Topic

I have a mechanic mate who sourced it for me using his own account, will have a word and see if he can do anything, as he does buy an insane amount of stuff from ECP.

Sundance

SundanceUK wrote: wrote:

Following on from my post in what ya been doing thread, regarding my flat battery and the speed it drains down at - most of us are experiencing this kind of issue come this time of year, I have been doing some of my own checks, similar to Mr Bluestreak, but thought this thread a better place to record my findings!
As some of you may have read, my battery drains down while standing and has now been fully drained three times since I bought it about 9 months ago. I find that I am needing to start my car every 3 or four days and run it for 10 mins at least to maintain a healthy charge in my battery.

So out with my trusty Fluke multimeter and Clip on ammeter and see what is happening to my battery and why it seems to be going flat so quickly.
First up, its a voltage check, and this is after the car has been standing overnight - I did a short run of about 12 miles last night. At least it started ok this morning, anyhow heres what the Multimeter showed when I checked the Voltage first thing.

As you see, its alarmingly low at under 12 volts - a good healthy battery should really be up to 13 volts or so....maybe I need to call a warranty claim on this one...

Now with the engine started, good news my Alternator brings the system voltage up to a nice and healthy 14.2 volts. Once the engine is turned off, the battery voltage slowly falls and holds, for now at about 12.4 volts, however this will drop with the car standing at about 0.1 volt per hour.

Now lets see how much load there is on the battery....here is a current reading with the bonnet open - note my TF has a bonnet courtesy light fitted, so this is on during this test. A current drain of 0.3 A is noted.

Now with the bonnet closed (simulated by pressing the bonnet switch) ..

And the load drops to 0.2 A, much as is to be expected.

Finally lets see what happens when we lock the car and set the immobiliser....

The current drain leaps to a whopping 0.8 A !

Now I am understanding why the battery is draining after such a short time. A bit of simple maths tells us that a 63 A/h battery having a drain of 0.8 A should maintain its charge for about 79 hours or 3 1/4 days. This is what I am seeing when my battery is failing after 3 or four days!
It now makes sense to me to fit a larger capacity battery, as there is room for it in the bay, so maybe a 80 or even 100 A/h battery will be fitted when I replace it.

Sundance

I just got myself a clamp meter and checked the amp drain at the battery after the car has been siting for close to half and hour and the meter read 0.2 A. Normally my F's battery goes flat if the car sits for about 2 weeks. I'm guessing this is because the security system isn't unlatching?

I solved my battery draining issue, by replacing the battery and also re-wiring the USB socket I fitted to an ignition switched feed instead of being permanently on. My battery now holds it charge and I can confidently leave it for a couple of weeks and know it will start ok.
Incidentally, I measured up the battery tray, and found that I could not source a larger battery that would fit in the space available. 63Ah is the best I could get.
My DC clip on ammeter is brill, one of the best bits of kit I own, and has solved many problems over the years both on my car and on the job at work.

Sundance