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12v Battery Monitoring

9K views 48 replies 17 participants last post by  Woodulike 
#1 ·
I fitted a CTEK battery monitor to my ID.3 about 48 hours ago, just to see what was happening with the battery whilst the car is idle.

Nothing too exciting so far, SOC seems to have gone from 100% to 98% in that time, but I’ll see what happens in the next few days. The tiny voltage drop seems to coincide with when I’ve used the WeConnect ID App.

I need to use the car tomorrow morning, but I’ll update as it sits over Christmas.

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#5 ·
CTX BATTERY SENSE

About £45. It's a sad state of affairs that EVs seem to need these. I have a manual display visible from outside of my LEAF due to similar concerns.
I haven’t suffered any 12v failures yet, I don’t think the car sits long enough unused, but I was interested in identifying anything that might cause a sudden flat battery as reported by other owners.

I had to replace the 12v on my GTE, at 3 years old.

The ID.3 12v battery is 61Ah, not sure if that’s a typical size for an EV or not.
 
#6 ·
Sounds typical. Ampera was 65 Ah I think. Swapped out my Bosch S5 after 3 years 'coz it went below 12.0 briefly, but battery is since doing well in wife's Citroen C1! Juuuust fits in! And has stopped her flat-battery-in-the-morning problems! :)
 
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#7 ·
Actually a lot of EVs have had much smaller 12v batteries than that.. I suspect (hope?) that car manufacturers are watching these threads during lockdown, with so many of their client's cars sitting idle (not to mention their own staff), and that in future 12v battery state monitoring will not just be part of the car's system it will be exposed to the drivers with guidance about when (and how) to consider charging them. In an even less ridiculous world, they'll incorporate a more efficient method for drawing power from the HV pack in an EV to top up the 12v battery, but I'm not holding too much hope for that.
Cars should just have a 12v charge socket under the bonnet. "Plug one of <these> in <here>". Sorted. Like my 1995 Corrado has now.. :)
 
#8 ·
Did pop bonnet and can see the neg charging stud, and presume the pos is under the plastic cover. So if dies at home can easily give it a charge

On fitting a battery monitor - was thinking a Victron one (have one to monitor small lithium off-grid house battery, so already using app). Question is around connecting - anyone got a youtube clip of attaching a monitor - concern is around attaching wiring securely without dropping the 12V supply, since I presume the car will moan/reset fully.


Is the monitor I use, comes with a sticky pad and fuse in wiring just in case.
 
#10 ·
You can slacken off the positive and negative battery stud nuts to slide a terminal in behind it (assuming your monitor has U shaped terminals?) without the main terminal clamp coming off the battery post.

I found bending the terminal 45 degrees made it easier to slide behind the nut.
 
#9 ·
I've done several now. Since you're essentially loosening the main clamp to attach the sensor you kinda have to hold the clamp against the battery post while it's not tight. Just be careful not to touch anything else at the same time. Yes it's a little risky that the car will lose power momentarily, but be careful. I've not broken anything yet ..
 
#11 ·
In the LEAF there are a number of always on fuses so I just used a fuse holder tap to get a positive and a negative connection to the body. This suited me as I wanted the display inside but visible on the dash through one of the A pillar windows.
 
#12 ·
I have too recently fitted a 12V Bluetooth monitor, probably the same as BatteryLife, since the app looks the same.
Rather than play with the 12 battery terminals, I found a more convenient and easily accessible place to fit it.
Under the +12V cover, mine had a spare terminal which I used for +12. For the –ve, I used the nearby headlight mounting point.
Yes, I tested it before fitting, both seemed like a reliable source for the 12V and less risk of disconnecting the battery inadvertently.
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Why is there a plastic bag stuffed in here? (Red Arrow)


Now the interesting bits…
During a home charge, the 12V is charged as well, monitor showing approx. 14.9V. Nothing new here. We all know both batteries get charged.
When HV finished charging, monitor shows 12.7V. I was hoping it would be higher, but that is what it is for mine.
I left the granny charger plugged in overnight to see if there was any ill effects. I can only say there was no significant 12V battery drain. Next day 12.69V.

