battery level

[Emperor]

Is there any gauges or other things that can sense how much power's left in the battery?

[CozmoNz]

Multimeter?

[AJz]

Multimeter?

[BlakJak]

A voltmeter (as a component of a multimeter also) can give you an 'idea'.
The voltage of a car battery drops as it weakens... when you're much below 12V the thing wont be able to do its job adequately.
Whether your car will actually start or not is kinda up to the car, but given that 12V is actually nearly 2 Volts below what a typical battery is supposed to supply (13.8V)...

I have a voltmeter in one of my radios and im pretty sure when I was much below 12V i couldnt get it to start. And Ive seen as much as 14.5V when the car is running.

Oh: Moved thread to Tech Questions. More appropriate there.

[Emperor]

Thanks BlakJak for the helpful reply.

[BlakJak]

Be warned its only an indicator, sometimes the voltage will be fine untill the battery is put under load, at which point it'll just shoot through the floor...

[3T-Rona]

u need a load tester to actually test how good ur battery is, stick a voltmeter on ur battery and watch it as u crank it, if the batteries charged and it drops below 8-9volts its time for a new battery.

[igor]

If your battery doesn't seem to be holding a charge you can do a discharge test on it to see if it is toast of not.

Basically you just wire something like a 50W lamp across the terminals, and time how long it takes to discharge to 10.8V from 13.8V.

[Emperor]

No, i'm just paranoid that it's gona go flat while I listen to music at a mates or something

[CozmoNz]

autospeed.com has a little gadget that you can setup to change colour (led, gradually changing), so when its fully red, you need to start up the car .

or go get an optima yellow top, you wont run that flat easilly (heavy duty batterys also ftw)

[BlakJak]

Depends on how much sound gear you've got,

I run heavy duty tranceivers from time to time on my car, I make sure i idle the car for 20 mins or so every few hours, have never had problems. I also keep a set of jumper leads

If your voltage were to drop much below 12V you may find you have a bit of fun starting the car up. Nevermind 10.8V, to crank a car takes a lot more juice than anything else the battery will be asked to do...

[Emperor]

Just head unit, 4 speakers, amp and sub.
How long(on average) does it take to drain a battery, say just listening to music?

I've already flattened the battery once, leaving the xenon lights on for 3 hours.

[BlakJak]

You'd wanna ball-park on somewhere between 2 and 4 hours if you had the whole lot fully cranked up, I think. Maybe more, but it depends on how good condition your battery is and infact what size it is. (Jap imports come with $hitty little batteries in them, among other things).

You could always throw a multimeter onto its volt range and park up with it connected, just see how long it takes to drop its voltage over time with everything running...

[Si]

Just had a look at what i can get thru work, it may assist you in your quest for metering of your battery unit, urls are below,
if you can wait till the 9th i can get you special pricing


http://www.jaycar.co.nz/productView.asp ... &SUBCATID=

http://www.jaycar.co.nz/productView.asp ... &SUBCATID=

http://www.jaycar.co.nz/productView.asp ... &SUBCATID=

[solidog]

HI there, everybody seems to have you covered, just a couple of things I thought I might add.

1 If you want to quickly check your batteries "charge" you can "load up" your battery by turning on your light, sterio, heater fan and anything electrical for about 15 seconds and then start her up. Then repeat in a minute or two. You should be listening for a slower sounding crank speed. If the car starts as per usual you should really start worrying about something important like gloabl warming!

2 Check the CCA (Cold Cranking Ability) of your battery, its on a sticker on the battery somewhere, good batteries these days go for around a hundy retail for over 300CCA, i've got a slim one in my levin thats has only not cranked once after playing music for about 4 hours (even then a little crash start and she was sorted!)