AC DC Adaptor fail

I think there are two types of AC/DC adaptors: battery charger type that can tolerate the output voltage being dragged down by the load; power supply type that cannot tolerate the output voltage being dragged down by the load. The failed adaptor is the latter. My working 18v adaptor is the former. To buy the right one, I need to search for battery charger. I can see some 21v 2A li-ion chargers on ebay. Those will work but too high an AMP rating for what I need.
 
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The replacement 431 transistor arrived. The only difference between the new and old part is that pin 1 and 2 has a resistance of 6 M-Ohm instead of 50 M-Ohm. The internet diagnostics procedure for the transistor appears to the wrong. Since there is a difference, I am assuming the old part is blown. But, putting in the new part did not revive the adaptor. Measuring the output of the transformer in the adaptor produced 0V. The damage to the adaptor is worst than thought, could be the transformer or the main chip. So, the adaptor a write off.

The happy news is that a new adaptor arriving at the same time is working. I am hopeful this will be able to bring my battery to the magical 16.2V. The adaptor is better than wanted, and able to keep the charge current constant at 1A regardless of the dragged-down voltage by the battery. At the time of purchase, I was rather hoping the adaptor being a little crappy and output less amps when the voltage was dragged down. I would be happy for a 100-200mA output. I have used this for half a day and it hasn't blown or got hot, only slightly warm. The battery state is satisfactory. It's coming back from the dead after being left drained in the winter months. It was at 4v and 560 m-Ohm of internal resistance. A good battery is 4 to 7 m-Ohm. My battery tool declared it 0% health.

charger-1a.png
 
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I kept the new charger going over night and the garage hasn't burnt down. I definitely need a fire alarm for the garage. Using the feel-by-hand gauge, the charger is warmer than wanted, but not hot.

The battery state:
15V while connected to charger
13.5V stand alone
7.9 m-Ohm internal resistance
Battery analyser indicates 98% charge. It's full according to convectional measure. I prefer non-conventional measure and keep charging.
Battery analyser indicates 48% wear life, meaning the IR needs to be around 4 m-Ohm for this particular battery to be like-new.
Battery analyser indicates 330 CCA, compared to the 430CCA of the battery spec
Bubbling could be heard, meaning the lead plates accepting less current than 1A. The excess has gone into electrolysis generating hydrogen

Conclusion:
The charger is capable of taking the battery to 16.2V stand alone, which is the maximum possible based on the chemistry of the standard battery. Whether the battery plate sulfation will allow that is a separate consideration.
The charger is over-powered in terms of amperage and/or voltage. By what amount: unknown.

Knowledge gained/reaffirmed:
The amount of current the lead plates can accept is variable throughout the charging cycle. The amount accepted could go up as well as down. The battery will accept any amount of energy until complete evaporation of the water in the electrolyte. Compared to other devices, the battery has an infinity draw for higher voltage electricity.
 
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The battery continues to make progress. Until that stops, it needs charging. The over-powered 1A current continues to cause undesirable bubbling.

Battery state:
15.76V while connected to charger, draw from mains 21W
13.9V stand alone
7.07 m-Ohm internal resistance
54% wear life
367 CCA

To tune down the charging current, I will be using a PWM motor controller. This breaks and remakes the charging circuit at regular intervals. The interval length is adjustable. The average voltage as well as current on the output to the battery is reduced accordingly. I need a single setting on the control knob that is good for the entire charging cycle so that the charger can be left unattended indefinitely. The controller itself consumes a small amount of power. But, the reduced feed to the battery reduces consumption on the mains, which in turn lowers the temperature on the charger adaptor. The temperature isn't high but I want it lower.

pwm.png
 
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My PWM plan got scuttled rather quick. My existing controller was bought to control PC fans, and I wasn't thinking about other applications. The controller can handle 15V max. Now I have to carry on regardless with the bubbling while I wait 2 months for a new max 28V controller.

pwm-3a.png
 
The battery progress slowed. Could be hitting the buffers now. There remains chance of progress improving if more sulfation is dislodged by the charging.

Battery state:
15.84V while connected to charger, draw from mains 18W
14.1V stand alone
6.91 m-Ohm internal resistance
56% wear life
375 CCA
 
Progress largely stopped. So, no use charging more. Now switching to my other adaptor: 18V, 1.2w mains draw, 40mA average output current. The output current is on a sine wave - it's just the way the adaptor works. This can be connected permanently. It is capable of charging batteries to 13.5V over a long period. I am testing this to see if the low power adaptor can maintain the battery at the current state or the state will decline because of the low power.

