Sean.
Active Member
Nearly 5 years old. Should I be worried? Maybe I’ll look up the service manual and run an inductance/CCA test on the existing battery.
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12 volt battery insurance/backup plan
- Thread starter M3noob
- Start date
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As others have said, if you think the battery is only good for 2 years (personally I'd say you should expect 3 years, and early failures were due to poor charging that Tesla has now fixed in software) then why not just replace the original rather than carrying around the spare?
12v batteries are bolted down for good reason - in an accident that is a heavy object that could do a lot of damage and get acid leaks on top of any physical damage it could do.
Lead acid batteries need to be kept charged so unless you regularly charge that battery it will end up in a worse state than your original.
If I felt the need to carry a 12v battery then I would have just gone with a small 12v motorbike battery and leads to use as a temporary replacement to get me out of a tight spot - carrying around a full size replacement seems overkill.
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I think the idea is that you can pop the bonnet using your small battery and then get access to the 12v battery in the car ... attach ye olde jump leads to any other 12v vehicle battery and hope that starts the car and lets you in. (Of course few people carry jump leads these days so it's probably going to need a call to AA or other rescue service anyway! Having said that I do carry my home made mini fob which contains the necessary 12v battery to start that process.)
This is my DIY mini fob that nowadays contains a plastic wrapped 23A 12v battery as well as my old keycard electronics (it was breaking after sitting on it once too often!)
DIY Tesla Key
A what I did to my Tesla today type thread. I wanted a backup for my phone key just in case my phone died in any way while I was out. I don't like carrying the key card around with me as I don't take a wallet out with me any more, and I'd only end up losing it or leaving it in the wrong...
teslamotorsclub.com
You can fit the MN23 with the leads behind the tow cover in the front bumper. Put one in a good plastic bag, then insulation tape it to the leads so its there when you need it. Just press on the cover around the 2 o'clock position and pull it out, then feed the wires back in once you've put the battery in place. Then you've a 12v right where you need it should the situation ever arise.
And in case someone is wondering if this means your frunk could be opened by a bad person… this battery trick only works to open the bonnet if your main 12v battery has actually failed.
All that is on board. I stow the rescue 12V in the lower boot so no spillage/crash disasters anticipated. I have a 12V lithium jumper battery (with a handy torch/beacon that signals SOS if required) stowed in the frunk and an MN23 secreted about the tow eye port. I charge the rescue battery weekly with a trickle charge when I am not gadding about.
All good, but I am sure, like 100%, that you can purchase a simple 12v battery at any petrol station in france. Why you want to carry it, really? You definitelly were not carrying spare batteries or alternators with you in your old ICE car, were you?
ISTR the M3 battery is an uncommon size. I'm unwilling to surrender to chance and the rape of a motorway service station/recovery assistant's assessment of the depth of my crisis. When I drove a 64 Lotus Elan back in the States, a spare battery option was a consideration ;-) Smith Electrics - still revenging the revolutionary war of 1776.
but what are the chances for it to fail?
it is always charged by your HV battery. Unless THAT fails (like for Mr miserable) but in this case you are in much deeper trouble than spare 12v battery.
just replace your 12V every year or two and that's it, if you are that afraid.
to be fair - you can buy the 116 (or whatever) li-ion battery and install it instead your lead battery.
in my opinion, which is worth 0 ofcourse) this makes no sense. Do you carry spare motor and other things? sh!t might happen to it as well.
it is always charged by your HV battery. Unless THAT fails (like for Mr miserable) but in this case you are in much deeper trouble than spare 12v battery.
just replace your 12V every year or two and that's it, if you are that afraid.
to be fair - you can buy the 116 (or whatever) li-ion battery and install it instead your lead battery.
in my opinion, which is worth 0 ofcourse) this makes no sense. Do you carry spare motor and other things? sh!t might happen to it as well.
Sadly I know what an inconvenience 12v failure is, although to be fair, it actually turned out to be a safety issue with the main battery that caused the car to shutdown.
Nevertheless I now have an MN 23 taped to the 12v wires behind the towing eye so that I can quickly and easily get into the frunk where I keep a more powerful jumper battery and most importantly a USB mobile phone charging cable (attached to a juice pack).
A major point I took away from my experience earlier this year was how long I spent on the phone organising the recovery (or not!).
I also carry a RoadHero spare on any long journeys and a puncture repair kit too.
The trouble with the dreaded 12v failure is that it's quite possible that you will have no idea it's coming.
It's just reminded me to fit one of those bluetooth battery monitors - I shall do it on Sunday.
Nevertheless I now have an MN 23 taped to the 12v wires behind the towing eye so that I can quickly and easily get into the frunk where I keep a more powerful jumper battery and most importantly a USB mobile phone charging cable (attached to a juice pack).
A major point I took away from my experience earlier this year was how long I spent on the phone organising the recovery (or not!).
I also carry a RoadHero spare on any long journeys and a puncture repair kit too.
The trouble with the dreaded 12v failure is that it's quite possible that you will have no idea it's coming.
It's just reminded me to fit one of those bluetooth battery monitors - I shall do it on Sunday.
But it's like failing ICE - in some cases it happens unexpectedly.
In general and normal use you should not have issues with 12V battery and in you case it was caysed by more serious underlying issue.
But as result you did not start to carry a spare 12V battery, especially in lower boot
It just makes very little sense.
12V on our X lasted 5 years, plenty of warning when it did start to not charge. The car essentially doesn't turn off and used the main traction battery, so vampire drain went crazy (5%+ a day) inorder to ensure the 12V didn't die completely
In your case even if you replaced the 12V with brand new one it would have died again almost straight away.
If the main traction battery is working the 12V shouldn't be a worry, having good break down cover on the other hand is a life saver in any situation.
Not naming any names, but the fact I was able to catch an evening ferry the same day as having a puncture at 10am was pretty amazing. Am 100% sure if I had been relying on Tesla recovery the half term holiday would have been cancelled!!