The key fob proximity does affect the car! As I approach the car, the fob starts to blink, I guess forever (well at least 5 minutes). At this time the battery voltage drops to 12.1V. My take is that the car awakes and obviously draining the 12V somewhat. Unfortunately I don’t have a clamp meter to see how much current was being drawn. But I suspect it is not a trivial amount.
I hung around for another 5 mins and key fob still flashing and battery monitor still at 12.1V. Could this be the infamous battery drain? The key fob being too near the car???
I moved away until the fob led stopped flashing. About 3 minutes later the 12V started to creep back to 12.6V. Car must have gone back to sleep.
I repeated this, but put the fob into a metal biscuit tin, but near the car. Same effect; well, we know a metal tin cuts off the signal.

As already stated, the mains was still plugged in, but finished charging, so the charge port light was off.
I used the App to initiate preheating. The charge port light came on (green) and I could hear some fans coming on. The house meter was showing a draw of 3KW. Good, it was preheating from the mains and not the HV battery. The battery monitor showed it was charging at a measly 12.9V, if one could call it charging.
I gave it 5 mins and unlocked the car. BTW, mine is setup to unlock when I touch the door handle, not as I approach.
When it unlocked, the 12V battery was still charging at 12.9V. However when I sat down, the charging voltage jumped to 14.9V. Yay, it was charging properly. The fans were still belting out due to preheat. So I turned them off.
I sat in the car for 15 mins playing with the menus to see if I could fathom the headlight setting (to set it so we drive on the left)… For another episode.

To summarise:
Having the key fob too near the car, keeps the car awake and probably drains the key fob as well.
I suspect my battery is on the verge of dying. 12.6V locked and key fob far away is not high enough in my books.
A 15 minute charge/drive per day is not really enough to keep the 12V battery from dying since I lost 0.1V in this one off experiment and the 15min charge was not enough to replenish the 12V drain.
 
#13 ·
If meter is showing 12.9V when car is also connected to the mains it is possible the 12V charging circuit is possibly just matching power requirements to such that there is no battery drain at that point. Thinking charger circuit may do this after it has seen the battery reach a 100% SOC state.
 
#14 ·
@ElectricMadMan I like your connections, will see if I can do the same with the BM2 I've got lined up. I'd suggest that you find a way to stop the unit flapping around. It's going to get the wires stressed & flexed as you drive, so maybe put something like a double-sided sticky foam pad to fasten it to side of battery maybe? Or giant cable-tie(s) around battery?
 
#16 · (Edited)
This looks like a very useful thread to me. Love our ID.3 of a few days, but it just died with the 12v battery at 3.85v when I checked (and photographed). Asked VW to fix and replace with a useable car, but seeing as I got it going again (spare key, 12v charger etc) and it is two days before Christmas during a pandemic, they seem not to have capacity to assist, unless it becomes completely unusable.

So I am keen to monitor the voltage and current and understand what is happening. ID.3 Life on 0564 software.

Please confirm the major suspects for overnight drain? My experience and reading suggests:

1. Keyless entry with keys close and activating car systems (should not be us, as Life is without this)
2. Regular phone app checks may be draining car 12v as car responds (seems the car has an active 4G, GPS, DAB aerial, so this may contribute)
3. Some heating/ventilation issue that occurs even when car is shutdown (anyone have further info?)
4. Central screen not closing down correctly (AA man theory on FB)
5. AC charger still plugged in, but finished, rumoured to cause 12v consumption issue
6. ACC radar using heater or staying live while car is off
7. Pre-damaged 12v battery after waiting a long time before shipping
8. Something else?

I think between us we can solve this, or at least explain it.

Evidence below of some current going to the active aerial.

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#18 ·
The current going to the aerial makes sense, otherwise the app wouldn't be able to work at all. Not that it excuses the complete draining of the battery of course.

I have read a couple of accounts that mention the 2.0 (0783) software doesn't actually "fix" the battery drain issue, but allows the main HV battery to keep the 12v topped up when not plugged in. This should prevent the problem of having a dead car almost overnight as some have experienced, but still doesn't explain the real cause.
 
#23 ·
A few days have passed and here are some more pictures of the battery monitor revealing interesting data.
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On the 26th the car was still plugged into the granny charger. No unusual activity, voltage 12.79 dropping to 12.76 just as I went out. You can see the outward leg lasting 1 hour, and similarly almost an hour on the way back and each leg, the 12V was being charged as expected. When I got back, plugged it straight into the granny charger. What is unusual is that it was not a nice steady voltage, but a constant pulsating kind of charging. It looks like it finished charging just after midnight.
On the 27th, after charging you can see the 12V battery is pretty close to 13V. Nice, after all it was being charged for a good 8 hours.
At midday, I took it out for a wash. The voltage activity was me being close to the car as expected when you wash it, but annoyingly, when I finished being "near the car" the voltage was 12.51. I lost what feels like a sizeable chunk of 12V just washing and being near the car.
Today 28th. I've put on a 12v charger on it. Trying hard not to be "another 12v" victim.
 