Battery state:
15.92V while connected to charger, draw from mains 18W
14.1V stand alone
6.77 m-Ohm internal resistance
59% wear life
383 CCA
 
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Battery progress were made within a few hours of using the low power adaptor. Disappointingly, it hit the wall and stopped progressing. The adaptor is capable of maintaining the battery at 13.6V indefinitely. This is the upper limit of what the 18v adaptor can do. Capacity and IR progress remain possible over a very long period. For testing and research, I need faster result. So, I am putting back the high power adaptor to see if it does anything.

Battery state:
13.63V while connected to charger, draw from mains 1.2W, feed to battery 40mA average
13.6V stand alone
6.58 m-Ohm internal resistance
62% wear life
394 CCA, Spec: 430 CCA, type 075

The low power adaptor works by outputting -25mA to +80mA over a 2 second interval in a sine wave (all numbers and waveform are eyeball estimates). The interesting part is that it draws power from the battery 20% of the time. From the experience of other people as well as my observations, I think this power draw is crucial for the charging process and what allows the low power adaptor to be effective. I will replicate this on the high power adaptor through the use of a timer switch:

timer-switch.png


During the scheduled off-interval, the LED on the charger adaptor will draw 20mA from the battery. The schedule could be 15 minutes on and 15 minutes off, or any other combination.
 
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The high power adaptor has reached the end of the road on what it can do without mods of PWM or timer switch. The end state is consistent and repeatable. I am putting back the low power adaptor to get the small amount of final gains it is capable of.

Battery state:
15.95V while connected to charger, draw from mains 18W, feed to battery 1000mA constant
14.1V stand alone
6.72 m-Ohm internal resistance
60% wear life
386 CCA, Spec: 430 CCA, type 075
 
The final state of the battery was reach quickly as expected. It's taken off charging for storage. I might play with it once I have the mods ready for the high power adaptor.

Battery state:
13.4V while connected to charger, draw from mains 1.2W, feed to battery 40mA average
13.4V stand alone
6.57 m-Ohm internal resistance
62% wear life
395 CCA, Spec: 430 CCA, type 075


Next I am preparing my 19 year old factory battery for summer use. It was charged with the low power adaptor until no progress, and stored for a while. Now charging using the high power adaptor. Bubbling can be heard. I have open access to the cells and don't mind losing water. Level on most cells are high from many years of dropping in Bat-aid tablets. I stopped using the tablets a few years back after they becoming less effective.

Battery state:
13.9V while connected to charger, draw from mains 20W, feed to battery 1150mA fluctuating - should settle to 1000mA
12.73.1V stand alone
12.75 m-Ohm internal resistance
17% wear life
203 CCA, Spec: 640 CCA, type 096
 
The high power adaptor has a negative effect on the battery and unlikely to change. I will give it a couple of more days and see what happens, but not optimistic. The car can start with a slight hesitation on 170cca. So the battery does have just enough power for use. The high power adaptor is a reasonable approximation for in-car conditions. The alternator would not be able to give the battery more than 189cca. The low power adaptor is known to be able to take this battery to 230cca that would be undone by the alternator.

Battery state:
15.95V while connected to charger, draw from mains 18W, feed to battery 1000mA constant
13.84V stand alone
13.68 m-Ohm internal resistance
14% wear life
189 CCA, Spec: 640 CCA, type 096
 
As expected, charging did nothing but to waste electricity, 18W * 24H = 0.432 KWH. Giving it one more day for luck. I suspect the use of Bat-aid over the years has modified the electrolyte chemistry. The state of the battery cannot be improved. Even so, if the state doesn't degrade, the battery will be useable forever as a summer battery for my light duty driving. The battery will be fed by a 18w 70mA solar panel in the car. A better 23V panel was able to bring the battery to 16V stand alone previously. 16V is wanted because that represents 0% sulfation in the lead plates.

Battery state:
16.03V while connected to charger, draw from mains 18W, feed to battery 1000mA constant
14.1V stand alone
13.69 m-Ohm internal resistance
14% wear life
189 CCA, Spec: 640 CCA, type 096
>1.3 specific gravity for all cells
 
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A brick wall was expected, and a brick wall was hit. There's nothing more to add. Putting in the low power adaptor to get a better looking cca number. There will be no practical use to it. As soon as the battery is charged by the alternator, the good looking number will be gone. The battery is going in the car when I have 230cca.

Battery state:
16.05V while connected to charger, draw from mains 18W, feed to battery 1000mA constant
14.1V stand alone
13.8 m-Ohm internal resistance
14% wear life
188 CCA, Spec: 640 CCA, type 096
 
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