Parasitic drain or batteries dying?

**Colmoore** · 30th May 2023, 11:02 AM

Gday All

Been having starting issues with the 110.
She’s got 2 lead acid batteries, a maintenance free 800cca aux and standard maintainable 1000 cca main
wired through an older SC80 (the non switchable one)

Batteries were dropping to11.2v - further if left for a few days and she would only clutch start.
Connected batteries to charger in various ways over the past few weeks:
Straight through management via Anderson
Straight to each battery via terminals
Then disconnected one battery at a time and charged for 18+ hrs.

Charger is a 10a 7 stage unit.

Here’s my log:

24.5.23: 830am : Both batteries were 12.2 on ignition but dropped under 11.1v on cranking and she wouldn’t start. Roll started it.
: 9:15am : Disconnected aux only and voltage went up from 12.5 to 12.8.
Cranker dropped to 12.4 then to 12.1 in a few minutes.
Disconnected positive feed from cranker to battery management via fuse link between batteries and voltage went up to 12.4.

Put both batteries on seperate chargers at 10am
Aux charging with 7 stage charger
Main/cranker charging on old school single stage charger
** cranker still connected **

: after disconnecting chargers from both (6hrs on charge this time)

Readings from multimeter:
Cranker = 12.89 - after 10mins = 12.75 - after 1hr 12.71v
Disconnected cranker (no batteries connected to vehicle at all, also disconnected ecu plug) at 5pm
Cranker - 12.71v
Aux = 13.5v - after 10mins = 13.17 - after 1hr 13.06v

Left vehicle stand with ECU disconnected for 5 days, no charging in this time.
main battery/cranker connected to starter and under drivers seat electrical but not to battery management.

Aux battery disconnected

Multimeter readings after 5 days
Main - 12.55
Aux - 12.83

The main battery is old
The aux is less than 4 years old.

Any thoughts?

Cheers
Col

**Tikka7mm08** · 30th May 2023, 07:36 PM

Is the main battery buggered and sucking down the other one with it (or vice versa)?

**Tote** · 5th June 2023, 10:05 AM

Do you have a Tekonsha brake controller?

Regards,
Tote

**drivesafe** · 5th June 2023, 11:38 AM

Originally Posted by Colmoore

Multimeter readings after 5 days
Main - 12.55
Aux - 12.83

The main battery is old
The aux is less than 4 years old.

Any thoughts?

Cheers
Col

Hi Col and with the batteries disconnected, then those voltages are fine.

BUT, try reconnecting the SC80 and see how fast the voltages drop.

The SC80 will draw a small amount of power but if the batteries drop very slowly( over 4 or 5 days ), all is well.

If the batteries drop say overnight then you have a problem.

NOTE, depending on the condition of the batteries, any battery sitting at 12.4v or higher, is good.

Also, try the link below for load testing your cranking battery.

Scroll down the page till you get to “LOAD TEST”
https://www.aulro.com/afvb/the-verandah/246755-line-auto-electrical-info-10.html

**Tins** · 5th June 2023, 02:59 PM

Originally Posted by Tote

Do you have a Tekonsha brake controller?

Regards,
Tote

Hmm... Have you had issues with these? Both my Discos have them which I never use....

**Tote** · 5th June 2023, 03:35 PM

Originally Posted by Tins

Hmm... Have you had issues with these? Both my Discos have them which I never use....

They do have a habit of causing enough drain to flatten a weak battery if the vehicle is not driven reasonably frequently. I have a flash one that was in the Disco 3 now in in the Defender and I know it drains the battery. I recently got a basic one for SWMBO's CJ10 Jeep so I could tow the trailer and it is unplugged due to it drawing current and flattening the battery (enough that an old 3.3 litre diesel with a glow time of 30 seconds or more wont start) if the vehicle isn't started for a couple of weeks. I just unplug the 4 pin socket at the back of the controller.

