Random battery dead flat.

Hey guys,

Past 2 months my battery randomly goes DEAD flat (ignition light dont even turn on).

I have replaced the battery with a CAT 760CCA, car kicked over fine for 13 days then today its gone dead flat again.

no lights left on, ie doors closed properly.
I have got uhf installed which is wired directly to battery which i turn on only when we go bush and this has been working fine for years so im confident its not the uhf.

I dont know how to diagnose a fault that is soo intimittant? any help is appreciated

maybe every time i get home i should turn the car off and back on to isolate an alternator issue. so if it does turn back on straight away then in the morning if its dead flat then something must be drawing power somewhere if so i may need a multimeter?

A multimeter will be of great help. It would be good to measure the current draw when it is sitting in the driveway turned off, as a reference point. Then if you measured it at intervals, maybe twice a week or something, you might be lucky enough to catch it having higher current draw.

I would also check the voltage of the battery, turn the car on and check voltage of the bettery, go for a good drive to charge a bit then measure again, then leave overnight say and measure voltage next morning again. Any decent differences you will notice.

Have a look for any loose connections, they may be loose enough that they are not always going bad, only sometimes. I used to have a rodeo and the battery lead on that i could pull off the battery post without loosening, even though it was done up as tight as it could go, it was simply old and stretched terminals.

There is every chance it could be the alternator, or something else for that matter. either way to die over 13 days is not on, there is something happening. How long do you drive it for at a time? Is it getting a good charge in or is it only short soft driving etc.?

Cheers
Mitch

Yep, I use a multimeter to measure the current draw and then start pulling fuses to isolate what's drawing the current. You may have to repeat this quite a few times as your problem is intermittent which is a real bastard to diagnose.

goodluck

Hey fellas,

I drive approx 30mins in and 30mins back so its getting a decent charge,

going to get multimeter today and start diagnosing...fkn intermittent bs faults

hey im just googling how to use multimeter to check milliamps...and apparently if u do it wrong u could blow up the meter...i have attached a picture is this the right setting and how do i connect it in "series" to the battery?

http://imageshack.us/photo/my-images/861/multimeter.jpg/

It's easy enough to do. 'In series' literally means "in line with", so it means you have to break the circuit and stick the multimeter into that circuit.

Steps:

1) Get your radio PIN handy and write down your tripmeter values if you use those for economy calculations

2) Remove the red POSITIVE battery lead

3) Attach the BLACK multimeter lead to the POSITIVE terminal of the battery

4) Attach the RED multimeter lead to the positive battery lead.

I tried to upload a picture but I keep getting an error. When Dylan fixes it I'll attach it.

I think your multimeter doesn't have enough range. It's a bit low on mA and if you turn ANYTHING on in your car, you'll blow the multimeter - that's if the current drain is not enough already!

Most multimeters (ought to be able to) measure up to 10A. I'm surprised you have one that only reads a fifth of an amp (200mA).

That looks right to me for that meter mate, on more expensive models they have more places to plug into, like mine has 4. To connect in series just disconect the positive battery lead, put multimeter red lead onto positive battery post, put black lead onto the terminal on the positive battery cable. Get what i mean?

Mitch

Did I get the bloody leads the wrong way around? Serves me right for having an autoswitching multimeter!

thanks fellas...yea i just got a cheapy $20 stanley meter...ok iv tried it but readings show 0 and im not game to turn the car on..have i got it on the right setting of 200m (A)

voltage check still works so assuming fuse has not blown...currently voltage sits on 12.58/7 and with car on 14.1 seems alternator ok

Yeah that's the highest setting you've got. If you're reading 0mA, there's something wrong. Our cars all draw SOME power.

I'd also take a look at the water levels in the battery (if possible). Check the voltage of the battery after it's been disconnected from the vehicle for 6-8 hours - remove the positive battery lead, measure the voltage, let the car sit overnight, and measure the voltage again in the morning.

You should expect to see some voltage drop as the battery stabilises internally, and it should drop to between 12.6 and 12.8V at the worst. If it's dropping any further and the initial voltage was below 13.2-13.4V, then you may have an alternator problem. If your starting voltage was 13.2-13.4 or higher, your battery may have some sulphation in it - crystalised deposits lead and sulphur that end up shorting the battery out and draining it.

Is this the only battery in the vehicle? A mismatched auxiliary battery on a direct connection will kill the main battery too as they both try to charge each other up - that's why they need to be isolated by either an isolator or an inverter/charger setup.

Do you have electronic rust protection?

thanks tony..its a brand new CAT battery 13 days old (CCA710)...i tried connecting both your way and mitches...still no readings..pretty confused right now...its like im back in science class sighs!

this is how i connected it...

http://imageshack.us/photo/my-images/30/img0358oy.jpg/

The problem with that meter is finding a means of testing it.