#30 ·
At midday, I took it out for a wash. The voltage activity was me being close to the car as expected when you wash it, but annoyingly, when I finished being "near the car" the voltage was 12.51. I lost what feels like a sizeable chunk of 12V just washing and being near the car.
At rest, a plain lead-acid battery will be around 12.7V fully charged, and about 12.1V at 50% discharge. Active discharge will make these figures lower.

In my previous (non-EV) experience, voltages between 12.7V and 13V are a consequence of "surface effect" (higher charge at the surface of the plates than deep down), and will reduce to the 12.7V level quite quickly once the battery is actually put to any use.

12.51V therefore isn't too bad a level for a lead-acid battery - likely in the 80-90% range. Still not good for a car to lose that amount that quickly, without realising it should fill it up from the far larger reservoir under the floor.
 
#24 ·
Interesting spike at ~14:00 while you were washing the car. Did you start it at around that time or do anything to allow the HV battery to charge the 12v? I'm amazed at the amount of draw during those four hours - what on earth was drawing around 4 Amps (1/2 of 60 Ah capacity ÷ 4 ~ 4 Amps) throughout that time?
 
#26 ·
From his commentary he ‘took it out to wash it’ so yes, I’m assuming the car was started.

How are you deducing Amps being drawn from a voltage plot?

When you go near/in an ID.3 with the key, all sorts of things switch on, not least the headlights do the welcome dance, you hear at least one pump start, possibly for coolant, and if you go near the door aperture then the instruments all wake up and fans start running even if you lean on the seat with a hand.

Probably all a bit unnecessary whilst you’re washing it, but I guess the idea is that it’s ready for when you get in and want to drive it.
 
#31 ·
I'm wondering if any of the issues with the 12v battery are a batch of bad batteries which the software which decides on charging isn't coping or monitoring properly. My previous car was a diesel Nissan Pulsar, once it was about 6 months old the stop start system became very intermittent, it would stop the engine sometimes, about half the time it just left it running, it never had a problem restarting (or starting from cold), at the time I just thought it was a poor system and not a 'fault' as nothing was ever reported or no other side effects noticed. At 3 years old the car refused to start, the AA jump started me but couldn't find an issue with the battery or charging system, it had just got a very low charge. 2 months later the same happened, this time the AA found a fault with the battery and swapped it. After that though the stop start worked perfectly every time (for 1.5 years until I got rid of the car) which made me wonder if the car actually knew something wasn't quite right with the battery for 2.5 years, not enough to warn me but enough not to risk doing the stop start.
 
#32 ·
VW have acknowledged a software issue is causing battery drain which 2.1 should solve at root cause. But maybe some battery hardware issues are tipping some over the edge.
I personally am not fiddling with settings, functionality too much on 0564, in case it triggers some software corruption.
 
#33 ·
BatteryLife has a new video up on YouTube...


His battery monitor seems to have caught a day of power drain, and the subsequent recharge triggered by the 2.0 software (0783).

It looks like the drain happens in lots of small bursts, with recovery times of maybe an hour in between. Charging was triggered by a recovered voltage level of 12.0V.

If I'm right in previous posts, that's about 50%... In a 60 Ahr battery, that's going to need 30Ahr to refill, or about 400Whr.
 
#34 ·
‘Solved’ is pushing it a bit! Certainly not solving the root cause problem.
But looks like 0783 includes a work around, I guess amongst a whole lot of other stuff.
The question is why didn’t VW do a recall and apply a patch specifically to implement this workaround?
Ps. Battery Life says in his comments that he believes VW don’t actually know what the root cause problem is😏
 
#35 ·
Definitely not solved ... But better than needing to sit in the car for 30 minutes every day.

A few more calculations...
a) Each peak drop is more than 0.5V, which suggests a hefty draw from the battery. Got to be more than 5 amps. On my leisure battery bank, I equate a voltage drop of 0.1V with a draw of 5A (so 0.2V with 10A etc), but that's a much bigger capacity.

b) There are maybe 25 such peaks over the 26th-27th, before an auto recharge is triggered. If 30ish Ahrs were consumed (half the capacity), that's about 1 Ahr on each spike.

That would be 60 Amps for 1 minute, or 30 Amps for 2 minutes. Doesn't look to be any longer than that.