Regards,
Tote

**Tins** · 5th June 2023, 03:39 PM

Originally Posted by Tote

They do have a habit of causing enough drain to flatten a weak battery if the vehicle is not driven reasonably frequently. I have a flash one that was in the Disco 3 now in in the Defender and I know it drains the battery. I recently got a basic one for SWMBO's CJ10 Jeep so I could tow the trailer and it is unplugged due to it drawing current and flattening the battery (enough that an old 3.3 litre diesel with a glow time of 30 seconds or more wont start) if the vehicle isn't started for a couple of weeks. I just unplug the 4 pin socket at the back of the controller.

Regards,
Tote

Cheers. That's interesting re the weak batt. Both my cars do that if the batt is old. Chased a parasitic drain on the D1 for a while.

Thanks, Tote.

**filcar** · 6th June 2023, 11:39 AM

Originally Posted by Tins

Hmm... Have you had issues with these? Both my Discos have them which I never use....

I had one in my Defender that developed a fault resulting in the brake lights coming on and staying on (even with the fuse removed), resulting in flat battery and melted high brake light lens on the door.

Going for a Redarc next time.

**DFender** · 12th June 2023, 11:05 AM

Before we write off the brake controller as the cause, I've been troubleshooting a parasitic power draw issue on a 2007 Defender 130 which I believe I have tracked down to the alternator.

When parked up, the car seems to be dragging around 0.6A at all times and eating the battery in a day or two. I troubleshooted by leaving the car completely off (no key in ignition) and removing all fuses, 1 by 1 and checking the draw with a clamp metre as I went. No success there, no matter what I removed, draw stayed the same.

After some googling - I found a few links about alternator diodes going, allowing the alternator to draw current even at rest. To test (again, car completely off and no key in ignition) I removed the alternator cable (brown) from the positive terminal and instantly the current draw dropped to nothing. Touching the cable back on, I saw a slight spark and current draw was instantly back at 0.6A. Removed again and nothing. Pretty sure it's the diodes.

Another avenue to test. At least it's easy to check

Cheers,
Matt

**Colmoore** · 23rd June 2023, 08:42 AM

Gday crew.

Thanks to everyone for your replies and ideas.

Batteries are holding 12.7 & 12.5v after being disconnected for the past 3 weeks!

I had a Tekonsha brake unit once, it drew lots of power & I didn’t rate it much but it was cheap!
Ive run Redarc brake controllers since, so it’s not that drawing power in my 110.

Btw, In the process of all this, I dug out the brake controller from behind the dash and found it’s a v3, identical to the one I pulled out of my written off 130 last year.
It was in my truck for less than a month and only used to tow my camper once

.
I’m selling it along with the loom, if anyone’s interested.

Been super busy so haven’t been on here for a bit but amongst work, family, life etc, I’ve been ploughing through my 110 wiring loom to chase the parasitic drain.
Auto elec isn’t one of my strong suites so I’ve probably spent longer than some would

*

My car’s been extensively modded, so there is a lot of extra wiring, some is functional, some obsolete and some superfluous; all I had to do was work out which witch was which

*

After checking all earths under the car, in engine bay, then all in the rear cabinets (compressor, 3rd battery, int/ext lighting, fridge, trailer connections and rear view camera etc) I began pulling the centre console and dash apart.
(I had access to my wife’s car for awhile, so I decided to go all in!)

Found the insulation on the active wire to the Kenwood sound system had melted

exposing copper every 20mm or so, over the whole length and it was a right pillock to chase through the middle of the loom

Also found damaged switch wire for the compressor, rear locker wire and a loose connection or 2.

Replaced the damaged wires and fitted a small fuse to the stereo active.
Now I’m in the process of grouping cables into split conduit, labelling them, cleaning and tightening every connection and hopefully she’ll be good for the next 17 years……..

All batteries have been disconnected during this process, so I’ll connect them back up and test everything I can before putting dash and cubby box back together.

Fingers crossed.
To be continued……..

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