Recovering from a REALLY flat battery?

BahnStormer77

BahnStormer77

BahnStormer
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I know why the battery is really flat (MMI unit is stuck in a loop "initialising" after a failed firmware update), but once I get the MMI unit out to send it for repairs (hopefully just a firmware reload), will I face any issues?

I assume the key coding will all be okay?

What about the MMI unit, once it comes back from repairs? (is it coded to the car or is there a PIN somewhere in the paperwork to re-enable it?)

How long to run the battery back up to decent level? I only use the car every 1-2 weeks, so I'm concerned that if I don't charge it enough, I'll be stuck in a never-ending loop of needing to jump start it.
 
I wonder under what conditions the battery would be flat as a pancake? The standard battery is quite a huge thing, and there's some clever electronics built into the latest ones I was told, so they don't actually go flat/dead?
 
I know what caused the battery issue - the MMI unit is stuck in a reboot loop of some sort: I attempted to upgrade the MMI firmware to 0900 via an SD card update. It was advertised as "genuine", but as it started, it suddenly flashed up a "NaviFix.LT" logo.... in hindsight, maybe I should have pulled the SD card then.... but a second later it said it was proceeding, but would "need to reboot several times".... a few minutes into the procedure the screen closed.... and it's never come back. Status on the DIS for all the MMI-based systems is just "initialising", but it was like that for ~6hrs... and when I checked the next day, I had to unlock the car with a physical key (and it wouldn't start), just a line of lights at the bottom of the dash..... now it doesn't even show the lights.
 
A decent run should charge it up, a cheap multimeter will let you see how it's holding the charge.
If you leave it for a couple of weeks might be an idea to hook it up to an 'intelligent battery charger' which will charge it and then maintain it in a conditioning mode, so safe to leave connected up for long periods.
I bought a sakura 1.5a for about £25 which, thankfully, brought back a £170 leisure battery I thought I had ruined.

Edit, my battery, a glass matting type, was so flat (about 3.0v) the charger wouldn't recognise it. I thought it was a goner but after a bit of googling I connected the flat battery to my car with jump leads and the charger to that, after about an hour or so there was enough juice in the dead battery to charge it as normal.
 
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  1. thanks for that, I'm considering that 1.5A Sakura... or for £10 more, the 5.3A one comes with Prime delivery too.... (HERE)
 
Stevieb2905 said:
Just double checked mine, it's actually the 5.3! Seems like a decent bit of kit.
Click to expand...

thanks Stevie - that does still do the float/maintenance charge once it is full?

I'm parked on the drive out front, so would probably prefer not to have an extension lead running out to the car 24x7, but I'll certainly do it for a few days to get the battery up to a decent state and then again if it has been a few weeks and I'm concerned about the car - its a petrol, so usually takes on first turnover, no need for glow plugs, etc to do their work...

I always used to have one of those emergency jump start kits in the car, but it's ten years old now and the batteries were well and truly dead... so I replaced it with one of these little things for £70:
Suaoki G7 Plus (600A peak, 18000mAh) + 80 PSI Air Compressor

Granted the air compressor is a separate little block, but the footprint is about the same as a 7-8" tablet computer, but obviously a bit chunkier. The great thing is that it's a backup phone charger, laptop power adapter and will jump start the car with ease, has an air compressor and fits in a neat little case that is about a quarter of the size and a tenth of the weight of just the battery part of the old unit... and that case includes all the adapters, clips, etc. It'll also re-charge off the car afterwards and has a tiny LCD power readout and LED torch on the side. (I'm not on commission, I promise, just impressed with how compact and effective it is)
 
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Yep it does the float charge, my car is in the drive as well, I run the extension lead out under the garage door and shove it under the car, I just leave the charger under the bonnet.
My cabby is probably due a new battery though, it's rarely over 12v, but I'll check out your product, sorry recommendation, as well :grinning:

Just looked at it, t's hard to believe such a small battery could turn over a 3.0tdi, the car's battery is massive.
 
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it doesn't flinch repeatedly starting he 3.0TFSI....

BTW - question... I assume the A6 has the Gel-type battery (maintenance free) not a lead acid type?
 
P1190424

Don't know about the A6, this is what's in mine, maintenance free.
PS I'm not really a sado who has battery pics to hand, honest, I only took it so I could google a replacement !
 

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Okay... not that sure now.... tried "Gel, 12V" and about 3-4 minutes in, it just starts beeping and the charging fails.
 
BahnStormer77 said:
Okay... not that sure now.... tried "Gel, 12V" and about 3-4 minutes in, it just starts beeping and the charging fails.
Click to expand...
I'm beginning to wonder if the battery is just so completely flattened that it can't recover until I take it for a long drive.
 
The smart chargers can have difficulty recognising a very flat battery (maybe they're not so clever after all).
I think I mentioned above how to trick it by connecting another in series. If your battery is not holding the charge though it may be like mine i.e. ******.

Edit, just to clarify I bought the charger to try and save an expensive leisure battery which was down to next to nothing, they are different from car batteries in that they are not meant to be totally discharged and I thought I had killed it. Thankfully it worked.

It keeps the car battery topped off as well but if it doesn't hold the charge it's probably had it.
 
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Stevieb2905 said:
The smart chargers can have difficulty recognising a very flat battery (maybe they're not so clever after all).
I think I mentioned above how to trick it by connecting another in series. If your battery is not holding the charge though it may be like mine i.e. ******.
Click to expand...
As a variation on your idea of tricking the charger into thinking there was a semi-okay battery there, I just jump-started the car, ran it for 20 miles, it seemed okay (headlights staying on after the car was switched off, locking/unlocking on the remote, etc... so then I connected the trickle charger and it has been on for the last hour without any errors.

I'll leave it overnight and see where we get to tomorrow...
 
That worked fine BTW. From being so flat that it seemed "unchargeable" to seemingly perfect... I'm keeping the mini jump start my in the car though!
 
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