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Discussion Starter · #1 ·
Fitted a 12V BMS temporarily (ie not going to drive around with it) yesterday afternoon.
Traces from overnight attached.
This is on a Family, running 2.0 - I’ll screenshot the hardware spec at lunchtime if I remember.
Car has been sat on drive unused since Saturday morning and won’t get used again until Friday this week.
Ignoring the blip at the start, battery starts at 12.13V and by about 5 am this morning had dropped to about 12.05V, at which point, the HV battery kicks in and gives it a lift.
The two minor dips are when I walked past the car with keys in my pocket on the way to and from the local shop.
B788DCA6-C19A-4863-92BD-883C3472676B.png
F7F850CB-E9AF-431B-AC96-B0FC5C180C70.png
A97F3933-DA35-4899-8DFC-8BFCD96EF117.png

(can’t get images in right order on my phone, but hope it’s clear enough)

Hopefully, this shows shouldn’t be a problem on some cars/ updated cars.
I’ll keep an eye on it for rest of the week.
 

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VW ID.3 Worst Edition & Tesla M3 LR
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It does this on 0564 as well, my (identically titled!) thread shows it happening.

The mystery is why it sometimes fails to step in and do a maintenance charge, and it would be good to identify what is happening that’s draining the 12v in the first place.
 

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Discussion Starter · #3 ·
It does this on 0564 as well, my (identically titled!) thread shows it happening.

The mystery is why it sometimes fails to step in and do a maintenance charge, and it would be good to identify what is happening that’s draining the 12v in the first place.
Oops, sorry - searched for a thread but obviously didn’t do a very good job!

If you’ve got the link to hand, I’ll post to that one instead.
 

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Oops, sorry - searched for a thread but obviously didn’t do a very good job!

If you’ve got the link to hand, I’ll post to that one instead.
No it’s fine, no harm in another one, mine was getting cluttered with other stuff and you’re on different software as well.

Which monitor did you get?

I’ve got mine as an early warning of any issues now really, it sends a notification when voltage gets below a critical level.
 

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Discussion Starter · #5 ·
No it’s fine, no harm in another one, mine was getting cluttered with other stuff and you’re on different software as well.

Which monitor did you get?

I’ve got mine as an early warning of any issues now really, it sends a notification when voltage gets below a critical level.
Same as yours, I think - the BM2 one from Amazon? Someone had posted some pics of that one in use anyway.
Auto Battery Monitor BM2... https://www.amazon.co.uk/dp/B08F9ZN5XW?ref=ppx_pop_mob_ap_share
 

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Can you get a gadget that plugs in to the 12V socket in the boot to 'jump start' the car? It occurs to me all you need to do is get the electrics working long enough for the HV battery to start charging the 12V battery.
 

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Most 12V 'cigarette lighter' sockets are only rated for about 10 to 15 Amps and fused accordingly, so you probably can't push an adequate current through them. There are plenty of clip on the 12V battery boosters available powered by internal lithium ion cells that should be adequate though. I keep one in my boot, but have not had to use it. The only down side is self discharge and you have to remember to pop it on charge every month or two.
 

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Can you get a gadget that plugs in to the 12V socket in the boot to 'jump start' the car? It occurs to me all you need to do is get the electrics working long enough for the HV battery to start charging the 12V battery.
Isn’t that a bit of a chicken and egg approach? Surely you need juice from the 12V battery to feed whatever is plugged into the 12V socket?
 

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Isn’t that a bit of a chicken and egg approach? Surely you need juice from the 12V battery to feed whatever is plugged into the 12V socket?
No, I thought I'd heard of jump start gargets which work the other way, putting power into the 12V. I'm prepared to be wrong. Maybe it only worked on old cars.
 

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You can trickle charge 12v batteries via the 12v socket, but only if the socket is still live when the car is switched off, which a lot of accessory sockets aren’t.
 

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Mine is the CTEK, but I prefer the graphs on yours, that’s why I was wondering which one it was. 👍
Daft question, but can these battery monitors be kept connected, or do they have to be removed when the car is driven? Reason I ask is that I had a 12V battery die on my i3, so I'd be interested in getting one of these monitors but I am not keen on fitting it and taking it off every time I drive.
 

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Daft question, but can these battery monitors be kept connected, or do they have to be removed when the car is driven? Reason I ask is that I had a 12V battery die on my i3, so I'd be interested in getting one of these monitors but I am not keen on fitting it and taking it off every time I drive.
So long as you secure it, so bumps etc don’t strain and break leads then yes can be left connected.

Some may include a sticky pad with monitor or a piece of velcro.
 
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