Strangest 12v yet (self charging!)

Faults and Technical chat for the Honda E
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EEEE
Posts: 603
Joined: Mon Aug 16, 2021 10:33 am

Post by EEEE »

I did a little work on the Prelude recently, and decided to drive that to work pretty much all week and left the e at home.

I thought I would check in on the BM2 to see if all was well on the 'e' 12v, and I saw something I hadn't seen previously. Anyone else seen similar? Perhaps this is honda doing a remote check/calibration/test?


Last few days of the BM2 - connected directly to my new 55ah Yuasa battery.

A normal day - Trip to work , pop out at lunch, drive back in the evening. Most days look like this.

Screenshot_2024-05-27-17-29-32-076_com.dc.battery.monitor2.jpg



HV charging session at 12:30am, 12v is floated at 13.3v as we all know. Have the day off, take the car for its service. 1 Hour journey starting 7am, use my diag tool to check no errors. 12v is not charged (this some times does happen, normally when it gets warmer and the overnight voltage is close to 13v). Drop off at dealer at 8am, lots of ups and downs whilst they work on it etc. Drive car home 3:30pm and run various errands including late night trip.

Screenshot_2024-05-27-17-29-34-169_com.dc.battery.monitor2.jpg



Long overnight HV charge of 3hours, 12v is charged, residual is 13v. Drive car once on the 18th to nearby pub, and back again a few hours later. Totally normal. Nothing to see here.

Screenshot_2024-05-27-17-29-36-251_com.dc.battery.monitor2.jpg



Car isn't used except to move it off the drive way midday so I can do oil change on the Prelude and Civic

Screenshot_2024-05-27-17-29-40-070_com.dc.battery.monitor2.jpg



Small overnight HV charge. 12v tapers off from 13 to 12.8v overnight and throughout the day

Screenshot_2024-05-27-17-29-44-818_com.dc.battery.monitor2.jpg



21st, Car is not used all day.

Screenshot_2024-05-27-17-29-49-682_com.dc.battery.monitor2.jpg



22nd, Car is not used all day - but what happens at 1:15pm? Full 12v charging for 5 hours. I didn't initiate it, I wasn't even there. No action I could see outside on CCTV. Same for 9:15pm... Timings seem suspect (8 hours after the first?)

Screenshot_2024-05-27-17-29-54-561_com.dc.battery.monitor2.jpg



23rd, another little charge after 1am (again, 1:15am, 12 hours after the first mysterious charging). Drove car to work this day, normal pattern.

Screenshot_2024-05-27-17-30-00-065_com.dc.battery.monitor2.jpg



Not used for the next 4 days, voltage slowly coasts down to 12.7v where it sits now.

Screenshot_2024-05-27-17-30-06-675_com.dc.battery.monitor2.jpg


Screenshot_2024-05-27-17-30-12-014_com.dc.battery.monitor2.jpg




Whilst there is nothing wrong with this, its the first time I've seen the car do anything with its 12v by itself not in response to any user input. In fact, its positively great news if the car now decides it wants to wake up and use a bit of power to keep the 12v maintained and properly charged. Even if its once a week or once a fortnight, its one less thing to worry about.

The car did have the HV battery module updated, but no release notes provided sadly.

Anyone else see anything similar recently?

Cheers,

Scott
'21 e Advance - Charge Yellow - E1702RR alloys
'17 Civic Sport CVT
'00 Prelude 2.2VTi

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peniole
Posts: 24
Joined: Wed Sep 27, 2023 7:17 am

Post by peniole »

How was the battery module updated? And when?

I've kept ours offline, trying to avoid phantom drains and never found the app at all useful.

Had the yearly service recently, but they never mentioned any update either.
OCD = obsessive compulsive detailer

'22 Advance
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EEEE
Posts: 603
Joined: Mon Aug 16, 2021 10:33 am

Post by EEEE »

The modules were checked and updated as part of its yearly service at the main dealers. Whether that is relevant or not I can't say, but I've never seen the behaviour before.
'21 e Advance - Charge Yellow - E1702RR alloys
'17 Civic Sport CVT
'00 Prelude 2.2VTi
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