Lowest possible voltage

TheInterceptor · 22-07-2010, 09:26 PM

Evening fellas

Ok this may be a dumb question....

What is the lowest possible voltage an au can have before it wont crank over?

Im usually doing somthing which has me using some form of electrical accessory for long periods of time (eg: stereo, computer, uhf...) so im stressing that ill kill the battery...

Cheers

Ride · 22-07-2010, 09:57 PM

Off the top of my head it would be around 10 or 11v. Any half decent inverter should have a cutoff when it gets to a certain voltage so you can still crank it over. Failing that an Optima or similar battery would be a wise investment, hard to drain those things.

Mr Hardware · 22-07-2010, 10:35 PM

You'll find it pretty hard to crank lower than about 330cca too

TheInterceptor · 23-07-2010, 10:17 AM

hm ok thanks gents

What about century batteries? Whichever the ones that NRMA give you when you get a flat.
Are they the better quality ones?

AMB · 23-07-2010, 10:50 PM

Using/flattening it won't kill it. But you do need to keep charging it back up.
A good battery usually reads about 12.6-12.7 volts on a meter. Once you start getting down to 12.2V its getting old and not holding a charge well, or its half flat and not being charged properly. If you're getting less than 12 volts its flat or buggered. If your battery is a bit old and you're worried about flattening it from using accessories, then get a new battery -it will hold plenty of charge and charge back up really quickly when you drive. How much do you need to start it?? all depends - my AU fires up with half a crank ( a nearly flat battery will do that!). MY EF needs to crank over 4-5 times before it fires.

TheInterceptor · 24-07-2010, 12:30 PM

Wow fires up with a near flat is pretty impressive. thanks for the info mate. iirc the battery is about a year old..i currently dont have a multimeter so i cant check voltage.

Ok one last question guys, is it worth getting one of these volt monitor things off ebay? just for peace of mind,
http://cgi.ebay.com.au/Car-LCD-Therm...item43a0821f7e

sleeper393 · 24-07-2010, 02:08 PM

use calcium batteries , not lead acid , they can be drained and recharged without any loss of performance , lead acids lose their ability to hold charge the more they are drained.

AMB · 24-07-2010, 07:41 PM

They are all lead acid batteries sleeper393. The ones with calcium are the completely sealed units (maintenance free with no or very low gassing). Some "calcium batteries" are deep cycle ones (which you are talking about), and are not really designed for cars, they are for continuous low power supply and can be drained until flat and recharged many times without harm. Ours cars need high cranking power (CCA), the higher the better. High CCA also means you can supply a PC and other acessories for quite along time without flattening the battery much. But you are right, you do need to keep these fully charged to make them last a long time, not like the deep cycle ones.

TheInterceptor, I wouldn't worry about getting one of those monitors, looks like a bit of gimmick. If you are only using the battery for an hour or so with the car off, then should charge up well enough if you drive for an hour or so each day. To be sure, I would invest in a good quality automatic CAR battery charger (starting from about $90 I think), and charge the battery every couple weeks for the whole weekend (the longer the better). Your battery will love it and last a long time.

sleeper393 · 24-07-2010, 08:43 PM

the one i have is from america , delphi 680cca, best battery ive ever bought, i've had a century , bosch , marshall , excide none compare.

TheInterceptor · 24-07-2010, 09:11 PM

Yeah ive been thinking a charger would be the way but i dont think im at that stage yet where i need it, so i cant really justify spending $90 on somthing id use once in a blue moon.
Would cranking the car over and letting it run for a few seconds help juice up the battery? or is that just a myth?

AMB · 24-07-2010, 09:18 PM

Now that's big. Can't remember seeing one that big that will fit in the battery compartment. My tractor battery is about 650 cca i think, but its about 50% longer than a car battery.

AMB · 24-07-2010, 09:44 PM

TheInterceptor, I think spending $90 to make a good battery last 6,7,8 years, and knowing you will never get stuck with a flat battery is a good investment, particulalrly since you are relying on it to run your PC etc. You don't use the charger once in a blue moon, use it as often as you like for as long you like, the more often the better. It uses bugger all power, and doing this reduces and prevents sulphation, the number one cause of battery failure.

Running your car for a while charges up the battery quickly to maybe 70-90%. The last bit gets a slower and slower trickle charge from the alternator, and takes many many hours of driving. So you end up charging the battery to 90%, then eventually you are charging to 90% of 90%, and so on, till the battery starts to sulphate and get old before its time.

