BM2 Battery Monitor

[kbjpick]

Interesting - I have never used preheat function so unaware. re above one consequence of having second car again (there was a hiatus between releasing one car and delivery of Ioniq 5) is that the Honda e is getting less use and hence 12v battery is sitting quiescent for longer periods due to inactivity - not good1

[londiniumperson]

I think the short answer to keeping the 12V battery topped up is not to worry and just leave it to the car.
There are optimal conditions as to leaving it for weeks on end but in the end it won’t make any difference. It’ll be like any other car whether BEV, ICE or hybrid which can all have 12V battery issues if not used for extended periods.

The main thing seems to be, is not to walk past with the key fob, repeatedly waking the car up but not using it.

[kbjpick]

unfortunately car is on direct route between house and outside world! I ALWAYS carry all keys with me - will have to put keys in Faraday pouch whilst in my pocket. My wife will not approve!

[advance2020]

I haven't been on this Forum for many months, so lost track of useful posts. However as 12V is essential to starting and driving your car, here is my recent experience.

I have now had to call out the AA twice because my 12V died, and it gave me more problems today. At least today I was able to Start my car, and move it out of my garage. But then it died. Previously it was just dead in my garage.

Fortunately today, I was able to disconnect -ve battery lead and recharge the 12V within 20 mins. It was 8.45V when it refused to let me engage Drive D.

Having phoned my Dealer, they recommend that the car is ALWAYS LOCKED when parked up. They say they have had reports from other owners, who leave their cars unlocked in a garage, and 12V drops voltage. This concurs with comments from second AA man, although the first thought the car might use less energy when left open.

So I share this, and welcome comments from others who may have had 12V issues.

[londiniumperson]

Welcome back.
Since the door switch was replaced on my car I’ve not had any issues other than when I’ve left the in accessory mode rather than fully on (green car with double ended arrow beneath).
FYI - I always lock my car when not in use.

[advance2020]

Recently installed a Quicklinks BM2 monitor as shown by MrEV on YouTube. Only had it installed since Friday 8 April, but has proved very useful. Been having SERIOUS problems with my 12V failing to hold charge. Now replaced with new, under warrantee. Battery dropped to 0% SoC on Tuesday 6V max, and would not respond to a charge, using a friends RAC battery charger, which was drawing 6A and then over 8A if leads were connected to my car. Only got home after AA jump started my car and they followed me home. Managed to recharge 12V overnight, enough to drive to Dealer. Recommend “plugging in” and charging HV as this puts 14.5V into your 12V at any State of Charge of HV.

To confirm 12V will be charged, when “plugged in” for High Voltage battery charging, at any SoC of HV
Not sure why others here are claiming 12V is not charging with HV @80% or above.
Not my experience. Maybe their 12V was at 100% SoC.

[advance2020]

For those of you that may, like me, leave your car in your garage for 2-3 days (or parked up in your drive) please take note. Having had issues with 12V I now have a new battery under warrantee. And the BM2 lets me know the 12V State of Charge (SoC).
Having seen the SoC drop from 98/94% to 70% in a few days of not being used (in summer) I have also seen it drop as low as 64% Low Power. See photos.

My car would still start up, but in the knowledge that SoC was low, I would “power up” and let the car recharge my 12V BEFORE driving away. The alternative is to plug in and charge the High Voltage battery, which will quickly restore 12V SoC. The car charges at 14+Volts initially and then drops to 13+Volts, which indicates the SoC has improved.

The fact is the Honda e has a lot of tech onboard- cameras, radar, sensors, regen, displays etc all running off the 12V system. If you go out for a short run 5-6 miles the car doesn’t have time to top up your 12V. I have got into the habit of letting the car “warm up” before driving away, if I know SoC is down in the 75-70% range.

Without a BM2 you won't know. Just checking Voltage is not enough.

[ZoeDave]

The fact is the Honda e has a lot of tech onboard- cameras, radar, sensors, regen, displays etc all running off the 12V system. If you go out for a short run 5-6 miles the car doesn’t have time to top up your 12V. I have got into the habit of letting the car “warm up” before driving away, if I know SoC is down in the 75-70% range.

Thanks for all the info. As someone who does low mileage, it's certainly something I need to be aware of.

What I do wonder is if keeping the 12V charged properly is related to distance or time with the car fully on. I ask because my commute is very short, only 2-4miles each way, but traffic is high and speed limits low, so it takes 10 minutes on an amazing day, and can easily reach 30 minutes. As a result the bum-milage on my drivers seat tends to be a lot higher than the odometer mileage! I hope and suspect that as there is no alternator, rather a DC:DC converter that should be running all the time the car is on, I should be fine.

[advance2020]

The fact is the Honda e has a lot of tech onboard- cameras, radar, sensors, regen, displays etc all running off the 12V system. If you go out for a short run 5-6 miles the car doesn’t have time to top up your 12V. I have got into the habit of letting the car “warm up” before driving away, if I know SoC is down in the 75-70% range.

Thanks for all the info. As someone who does low mileage, it's certainly something I need to be aware of.

What I do wonder is if keeping the 12V charged properly is related to distance or time with the car fully on. I ask because my commute is very short, only 2-4miles each way, but traffic is high and speed limits low, so it takes 10 minutes on an amazing day, and can easily reach 30 minutes. As a result the bum-milage on my drivers seat tends to be a lot higher than the odometer mileage! I hope and suspect that as there is no alternator, rather a DC:DC converter that should be running all the time the car is on, I should be fine.

Hi,
If you are using your car daily, you shouldn’t have any problems. Your car will be charging your 12V (if needed) while you are crawling in traffic.

[advance2020]

A short follow up to my post yesterday, which confirms my original.
My High Volt SoC was 76% this morning, so didn't really need to “plug in” my granny. But my 12V was at 72% which soon dropped to 70% so I plugged in for just over an hour. High Volt now at 85% and 12V a healthy 99%
You can also see 12V Voltage dropped to below 12V for a short while - see graph.
Lights on, display on, car thinking, while I reset schedule, charge limit etc
It doesn’t take much system activity to bring voltage below 12V, although it will recover, once car is shut down.