Dead Honda e

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 »

Welcome to the club! The only thing you can do to stave off flat 12v battery is:

1) slap in new battery, larger if your feeling adventurous. This only masks the problem however.

2) fit a bm2 battery monitor. It won't fix the problem, but it will give you a lot of detail when it happens again and might help pinpoint the as of yet unknown action that causes the intermittent drain (most likely door handles or door latch micro switches), alongside the rare android update for infotainment.

3) If you are so inclined, join the effort to investigate what causes it. My car is out of warranty now so I'm quite happy to start probing it and experiment.

As you say, it's madness to fit a 12v charging port externally. I was close to doing so, but it's not the solution. I had wanted to fit a higher amperage connector somewhere external so the car can be jumped back to life, as additional charging isn't the way to go. Perhaps a resettable 12v low voltage cut out relay/circuit is more appropriate, with an externally accessible reset switch. I'm sure they exist. Unlocking the car with the key, then doing the bonnet , then jumping it is a bit of a pain. I could just about accept pressing a button lol.

One thing that may help is slower mains charging. The battery is held at 13.3v float during HV charging. If you can set your charge rate on your charger to the lowest setting, your overnight charge session becomes longer, and so the 12v is floated for longer. That's not bulk charging, but it's probably better than less time charging.
'21 e Advance - Charge Yellow - E1702RR alloys
'17 Civic Sport CVT
'00 Prelude 2.2VTi

s2ke
Posts: 23
Joined: Fri Dec 20, 2019 7:00 am

Post by s2ke »

JondaE wrote: Sat Jul 06, 2024 11:29 am Another dead E owner here. It's happened to us three times now. I really appreciate the information in this forum thread - it's good to know we're not alone. Our E is a 2022 Advance, which my wife bought ex-demo in August 2023. A couple of months later it was dead on the drive one morning. We called Honda Assist - AA came out and fast charged the 12v battery into life and told us to go for a long drive to charge it properly - which I found amazing at the time as I thought the need to drive to charge the battery was limited to ICEs. Thanks to this forum I've since learned a lot more about the E's charging system and the seat belt trick which does seem to work.

Just prior to this particular failure, the car had been trying (and failing) to pull an OTA update and we figured that might have had something to do with it. We did the update via mobile phone Wi-Fi and all was fine after that and through the winter.

In early June we woke up to it dead again. This time there'd been no sign of the car needing an update. I measured the 12v battery with a multimeter: 7v. We called Honda Assist - AA man came again, and did a fast charge to get the car on. This time I left the driver's seat belt plugged in and the car on, sitting in the drive. The main vehicle battery drained about 2% over the 90 mins I left it on, but the 12v system was fine (though my meter had gone on the blink so I didn't measure the voltage at the end of this period). We booked it into the local Honda dealership who said it it had an outstanding recall for a software update (the car hadn't notified us in any way, and neither had Honda). After a couple of hours they phoned and said "Software update's done - you can collect the car", but no-one had checked the battery or investigated the fault. We pointed this out, and they went away and did a battery test (which said the battery was "good"), and also said the software update had contained a fix for the 12v charging system, so all our problems would be solved. We were happy, to say the least.

Got home yesterday after a week away, and the car was dead again. It had enough power to open the charge cover in the bonnet, but not enough to accept a charge (the main battery was on about 60%). I managed to open the driver's door with the physical key and open the bonnet, and then connected a bench power supply to the 12v battery, which was reading about 7v. After charging at 2.5A for about 90 mins, the battery voltage was up to about 13.5 and the car appeared to be working fine.

I suspect that in our case the battery capacity (it's still the original battery) must be quite depleted, since I didn't think the voltage would have come up so quickly at that rate of charge. But there's obviously a current drain while the car is off, and Honda obviously knows there's an issue and hasn't been able to fix it yet.

Whilst my current thought is to attach a charge port to the front underside of the car for easy 12 trickle charging, this seems MADNESS for an EV that we have to plug into the mains regularly anyway. Having two separate charging systems to run an EV is the type of thing you'd expect the factory to be doing on very early prototypes, not customers on quite expensive production models.
One of your door handles is doing this. I had repeated issues like you described and eventually got a ticking from a relay, it turned out the pass side handle was sticking a bit.

I really didn't notice this physically. I had the same issue with a new battery. A quick strip and lube and no problems since and the car can sit for a long time without a nudge (I have a battery monitor on there now)
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