Dead battery?

[P3rks 11]

I'm having an issue with battery drain on my VR (OBD2).

 

The car starts a little sluggish sometimes but when running everything seems fine.

 

Battery voltages are:

 

14.10v when idling.

13.2v (approx) with every electrical item on, although the idle fluctuates trying to keep up with the load (pre OBD2 the idle just bogged down).

12.2v (approx) when charged and removed from the car.

11.95v (+/- 0.05) with the car switched off and once the fan/aux pump after run has completed (it does actually drop lower than this, but it creeps up again once the after run has finished).

it drops as low as 9v when cranking.

 

The alternator is 120a and the wiring and alternator are good I've tested volts at various points around the wiring; lives and earths with pretty much about 0.05v drop max though out the car.

 

As far as I can tell there is no battery drain when the car is not being used - other than the alarm which does state in the handbook that it wont adversely affect the battery for about two weeks. Although the Aux pump and fan after-run really saps power at about 0.01v/0.02 per second whilst they are running. If I leave the ignition on, without the engine running, a door open so the interior light works, stereo on etc.. Pretty much if I use the battery without the car running the battery looses power very quickly and the car won't start - I either have to bump it or trickle charge it from the main for about 10 minutes. Even with the interior light on the battery looses 0.01v per second - Surely that's something you could keep on for days from a 12v battery without major adverse affects?

 

Have I just got a dying battery or is there an issue with the car pulling too much power?

Edited July 3, 2013 by P3rks

[fla 9]

there may be a short - I found that I had one of the three 'auxiliary' connections on the top left of the fuseboard was causing a short (the one that runs to the heated washer jets). So I just disconnected this and it is generally ok, although mine does also randomly suffer from slow cranking every so often, even if I've turned the car off an hour ago. Mind you, it did take ages to track this one down.

It might just be another corrado querk!

[P3rks 11]

How did you narrow down the location of the short?

 

My issue is that there is no obvious drain, so other than pulling everything out I wouldn't know where to start!

Edited July 3, 2013 by P3rks

[dr_mat 0]

Disconnect the battery when "fully charged". If it reads less than *exactly* 12.6 volts on a voltmeter then it's a faulty battery.

 

The voltage drop does sound too much. It should be capable of still being essentially fully charged after the overrun fans have been running.

 

Some maths.. Battery capacity is nominally 50 or more Ah, so it should deliver 50 amps, for an hour. Overrun fans are around 20 amps, so run that for five minutes and it'll knock maybe 3.3% off the battery charge, which would still read 12.56 volts...

 

I think you have a faulty battery unless as suggested above there's a serious short out happening.

 

Your charging voltages sound fine by the way.

Edited July 3, 2013 by dr_mat

[fla 9]

How did you narrow down the location of the short?

 

My issue is that there is no obvious drain, so other than pulling everything out I wouldn't know where to start!

 

Yes, went through pulling fuses but of course none had any effect. Then started looking at the 'unfused' circuits and used a multimeter to check for continuity between any of them. Timewise it took a good few days, progress was generally very slow.

[GusPW 0]

2nd vote on dead battery. see if a garage will check it with a load tester.

why the 120amp alternator? it needs to be balanced with the size of the battery and the amount of drain and therefore charging required.

if everything else is standard then the alternator might be overcooking the battery?

[dr_mat 0]

why the 120amp alternator? it needs to be balanced with the size of the battery and the amount of drain and therefore charging required.

if everything else is standard then the alternator might be overcooking the battery?

 

I don't think this is an issue - the alternator provides *up to* 120A (nominally), but the regulator on the side controls what it actually outputs, and that is led by the drain that the car places on it. It's not impossible to have an alternator that over charges the battery, but the charge voltages reported above look normal - 13.8 to 14.2 volts is what you should normally charge a 12V lead acid battery at.

[P3rks 11]

Yes, went through pulling fuses but of course none had any effect. Then started looking at the 'unfused' circuits and used a multimeter to check for continuity between any of them. Timewise it took a good few days, progress was generally very slow.

 

Sounds fun! I'll try the battery first as I know it's old, plus it's easier than this route!

 

2nd vote on dead battery. see if a garage will check it with a load tester.

why the 120amp alternator? it needs to be balanced with the size of the battery and the amount of drain and therefore charging required.

if everything else is standard then the alternator might be overcooking the battery?

 

Well, before I went OBD2 if I turned on a lot of electrical items the load became too much and the idle revs dropped, to the point where it had an adverse effect on the charging and the headlights dimmed drastically etc. I had a 120a alternator from a golf VR lying around, so I swapped my original 90a along with the wiring. Firstly to see if it made any difference to my issue (which it didn't) and secondly because I have a sub/amp, uprated headunit/speakers and also a upgraded headlight loom with some decent bulbs. My battery is currently a 096 with a 74ah and 700 crank powerr, so it's pretty beefy compared to the original Corrado one.