An indicator globe (21W) needs almost 2A (2000mA) which is 10 times what your multimeter is capable of reading, so trying to use a test lamp to see if the multimeter works destroys the multimeter. It is possible that your multimeter has already blown a fuse due to the large current involved.

200mA is nothing. It's 2.4W, or HALF of a cabin light, and just over half of an instrumentation bulb. I'm stunned that they put such a beast on the market.

oh man that is sad...what a useless tool. going to get a decent one...

also..i dont have rust protection

Try this one for size:



Click on the picture to go to Jaycar's page. It's $24.95, stick the black cable in "COM" and the red one in "10A", turn the dial to 9 o'clock (the blue "10") and Bob's your uncle.

dam..i just got one from sca $40 with the 10 amp..bah anyways its currently drawing only 0.17 but at first it sit around 0.9-1.5 then drops to a stable 0.17... its going to be a pain trying to find the cause since this happens almost every 2 weeks ish...

That initial onrush of 0.9A is what blew your previous multimeter up. At least now you have a good one, so let's get on with it.

As the battery is reconnected, the ECU is going to start in "standby mode" so that it can be ready for events. The BCM (Body Control Module) also starts and goes into standby mode, waiting for you to press the button on your key to lock/unlock the doors. As these devices start, they'll use a little more power and then they'll settle.

At 0.17A, you're looking at about 4A lost per day, or 28A per week. Your battery should have an "RC" value written on it - it's probably around 100 or so. You should be able to start your car after 2 weeks of sitting there (battery at about 50% charge should still turn the starter over).

There's GOT to be something else happening. To be so flat that you can't see a dash light, the ECU must be incapable of starting and from what I can see in the manual, that's at about 11V or below.

It's time to pull relays and fuses. In the fuse panel beside the dash, I think the top left fuse is for the ECU. Pop that sucker and see what the current draw falls to, if that goes all the way to 0, then the problem is either going to be in the battery, or in the way the battery is charged - could be a leak in the regulator, or corrosion on the terminals/plugs. If you've had your vehicle under water, I'd pay particular attention to the alternator.

Old Tony

Mate, your way or my way as far as leads go should be good, i too have auto-switching meters. Mine are all Fluke industrial jobbies. I just work on red goes in black comes out, same as in all the power circuits i work on (within reason).

Nismo, everything old tony has said is what i agree with so im not going to go and repeat what he said.

Whatever you do DO NOT start the car while measuring the amps. turn ignition to on at the most, but do not turn it over.

Measuring voltage and starting the car is ok, as voltage is always measured in parallel, not series.

As i have already said, give all the connections a pull/twist test. Or even just throw a spanner on and make sure they are tight. Otherwise i still agree with old tony.

Mitch

thanks heaps guys...will start investigating...thanks hepas again for ur help...will update once i have news

You wouldn't read about it, the same thing has happened to me, a couple of weeks ago I discovered my battery was totally flat, so flat that it just wouldn't take a charge anymore. As it was the original battery (2007) I replaced it and thought my problems were over, however thismorning I went to start the Navara and nothing, I measured 1.5 volts on my new battery, I did manage to charge it up and start the car, but in doing so I shorted out the posative battery terminal to ground when the charger slipped, now I have blown 1 of the fusible links in the terminal, so guess it;s a new 1 of those on monday, then to start diagnosing just why the battery goes flat, there are no modifications to the electrical system at all , I don't use the car much at the moment, so I guess I'll have to make an effort to start it every few days ????

Working on the assumption that a car alternator won't charge the battery more than about 70% of its capacity - let's be optimistic and say 75% - let's look at the numbers.

If the average continuous draw is about 0.17A (and for the sake of simplicity we won't bother with the startup current) we're drawing about 4A per day (see previous post in this thread).

With a battery capable of 75% of the 95A of reserve capacity (RC), you can draw on 71A before the battery is absolutely dead flat. That's just under 18 days - a little over 2 weeks.

It will not last that long though. As the voltage drops, devices requiring power will start to increase their current draw because what they need is wattage - which is volts times amps - so if they need 0.17A at 12V (2.04W), when the battery falls to 10A they need 0.2A - see how the current rises? There's also damage to the battery to consider, below 10.75V the cells of the battery start to destroy themselves.

My advice would be to go out and give the vehicle a decent run once a week. Not only will it help with the battery but it will make you use up the fuel, and stale diesel will cause issues on its own - like destroying fuel filters ($175), fuel pumps ($4,000) and possibly injectors ($400 each).

If you don't have a problem with the fuel risk, then get one of those little solar panel things and whack it on the dash, with the vehicle in the sun during the day. It won't stop the drain, but ought to give you some extra days of storage. To stop the drain, you have to supply better than 4A during sunlight time - over 5 hours, you want something that can deliver about 10W, which is a fair sized panel compared to your dash.

It's easier, cheaper and better all-round to find the time to take it out for a run for an hour, once a week.