[rontcarb]

I am a first time BMW owner and have a month old 2024 BMW X5 PHEV. Dealership recommends the 20/80 rule for charging, but with only 40 or so miles of electric, its impossible to leave with 20% in and 80% is only like 32-38 miles of electric. I have read a variety of information researching online outside this forum with a variety of opinions stating you should or should not charge above 80% and some saying just charge 100% no issues, no long term battery problems.

Would like your insights into charging habits, and what makes sense. Prefer to know from a scientific perspective if you have it, as so many opinions around. Practical experience also valuable, as its my first PHEV.

[jad03060]

In a BEV with the possibility of DC fast charging, stopping the charge at 80% makes sense, as most can go from 0-80% fairly quickly, but it can take an equal amount of time to eventually get that last 20%. Various reasons for that, but heat is a big part of it. When charging more slowly at home, heat buildup isn't typically a big issue, nor, assuming you're charging overnight, how slow it might take to get that last bit. One of the things the computer will do on occasion is to do what is called cell balancing, and that does not generally happen until after it senses a full charge.

I've had a plug-in vehicle since 2014, and have always just plugged them in when I got home and left them there. Over that time, I did not see significant battery degradation. The X5 doesn't do DC fast charging, and has a decent battery logic control system with active cooling.

I just plug mine in and leave it. I suppose if you planned to keep it for 10-years, it might help a little, but in 10-years, you'd probably want a new one as the tech will be likely significantly improved.

[nZtiZia]

Originally Posted by rontcarb

I am a first time BMW owner and have a month old 2024 BMW X5 PHEV. Dealership recommends the 20/80 rule for charging, but with only 40 or so miles of electric, its impossible to leave with 20% in and 80% is only like 32-38 miles of electric. I have read a variety of information researching online outside this forum with a variety of opinions stating you should or should not charge above 80% and some saying just charge 100% no issues, no long term battery problems.

Would like your insights into charging habits, and what makes sense. Prefer to know from a scientific perspective if you have it, as so many opinions around. Practical experience also valuable, as its my first PHEV.

that rule is for full EV vehicles since they access to the full battery capacity. the 50e doesn’t; it only has access to 19.6kWh of the battery’s full 29.5 kWh capacity (U.S. models), so when you fully charge it, that’s only 67% of its full capacity. this ‘buffer’ helps prolong its battery life which is the premise behind the 20/80 rule. IOW, battery prolongation for the 50e is already built-in, so you’re fine to charge fully.

that’s not to say you won’t see some degradation over time. that’s inevitable with all batteries, but you shouldn’t have significant capacity issues for at least 8-10 years while the battery is under warranty (actual warranty period is state-dependent)

[cellarrat]

Yeah I don't think you need to worry about that. BMW has limited the maximum charge levels on the battery, in part to ensure that they don't have to replace the battery in the 8 yr/80k mile warranty. Charge it to the max, and you are well within the safe range