battery life and amplifiers

All my car stereo gear is sitting on the shelf in a cupboard for the very reason you outlined above. I don't really have an answer but many and lots would be in the answer if you wanted to use the stereo camping all night. Maybe consider a genset

Leroy

Is it worth carrying 2 x 750AH batteries to make that level of noise away from home?

isnt the old formula, watts , divided by volts, equals amperes? if not have a look on the amp. or the spec. sheet

Hi there Rock Crawler, I have been to a few car shows, sound offs etc and they all seem to be running from 240 volt mains, so presuming they are using invertors or some thing of the like to keep the power up. I only had one pioneer amp in the hilux was 800w 4way with splits up front and 6 inch in the rear doors but could run virtually all day without any probs and still fire the lux up at the end of the day. Obviously it wasnt drawing anywhere near the power you have and if you have the amps that run the fans in them and speed up as you increase the volume then thay would draw a fair bit as well. If you have 240V available might be the thing to look at but if no where around then maybe 3 deep cycles. I would imagine you would have to see what current there drawing at certain levels and maybe approach JCar/sparkie and see what they come up with. Regards Steve M

You have about 2000 watts of power consumption, most amps are only about 80% efficent as the rest goes in heat.

If you ran the amps flat out at max power you need about 170 amphours but most amps for music will run at about 70% due to peaks and troughs so you could say you need about 120 amphours.

Now the catch, deep cycle batterys are rated over hours so if you had a100 amphour battery you may only get 80 amps out of it in the first hour before it is totally flat due to voltage stability but over 20 hours you may be able to get say 6 amps per hour giving a total of about 120 amphours.

NO battery is designed to be run totally flat.

Batterys are very hard to explain over the net.

Do you know how big 2 x 750ah batterys are and how expensive.....expect EACH battery to weigh around 250 plus kilo's, measure about 750mm X 500mm X 400mm and cost over $1500 then how are you going to charge them? Expect to pay $3000 plus for a charger.

Don't get amphours and cranking amps mixed up they are differant.

Regards Richard

I have a string quartet in the boot :)

Sorry Rock Crawler. Didn't hear that but what is the point

Suspect you have a bunch of issues. First one will be how the power has been reported. Some are by channel others are total split by channel, some are power consumption. If it is true by chanel (normally the way expensive Hi-Fi gear is reported) your 800W amp is really 3200W. Depending on the type of amp it may use 50% of the rating when it is turned on with no signal. Then again, you need to look at the charts for the battery. It may not last long with a 150A draw. You will need to get some specialist gear to measure these sorts of currents.

Steve

Hmmm how long is a piece of string Eric??

Its a hard one as it really depends on the music you are playing, because its so transient in its power demands, ie from a few watts rms to hundreds in seconds, ie lots of low bass rolls etc big power draw as amps approach clipping, easy listening only draws a few amps and barely touches the headroom in the amplifiers.

Check the fuse ratings on the amps this will give you the best indication of the max draw possible, as amps are rated so diffently by different makers. For example my soundstream reference 300 amps are IASCA rated at 37.5w x2, so you can run 2 amps in a comp car and be in the 150 watt class. But these amps switch into high current mode when you drop the impedence load on them, and produce 300w at 1 ohm load, stable to a quarter ohm :-) .. They run a 30 amp fuse.

So its a hard one to judge, my fairlane was good for 30 minutes or so on a n70 size batt. And i used an overdriven 80 amp alternator from a magna of all things !! so the charge rate was up at idle, and seeing as the old ford didnt rev past 4500 it was more than happy being overdriven, i also ran extra 4 guage earth cable from block to batt, and ran 4 guage from alternator to batt. Worked real well.

The best batts to use for stereo work are the optima yellow top version, very low internal resistance so they charge quick and also discharge quickly in response to amp demands. Buy as many as you can afford and fit in. (within reason of course). You can even run an isolator to keep one batt good for starting, just like fridges etc... A lot of yanks seem to run the gmc "ambulance" alternators, about 160 amp with a gilmer drive.

hope that helps a bit.
cheers Brad.