80% Charger

[FFEGuy]

I like my Focus Electric a LOT, and I hope to have it a long time. One of the missing features in the Focus is an 80% charge option. Other electric cars have this, and it is apparently valuable in extending the life of the lithium ion batteries. Of course, we can remember to unplug at the right time, but that is not very convenient.

I finally got around to dealing with this in a better way by installing a simple spring wound 12 hour Intermatic clockwork timer switch on the power to my Clipper Creek level 1 charger. I consulted with the people at Clipper Creek before doing this, and they said it wouldn't do any harm that they could think of. Using it requires a little mental math: My level 1 charger provides about 5.5% of battery charge per hour, so after consulting the battery charge percentage on the 'my Go Time" screen, I simply dial in the right amount of time before plugging in. If you have a faster level 2 charger, an Intermatic timer switch with a shorter time scale would work in the same way. When you want a full charge, just dial in more time. This has been working well for me.

I have nice photo of my timer installation, but I can't figure out how to insert a picture in this posting.

- William Thur

 

[NightHawk]

But with the FFE, 100% charged isn't really 100% since Ford limits the usable battery to about 19.5KWH out of almost 24KWH total - so Ford is kind of already doing the 80% charge limit built-in.
I haven't heard reports of FFE owners having HV battery life issues as reported by other electric vehicles like the Nissan Leaf, so Ford's approach seems to work and makes it easier to not worry about how you charge.

 

[NightHawk]

I have nice photo of my timer installation, but I can't figure out how to insert a picture in this posting.

To add a photo, just upload the image file to a free internet upload site such as http://postimage.org/ that will provide a link to the uploaded image file.
Then click the "Img" button on the forum's post a reply page to insert the img code and then past the link to the uploaded image file.

 

[jmueller065]

Yes the general consensus around here is that hacking up a device to limit you to 80% charge is not necessary in the FFE. There are plenty of people on here with over 30,000 miles on their FFE and no appreciable (nor noticeable for that matter) battery degradation.

If you insist on doing something you can use the value charge feature and program it to charge as late as possible. Thus the car only gets a full charge just before you leave in the morning. For instance: You could have it start charging at 3am every morning so it will be full for your 6/7am commute. Thus the car will only be at its reported 100% charge for less than an hour (and remain at a non-100% level throughout the day).

Ford was very conservative with the battery state of charge (never goes below 10% or so actual and never goes above 90% or so--even when the car reads 100% full).

 

[brogult]

There have been discussions about this before. I would like a partial charge option, but not for battery life. I don't think the battery life thing is an issue for a couple of reasons.

1. The temperature/charge degradation of those Li-Ion batteries for which this has been studied starts when the temperature goes over about 90 degrees or so and the cell voltage is 3.60 volts or more--this is not 80%, but rather more like 50%. Cell manufacturers commonly ship their cells at about a 40% state of charge and I think this so that they will not be damaged if they are subject to high temperatures during shipping.

2. If you browse the Nissan Leaf forums for discussions of battery condition (they call it "losing bars"), you'll see a lot of people that have lost significant range (30% or more) who did use the 80% charge option, never quick charged, but lost battery capacity anyway. They are all in high-temp areas like Phoenix. The FFE has temperature control and probably different battery chemistry, but the Leaf example just gives us an idea what may or may not happen.

http://www.electricvehiclewiki.com/Real_World_Battery_Capacity_Loss


3. If you leave the FFE plugged in, it will balance the cells and if temperatures get high enough, will actively cool the battery. Everything I know indicates that keeping the cells balanced and cool is more important than 80% vs 90% (the full mark on an FFE) charge. If you needed to store the vehicle unplugged in a hot environment, you should run the battery down to 30-40%.

AFAIK, nobody has reported any significant range loss on an FFE, although there have been a very few outright battery failures. The sample size is much smaller, of course (75K Leafs delivered vs. about 4600 FFEs), but if you look at the link, you'll see there are a LOT of Leafs with battery degradation, some at pretty low miles.

All that said, I'd like your idea--if we could figure out how to install in on the car! My use for it would be when I'm out using a public pay-by-the-kWh charger and only want to buy enough juice to get home.