battery drain
 

having had problems with the battery draining when my D2 A8 was left standing for any length of time I checked the parasitic drain in the approved manner using a 1ohm 10watt resistor
it seems to be running at about 100mA
is that about normal for an A8 ? seems a bit on the high side to me

How does one check with a resistor, would love to know your technique

for comparison, my current D2 S8 draws around 0.18A (using Maplin clamp Amp meter) and has very few options, my previous D2 S8 drew over 0.2A

A simple calculation, 0.1A over 24 hours is 2.4Ah capacity per day
If you have the standard 85Ah battery, and if it was fully charged, at your current rate of discharge it would take roughly 18 days to drain down to 50%
If your reading is correct, I suspect your battery is either discharged, or heavily sulfated and wont hold a charge.

Check your open circuit battery voltage. When fully charged, check its open circuit voltage, then leave disconnected for 24 hours and check voltage again, or connect a 12V bulb or something that draws a decent current accross the battery briefly, leave to rest for 10mins and check the voltage again. If the open circuit voltage after standing or brief load drops significantly from fully charged voltage, lets say from 12.7V to 12.3V or less, then your battery is heavily sulfated and hasn't got much of the original capacity remaining. On the web there are articles which reference open circuit voltage to state of charge. From memory, 12.0V or below is pretty much fully discharged.

well , as your's is running at about 180mA seems mine isn't bad at all !
my battery is excellent but , as you know know , this 100mA drain will half discharge a standard battery in a month [ pretty common when I am away in my motorhome ] at which point the voltage will be down to maybe 12.3 volts and there isn't enough to start the engine if it is at all cold

delboy , presuming you have a meter and a couple of spare crocodile clips £1 at maplin's will produce what you need


https://www.youtube.com/watch?v=B__DqK90IIc

Ah, yes, a month will kill it.
According to the interweb, if you leave your lead-acid battery sitting below 50% charge state for a significant lenght of time, it will form lead crystals reducing its capacity.
So going by the web, I doubt your battery is in a excellent state if you left it drain to zero for a month.
Also depends on the electical systems of the car, on my current S8 the old 110Ah battery could still just about start the car even when it was fully drained down to 11.9V

I have not measured drain current on mine but I have 6 years old 88Ah 730CCA battery which according to conductance tester have 61% capacity left and 630CCA and it recommends to replace the battery. If car is left alone for 2 weeks battery voltage will drop from 12.6V to 12.2V but it does start just fine at this voltage. I have had battery to drop to 11.5V in the past and it still started car but engine was barely turning over.

My 110Ah Varta must have been truly toasted by the previous owner, only 2 years old according to purchase receipt, and it was draining to 12.2V after sitting for just 5 days after being fully charged. How easy/cheap is it to do a conductance test, just out of curiosity?

There are several different testers on the market starting from about £20 to several hundred depending where you buy and what brand you want. I have a one like this for about £30: http://www.aliexpress.com/item/2015-...272748629.html

It's not the cheapest but it can test battery either in or out of the car and also can test starting and charging on the car. Only drawback is that it is for batteries up to 800CCA, you can still test higher CCA batteries just by setting it to 800 but results will be somewhat limited and a bit off. There are testers capable of more CCA but more expensive.

Thanks +++
£20 is very reasonable, I might get that one. The 110Ah is no longer in the car, I'm just curious what capacity is left on it.
Although I just realised I could charge it up to full and put a small load on it and record the capacity drained over a period of time. I have one of those RC multi meters which records mAh taken out of a battery, Ams and Volts.

not sure it is of great value to measure how much life is left in the battery , it either works for you or it doesn't , its a consumable product after all ; being a motorhomer [ with 3 batteries ] I am always watching them [ built in meter ]

on the A8 [ 95Ah 800CCA ] I have just fully charged the battery then disconnected the earth immediately and left for 2 days ; as you will all know a brand new battery will give you 12.7 volts but that doesn't last for more than a couple of weeks before it drops to something like 12.6 ; mine is reading 12.63 so I am more than happy with the amount of life remaining

with regard to drain tests I first used a clamp meter , but frankly I wasn't satisfied that it was sensitive enough which is why I sported £1 and made the resistor test lead

frankly goran I suspect you have had something draining the battery on both your cars ...searching around I found that top end mercs are renowned for a heavy draw but that 60mA would be pretty normal on one of those...I shall carry on looking , maybe you should sport £1 and do the same !

incidentally , if you give your 110 battery a long slow charge then leave it for a couple of days what sort of voltage do you get ...anything around 12.5v and it has a lot of life in it if you can reduce the draw !