 

I don't think this is an issue - the alternator provides *up to* 120A (nominally), but the regulator on the side controls what it actually outputs, and that is led by the drain that the car places on it. It's not impossible to have an alternator that over charges the battery, but the charge voltages reported above look normal - 13.8 to 14.2 volts is what you should normally charge a 12V lead acid battery at.

 

Good to hear! I thought that was the case. In all honestly I just swapped out the 90a for the current 120a to see if it made a difference and to narrow down the issues. I just left it on. My GF always said bigger was better.

 

 

On another note.. I tried a mates really old battery which has been sat for years. It's the same sized 096 with a 74ah but with a 640 crank. It has very similar voltages as above, although the resting is just over 12.1v so I know it's tired. But it's holding it's charge better than the battery I originally questioned. So I'm going to say I have a crap battery and need to get a new one.

 

Looking at new batteries and i have done the research this one is the forum recommendation, 74ah with 750 crank:

 

http://www.battery2u.co.uk/type-067-096-varta-car-batteries-E38-silver.aspx

 

But, I've also seen this one 77ah and 780 crank..

 

http://www.battery2u.co.uk/type-067-096-varta-car-batteries-E44-silver.aspx

 

It's cheaper by a few quid, 15mm taller but it will fit no problem as it's the same hight as my current battery. It's heavier but has better ah and crank power.. Any reasons not to go for this one?

[Supercharged 2]

Take your car / battery to halfords and get them to test it... proper Bosch tester will show it it's knackered.

 

If you have a trade card buy the Bosch battery with the 5 year warranty - if not then go to VW / TPS - should be cheaper for Varta batteries than the links above if you get a bit of discount.

[dr_mat 0]

I don't think it's worth having a larger battery .. more weight is never a good thing, and it won't even last any longer if it's allowed to discharge..

The best investment you can make is a trickle charger so it never goes flat - if it never discharges significantly it'll last you ten years.

I know only too well that a battery that's allowed to go flat often will only last a couple of years.

 

FWIW if you want to run the ICE without running the engine you want a separate deep cycle battery for it. Normal starter batteries are designed to provide big current for vey short times, then be immediately topped back up, they degrade very fast if you actually let them drain.

Edited July 4, 2013 by dr_mat

[P3rks 11]

That's good to hear. It's just slightly better with higher ah and crank and not that much heavier. Swings and round a bouts really, but I just want the best performance for the money; that 0.8kg extra weight doesn't bother me do much.

 

The car is actually a daily at the moment so no point of a trickle charge. Plus not bring garages I don't want a cable hanging out if the kitchen window every night!

 

I hardly run the stereo when the cars not running. It's nothing stupid anyway, just decent speakers for better sound rather than thumping madness it's hardly ever put about volume 5 anyway. But if I'm sat waiting for 5 minutes when picking someone up it'd be nice to listen to music without the battery going flat. Something which a normal battery should be able to cope with.

[dr_mat 0]

I'm quite happy having a cable hanging out the window myself .. ! Will save me sixty quid every two years for a new battery! :)

Yes, the standard battery should have no trouble with a bit of use of the sound system and the run-on fans and all that stuff, whether it's a 52Ah, 64Ah, or 75Ah. It's the guys who sit at shows with the sound system on all day that need the separate battery..

 

If you do fancy a trickle charger I'd recommend these:

http://www.optimate.co.uk/

 

There are other similar products, and they're probably all as good as each other. Basically there's a set of spade terminals you can leave permanently attached to the battery and just run a small socket out the car somewhere. Hook it up when you're at home, unhook it when you leave. The charger will report the drain rate on the battery so you can see if you've left something on or your battery isn't holding charge. The only issue I had with it was the plug terminals got corroded after a couple of years, but they have a new design that doesn't suffer that now.

Edited July 5, 2013 by dr_mat

[Dox 22]

I always buy heavy duty batteries as soon as cranking starts to slow down in colder weather on all our cars. My VR6 will sit for months and start immediately as and when needed without a charge (no radio currently in the car and sorn) HD Yuasa battery

 

Compare the readings with another known good car to see if the meter is reading correctly, make sure all the plates inside the battery are submerged in acid, see if any cell bubbles excessively when under load.

 

Check the security and cleanliness of all connections - battery posts, alternator and ground (body and engine / gearbox)

[J.C 10]

Get a clamp meter,

http://www.ebay.co.uk/itm/1000-AMPS-DIGITAL-CLAMP-METER-MULTI-TESTER-CURRENT-C831-/320535806626?pt=LH_DefaultDomain_3&hash=item4aa16c42a2

this is a VERY cheap one but should be ok for what you want to do.

Just clamp it round the main negative (or positive, as what current goes in, comes out back to the battery)

check the current drain when everything is off, then turn on various items and see what draws too much current,

if you have an issue with one or more circuits, this method will show it up

[dr_mat 0]

Clamp meters only work with alternating current, won't read anything at all on a car with 12v DC.

