Battery secrets - radio kills car?

[Bob Kontak]

In brief, I have experienced many car battery deaths where you play the radio, have the doors open, mess with headlight connections, blah, blah, etc. without engine running.

Charge it for a very few minutes at 40 amps and it starts with no further starting issues.

Does this, assuming minor current draw, suck down some turbo starting power?

[pwd72s]

40 amps is a heavy hit to an AGM battery...be careful.

[Bob Kontak]

Originally Posted by pwd72s

40 amps is a heavy hit to an AGM battery...be careful.

That is a good tip, thanks.

I don't see them in cars but that could be an assumption and I think I am looking at a lead acid battery.

[asphaltgambler]

If this is indeed a AGM battery - their discharge rate is not linear like a lead-acid battery. After some use the available amperage will fall off a cliff.

AGM's are great in many aspects but do not tolerate repeated over charging, deep cycling and vibration.

Lithium ion batteries for automotive use are the answer but are still too expensive ...............for now.

Conventional automotive batteries in good condition, should be able to supply a radio, lights, door open for a while - maybe an hour or more and still have reserve to start the vehicle.

[Bob Kontak]

Originally Posted by asphaltgambler

Conventional automotive batteries in good condition, should be able to supply a radio, lights, door open for a while - maybe an hour or more and still have reserve to start the vehicle.

It has to be batteries are on the edge when I experience this.

[red-beard]

Originally Posted by asphaltgambler

If this is indeed a AGM battery - their discharge rate is not linear like a lead-acid battery. After some use the available amperage will fall off a cliff.

AGM's are great in many aspects but do not tolerate repeated over charging, deep cycling and vibration.

Lithium ion batteries for automotive use are the answer but are still too expensive ...............for now.

Conventional automotive batteries in good condition, should be able to supply a radio, lights, door open for a while - maybe an hour or more and still have reserve to start the vehicle.

There are lots of AGM batteries that are designed for deep cycling. During Bulk charging, you can pour energy in. But you should slow down charging once they reach 14V, to prevent off-gassing. Good charging circuits do this. Most car chargers are crap.

[red-beard]

One thing I've noticed on my parents car, if someone leaves a cheap charger in the 12V always on socket, it can discharge the battery in about a week. I suspect these cheap chargers use a simple voltage divider circuit to make 5V usb power, and constantly drain the car.