Are you sure your resistor in series method is accurate? What's your multimeter's resolution/accuracy when measuring voltage and resistance.
Seems to me you are multiplying error bars of several different measurements (battery voltage, voltage accross resistor, resistance, etc) and your R2 (the resistance of the whole car) is an unknown? Have a go at calculating your error bars for fun :)

The meter I bough claims 0.01A resolution and +/-2% and 5 units precision, for my measurement of 0.18A I work out the error to be +/-0.054A a bit high, true, but to get a much more accurate current reading you will need to spend several hundred pounds on a accurate meter.
http://www.maplin.co.uk/p/uni-trend-...FezHtAodmRIAhg

supposed to be accurate to 1mV , checked it against my nephews professional meter and it seemed to be about that . I suppose it doesn't matter if it is slightly out as long as it is consistant , certainly more precise than the cheap clamp meter I tried

latest development ...went to check the voltage on the battery after another 24 hours and it had dropped by .03 volts ;at this point I noticed that , with the boot open as before , the indicator lights beside the door lock buttons were illuminated even though the doors hadn't been locked and the doors hadn't been opened ...that doesn't seem to be correct , or does it ? unfotunately I tried the lock/unlock buttons on the remote without checking the doors had self locked last time I was in the car , just opened the boot which wasn't locked so I guess not

anyway , pulled the central locking pump fuse and the drain dropped by 10mA to 90 , probably because the boot lights are on the same circuit and , at a guess , they were pulling that ...can't remember what festoon bulbs are rated at ; at least I know that the pump can't be the problem

looks like I will have to pull each fuse to see if anything is giving a serious drain , seems crazy that you couldn't leave the car at the airport for a couple of weeks and be sure it will start even with a good battery

If you are coming to the meet you are welcome to borrow my clamp meter to confirm.
A 0.1A drain will in theory drain 16.8Ah capacity in 7 days, so a healthy 95Ah battery fully charged should be able to cope with this for a couple of weeks.

I can roughly correlate my clamp meter reading. I am now using a 31Ah LiFePo4 battery as my starter battery. These have a fairly flat & linear discharge curve between 90% and 10% SOC so state of charge and voltage correlation is fairly accurate.
For example, Sunday evening 9pm after driving around at the weekend the battery will read 13.27V in circuit after resting (I know I should be reading open-circuit, but these batteries have a very low voltage sag under light loads).
13.27V nicely correlates to 80% SOC. Not driving the car for 5 days or roughly 110 hours on Saturday morning the battery in-circuit voltage is 13.07V, roughly 35% SOC
This roughly equates to 14Ah drained over 110hours, or an average sleep mode current draw of 0.127A, so the clamp meter is not too far out.

http://smg.photobucket.com/user/o0ps...yLg-1.gif.html

thanks for the offer ...but as I live 800Km south of Calais I hadn't considered attending !

PROGRESS !

in the boot fuse box is a fuse for what is described as radio telephone loudspeaker ; remove that and the drain drops to under 50 mA !!!
don't have a telephone , might have been an analogue fitted as OE I suppose , now removed

not quite sure what runs from this fuse , so checked radio , doesn't work without fuse , so put fuse back .......CD stack in boot resets as it always does when you connect the battery ! so clearly that is included ; so unplugged that , not the problem because the drain figures stay exactly the same

so it looks like the drain comes either from something left over from the telephone days [ if there were any ] or something powering loudspeakers [ which I don't understand ]

m'aidez or mayday if you prefer

Can you be explicit on which one and exactly where please.
I know my car did once have a phone car kit (partly removed, keep finding stray cabling), though it was most likely separately fused via a piggyback that I haven't found yet.

the boot fuse box on my FL has the facility for 6 rows of fuses although all I have is [ from left to right ]

a jumbo fuse for ABS in row 1
a 20 amp fuse above a 25 amp fuse in row 3 , the upper fuse being the radio fuse referred to ....but don't you have a diagram inside the cover ?

incidentally , the radio aerial also seems to be fed through this fuse , mine appears to have the famous broken plastic cog ...the motor turns correctly but it doesn't move

a little research suggests that the radio amp is underneath the CD stack , no idea how I test for a fault if I take it out , my rear speakers don't work [ unless there is a control somewhere ] which could be connected ; the sound quality from all the front speakers is just fine

That could be simply down to Bose/non-Bose coding in the head unit.
Do you have a Bose system or not and what is the head unit, e.g. RNS or Symphony?