If VW don't know what's causing it, it looks like it should be easily traceable!
 
#36 ·
This might help.

I saw one of those tacky ads on Facebook, and got this monitor for ‘free’ which is actually £11.43 delivered.


it seems to show the 12V battery level, as well as the HV SOC.

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the Bluetooth range is a bit crap as it won’t even work through my garage door, but still.
 
#37 ·
I've been upgraded to 0783, but it looks like I still have a battery drain issue.

The traction battery was at 82% when I arrived home last night, and at 78% this morning. I guess the 12V battery needed a hefty recharge overnight. That's about 2.3kWhr, which sounds an awful lot to recharge a 60Ahr battery (ie 720Whr capacity). I suspect the 12V is now fubar.

I have a monitor to fit, once daytime temps get warm enough...
 
#40 ·
Another small update.

I opened the bedroom curtains this morning and noticed the green charging light was on.

Wondering whether I’d inadvertently set a departure time going or the car had decided to charge to 100%, I checked the App and it was as I’d left it.

I checked the CTEK monitor in the App, and it was at 11.8v but climbing steadily. Temp was 0c. It looked to me like the car had decided the 12v was getting too low and was trickle charging it back up. As my car is always plugged in, this was using some charge so the car was topping that up at the same time.

Probably how it’s designed to work, and probably what doesn’t kick in when others find the battery flat. What I don’t know is what is drawing current from the 12v when idle, but looking at the graph in the App something is nibbling away at it.

The car is completely covered in a uniform frost, with no hot spots around the antennae or windscreen.


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Last time is used the car was 11th Jan.
 
#42 ·
We all know for keyless entry cars, bringing the key near the car wakes it up and the 12V gets used up...
There is a way to minimise it, in fact not use any at all, but it's not for everyone.
I inadvertently left the car unlocked one day (in the garage). As I approached the car with the key, the familiar 12V drop did not occur, huh?
I touched (not yet pull) the door handle expecting to hear the unlock, nothing... no lights, no clicks, no whirring of fans. I thought, oh, no, this is it 12V victim...
But the 12V monitor was showing fine all the time, I monitor it 24/7 I dream 12V...
Pulling gently on the door handle, the door opens and Phew!, the lights, fans, clicks all the familiar noises are present.
The 12V barely drops, but I have now sat on the seat and it jumps to 15V. Play, Play, Play, Play Play...
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See, entered the car and no significant 12V drop, if anything it was 0.1V higher after playing for 1/2 hour.
Leaving the car unlocked is not what I am recomending, just an observation....
 
#43 ·
Well it's been a month and our 12v battery is dead..............In our Kia Picanto!

Turns out leaving an ICE car sat around for a month or so only using it to do a mile or two isn't a good idea so I've got the battery out and I'm charging it up now but I don't hold out much hope it couldn't even do the central locking!!
 
#44 ·
My wife collected my car from the garage late this afternoon, after the update to 2.0 was finished. I got in the car just after 9pm to check the headlights don't point at the floor and I have the amber warning that the 12V battery is low and needs driving to charge it up. My wife doesn't remember seeing any warnings or any amber lights on the car but it is the first time she has driven it. The car has sat at the dealers for several days while it has been updated and I expect that has been enough for the battery charge to drop too low. I went for a drive for about 30 minutes but it still have the warning. I realise it needs a long drive to fully charge it but that's not something I want to be doing at this time of night. I've left the car plugged in and charging the traction battery and hoping it will charge the 12V battery sufficiently to switch on tomorrow morning.
@Tooks, have you seen your battery getting low any more, or have you seen it top the battery up again while you are parked and charging?

I hadn't bothered getting a battery monitor as it very rare the car isn't driven every day so it semed unlikely I would have a problem. I do have a electrical tester that will measure voltage. Maybe I should test the battery voltage with that now and again in the morning.

I will find out if the updated software charges the battery up when it gets low.
 
#45 ·
I've left the car plugged in and charging the traction battery and hoping it will charge the 12V battery sufficiently to switch on tomorrow morning.
@Tooks, have you seen your battery getting low any more, or have you seen it top the battery up again while you are parked and charging?
Since my post 6 days ago, nothing to report and the battery has stayed above 12v, and the car has only been a couple of miles to the Drs surgery and back. Checking the monitor voltage and SOC log just now, it’s been fairly static.

I think now that you’re plugged in and charging it should raise the 12v battery voltage as well, and I expect by the morning the warning will have gone?
 
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