 

Note that the ad says:

"AC/DC voltage. AC current 0.1A to 1000A"

-- i.e. it's AC only for current measurement.

 

If you want to measure the current draw on a DC circuit you have to place something in the circuit, i.e. you have to disconnect the battery then connect your meter in between the battery and the cables.

 

I've done this before (but be careful .. you can get a hell of a shock off it), and determined that my completely normal Corrado VR6 will flatten a standard battery in about three weeks.

[J.C 10]

Sorry

didn't look at the specs,

I'll find one which measures DC

Clamp meters only work with alternating current, won't read anything at all on a car with 12v DC.

 

Note that the ad says:

"AC/DC voltage. AC current 0.1A to 1000A"

-- i.e. it's AC only for current measurement.

 

If you want to measure the current draw on a DC circuit you have to place something in the circuit, i.e. you have to disconnect the battery then connect your meter in between the battery and the cables.

 

I've done this before (but be careful .. you can get a hell of a shock off it), and determined that my completely normal Corrado VR6 will flatten a standard battery in about three weeks.

 

---------- Post added at 4:58 PM ---------- Previous post was at 4:57 PM ----------

 

Try this one

http://www.ebay.co.uk/itm/MASTECH-MS2108A-Digital-Clamp-Meter-Multimeter-AC-DC-Current-Volt-Tester-UK-/110948414049?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item19d50a7261

[dr_mat 0]

I'm not aware of any possible way a clamp meter can measure DC, that would be a new area to physics. :)

(Unless it's an iron vane meter, which is useless on small currents and unreliable.. says wikipedia!)

Edited July 5, 2013 by dr_mat

[Supercharged 2]

You can get DC clamp meters - the AA patrols use them along with a wireless ipad like screen - excellent for diagnostic work, pulling fuses etc

[VR6 Gar 10]

May be worth a quick look on ebay for batteries.

When I last bought one for my S4 it was cheaper from ebay delivered than anywhere else. How with its weight I don't know, but it was a proper one like Bosch or Varta.

 

I run a cheap solar charger to keep mine topped up.

Did a test on my S4 and had a very slight negative(charging) reading with the charger plugged in. Only cost circa £15 from Maplin and can be used anywhere.

 

---------- Post added at 5:23 PM ---------- Previous post was at 5:21 PM ----------

 

May be worth a quick look on ebay for batteries.

When I last bought one for my S4 it was cheaper from ebay delivered than anywhere else. How with its weight I don't know, but it was a proper one like Bosch or Varta.

 

I run a cheap solar charger to keep mine topped up.

Did a test on my S4 and had a very slight negative(charging) reading with the charger plugged in, thus stopping the alarm/ stereo etc discharging the battery whilst sat. Only cost circa £15 from Maplin and can be used anywhere.

[dr_mat 0]

I take it back, they have developed DC clamp meters indeed. :) They work differently, i.e. it just measures absolute magnetic field - so you have to set a zero baseline "near" the cable, then clamp over the cable and measure the difference.

Never seen that before, but no reason it can't work. It's not as accurate as an inline meter, but a lot less hassle. Like it. :)

 

I wouldn't bother with a solar charger though, the amount of charge they generate overall is absolutely miniscule (unless you buy a huge one). I had one for a while and it did nothing to cover even the small trickle drain off the alarm etc. It also only actually covered the losses from about 10am to 4pm on a *really* sunny day, then one cloud comes over and it's not able to do anything at all. I considered it a waste of money .. :-\

[J.C 10]

I've been using DC clamp meters for 10+ years diagnosing electric forklifts, When you're dealing with 100A+ current draw, they're a lot more practicle than using a shunt, I found my Fluke clamp meter to be very acurate when compared to calibrated in line meters, obviously a cheap £20 ebay item will not be as accurate but will give an indication of a circuit drawing current when it shouldn't be,

[dr_mat 0]

I've never seen a DC one before (though it looks like the iron vane design is pretty old). I've used plenty of AC clamp meters though.

I see there's now even a clamp meter that claims to read current in multi-core mains cable, i.e. where it's not possible to separately clamp the live and neutral.

[fla 9]

I wouldn't bother with a solar charger though, the amount of charge they generate overall is absolutely miniscule (unless you buy a huge one). I had one for a while and it did nothing to cover even the small trickle drain off the alarm etc. It also only actually covered the losses from about 10am to 4pm on a *really* sunny day, then one cloud comes over and it's not able to do anything at all. I considered it a waste of money .. :-\

 

Did you plug it into the cigarette lighter socket? If so, that doenst do anything, perhaps there is something in the wiring preventing charge reaching the battery. I checked with a meter. I wired it directly to the battery and this actually did help. Just need to run the cable through the bulkhead now.

[dr_mat 0]

I did plug it into the ciggie socket, yeah, and that would work fine if there was enough juice, but actually the measurements I was getting off the solar panel itself weren't sufficient to do anything, let alone what finally got to the battery.