12V battery drained in 48 hours whilst locked

When I was researching LFP chemistry back in 2010/2011, there was a massive amount of information on the net, I developed a rather crude spreadsheet that linked authors with claimed technical understanding .... and a pattern developed ... the cut and reword claim to research and with a further look at what each in this group were saying, was the same stuff, but no where was there any hard data backing it up.

The outliers became more interesting, digging through those to find the basis of the cut a paste groups information, showed a lot of summation and assumption and extrapolation being used from basic manufacturers documentation ..... and a lot was the result of not understanding what the Chinese to English translation was actually saying .... as an example, cells charged at 3C to 4v .... from there they determined that LFP should be charged to 4v every cycle ... what they missed was the wait for 1 hr before discharging ..... and if you tunnelled deeper, the rested voltage was 3.4v ..... the 3C charge rate was beyond the cells acceptance rate as it approached 100% SOC, the rest time of 1 hr was for the high surface voltage to settle as the lithium ions found a spot to settle into the graphite ....

A I faced with the same information and the percentage that said the same thing, was clearly the correct information, the outliers were discarded because some of them didn't come up with the same numbers ....

The only way I could sort fact from fiction, was to buy cells and test multiple cells each time to gauge what worked and what was nonsense ..... In 2011 $10,000 was a solid investment in stock to be torture tested, but as a result, I discovered, none of them were completely correct, some got close, most simply destroyed cells .....
These same charging parameters are being used in the BMS of most drop in batteries .....

Use AI as a base line and do research from there, it might be close on somethings, it will be so out of touch on others that the bloke on the stool beside you at the pub is likely to know more about it than the AI search engines ....
The problem is, a lot of these start up AI search engines, prioritise results from other AI generated "facts" ..... the blind leading the blind at an incredibly fast pace, backing each other up until someone has to intervene and set them back on course ... Elon Musk's Grok is a classic case of going off the rails by analysing information it had previously published and a lot of the other AI copied, therefore, what it said first was confirmed, then added a bit more to see if it was going in the right direction, copied by other AI who now believed they were on a good thing because so many other AI agreed ... then Grok was reassured he was headed in the right direction .... and rail completely off the rails :LOL: All within a few hrs

T1 Terry
 
I've had a reply from MG Customer Service today.

my question
"Should the high-voltage (traction) battery maintain and monitor the 12 V auxiliary battery even when the car is switched off and locked?"

Their answer
"It is possible for the system to monitor the 12 volt auxiliary battery, however this typically occurs only when the vehicle is actively charging or when the vehicle is being driven. When the vehicle is left unattended and remains unused for an extended period, the 12 volt battery may naturally lose charge, as would be expected with any motor vehicle under similar conditions."

I'm not sure exactly what to make of it, but it is in line with what the local MG garage told me, but contrary to other info I've gleaned, I did have a thought that it just may have been created by MG's own AI, who knows?
 
I've had a reply from MG Customer Service today.

my question
"Should the high-voltage (traction) battery maintain and monitor the 12 V auxiliary battery even when the car is switched off and locked?"

Their answer
"It is possible for the system to monitor the 12 volt auxiliary battery, however this typically occurs only when the vehicle is actively charging or when the vehicle is being driven. When the vehicle is left unattended and remains unused for an extended period, the 12 volt battery may naturally lose charge, as would be expected with any motor vehicle under similar conditions."

I'm not sure exactly what to make of it, but it is in line with what the local MG garage told me, but contrary to other info I've gleaned, I did have a thought that it just may have been created by MG's own AI, who knows?

It does explain why there are so many issues with 12v batteries dying.
 
If your car is going to be left for extended periods it might be worth investing in a switch.

 
I removed the permanent live from the fuse box to the Viofo A229 pro dash cam, and fitted a new short 23cm USB type A to USB type C cable (amazon details below) to the USB a socket to the left of the rear view mirror on my S5, it's very neat and very little cable is seen and switches off when the car is turned off.

I've been monitoring the 12V battery voltage, but using the car most days, it's not being left long enough to drain much voltage, it's too early to form a decent judgement, but I think the 12V battery isn't draining as quickly as before. MG said the dash cam was was pulling an abnormally high current from the 12V battery.

Cable details
Its important to buy the correct angles on both ends, otherwise it'll look ugly and show more cable than necessary, which I can't stand seeing :ROFLMAO:.

HUHANGGod Gold Plated Angled USB C Cable Extension 90 Degree Type C to USB 3.0 Left Angle Male Converter Data Sync USB-C Adapter cord (90°Type C-USB A Right). -- £6.99 incl delivery.
1768940555545.webp
 
I've left my current car and previous two evs for several weeks at a time without any issues.
The wife's MG4 has been a pain in the preverbial at times but never had a dead battery (although some 4's have)
There has to be an issue with certain MGs and MG need to figure it out
 
The only one of my 3 x MG4s that had a flat battery was the one that tried to bulldoze a white wooden guide post, setting off the airbags, 4 way flashers, really annoying internal alarm and the "abandon ship" message blinking on the drivers display ..... the only way to stop it is disconnect the 12v battery .... which no one did, so every scrap of stored energy was drained from it ......
It did recharge and is now the start battery for my 6.8 ltr diesel slant 6 Ford Cargo 1113 20ft container carrier/car carrier/equipment carrier/work bench .....
The silver repairable write off starts every time, even if left for mths, so they had it right with MG4, it seems they have dropped the ball since then .....
Probably the usual Chinese tradition "I can buy this item cheaper from another source" and what was a reliable product turns into problem child ....

I simply gave up getting things made in China, they started out great, ended up costing me more than I sold them for to fix .... if they could be fixed at all

A good friend had a camper trailer building business, couldn't compete with the Chinese imported product price and made the fatal error of buying a test batch from China. He inspected them all and was happy with the quality, so ordered a heap more ...... slightly more expensive .... and utter rubbish, it destroyed his reputation and his business that he had spent so much time developing ..... sad, but that is the way these things go .....

T1 Terry
 
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