Electrical problems due using battery charger as a jump starter

Question

I have a 2003 honda civic, and the car battery went dead on me. I didn't have a jumper cable with me, but I had a car battery charger. So, I hooked it up to the battery and tried starting the car. Unfortunately, it didn't seem to give it a jump. Without recharging the battery completely, I was soon able to get a hold of some jumper cables and tried giving it a jump start. But now, even with the jump start, The car won't turn over... The electricity certainly comes on but when I turn the key, the dashboard lights (spedometer, etc.) flicker on and off rapidly and the engine makes a flickering noise, but nothing nearly close to the normal sound when I start the car.

I'm still in the process of charging the battery, and I can't test it out yet. But did I just fry my electrical system? Is there any way to know for sure without taking it in to the shop?

Answer 1

No, I don't think you fried anything. All that's happening is that the electrical system can't supply enough current to power the starter motor, so the voltage drops when it tries to. The "clicking" sound is the starter solenoid. When the voltage drops from trying to operate the motor, the solenoid (big relay) no longer has sufficient power to keep it actuated, so it clicks back to the off position. Then, the voltage returns to normal (because it's no longer under load) and the cycle repeats. If you ever played with beginner electronic kits, you probably made buzzer/clicker circuits with the relay; it's the same principle.

If things don't work after charging the battery for an hour or so, your battery is probably dead and needs to be replaced. If the charger you're using is a high-amp one that's supposed to be capable of starting, and you were using it on the high-amp setting, then you almost surely have a bad battery. In that case, it might be possible to start the car with the battery terminal removed (using just the charger) then reconnect the battery just to get to the shop and replace it, but if you have any other means of transportation, I'd avoid driving a car that you can't reliably restart if it stalls. :-)

Answer 2

I don't think you fried anything either.

Besides the battery, though, there's the possibility that the cabling between the starter motor and the battery isn't providing a good enough path for all the current needed.

There's usually one big cable going from the (+) side of the battery directly to the starter, as well as another big one from the (-) side to the chassis of the car. A cool trick is to measure across these with a volt meter while they're under load (someone is trying to start the car at the same time). This can help narrow down a starting issue quickly.

If you're 'losing' voltage in a cable, you can measure the drop from one end of the cable to the other, or on opposite sides of a connection. A large (>1v) drop in a cable or two can add up and cause the same symptoms as an ailing battery.

Answer 3

It takes between 300 and 1000 amps, especially at the start of cranking, to crank over an engine. Lead-acid batteries aren't very good batteries generally, but they are very good at supplying a huge surge of power, and they're cheap. So they are perfect for engine starting.

I didn't have a jumper cable with me, but I had a car battery charger. So, I hooked it up to the battery and tried starting the car. Unfortunately, it didn't seem to give it a jump.

A "jump starter", the kind with huge battery cables, is largely responsible for that 200-1000 amp surge of power. That presumes it can make a very solid connection to the battery. If the battery connection is not solid, it will refuse to start, exactly as you describe.

However, a "battery charger" is designed to provide 5 or 10 amps and provide it for a long time. Using this type of charger is a job for the patient. If it is (mis)used for jump starting, it might provide 30-50 amps until it burns up. They make larger boost chargers capable of more; see the device's rating.

So, to use a normal battery charger this way, put it on for at least an hour to put a few amp-hours into the battery. Really, a battery is typically rated ~100 amp-hours (diminishing as it ages and is abused), so leave it on all day for a decent recharge.

Now if you do all that and it still doesn't start, remember the part where I said lead-acid batteries are lousy but cheap? The "lousy" part is they only have a 4-6 year practical life. The symptoms you describe are totally consistent with a battery at end-of-life. The "cheap" part is they only cost $100-ish new, if you are a sharp shopper. Changing one is literally 4 bolts, however they are heavy as beans.

Even though they're lead which is poisonous, society is really, really good at battery recycling with over 99% of car batteries truly recycled into useful things. In fact the new battery will have a $10-20 core charge that you will get back when you return the old battery.

If you find yourself with an old car battery and no opportunity to collect a core, leave it at any auto parts store -the'll throw it in with the others and collect a few dollars for it from the scrap dealer.