How long will battery hold up from playing radio??

[TFB1]

Originally Posted By: eljefino
FWIW your battery is probably rated at around 80 amp-hours. With a 20 amp fuse, a 2 hour performance should only run it (less than) half dead and it will still start the thing.


Agreed, unless you really had it "thumpin" I doubt the draw would be even 10 amps, so should last at least five or six hours and still start the car...

I'D suspect you have a low capacity battery...

 

[FADEC]

Wasn't playing loud at all. It's the stock system. It is the upgraded Bose system.

 

[FADEC]

Can a battery pass the load test and still be bad???

 

[InvalidUserID]

One reason why I wouldn't want to go to a drive-in movie.

 

[The_Jeff]

Originally Posted By: JHZR2
A typical automotive battery may have around 40 Ampere hours.


My motorcycle's is 16.

 

[JHZR2]

Originally Posted By: eljefino
Originally Posted By: JHZR2
A typical automotive battery may have around 40 Ampere hours.


My motorcycle's is 16.


But at what rate? 24hr constant current most likely? So it's drawing less than 1A to achieve that... Lead acid batteries loose access to a ton of their nameplate energy the more continuous load they see. Plus, every 8C above 25 degrees C that the battery lives at, it's life is halved, which means less energy..

 

[rjundi]

Originally Posted By: daddi
Can a battery pass the load test and still be bad???


My MDX battery passed but was bad. Mechanic did not believe until he left ignition on 10 mins with Nav, dual climate, Bluetooth, ignition and radio going. Also lights on in his garage. Dead.

 

[antonmnster]

My work trucks seem ok to run the radio for at least an hour. Running the stobes is ok too, for maybe an hour if the battery isn't too old.

 

[JHZR2]

Originally Posted By: rjundi
Originally Posted By: daddi
Can a battery pass the load test and still be bad???


My MDX battery passed but was bad. Mechanic did not believe until he left ignition on 10 mins with Nav, dual climate, Bluetooth, ignition and radio going. Also lights on in his garage. Dead.


Similarly a battery can have an internal short out of the blue, when looking like a normal, strong battery...

 

[daves87rs]

Not an issue with my cars...

 

[rjundi]

My experience is that a weak battery in a vehicle lots of electronics (2007 Acura MDX) makes for some really crazy gremlins. I thought purchased a car with some serious problems as things seemed haywire with errant check engine lights, air bag system disabled (low power), resetting Nav and Radio codes, lost presets on radio, seats, mirrors etc.

Called the Acura dealer and nice person said change your battery before you bring it in. Car has been trouble free since.

Apparently recent Honda/Acura OEM batteries are not that great.

 

[SteveSRT8]

One of my employees has an older Buick, top of the line but tired.

He had been having strange issues, and then it wouldn't start.

Whatever the reason, with a new battery the car is really different, and it's for real, not just his imagination.

The more electrically complex a vehicle is, the more important a battery becomes.

 

[Bamaro]

Some variables:
Condition of the battery
Radio or CD playing
Normal draw of radio
Volume

I would expect that if all is relatively normal, 90 minutes should be achievable.

 

[brianl703]

Originally Posted By: JHZR2
A typical automotive battery may have around 40 Ampere hours.


Most of them are at least 60 amp hours now. Johnson Controls says you can divide the reserve capacity in minutes by .6 to get the amp-hour rating.

The Johnson Controls group 48 battery is a 75 amp-hour battery. I've had the radio playing in my Saab 93, which uses that battery, for well over an hour.

The puny battery used in the Honda Civic may only be 40 amp-hours.

 

[FADEC]

Thanks for all the comments and advice. I think I will end up buying a new battery mainly for my peace of mind. If it still has a short run time with a new battery...well then I guess thats just the way its designed. Tom

 

[andrewg]

Run my radios in both cars for at least 1/2 hour as I sit in my work parking lot every work day. Never had an issue.

 

[meep]

the above math examples are the way to go.

assume 40 AH battery, pretty common.

assume 5A draw for radio, which is high for a stock HU, but if there are multiple amps at idle, is very reasonable and maybe even low.

safe run time avoiding a deep cycle.. so just top 20%; = 8AH available - 1 3/4 hours.

50% discharge (auto batteries don't like this); 20AH available = 4 hours

80% discharge (vehicle may not start); 32AH used, 6 hours.

however, if the key was on, cut the runtimes in half.

Were the interior lamps on? modern luxury vehicle may have 4 ceiling lamps, 2 floor lamps, maybe 4 door panel lamps... 10 bulbs at ~10 watts each (averaged) = 100W = 8 amps....

so radio + lights = 13A

20% 45 minutes
50% 90 minutes
80% maybe 2.5 hrs.

 

[SwampSurvivor]

I've gone to many a double features at drive in movies with the radio going for 4 hours ... never once had a problem.

It isn't uncommon for me to leave the radio on in the Cherokee when I'm working on it ... and I've killed the battery on that numerous times. Always fires up after an hour of playing the radio.

Granted, I'm convined I could start it on a AA battery. Real easy to start. Only has to have 1 revolution and it fires up!