Big battery drain

**swarover** · 17th March 2018, 08:26 PM

Hello All,

Have a problem one or some of you may be able to shed some light on. Searching us here and the Disco 3 UK forum, I can't find a similar issue: My 2005 TDV6 D3 has started flattening its battery very quickly while turned off; within a day or so a few days ago, and today six hours after installing recharged battery. Battery is a 20 month old Exide 820CCA as spec for this car.

Problem first noticed on Tuesday morning as a slightly sluggish start, drove 100 km and left the car all day, started again ok (can't recall that start's characteristics) and drove back 100km. Thursday morning (40 hours after switch off Tuesday) no start, dash lights/symbols flashing, voltmeter said 10.34 volts. Removed and charged battery (as advised by battery supplier who I called for advice) until green light on my charger (Waeco Perfect Charge W8) lit as fully charged - where it read 13.69 volts. Friday morning battery siting on bench at 10.79 volts, suspecting battery breakdown, I took it (in a different vehicle) into supplier for them to check and discuss solutions. Supplier charged battery with their machine and load tested it, which it passed no problem. They had been quite prepared to replace it under warranty, but it stacked up. Battery read 12.75 volts after two load tests, and I brought it home.

Installed battery this morning and worked ok, started with normal flourish of a full battery and showed 14.35 volts charging. However, during a 15km drive it did exhibit a slightly sluggish start on the one start in that drive around. Returned home, turned it off and left it for 6 hours (unlocked), tried start again to no avail, battery reads 10.68 volts.

Last weekend I drove the car on some very bad corrugations for about 40km of 100 km of gravel road and track driving, which may have messed something up. BTW the quite wonderful car has done just shy of 440,000 km, so its pretty well run in.

What do you think, a serious drain somewhere, or a crook battery that cheated the load test?

Thanks in anticipation.

Nathan

Tombie · 17th March 2018, 08:28 PM

Likely the alternator has done a diode... a not uncommon issue. Can lead to fire so get it checked.

**scarry** · 17th March 2018, 09:28 PM

If its on its original alternator,its done very well...

**swarover** · 17th March 2018, 11:05 PM

Thanks Tombie and Paul,

The original alternator died and was replaced at 334,000 km, 96,000 km ago. It's charging fine, something causing the drainage quickly, could that be an alternator diode? No alternator lights or any other faults. Or the battery's iffy, which is sitting just now at 10.48 volts.

Nathan

**Geedublya** · 18th March 2018, 07:13 AM

Put a clamp meter on it with the engine shut down, if you see a large current drain further isolate to determine the problem. If you are not capable of this sort of troubleshooting take it to an Auto Electrician.

As stated above I suspect the alternator, they have been known to fail even with relatively low kms.

**Graeme** · 18th March 2018, 10:20 AM

A voltmeter would show if the alternator is attempting to charge properly with the engine idling then what happens to the voltage when the engine is stopped.

**swarover** · 20th March 2018, 11:11 AM

Turns out it was the battery. Took it back to supplier again yesterday (400km round trip, again

) after charging it (again) to allegedly full and trying it to no avail in the car. Charged yet again to allegedly full, left it 24 hours and took it back to supplier, who found it to be cactus and they happily replaced it under warranty.

Cheers,

DiscoMick · 20th March 2018, 12:35 PM

Yes, doesn't surprise me. If a battery fails it can seem OK on a test, but then when put under a load can fall rapidly.
A 100 km trip should have been plenty to charge it, if it had been healthy.

Might also be worth thinking about the operations of the smart alternator, which can drop the output once it thinks the extra power is not needed to run the vehicle. We had this happen recently on the wife's Mazda, which had been doing lots of short trips and eventually the battery warning light came on. Charging it overnight fixed it.
Might be worthwhile putting the battery on a charger once a week and giving it a good session to keep it healthy.

Tombie · 20th March 2018, 03:40 PM

Mazda is vastly different in its operation to the D3.

However, lots of short trips in any vehicle means the battery is always on a road to failure, often never getting over 80% (this is where the myth about alternators not charging batteries spawned from).

A monthly session on a charger in the driveway is great for longevity. Make up a 12S connector and you don’t even need to lift the bonnet!

**Aussie Jeepster** · 20th March 2018, 08:55 PM

Originally Posted by Tombie

Mazda is vastly different in its operation to the D3.

However, lots of short trips in any vehicle means the battery is always on a road to failure, often never getting over 80% (this is where the myth about alternators not charging batteries spawned from).

A monthly session on a charger in the driveway is great for longevity. Make up a 12S connector and you don’t even need to lift the bonnet!

Tombie.
If you were to wire up a 12S plug, I'm guessing the (-) from the charger would be pin 3 and the (+) from the charger would be pin 4 - yes? Or would it be pin 2 for the (+)??
Alan

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