Thundarian wrote: ↑Fri Oct 09, 2020 11:20 am
Does this mean if you were to leave the car unused for a month or so, you'd need to plug in not just the main charging cable, but another one connected to the 12V battery to stop it going flat?
When parked the car should occasionally charge the 12V battery, but manufacturers never seem to tell us what the schedule for recharging is. All the Owner's Manual says is (on page 16), "There are two types of batteries used in this vehicle, a standard 12-volt battery that powers the airbags, the interior and exterior lights, and other standard 12-volt systems, and a high voltage lithium ion battery that is used to power the propulsion motor and recharge the 12-volt battery. When the power mode is set to VEHICLE OFF, recharging will be suspended for about three days if the power mode remains on VEHICLE OFF". It doesn't say what the charge schedule is after 3 days.
The first generation LEAF had a similar system, but like a lot of BEVs it seems that they don't do a very good job of maintaining the 12V battery. Because the battery does not need to supply high power to turn an engine over, it seems that the manufacturers try to get away with charging the 12V battery as little as they can (as that helps extend the car's range by reducing drain on the Li-ion battery pack). However, lead-acid batteries prefer to be kept at 100% charge and the result was that quite a few LEAFs, and some other cars, ended up needing replacement 12V batteries after only a year (or less). With the second generation LEAF (from 2018) they seemed to have improved it, but I had already got into the habit, like many other LEAF owners, of charging the 12V battery once a week with a smart battery charger, as a preventative measure (and the 12V battery was still fine after nearly two and a half years, when I sold the car).
After I had owned the Honda e for a week or two I connected up my smart battery charger, and it charged the battery very quickly (in just a few minutes), implying that it was already at a high state of charge. But in the following weeks it has taken much longer to charge the 12V battery, around 2 - 3 hours at least (it's a 3.5 amp charger), similar to how it was on my LEAF. I don't know if that's normal even on an ICE car, but I will continue to put the battery on charge once a week as a preventative measure. (I tend to mostly do short trips, and not drive every day, so it's probably beneficial for me to do a weekly charge, but for people who drive their cars for at least 20 minutes a day for at least 5 days a week it may not be needed.)
If you're going to leave the car parked for a month or more, then if it was me I'd be tempted to leave a smart battery charger/maintainer connected, just to be sure, although the car should maintain the 12V battery (unlike an ICE car).
Does he think it's charged using an alternator driven off the main traction motor?! 