I went to stop&shop this afternoon. When I came out, I couldn't start the engine. Looks like the battery is gone, but I didn't notice any sign at all before. I called AAA and they jump started my car. The battery electrolyte level is a little bit lower than the minimum level. I then drove home, stopped the car and left the engine on, tried to opened the hood (so I might be able to add some distilled water into the battery cells) and the engine stopped suddenly. I think the battery is dead. But why the engine stopped when I tried to opened the hood? Is there anything else wrong with my car? Does it really need the power from battery to open the hood? I have to admit that I know little about car, but this is really wired to me. Thanks for any information.
No decent alarm will activate with the engine on. The battery could have been drained because the alternator wasn't charging it (at least not sufficienctly). In that case the battery's reserve capacity was used up and your engine stopped right then. The charging system should keep the car running after starting, so that's the primary suspect.
If the charging system isn't working, you'll be replacing the battery again or get stranded somewhere you don't want. Also, you should not charge a drained battery by driving around because this stresses the alternator too much and can cause it to fail early ($$$). Always charge up a drained battery offline. Autozone can perform a free battery test (don't know if they'll charge it up for you).
Repeated deep discharges are not good for either the battery or the alternator. The battery will have a sulfate deposit on the plates that it can't recover from; the alternator will overheat trying to charge up a weak battery. That's why I change out the battery every 5 years no questions asked. At ~$45 (Walmart, made by Johnson Controls although the ~$80 AC Delco maintenance free is my preferred battery) it's cheaper than doing my own oil changes in as little as 2 years.
So it's the usual suspects in an electrical system test. You need to find out if the alternator failed (given that your engine quit while running), all the cable connections are clean and tight, no excessive current drain (>300ma?) when off, the alternator belt is properly tensioned, and that the battery can still hold a charge.
I have had the same problem with other cars although opening the hood and having the car die isnt one of them
It sounds to me like the battery may have a shorted cell(internally ) a build up of sulphides is usualy the reason, usually caused by old age .
You dont say if the battery connections are clean and you have a good clean solid ground ?This is paramount to having a trouble free electrical system.
That would be the first thing to check.
I`m guessing here but you need to check out the alternator output with a DC voltage tester (cheap at any auto parts store )
When running ,the alternator should be putting out around 13.5 -13.8 volts DC.
Measure across the + and - negative terminals.Be sure to keep the polarity of the tester correct (red +, black - )
If it isnt you probably have blown a diode in the alternator .
Having an alternator try to charge an almost dead battery will stress the alternator to a point of no return(been there done that)and having to replace the alternator with a new one or rebuilt one.
The battery when tested with the car NOT running should read at least
12 volts DC.
If it doesnt then your batery is due for replacement.
But FIRST,? charge your battery with an outside source battery charger and see if it holds a charge .
If the battery wont hold a charge ? you can tell , because it will never come up to full charge , no matter how long you leave it on the charger.
Leave it on charge over night and if it doesnt come up to charge(less than 1/2 an amp by morning ) you have a dead cell in your battery and it needs replacing.
When replacing the battery make sure ALL connections are free and clean of sulphates ( the green stuff that collects on terminals)
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