Battery / charging probs

**RichardB** · 04-16-2006, 05:05 PM

Hi guys I am having some problems with my battery. Basically my computer would only run with the engine off for a few mins before shutting down. I decided to splash out on an optima Yellow Top. I replaced my standard battery with the Optima as I didnt see the need for a dual battery setup.

Anyway it now still does the same thing. If the car has been running I can watch a dvd or play music at a reasonable volume for half an hour easily. But if I go to the car at lunch time and have not ran the engine first then it will only run for a few mins before shutting down due o low voltage. I have installed a voltmater on the line that goes to my car pc and it shows it as about 12v when it starts to shut down, with my digital multimeter I get 11.7v at terminals and 11.3v at the power supply so a 0.4v drop down the line.

What is annoying me is my car has an 80amp alternator (88 Volvo 740) and should be able to charge the battery sufficiently even on short trips. I cant understand why the battery would discharge so quickly overnight, other people on here are saying they can run for hours without the computer switching off, what am I doing wrong? Perhaps I will wait until I have done a longer journey (100 miles) and see how it is after a better charge, or shall I contact Optima or my supplier about getting a replacement?

I am running an Alpine head unit
Planet Audio 3ch amp running my front components and 10 inch CDT Audio sub
Opus 150w running
MSI motherboard
Athlon XP 3.2 (I think)
1gig ram
64mb geforce2 mx graphics card
DVD drive
Sound card
USB GPS
Linitx touchscreen

I think that is everything.

Anyone got any advice for me?

Cheers,

Richard

**TruckinMP3** · 04-16-2006, 05:19 PM

Go to an auto parts store that will diagnose your charging system for free.

Test with the PC off first, the on.

That will tell you what to look for as a solution.

Three parts that need to work well for the charging system:
Battery
Alternator
Voltage regulator (often overlooked)

BTW: searching would have shown you similar threads with the same advice.
carputer reboot issue

**RichardB** · 04-16-2006, 05:37 PM

Cheers for the reply. Im sure the alternator is ok as even with all the electical items in the car turned on if I rev the car to about 3000 revs then the voltmeter is seeing 14v as it should. I did a serach but didnt find anyone with the exact prolem ive got, my system runs perfectly with the engine running only have problems with it off. I have just been reading about "the big 3" and I think I will upgrade all those. I am also thinking of changing to the alternator off the turbo model which is 100amps.

I will try get to a garage to get the charging system checked. Can I not check most of it myself though?

Cheers,

Richard

**TruckinMP3** · 04-16-2006, 06:10 PM

Sure you can check it, I have just used the parts store to get it done. Less than 10 minutes and no fee.

**JasonWW** · 04-18-2006, 11:29 AM

Is the power wire going to your PC big enough for it's length and check to make sure all the contact points (fuses, splices, connectors, etc...) are in good shape with no corrosion and are nice and tight. It sounds like your PC is getting less voltage than the battery has and is therefor thinking the actual battery is low and it's turning itself off.

**RichardB** · 04-18-2006, 06:11 PM

Yes the cable is thick enough, its 8 gauge all the way from battery and the earth is shared with my stereo and goes from 8 to 4 gauge. Like I said in the first post I am getting a 0.4v loss over the cable. I think the problem could be that the pc is using too much power while in hibernate. The GPS is still on so using power and whatever other power is needed. Is there a way to stop it using this extra power other that disconnecting the gps except when im using it?

Cheers,

Richard

**JasonWW** · 04-18-2006, 10:31 PM

Originally Posted by RichardB

I think the problem could be that the pc is using too much power while in hibernate. The GPS is still on so using power and whatever other power is needed. Is there a way to stop it using this extra power other that disconnecting the gps except when im using it?

Your battery voltage should be higher than 11.7 after the car sits awhile. It should be around 12.3-12.4v. Since hibernate is basically "power off", unlike standby, then something is drawing your battery down.

After driving the car for a while measure the voltage at the battery. It should be 12.4 or so. Let it sit like you normally do and then measure it again. If the battery is going down to 11.7 or so then something is draining it.

Aside from the 0.4v loss, if you know that the GPS is still getting power when the PC is off, then that is your problem. It is a known problem that certain models of GPS combined with the Opus will drain the battery. For most people with this problem it takes a couple of days for the battery to drain. Maybe your GPS is a bit more power hungry? The problem stems from the Opus not having a hard off option.

I'm having a similar problem, but I don't have a GPS. Still, something is draining my battery over a 24 hour period. Check these threads:
opus draining battery?
Opus 150 +5vsb mod and standby, cannot have both?
OPUS simple question

You may also be able to wire a relay into the 5vsb wire between the PSU and the mobo. The purple wire. http://pinouts.ru/data/atxpower_pinout.shtml

First, I'd try unplugging your GPS for a day or 2 and see how the battery responds.