Dead battery following alarm/electrical oddities

sludge wrote:

Edit: some talk about earth bolts, this is something I'm wanting to follow further, I just need to find a guide of all the known earth points on the MG TF.
 

Maybe this thread could help you:  https://www.the-t-bar.com/forum/roverlike-s-guides/97850-mg-f-tf-earth-points-locations-guide

You are a star! I had already been using your fuse/relay guide for help to find all possible blown fuses, I should've guessed you'd made an earth guide as well.

Take a look, maybe something else could help you as well, like boot hinge guide:  https://www.the-t-bar.com/forum/roverlike-s-guides

The boot hinge loom has already been highlighted. You need to open this up and check for broken wires. This happens to virtually every one of our cars due to bad design. Broken wires in there can cause a plethora of strange electrical issues!🤔

Another quick update, the battery tester came quite early this morning (gotta love Amazon) and immediately I wanted to see what was going on. Wanted to be as concise as possible, so pulled the battery again and put the tester on. Weirdly enough, the screen just flickered on and off. I reseated the clamps and got it into a position where the screen stayed on and it could 'start up' I suppose you'd call it.

Immediately though, "Er3" which according to the book means "This symbol indicates the tester is abnormal or the battery capacity is beyond the test range." Now, that last part is what threw me off as it's a tester for 12V lead acid batteries, and it has a test range of 5-20V so that would tell me that it's likely below the 5V threshold. But then it makes me curious as to how my charger again immediately told me the battery is fully charged.

I'm waiting for a friend to come over and I'll be using the charger and the tester on a known working battery, just to rule out a failure with them (very unlikely, but you have no idea h ow unlucky I am). Assuming they work, I will likely have to get a new battery but that scares me as there were no signs of degradation on the current battery. It's an Exide EB602 that came with the car but doesn't look too old.

Considering I was getting the strange door open beep on Saturday evening after an uneventful 2 hour, 77 mile drive, I don't want to spend £80/90 on a new battery only to have a fault kill it within a day again.

I'm new to MG Rover so I can't offer too much but with the advice of others, you trying a known battery I think you will home in on the fault.
If your battery is good it's time to look at the boot wiring loom I think!
Good luck!

David Aiketgate wrote:

The boot hinge loom has already been highlighted. You need to open this up and check for broken wires. This happens to virtually every one of our cars due to bad design. Broken wires in there can cause a plethora of strange electrical issues!🤔
 

I know it did, and I'd already checked in there yesterday and not seen anything that would cause concern. I will certainly have it all out again though to confirm once I know for sure if my battery is ok or not

One point about battery chargers; they are not all equal.
The old fashion charger was grunt from the moment it was connected, modern electronic devices tend to pussyfoot around their job.
They won’t, for instance, take a depleted battery & pump it up. Take my big electronicless charger, it will happily dump an almost limitless amount of current & it sounds like I’m trying to restart the heart of triceratops from a distance.
To spoof some of the more recent offerings into realising that they have got a job of work to do, is to connect a second reasonably healthy battery in parallel for a few moments before it’s safe to allow your charger out on its own.
“Not a lot of people know that”.
M

+1 For Airportable's advice. Put a pair of jump leads between yours and a 2nd battery. Then attach the battery charger and leave it like that for an hour or ideally several. Then take one of the jump leads off and leave the charger working on just your battery alone. Check that the charger is now applying a charge and if so now leave it to charge for several hours.

You mentioned you had got/ were going to get a multimeter. What is the voltage reading across the battery at present ? This would quickly confirm why the load tester could not show a reading.

Notanumber wrote:

+1 For Airportable's advice. Put a pair of jump leads between yours and a 2nd battery. Then attach the battery charger and leave it like that for an hour or ideally several. Then take one of the jump leads off and leave the charger working on just your battery alone. Check that the charger is now applying a charge and if so now leave it to charge for several hours.

You mentioned you had got/ were going to get a multimeter. What is the voltage reading across the battery at present ? This would quickly confirm why the load tester could not show a reading.

I'm definitely going to try this once I have the second battery available to me later.

As for the multimeter, I misplaced mine some time ago so waiting for the new one to arrive from Amazon at some point today. Annoyingly they got sent as separate deliveries. Once it comes, I intend to confirm the actual voltage on the battery currently.

One more quick update for now, because I feel like an idiot and I want those who said this before to get the validation they deserve; having left the battery for a few hours whilst I worked, I just went back to it and threw the tester on real quick to see if anything had changed. Immediately it was giving me a reading of 9.8V, 9.7V, 9.6V and going lower and lower, presumably from the stress of the tester being connected.

I put it back on the charger which as had done so far, immediately said it was full and when I put the tester back on it was at 10.1V, 10.0V, 9.9V and so on. So something is happening there that doesn't make sense, either the battery can't hold a full charge or the charger is crap like others have eluded to.

More importantly for this update though, and the reason I feel like a moron. So many mentioned checking the boot wiring loom, and I had looked - AT THE WRONG ONE. I just opened up the actual one on the hinge that you all so kindly pushed me to and it like a horror movie in there, see attached image. Of the seven wires I can count, 4 are cleanly disconnected with the others hanging on for dear life. I'm surprised it took this long for issues to arise. As soon as I finish work I'm gonna head to B&Q and grab a bunch of smaller gauge wire, as I only have big mains power style stuff, and go to work repairing them all and extended them too as others have suggested to ease the pressure on them when opening and closing the boot lid.

 

Wow! What a mess and pointed out by those in the know.
I am learning so much about these cars since I joined this Forum.
When you have sorted out that wiring check with the multimeter what the alternator is putting to the battery.