My radio aerial is built in to the rear screen.

PS The BOSE amplifier (if present) is located below boot floor level, beneath the CD changer.

Yes and I have some additional fuses too - rear seat adjustment for example.
BUT that fuse I'd always assumed was for the amplifiers in the rear speakers, so that's probably why you have no sound from the back. :tuttut:

With Bose, there's a separate amplifier (as described under the CD changer) but with non-Bose the amplifiers are less powerful and are attached to the rear parcel shelf speakers. Take the covers off beneath them and you'll see.

In both cases these also drive the speakers in the rear doors, which are the MAIN rear sound, the parcel shelf ones are purely for bass notes.
The front speakers are driven directly from the head unit, I think maybe even with Bose installed.

the box under the CD stack turned out to be reversing sensors !

so thanks for the gen on the rear speakers , will look there ..maybe the source of the current leak !

Well curiosity got better of me, I tested 150ma drain current from the battery on mine. Car unlocked and waited until light in the boot goes out before measuring. Tested with multimeter at 200ma range in series without any resistors or anything else. Removed the clamp from battery but pressed it to the battery terminal so there is current going to the battery, connected 1 lead from the multimeter to the battery, other to the cable and then moved clamp away from terminal to make the current flow through the multimeter. This was done to avoid high current and possible damage to multimeter at the moment of connecting. Car has factory CD changer, SatNav and working phone and aftermarket alarm.

sounds a lot to me ...try pulling the radio/loudspeaker/telephone fuse in the boot and see what you get !

Mine is PF, haven't got any fuses in the boot.

presumably there is a radio/loudspeaker fuse in the main box then ..try having a look there !

well , progress ..of a sort
having found that removing the phone/radio/loudspeaker fuse reduces drain by 30mA and to an acceptable level I put it back in and removed components one at a time
phone ...never been fitted by the look of it
CD stack .......no reduction
electric aerial ....no reduction
back parcel shelf bass speakers [ nokia 4DO 035 401 25Y ]that don't work .....no reduction

so that seems to just leave the radio itself + door speakers [ audi concert ...in the handbook for that it mentions bose without saying for which parts ] ; could that account for 30mA on it's own ? incidentally it appears to need a code [ tear out strip in the book ] but when I have disconnected the battery it works just the same

anybody any idea what the radio draws normally ?

I did find the fuses in the boot, I have not noticed them before on my car because they are under the cover but I have seen them on somebody else car without removing any covers, I guess they were missing the cover, that made me think I do not have any in the boot. Anyhow found the radio fuse and it is drawing 1.2A with radio on silently, drops to 0.5A when radio switched off and then to 7ma after half minute or so. So it is not radio drawing current on mine. 150ma is a bit more than I would like but car still starts fine after 2 weeks without use and on old battery so cannot really complain.

thanks! 7mA sounds like the sort of figure I would expect , but 4 times as much , as I have ??? sounds like enemy action ! if I had your radio [ do you have a concert ? ] it would solve my problems ! I didn't realise that you could change the settings from standard to bose , my system being standard if it has been changed to bose it might have caused the problem [ can't check , don't have the kit ] ; as the radio is constant live could maybe find a way to put a switch in the circuit to isolate it , sounds like mine isn't switching off !

you say that the car starts fine after 2 weeks at 12.2 ... I have been checking the voltage drop over 4 days and it is down by about .12 volts so starting after 2 weeks would be about 2 weeks might be possible from what you say , would probably need 12.3 with winter temperatures where I live even though I head for the sun when it starts to go below zero !

anyway have started again , put the battery on charge and will test daily for a couple of weeks , my 90 quattro 7A 20valve may be on it's last legs but fine for running around locally which is all I need until I go to england to visit my daughter in the new forest in july

don't forget to post what your problem was when you discover why your drain is 150mA

ps , maybe the reason that the other A8 you looked at didn't have a side panel was because the owner needed frequent access to the battery !

this is driving me crazy
pulled radio , debranched 12v feed plug , checked that there is now no power to radio , aerial or CD stack ; don't have phone [ never did I think ]
so now power drain on battery drops by 30/40 mA the same as when I pull the fuse ?

nope , no reduction at all

as Alice said , curiouser and curiouser

any ideas as to what to do next seeing my theory that it is the radio has turned out to be erroneous ?

