Tuesday, October 25, 2011

Battery Life

Hardy Huber on battery life

Hardy Huber is the mastermind who invented the TravelScoot.  Recently Elford in Helsinki, Finland sent me an email correspondence he had with Hardy about the lifetime of the lithium ion batteries.  You can read more background on this on the post titled "Scooter gang of Vuosaari."

I have two of the regular size lithium ion batteries.  The first was purchased 2 1/2 years ago.  I'm just starting to see some decline in how long this battery holds a charge, but it's still very usable.

This is what Hardy had to say about battery life:

Every Battery starts deteriorating the moment it is made. In other words, capacity is very slowly decreasing. Eventually there will be a moment where distance is not satisfactory anymore. Rebuilding is not an option because the electronic inside has been improved several times, so all what may be usable is the housing.

To get an idea about the condition, I would chose a round course with a known distance and ride with two fully charged battery until one shut down. Since your wife recently got a new scooter you could compare old against new.

1 comment:

  1. Greetings, all! It's a treat to find such a comprehensive resource on the Travel-Scoot scooter.

    By way of introduction, I've recently picked up a used TS in the hopes that my sweetie and I can finally get back to our former habit of wandering around the places we travel. We've been restricted since I got Morton's neuroma (an inflammation of the metatarsal nerves similar to Carpal Tunnel Syndrome). I can only walk a few hundred yards before my feet give out (or is that a few hundred feet before my yards give out?).

    I know we probably won't be able to wander for 8-10 hours at a stretch the way we used to. But if we can get in a couple of hours of sightseeing, and supplement that with some bus touring, at least we'll get something of the flavor of our former glory days.

    I'm not a battery expert, but I do have a fair bit of experience with rechargeable batteries in various forms and applications, including electric vehicles. So here are some suggestions that might help you get the most life from your expensive batteries.

    First, a little background (those who aren't technically inclined may want to skip the next 2 paragraphs).

    From what Hardy says on the TS website about not leaving the "official" lithium batteries in a hot car, I'm guessing that his batteries are Lithium Cobalt type. These are about as good as it gets for energy storage per pound (specific energy, or SE).

    The downsides of LiCo are the aforementioned matter of heat (flaming batteries ain't no fun), and their calendar life. As Hardy says, the darn things deteriorate just sitting there next to the scooter, even if you never use them.

    So, with that, a few things you can do to minimize this.

    First, if you're not going to use the lithium battery for a while, don't charge it up full! Try to leave it at about 70% charged.

    One way to do this is to charge it up, then run it down a little. Use about 30% of your range after charging.

    Note: A lead battery always be stored at 100% charged.

    Second, store your battery in a cool place when you're not using it. I keep my spare lithium portable drill battery in the fridge.

    Third, try to use the battery every couple of months, to keep it exercised. Batteries are like people. If they sit around and veg out all the time, they get all flabby and out of shape, and lose capacity.

    My TS came with a good lead battery. It's heavy! Being a little bit cheap, I'm building my own lithium battery.

    I'm using a newer type cell, lithium iron phosphate (LiFePo4). These are intrinsically safer. They won't catch fire in a hot car. They're a little lower in SE than LiCo, but they deteriorate more slowly when stored.

    I figure my battery will probably weigh about a pound or so more than the official TS lithium battery. I'm hoping for a 4-5 year life. It should cost me about 30-40% less, though that doesn't include my labor in building it.

    Its nominal capacity will be about 260 watt-hours. How that will compare with the official battery isn't quite clear. On his battery page, Hardy is a little vague about his lithium battery's actual capacity.

    In one place he says it contains 24g of equivalent lithium, which would make it a 300 watt-hour battery.

    In another place, he mentions 9.6 amp-hours. He also mentions a maximum voltage of 29v. That strikes me as a bit high for a 24v nominal motor, but if true, that would make his battery capacity 278 watt hours.

    If any lithium-battery TS users out there are brave, and own accurate voltmeters, I'd be very interested in the voltage you measure (carefully, no shorts please!) at the battery terminals at least 24 hours after charging.

    And if anybody's potentially interested in a lower cost DIY lithium battery, I'll keep y'all informed about how the project is going.

    Thanks again for the blog!