Necessity is the mother of jugaad !!!
This is what I realised during the lockdown.
The following story gives an account of how I went about charging a battery at home using a rather unconventional procedure with whatever I had on hand.
This technique will work brilliantly in crunch situations when charging centers are closed ( weekends/ holidays) or one doesn't have a battery charger.
The Problem
A car was parked at a remote parking inside a gated community on March 21st 2020 thinking that we could get the car back in operation around March 25th but that never happened.
The car remained there all of April, and the first time one could move out with restrictions was in the first week of May 2020.
After about 50 days, when we went to the car, its 85Ah battery, which was already 3.5 years old had expectedly run down.
The idle voltage was surprisingly 11.6V but there wasn't enough juice to crank the car.
Jump starting also didn't work, leading us to believe that one cell in the battery must be terribly weak.
I dismantled the battery and brought it home, and enroute found that no battery center or auto electric center was open.
The Idea
I came home and was thinking of what to do when my eyes fell on my laptop charger.
It suddenly dawned on me that this is an AC - DC converter and might be useful.
I examined the name plate which read output 19V DC 3.42A.
What next? I went about figuring a way out to use this as my battery charger.
The apparatus used was
1. Laptop charger
2. A 21W bulb
3. few cables
4. some insulation tape
5. two clothesline clips
6. Multimeter
Preparations
1. Opened all vent plugs on the battery
2. Ensured that the job was performed in a well ventilated area
The Execution
The inner pin of the laptop charger is the positive and the outer metal covering is the negative.
Since the rated amps of the charger is 3.42A, I didn't want to just connect some cables and end up blowing the charger due to high current, hence used a
current limiter in the form of a 21W bulb.
At the rated voltage of 19V, this would ensure that the current flow would be no more than 1.1A
1. Prepared a wiring for the +ve side with the bulb in series ; a bulb holder would have been lovely but I didn't have one and so made do with some insulation tape
2. Connected the +ve cable green to the +ve pin of the charger, and then the pink cable from the bulb to the +ve of the battery using a clothesline clip
So the +ve end line up was:
Charger -> green cable -> bulb -> pink cable -> battery +ve terminal
3. Connected the -ve cable grey black to the -ve of the charger using insulation tape
Warning : It is very important to ensure that the
+ve and -ve cables don't touch
4. Connected the -ve cable to the -ve of the battery using a clothesline clip
The -ve line up was thus:
Charger -ve -> grey black cable -> battery -ve
5. After ensuring that the connections were secure and proper, switched the charger on
6. The bulb was seen glowing and after a few minutes, measured the voltage on the battery to be 12.5V
7. Measured the voltage on the battery every 30 minutes, and at the end of 6 hours it was approx 13.1V
8. Suspended charging in the night and resumed the next morning at 7
9. When the battery voltage read 13.5V, I could notice bubbles, to indicate first signs of success, and as the battery charged, the bulb glow became dimmer
10. Continued to charge till the battery voltage read 15V ( I didn't want to go beyond this since I know that the typical voltage a 12V battery sees with car running is no more than 14.2V)
11. At around 15V on the battery, I unscrewed the charge indicator sight glass and dipped it into each cell to measure the state of charge.
It would move between white and green indicating that the charge was adequate.
However, cell no.4 showed next to no bubbles plus the charge indicator was in white, and this had me thinking.
12. Eventually stopped the charging at approx 4pm to take the total charging time to approx 15hrs
13. Approx. 30 mins after stopping charging and disconnecting the cables from the battery, measured the voltage to be 12.4V, which, in my view, was good enough to start the car.
Moment of Truth
We took the battery the next day to the remote car, and it started in a flash.
I was concerned about cell no.4, but there was some life left in that cell, I believe.
The battery eventually packed up in end June because cell no.4 went totally dead, but this effort of reviving a battery from dead using a laptop charger worked quite well.
The only "consumable" was the bulb, which went kaput after this marathon operation.
I repeated this on a weak 65Ah battery and it worked very well.
We may have battery charging centers, we may have battery chargers, but when we have neither, we still have ideas that can be executed successfully !!!
Note : I've tried this method out at my risk after conducting risk assessments, and have seen success twice with no damage to the charger or the battery.