Sorry I can't use the quote button anymore, hasn't been working since the forum went down.

TheInterceptor · 24-07-2010, 09:54 PM

mm ok then, il look into getting one then, it does sound to be a good investment. I guess it pays off in a few years when you'd normally fork out $100 or so for a new battery. But yeah, didnt know about this.
Thanks for all the info mate.

sleeper393 · 24-07-2010, 11:07 PM

Quote:

Originally Posted by AMB

Now that's big. Can't remember seeing one that big that will fit in the battery compartment. My tractor battery is about 650 cca i think, but its about 50% longer than a car battery.

http://www.battery-usa.com/images/BU...mary_Image.jpg
10 1/2 in long , 685cca

http://www.battery-usa.com/Delphi_Au..._Batteries.htm

AMB · 24-07-2010, 11:58 PM

10 1/2 in, that's 267 mm long, way too long to fit in the battery shroud of both my EF and AU. The biggest battery I can fit is 9 inches long (228 mm), and it just fits, very tight. What car you got sleeper 393, the size of battery compartment hasn't changed in years.

sleeper393 · 25-07-2010, 11:13 AM

i have an au series 3 , i measured my battery this morning , yep just over 9 " but it is a delphi 685cca , maybe australian delivery battery, dont know ?? to suit our vehicles.

GS608 · 25-07-2010, 11:46 AM

What sort of voltage should it be at while the cars running? 13.8-14?

Mr Hardware · 25-07-2010, 01:29 PM

Yeah, about that xr-chief. 13.8-14.6 is normal. the alternator would be voltage regulated to something like 14.6 or so.

GS608 · 25-07-2010, 02:03 PM

hmm thats strange, i'm getting all the right voltage but the battery/alternator light every now and then, it is definitely charging right as the lights don't dim at all when revving the car and the battery hasn't died yet. Bloody dodgy Ford electronics lol

Mr Hardware · 25-07-2010, 02:33 PM

Last time I had an alt die on me (not a ford) the CHARGE light on the dash would come on intermittently, and my multimeter would drop to 12.6v at the same time.

AMB · 26-07-2010, 08:59 PM

About 14.2 V is what I've measured on many alternators in good working order. Had one once that was putting out only about 13.8, and found that it's brushes were just about gone. Oily brushes might do that to.
I've got that alt light gremlin in my AU. Comes on now and then for a while then goes off when ever it wants. Almost bit the bullet and bought a new alt a few times, just to find out if that's really the problem. But its working just fine (14.2 V even when alt light is on), and doesn't overcharge the battery. At first I could thump the dash and the light would go out, then after a while it took 2 thumps, then 3 thumps, now thumping doesn't work anymore. But it does tell me that the problem is in the cluster, bad contact somewhere maybe. Can't get the cluster out though, it's glued in really hard and won't budge, tried pushing from the back etc, no luck.

Auturbo6 · 30-07-2010, 11:22 PM

Quote:

Originally Posted by AMB

About 14.2 V is what I've measured on many alternators in good working order. Had one once that was putting out only about 13.8, and found that it's brushes were just about gone. Oily brushes might do that to.
I've got that alt light gremlin in my AU. Comes on now and then for a while then goes off when ever it wants. Almost bit the bullet and bought a new alt a few times, just to find out if that's really the problem. But its working just fine (14.2 V even when alt light is on), and doesn't overcharge the battery. At first I could thump the dash and the light would go out, then after a while it took 2 thumps, then 3 thumps, now thumping doesn't work anymore. But it does tell me that the problem is in the cluster, bad contact somewhere maybe. Can't get the cluster out though, it's glued in really hard and won't budge, tried pushing from the back etc, no luck.

Have damaged many an Au cluster trying to remove it, the most recent one was on my car, came out in three pieces, clear plastic then black plastic and last but not least the cluster. 13.8 to 14.2 is normal for an Au and is dependant on battery charge and condition.

atomiclord · 08-08-2010, 04:50 AM

Just for the OP, my alternator died yesterday 130km from home (visiting the 'rents). Battery still cranked over the EGAS engine at 11.2V in the diagnostic mode (didn't have a multimeter with me).

One recon alt later and all my birthday money from friday is gone :(

TheInterceptor · 08-08-2010, 06:47 PM

ooh thats gotta suck mate, not the best place to have the alternator pack it in.
yeah im prolly going to get diagnostics mode back on and il check that every now and then when using accesories. Gotta love diag mode

Thanks for the info and happy b day :P