I went to start the car to go to the garage to fill up with fuel prior to setting off for a week in Wales. Unfortunately the battery was utterly dead. The voltmeter showed 2.7V It is a Hankook MF3100-1000 purchased from Battery Megastore nearly five years ago & had shown no signs of problems before. I tried charging overnight but it only showed 10.7V so looks like it is totally knackered.

I have an old battery I bought form Halfords about nine years ago. It worked well in the car for four years until I swapped it for the Hankook as BMS had a good deal. This had last been charged over a year ago but still showed 11.7V. I put this in the car & was able to jump start using the another old car battery I have that won't fit the P38. I put the Halfords battery on charge overnight & in the morning it showed 12.7V & had sufficient charge to use the remote locking/unlocking but not to start the car. I decided to order a new Hankook MF3100-1000 from BMS & have it delivered to our Welsh holiday cottage. We set off for Wales making a detour via Halfords to buy one of those Li-ion jump start battery packs as unfortunately the one that I bought about ten years back was knackered & no longer functioning. My wife sat in the car with the engine running while I popped into Halfords to collect the device which cost just over £100.

We made a couple of stops on the way. Once for coffee & a sandwich where I was able to start the car normally but when we stopped for petrol about half an hour later I had to use the jump start battery pack. When we arrived at the cottage I had an email form BMS confirming the order but with the delivery address as my home not the holiday cottage. I think the mess up must have been with their ordering system as I recall setting a delivery address different to the billing address & even added a note explaining why the delivery address was different to the billing address. I briefly considered ordering another Hankook MF3100-1000 from BMS delivered to the holiday address then return the other battery when I get home. I then decided the hassle & expense of shipping back a 25kg battery didn't make sense.

We have now been in Wales for five days with a nearly dead battery but have been managing OK. The car always starts easily & when hot usually doesn't need the jump start pack. Using the jump start pack only takes a minute or two & hasn't been much of an inconvenience but I will be glad to get back & fit the new battery that was delivered in under 24 hours. Lead acid batteries don't usually suddenly fail without warning but it does happen sometimes & this one was outside its four year warranty.

We arrived back in Essex OK after a week in Wales. I had to use the battery jump start pack a few times but usually when the engine was warm there was enough juice left in the battery to start it. On the 300+ mile journey we stopped for a coffee & sandwich then again for fuel & on both occasion the car started OK. We encountered a lot of heavy rain on the way back but reassuringly my sealing of the pollen filters etc meant no rain ingress. I seem to have fixed the leak from the overflowing A/C drains too so the passenger carpet is bone dry.

When we arrived in Essex I found the new Hankook MF3100-1000 waiting for me. I charged it overnight & fitted it to the car so it should now be good for another 4-5 years.

It seems odd to me that it just suddenly died. I've got one that I took off my car a couple years ago that I can still put on charge for a couple of hours and it is still usable.

Gilbertd wrote:

It seems odd to me that it just suddenly died. I've got one that I took off my car a couple years ago that I can still put on charge for a couple of hours and it is still usable.

It seemed odd to me too. It has always started really easily with the new starter motor you fitted 3+ years ago. From some Googling sudden failure of lead acid batteries does happen but is unusual. I will try leaving it on charge for an extended period to see whether it can recover at all.

I had a MF31-1000 do the same a couple of years ago. Was fine for about 7 years, and then seemed to suddenly drop to << 8V overnight. I did a recovery charge using my Ring charger which got it to hold about 12.2V, but the battery clearly needed replacing.

There must be something inside that finally gives up doing the chemical reactions.

Nigelbb: Impressed that after dropping below 3 volts for some time you could even get it to work ok with a Jump Start !
Hankook must be good..

With issues like this - and assuming it is not anything too obvious like the BeCM is not 'waking up' spuriously etc,
the best (only ?) way to diagnose this further is to use a clamp DC meter to look for parasitic drain/s of course on
the +ve feed - the usual way being to lock the car (and spoof the bonnet/catches) and watch and wait !!

These days there are lots of 12V Battery Testers around on e-bay - not the 'load' type - that can provide lots
of useful data StateOfHealth and StateOfCharge in particular.... as batteries age.

PS: As you may know Lead Acid batteries really don't like being below 11.8 volts for a while...
as they will suffer a permanent chemical change. Pulse 7-stage chargers etc can recover these
batteries to an extent but any/the reversal of sulphination is limited....

davew wrote:

With issues like this - and assuming it is not anything too obvious like the BeCM is not 'waking up' spuriously etc,
the best (only ?) way to diagnose this further is to use a clamp DC meter to look for parasitic drain/s of course on
the +ve feed - the usual way being to lock the car (and spoof the bonnet/catches) and watch and wait !!

As well as spoofing the bonnet switch (easiest jus tto unplug it), open driver's door & close the latch with a screwdriver. That way you can check BECM fuses for drain current while the car is "locked"

The plot thickens...

Today I went to start the car for the first time in a week & found the battery utterly dead. Too dead to even jump start with my jump start pack. The voltmeter read 3.7V. As luck would have it the MF3100-1000 I took out 3 weeks ago had been revived by leaving it on my Ring charger for a few days. I took out the new dead MF3100-1000 & put back the old working MF3100-1000.

The car started easily & all is good except I've obviously got something draining the battery & that is what drained the battery 3 weeks ago. It's obviously not an enormous drain like leaving the lights on as it's OK left for several days. I did notice when after I put the good battery on & before I even put the key in the ignition that I could hear crackling coming from a couple of the speakers. There was no pattern or rhythm to it just random soft crackling. What could be causing the speakers to crackle when the car isn't switched on? It's got to be related to the battery drain hasn't it?

If I remember correctly, I think you've got the DSP system? The DSP amp shouldn't be powered up unless the ignition and radio are both switched on. There's a wire from the head unit that signals the DSP amp (and the sub amp) that it has been switched on and only then should the two amps power up. It sounds like for some reason, they are staying powered up intermittently.

Can anyone recommend a reliable & reasonably priced DC clamp multimeter that I can use to investigate the battery drain? I have ordered two different models from Amazon & returned them because they were useless. They cost £35 & £50 respectively. I'm prepared to pay more if the bloody thing works reliably but obviously not hundreds of pounds.

This https://www.amazon.co.uk/Multimeter-Resistance-Capacitance-Frequency-Temperature/dp/B06XW6FMWQ/ref=sr_1_41 is the one I've got. On the 2A DC setting it will read down to under 20mA (or 0.02A as it shows on the display). When you switch it on, it defaults to AC so you have to press the function button to change it to DC and then the zero button before clamping it on the cable otherwise it reads the magnetic field of the planet.....

Gilbertd wrote:

This https://www.amazon.co.uk/Multimeter-Resistance-Capacitance-Frequency-Temperature/dp/B06XW6FMWQ/ref=sr_1_41 is the one I've got. On the 2A DC setting it will read down to under 20mA (or 0.02A as it shows on the display). When you switch it on, it defaults to AC so you have to press the function button to change it to DC and then the zero button before clamping it on the cable otherwise it reads the magnetic field of the planet.....

Thanks Richard. The choice of models is bewildering so personal recommendation is essential. I have ordered with delivery next Sunday.

That's the same DC Clamp Meter I have : Note it switches off after a few minutes (don't they all ?)

This was irritating as with one case I planned to point a CCTV camera at it and monitor it regularly from indoors...
(and I am not joking). Higher spec. (PSU powered) DC Clamps that stay on exist of course but are £££