Write to Audi and ask what normal sleep mode current is for a D2. You could be chasing a non-existent problem if D2s have a larger sleep mode current due to all the systems in the car.
We now know of 4 cars, two of mine, Ainars's and yours which drain 100mA and above, can all these cars have a problem? or is this normal for this type of car?
Anyone else measured their current drain? Please post.

well ain has the same circuit as me , and has a drain of 7mA whereas mine is about 40mA ; obviously cars vary according to what equipment is fitted but as this particular circuit is limited to radio and ancillaries it seem impossible that there could be so much variation...unless there is something related to the phone which neither of us have !!!

I've checked around the rest of the car and there is nothing which seems to be excessive so mabe contacting audi to see if there was something fitted as OE on this circuit would be a good idea !

in the middle of my test to check the voltage drop on the battery while it sits in the barn

this morning opened the boot , lights came on , tested battery , shut boot , walked away then realised I needed the torch I had left there

opened boot , lights DIDN'T come on ; suddenly realised that normally they don't !
if I understand correctly , if the battery is connected the lights should ALWAYS come on ; tried pressing the buttons which get pressed when you shut the boot ...no reaction
is there something here I don't understand , could this be the answer to a maiden's prayer [ so to speak ] ?

Faulty microswitch in boot latch?

Quite easy to take out and dismantle or just disconnect.
IIRC I have one, maybe two, spare such microswitches from my own "expeditions" in this area.

spot on HP , just gave a spray with wd40 , opened and shut a few times et voila

ta muchly

Hmmm, that's how mine started and the latch innards were damaged and eventually broke. I'd take it out and have a look.

here's the result of my voltage drop test
first result a couple of days after charging , they daily
12.80
12.70
12.66
12.60
12.54
12.52
12.50
12.48
12.46
12.44
12.42
12.40

at which point I gave up and put back on charge ...as you will all know sulfation really takes hold if your battery gets below 12.40

so I seem to have a fortnight , well maybe , who's to say the alternator will charge up as much as the battery charger did
anyway , I went to amazon and invested £4 or so in a 500mA battery charge maintainer , switches off when fully charged , cuts back in again when the voltage drops

just to add , somebody here advised contacting Audi at milton keynes so without much confidence I sent them an Email with my problem

had a phone call , nice young person said have checked your OE spec on our computer , your radio aerial/CD stack /concert radio is as factory fitted , we didn't fit either sat nav or phone , and if disconnecting what you have doesn't cut the drain we can only suggest a visit to an audi dealer who can plug in his computer and maybe find the problem

ok , didn't fix the problem but very helpful anyway to somebody with a 15 year old car

looks like my solution is going to be to run a cable from the fuse to the dash , fit a switch [ got a blank space ] to isolate the loom wiring that feeds the ICE , must be a leak from that !

the 8 not being in use for much of the last 12 months resorted to just disconnecting the battery for much of the time
however now back in fairly regular use so am going to re-address this problem as it is a PITA !

just had a thought ; the radio doesn't lose it's code when the battery is disconnected [OE ] ....why not ? [ probably because I still have the nice tear out strip from the owner's manual ! ]

could this possibly mean anything ? is this normal on an early FL ?

I suppose I could just hot wire to the ignition circuit but that would mean turning the key to put on the ignition when parked ...hardly a good idea ! have given up the idea of putting a switch in the circuit , would certainly forget to switch it off !

How about putting a latching relay to supply the offending kit?
If you use the correct one and feed it from the ignition then it will cut off when you switch ign off.
To switch the relay on and therefore supply the radio etc. you press the button. To turn it off you can either press the button again or switch ign off.
This means you cannot forget @cos the latching relay does it for you.

http://www.ebay.co.uk/itm/Latching-relay-board-with-single-pushbutton-input-to-latch-unlatch-relay-/111978409246?ha.
sh=item1a126eed1e:g:rbQAAOxyVLNS3kXv

The same supplier does a plastic box for it to fit in
I have used two of these in our buses and have another one ready to put in my A8.

thanks ray , sounds like a plan , didn't know that existed
when I have the battery fully charged again will pull the radio , disconnect the live feed , leave the main fuse in and double check that this cures the drain [ have already done that with the CD stack to no effect ]
if that works will get one of those gizmos
if I read the spec correctly one needs just a flash of electricity to start up [ a bit like a bell push rather than an on/off switch ] ; got a spare slot in the row of switches on the dash ....is there a matching switch for something else that could be used ?

incidentally , rear seat entertainment ? have forgotten such days !

Correct.
I use a momentary push button from Maplin. It has a LED in it that I connect to the relay output (as well as the load, in effect in parallel) to denote that the relay is latched in the "On" position.
I'l try and find the Maplin part number when I return home.

RSE is for when we have the grandkids on long journeys.