Need Some Help With Battery And Aircon Gremlins

[petchyboy]

Bit of a rundown. Battery is near new (centurion smartdrive) been checked twice for faults and returned nothing operating as it should....

Car lasts about 2 days max with a full battery before it won't start. Fully charged battery shows 12.9v during the start/cranking it drops to 7.6v briefly and once running either idle or 2000-3000rpm it's sitting on13.97v

The current draw with everything off is 1amp briefly (computers?) then settles at 0.29-0.30amps.

I've read elsewhere that when the battery voltage drops below 9.6v during start the air con compressor won't run, which would explain why I've had trips with no air con. I've just been on a trip to Brissy (500km each way) and both times stopping about half way for fuel the aircon has refused to work for the next stint which is frustrating with a temp of 35c outside.

Any ideas as to what is causing the massive drop in volts during start and what appears to be a highish current draw based on other posts I've found? I've tried pulling fuses and yet to find anything that causes the current draw to reduce slightly.

Car is an 09 xr6t with tech pack and premium sound, besides that no other aftermarket electronics have been installed. This has been happening for the last couple of years only, I've had the car since new and I think it's the 3rd battery I've had. Now I have the car on a 3 stage 12v 1.6amp charger which keeps the first start normal. Subsequent starts are generally ok, short runs and I'm in trouble by the 3-4 start up with computer faults and slow crank.

Thanks.

[Ralph Wiggum]

You need a decent auto sparky on the case mate.

I would suggest-

Proper Battery Load Test

Bench Test the Alternator

Test the Starter Current draw/volt drop (at the starter) pending results -

Bench Test the Starter

Test the Alternator Control Voltage under load.

Also what CCA is the battery? 1.8amp charger is going to take a very very very long time to charge anything over 550cca especially given the .3amp draw.

[Ralph Wiggum]

Also is that particular battery a calcium cell? If so it will need a higher charger voltage (up to around 14.8v) to full charge.

Re-Reading your post my money is on a sad starter motor drawing excess current from a battery that needs a good high Amp charge (assuming is passes a decent load/capacity test)

[Lennox]

Hmm fg? My alternator died at just over 100,000km.

[petchyboy]

Thanks for the reply. The link below is what's in there now. CCA 540

Car sits for long periods of time so it doesn't bother me that it takes a while to fully charge up, overnight is generally fine next morning.

http://www.supercheapauto.com.au/online-store/products/Century-Car-Battery-57EF-540-CCA.aspx?pid=287262#Recommendations

Cars done 70,000km

Edited 10/11/15 03:37 AM by petchyboy

[Ralph Wiggum]

A charger that small is really only useful to maintain a battery in a full state of charge. Do you have access to a larger charger (ie 8amp to 10amp) that can be used to fully charge it?

[petchyboy]

Unfortunately not, overnight the charger will show the battery is fully charged, perhaps it's not getting properly charged?

[Ralph Wiggum]

It's not.

[petchyboy]

But surely a 3hr drive would get the battery fully charged from even a slightly undercharged battery to start with? Either way I'm down in Melbourne for a service in 3 weeks so I'll have them fully investigate what's going on as its past my knowledge limit by a fair bit now. Either starter motor dodgy or battery tests that have been done are wrong and the battery is indeed shot.

What should the nominal current draw be from a the car whilst off?

Much appreciate the help

Edited 10/11/15 04:13 AM by petchyboy

[masda74]

Right now, I can't remember which battery I got exactly, but I did get a 620CCA battery

it was either the 67 or the 67EF on the Supercheapauto webpage.

Anyways, from what I have read, you have done a 3 hour trip and you still had battery problems when you had the pit stop.

Isn't that a clear and positive identification, that your problem is the alternator??

Battery is near new and I doubt that is the problem(however it is possible). but if the alternator is on it's way out, it's not gonna charge the battery during a 3 hour.

Hence the reason when you charge it over night, it starts up fine first thing in the morning. Once you have made a few more trips, you start to have issues

I am no expert here, Ralph has more knowledge and experience, but that is what stands out for me.