To charge or not to charge ...

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Nov 17, 2014
Hickory, NC
Although I do not post a lot here, I use this forum (along with some of the blogs from its members) as a great source of information. I have done research on this question so forgive me if I missed the answer somewhere ...

I have a 30 mile (one way) commute to work. I am lucky enough to be allowed to charge at work (Level 1). During the winter, I needed to charge at work so that I could run the heater and be comfortable in my vehicle during my commute (I do pre-condition at home using Level 2 charging). Now that we are heading into summer, I don't necessarily need to charge at work to complete my commute. I usually get to work in the morning with 65% left in the battery (vs. as low as 50% during the winter). And around 30% left when I get home (without charging at work).

My question is this ... to prolong battery life as long as possible (I bought my FFE) is it better to only charge once a day at home using Level 2 (using 70-80% of the battery)? Or is it better to charge at work with Level 1 (using only 35%), then again at home with Level 2 (using 35% again)?

OR, Am I overthinking this?

And Yes, I know I am missing out on the "Free" electricity by not charging at work, but I am more interested in what would be best "long term" for the battery. Since I own my FFE, prolonging battery life is my top priority.
I don't think anyone really has a definitive answer.

A couple points to think about:
  • Plugging in at work but not charging may allow the car to run the TMS to cool the battery if needed on hot summer days (i.e. set up Value Charging so the car doesn't charge even though it is plugged in)
  • 120V charging cannot support both charging & running the TMS so plugging in & charging at work would likely only increase the battery temp
  • The lower the SOC of the HVB the more cell voltage variance, charging during the day would yield a higher average SOC and less voltage variance
  • Overall the charge cycles on the HVB should be roughly the same
I would charge because I believe any negative effect would be negligible, and I always like to have the highest SOC possible in case I go somewhere I wasn't planning on.
What I took away from earlier discussions on this forum, was that letting the batteries sit at a high temperature, while also at a high SOC, is most damaging to them. The batteries are supposedly "happiest" at a moderate temperature, and around 50% SOC. But I guess it'll be several years before we find out whether being extra careful makes any difference at all.

Based on the above (and what hybridbear said) I don't always fully charge overnight, and I don't plug in at work in the summer except when I might need more juice for errands after work.
Never thought of this but if my garage at home gets hot, I should always choose L2 so the car has a chance to cool the battery. With L1 charging, the cooling system never kicks on. When I use our L2 charger, I hear it fire up quite a bit.

Living in Hawaii, it's cool year round except for a couple of hot months in fall. I may switch to L2 for those months since I keep our garage closed at night.
I am not saying that it is wrong, but my 2015 definitely activates TMS when charging on L1. I plugin in the sun sometimes at work and if it has been sitting for awhile you can hear the fan whirl up and feel it just like at L2 EVSEs (also in Honolulu). Also it can pre-cool the car at 65 F (slower than 3 min though) and will still maintain charge and not reduce finish time for me. This is all using the Ford supplied cable. I am not sure if this is a new thing in 2015 or the outlet I am using is somehow forcing the ford cable to do more than it is designed for or what, but it works. Though I am sure it couldn't do heat this same way.