Hi all. I got a flat battery on my car. Its been parked for 3 weeks because my hydraulic clutch linkage needs a new cylinder. I'm short of readies and monthly pay has left it be for 3 weeks. I thought I'd best start the engine, to keep it happy. Battery dead. My cheapo charger gave up the ghost, so I've used a transformer out of an old charger. Its huge, it used to be able to start a car, but one of the big diodes blew. S I took the tranny, stuck a 25amp bridge rectifier on it and a 6,800uf cap.
No Load = 16.5v
Load = 13.5v
Batt = 13.3v
Drawing 500mA, fully topped up 2 year old battery. It won't start the car. I hear a single click of the solenoid, then nothing. I have topped it up with distilled water and the specialist I bought it off, tested it and said it was fine.
There are no Hydrogen gas bubbles coming off the plates, that can't be right. And is my charger correct?
Can you shed some light, please? The car has never had a starting issue.!!!
No Load = 16.5v
Load = 13.5v
Batt = 13.3v
Drawing 500mA, fully topped up 2 year old battery. It won't start the car. I hear a single click of the solenoid, then nothing. I have topped it up with distilled water and the specialist I bought it off, tested it and said it was fine.
There are no Hydrogen gas bubbles coming off the plates, that can't be right. And is my charger correct?
Can you shed some light, please? The car has never had a starting issue.!!!
Flooded lead acid batteries don't usually out-gas much under "normal" charging. The voltage would have to be a bit higher ('equalization' charge) to really start bubbling noticeably. Usually if you take the caps off,and stick your ear over one of the filler holes you can hear it 'hiss' a bit,kinda like fizzy soda-pop does.
Be sure it's good and charged,and your battery connections are clean and tight.
On a somewhat similar note,I've noticed on these newer cars that dirty/corroded battery terminals can really screw with the electronics/computer stuff.Our car was doing some odd things,the ABS light coming on,etc. for no apparent reason. Once I cleaned up the (mildly)dirty terminals,it hasn't misbehaved once so far..Kind of odd,because poking around with the DMM while not running/starting/running showed that all voltages were in range of what's to be expected,but for whatever reason the 'brains' weren't happy.
Be sure it's good and charged,and your battery connections are clean and tight.
On a somewhat similar note,I've noticed on these newer cars that dirty/corroded battery terminals can really screw with the electronics/computer stuff.Our car was doing some odd things,the ABS light coming on,etc. for no apparent reason. Once I cleaned up the (mildly)dirty terminals,it hasn't misbehaved once so far..Kind of odd,because poking around with the DMM while not running/starting/running showed that all voltages were in range of what's to be expected,but for whatever reason the 'brains' weren't happy.
You should see a little higher voltage than that on the battery. 13.8 to 14.4 is a normal range for a lead-acid battery.
If you have a regular bench power supply that current limits without destroying itself, set it to 14.4 volts and charge the battery from it. I saved myself from a walk home more than once that way. It only took about an hour to get enough juice into the battery to start the truck. An overnight charge should be plenty. A 15V laptop supply with a 1 ohm resistor in series ought to work, too.
And, yes, corroded terminals are bad. Emery cloth, a wire brush, a knife, or there must be some chemical that will work. If the battery has been load tested, that's gotta be the problem.
If you have a regular bench power supply that current limits without destroying itself, set it to 14.4 volts and charge the battery from it. I saved myself from a walk home more than once that way. It only took about an hour to get enough juice into the battery to start the truck. An overnight charge should be plenty. A 15V laptop supply with a 1 ohm resistor in series ought to work, too.
And, yes, corroded terminals are bad. Emery cloth, a wire brush, a knife, or there must be some chemical that will work. If the battery has been load tested, that's gotta be the problem.
If it remained completely dead (flat) for a significant amount of time, it's capacity may have diminished. If after charging for several hours it still drops immediately to below 11v when you try to start the engine, it's probably going to have to be replaced.
If the voltage remains well above 11v when you try to start the engine but you only get the single click, you need to check the wiring and connections.
A headlamp isn't a reliable test for a battery. It probably only draws about 5 amps of current. To test an average starting battery, you need to charge it fully and draw at least 50-100 amps from it for 10-15 seconds while monitoring the voltage.
If the voltage remains well above 11v when you try to start the engine but you only get the single click, you need to check the wiring and connections.
A headlamp isn't a reliable test for a battery. It probably only draws about 5 amps of current. To test an average starting battery, you need to charge it fully and draw at least 50-100 amps from it for 10-15 seconds while monitoring the voltage.
A good lead acid battery that is completely discharged wont gas much at a few amps unil it becomes charged, and they're only about 75% efficient, so don't expect more energy out than you put in. It will take several hours to charge a complety dead car starting battery with a few amps. Even in a good battery the cell resistance will rise quite a bit until it starts to take a charge, so it's normal for the current to slowly rise and then fall toward full charge. If you've had the battery on the charger overnight and the terminal voltage still drops severely under starting load you almost certainly have a bad cell. It would be shame on the battery to have this happen in only 2 years, but sometime the plates will crumble away and leave a high impedance cell even if it is full of electrolyte. Most likely the battery will take a charge and leave you looking for the problem elsewhere.
A headlamp isn't a reliable test for a battery. I agree, not a proper load test is it?
Hi sir, I have got it started. The charger I borrowed did the trick. Its funny, I would have thought the old raw full wave supply I knocked up would have done the job???
Hope I don't need a new battery just yet. Anyway, thanks Perry Babin and others. I'm greatfull for your help.
Fuzzymuff
An externally hosted image should be here but it was not working when we last tested it.
Hi sir, I have got it started. The charger I borrowed did the trick. Its funny, I would have thought the old raw full wave supply I knocked up would have done the job???
Hope I don't need a new battery just yet. Anyway, thanks Perry Babin and others. I'm greatfull for your help.
Fuzzymuff
One trick I used was to connect a light dimmer, capacitor (1uF or less for a UPS battery, about 5uF for a car battery, use about half the capacitance for 240v), and high current bridge rectifier to make a desulfator. The dimmer and capacitor put out current pulses which help remove sulfation. I have used that on 2 car batteries so far and it works great. It does not work as effectively for UPS batteries.
Maybe a simple circuit can be built to charge a 5uF capacitor from the mains and periodically discharge it into an unused car battery in order to prevent sulfation.
Maybe a simple circuit can be built to charge a 5uF capacitor from the mains and periodically discharge it into an unused car battery in order to prevent sulfation.
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