mA (C/10) for 16 (C*16) hours.

This assumed the batteries had been drained fully. In the case of partial discharges and the sort of rotating regular power-cuts we had in the late-1970s industrial-action/pit-strikes/3-day-week era a system was developed where the batteries were recharged at C/3 but this was also accompanied by what was indecorously known as 'burping'.

Fast-charging of lead-acid batteries causes the plates to become covered by a film of microbubbles of oxygen or hydrogen: this raises their effective impedance and so a significant amount of the power you're feeding to them from the charger gets wasted as heat overcoming this bubbly boundary-layer. The answer was to periodically take a *massive* discharge from the batteries - I'm talking 10,000 Amps for half a second - which gave them a sort-of electrolytic shake-up and caused the plates to slough-off their microbubbles.

I'm not suggesting you do this to your battery.

[Techman]

I hadn't seen this thread before.

So just for reference, here's a brand new one still in its box from my collection.

Note that the date code on the bottom left of the label on this example is January 1959.

It just needs the acid adding and away you go........

The bit that isn't showing on the top of the enlarged picture of the label says "charge at 3 Amperes".