Charging dead battery via alternator. bad?

[azncapcom]

I heard its a bad idea to jump a dead battery and let it charge via alternator. Apparently it strains the alternator too much and can destroy it or shorten its life span?

is this true or just crap?

Also roughly how much of the battery would have been drained if HIDs were left on for say 3-4 hours? For comparisons sake, lets say a regular battery for a V6 Sedan.

[700mb80min]

You can boost a dead battery then go for a highway drive to charge a battery . But it does put a load on the alternator so don`t make a habit out of it . As far as the lights , all are different and some vehicle models have a " reserve " that it will store just in case this happens .

[l69norm]

Use a charger if possible. Cars take a lot of juice to run under normal operation and some cars have an undersized alternator. The extra load from charging a dead battery can overload a good alternator.

It can become a vicious/expensive cycle:
1. dead battery kills a good alternator
2. replace the dead battery, not realizing the alternator is bad too now
3. dead alternator kills the new battery
4. replace dead alternator and possibly the new dead battery

[Pete_Coach]

I heard its a bad idea to jump a dead battery and let it charge via alternator. Apparently it strains the alternator too much and can destroy it or shorten its life span?

is this true or just crap?
Also roughly how much of the battery would have been drained if HIDs were left on for say 3-4 hours? For comparisons sake, lets say a regular battery for a V6 Sedan.

The alternator charges the battery while driving. It also supplies electricity for your car. The alternator was never meant to charge a dead batter but it can...if you drive for a very long time.
So, is it true or crap? Is it crap, yes, the alternator can charge the battery. Is it true, yes, the alternator will work harder to bring the battery up to 13 volts while supplying the electrical power to the car and may get hot enough to cause damage.
How long does it take to drain a battery? Depends on the strength of the battery to begin with. HID's are a very high current draw and I don't even think you can leave them on. I think the car has to be running to turn them on even. Also, there should be a relay to shut them off. (could very well be wrong and there will be many to point that out LOL).

[azncapcom]

The alternator charges the battery while driving. It also supplies electricity for your car. The alternator was never meant to charge a dead batter but it can...if you drive for a very long time.
So, is it true or crap? Is it crap, yes, the alternator can charge the battery. Is it true, yes, the alternator will work harder to bring the battery up to 13 volts while supplying the electrical power to the car and may get hot enough to cause damage.
How long does it take to drain a battery? Depends on the strength of the battery to begin with. HID's are a very high current draw and I don't even think you can leave them on. I think the car has to be running to turn them on even. Also, there should be a relay to shut them off. (could very well be wrong and there will be many to point that out LOL).

I've read around and apparently HIDs use less power than a traditional bulb... i thought HIDs use a lot more power too... but seems like most people are saying it uses less. Also they do advertise that they use 35W compared to 55W from traditional bulbs. Also about the not being able to leave the HIDs on with the car off, thats false. I can leave my HIDs on with the car off, (although it turns off automatically after 30 seconds when i walk away from the car). If the smart key is inside the car, the lights will stay on until you turn it off. Thats what i don't like about the auto headlight feature... it should still turn off if the smart key is inside the car. What if you wanted to take a nap in the car? You would have to turn the knob from auto to manually OFF for it to turn off if it is at night or you are parked in a underground.

[BinaryJay]

Probably the most expensive and least efficient way of charging a battery but sure, you can do it.

[l69norm]

I've read around and apparently HIDs use less power than a traditional bulb... i thought HIDs use a lot more power too... but seems like most people are saying it uses less. Also they do advertise that they use 35W compared to 55W from traditional bulbs. .....d.

Hids draw less than halogen during normal operation. Hids do have to ignite the bulbs using high voltage, then they switch to low voltage for running. For the initial ignition phase, Hids can draw up to double the normal current for as long as 45-60 seconds.

This is why a separate heavy duty relay harness is recommended. The hid ignition current can eventually toast the stock wiring and lighting switches. These are really expensive to repair.

Btw, many replacement altenators have warnings in the box saying that the warranty is void if you attempt to charge a dead battery with it

[qaz393]

I heard its a bad idea to jump a dead battery and let it charge via alternator. Apparently it strains the alternator too much and can destroy it or shorten its life span?

is this true or just crap?

Also roughly how much of the battery would have been drained if HIDs were left on for say 3-4 hours? For comparisons sake, lets say a regular battery for a V6 Sedan.

depend on car. what model? i think lexus is250?

[qaz393]

dont worry about the alternater dying just because it charges your battery