ElectraGirl: How Long Does the Battery Last?

Saturday 14th March 2015

How long does the battery last? This is one of the questions we are asked the most often from people when we are out and about showing off our Electric Cars – I think that they are really asking, How far can you drive on a single charge?

2012 BMW ActiveE miles trip headerAs we’ve found out over the years there really isn’t a definitive answer. The range on the cars guess-o-meter will give you an idea but after many drives we have found that it is all down to the way you drive the car. Drive nice and gently and you will get more miles out of your battery, drive fast and you will see your miles disappear at a rather quicker rate. I would say it is one of the more difficult questions to answer accurately.

One day three years ago we decided that we should test the theory out with our 2012 BMW ActiveE. You know, just to see how far we could drive on one charged battery. Here’s what we found.

We planned a Sunday afternoon drive with the ActiveE, going out for a fun drive rather than driving for necessity, even though driving the ActiveE was always fun regardless. We wanted to see how well the battery did and what kind of mileage we could actually get. The weather didn’t look good when we awoke to fog and rain on the Sunday morning, but we’re British, after all, so that wasn’t going to stop us. Fortunately by the afternoon the rain had stopped and the sun had started to make an appearance so it looked like our drive would be rather pleasant.

2012 BMW ActiveE Bridge-1We set off with my Sidekick adamant that he knew where we were going, he said that he had a drive all planned out. Jolly good! Although, we had only been driving for ten minutes when we had to stop and switch on the Satellite Navigation as he suddenly wasn’t quite so sure anymore! Hmm – It turned out that we had already gone the wrong way! A good start. With the car now going in the correct direction, we settled back to enjoy the drive and take in some new scenery. The day was warm enough that we could turn off the HVAC, so we were able to drive along so silently. The HVAC is actually quite noisy, I guess that this is what happens when you don’t have an engine drowning out everything else, you actually hear things that you wouldn’t normally hear in a petrol car.

The range remaining display on the ActiveE seems to be quite true to what it says, it does seem quite stable. Often when we first get in the car in a morning the difference between the range reported in regular mode and Eco mode is quite significant, there can be as much as a 12 mile difference.

The ActiveE has “Eco mode”. When you engage “Eco” the car reduces the sensitivity of the accelerator and reduces the power to the HVAC. This encourages you to drive more gently and reduces the heating and cooling power demands. Basically, you give up some comfort and fun for more miles.

2012 BMW ActiveE Bridge-2We had left home with 98% charge (it was still charging when we unplugged it) and we had an approximate range of 80 miles in regular mode, and 96 miles in Eco mode. We ended up driving over 80 miles that day and still came home with 16 miles to spare. How could that be? Well, we drove for about four hours, most of the driving was on 35 mph roads with the odd 50 mph blasts thrown in and the occasional slow 20 mph road. As we drove very economically, the car began to re-evaluate the available range. When we checked the battery level it had climbed from the starting point of 80 miles up to a 96 mile range in regular mode, hence the 16 miles still remaining at the end of the day. So, if you drive gently you can really get quite a few more miles out of your battery and its predicted range will go up. The predicted range looks at how you drove the car the day before and guesses how many miles you will get out of the battery determined on the previous days driving. Which is why I would always see a higher predicted range than my Sidekick would – Just saying!

It seemed that on our drive, that by driving gently in regular mode, the difference between the regular mode estimate and the Eco mode estimate had converged. At one point during that day, at 50% battery, it was only a three mile difference. This makes us believe that it is all down to the way the car is driven… drive gently and you get almost the same amount of miles in Comfort mode as you would in Eco mode. Driving on the motorway, the miles go down quicker due to the increase in speed… the faster you go the more energy you use – it’s all down to the wind resistance.

We really enjoyed just driving that day, it made such a change from our usual day to day planned driving. We didn’t have to be anywhere in particular, there were no children to be dropped off or picked up, no time constraints… it was driving just for pleasure. We’d rather like to be able to do this more often, but alas work and life seem to get in the way!

Next time we do this it will be in the BMW i3, but we’ll wait for the snow to go and the roads to be a bit better and see How long the battery will last!

2012 BMW ActiveE Spruce-Run-1Oh, and to answer the question How long does the battery last? Well we haven’t got a definite answer as there are too many variables to take into account but on that particular day it latest at least four and a half hours.

We talk about winter range but, what kind of variation are you seeing with range between driving hard and driving gently?


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  • Nice insights to a tough question. nn”How Long Does the Battery Last?” for non-BEV drivers is like “When do I take my foot off the accelerator and press the brake pedal?” for non-drivers. As ElectraGirl has explained u2026 it depends, but with a bit of experience it doesn’t matter, as there’s no single answer, rather a whole family of valid answers. nnWhen asked “How Long Does the Battery Last?” u2026 I have found people are asking two different questions:n1. ‘How far can I drive per charge?’ (or, How far can I travel from home?)n2. ‘How long can the battery be used before needing replacement?’nnFor #1, I explain that with home charging an EV driver can always start the day fully charged! In terms of roaming, a bit of info on time to quick charge and a look at a map (plugshare) helps explain what is (is not) realistic.nnWith #2, I tend to favor a tire analogy. Explaining that capacity will slowly degrade with miles traveled and calendar time. If follow-on question is about replacement cost u2026 I rephrase to be in terms of cost per mile (km), vs. a future balloon payment. (battery + electric cost per mile are favorable vs. cost of gasoline & oil changes).

  • Benidorm7

    Some of us are actually asking how long before the battery needs replacement. A new Leaf battery is $5,000 + tax and installation- there goes your savings on gas and oil changes. A new Tesla battery? Between $20-40,000. That’s a lot of gas. And good luck selling your used battery car- when a buyer needs to spend enough to buy yet another new used car just to make the BEV run. You can find Leaf’s pretty cheap now- maybe that’s why. And maybe why Toyota thinks Hydrogen is a better battery.

    • Electra Girl

      To answer that question, Plug In America carried out a couple of battery studies on the Rav4EV and the Tesla Roadster – two cars that have been around long enough to derive meaningful data from. The headlines, Tesla Roadsters lose about 15-20% of their battery capacity in 100,000 miles.nnhttp://www.pluginamerica.org/drivers-seat/battery-study-updates

    • Hydrogen flunks the math test. Looking at the Hyudai Tucson’s specs, a kg of Hydrogen will take you 47 miles. It takes 60 kWh of electricity to make a kg of hydrogen. That same amount of electricity will take my Leaf over 200 miles. nnAs to loss of battery capacity, $5K is the cost right now, but this price will come down over time, and it will probably be possible to recondition battery packs by swapping out cells that have lost capacity with newer cells. Also, it is possible that third parties will offer replacement packs with greater range in the future, say someone who is buidling a huge battery plant and wants customers for its batteries?nnCars are becoming more solid state and like computers, i.e., upgradable. Five years from now I may simply upgrade my battery pack for a few thousand dollars and get double the range.

    • My Smart ED has a battery pack designed to run 3000 full discharge/recharge cycles until it loses 20% of it’s maximum storage. In 1.5 years of driving, and through two winters with brutal one month long -10C “highs”, I’ve not seen any measurable loss of range. If may be that after 10 years of driving, I will have done 2000 full charge/discharge cycles, so I’m expecting a long lifespan out of this car.nMeanwhile, enjoying this deceptively quick and fun electric car every day!!