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Battery Tools · 20 June 06
Hey, we’re getting closer to settling on a battery! Those who have been following the comments elsewhere may have read that I started looking into the Odyssey Hawker PC2150 battery. More expensive (nothing like NiMH/Lithium prices) and from everything I’ve read they are well built (mil spec) and able to take or dish-out lots of power.
Of course John Westlund then jumps into the comments and mentions another, cheaper battery and doubt sets in…
Welcome to the whacky world of EV Batteries!
The whole battery thing has more or less brought everything else to a standstill. When making an EV the battery really dictates pretty much everything else, both physically and psychologically.
Physically it influences where you put other components, how much cable you’ll need for interconnects, metal-work and welding requirements, weight distribution (and therefore suspension), the type of charger, and whether you’ll need more battery management systems.
Psychologically the process will try every bit of patience you ever thought you had. You’ll start off confident and with purpose only to end up full of doubt and confused, checking and re-checking a hundreds of websites, making phone calls, staring at spec sheets, and computing peukert until you puke.
There’s a lot to be said about going with a kit where all of these designs and decisions have been made for you.
But I’m not here to whine, I’m here to share.
I’ve pointed to a couple of EV Calculators in the past and, trust me, I’ve spent countless hours using them over the past months. There’s a few problems: neither of them have Eve’s specs or include most of the batteries I’ve been researching (so lots of typing and re-typing), they don’t save/bookmark your setup, and the pages themselves are huge.
I’m not trying to cut them down, they have been a godsend, just saying that there’s data and features that I’ve wanted to add. That and you know how I like to pretty things up. ’:^)
Over the weekend I spent some time doing just that: modifying the existing code, loading data into databases, messing with user interface ideas, and adding new features. Ladies and Gentlemen, let me introduce the all-new EVConvert.com EV Calculator.
First a few disclaimers:
- this is a work in progress (i.e. bugs!)
- the data is was gathered on the web (i.e. bugs!)
- it probably doesn’t work in IE (who cares! uh, sorry, I mean: bug)
- more features coming soon (i.e. new bugs!)
The basic premise is that you pick a vehicle, motor, battery, and controller, tweak a few of the additional parameters and then click calculate. If everything is working correctly (and it may not) you should see numbers show up in the range columns. The data blocks have little arrows which expose even more data.
The goal was to provide a one-page interface that makes it easy to tweak a parameter and see the change quickly, yet still be able to expand the layout when more information is needed.
- database driven design (with AJAX for buzzword compliance!)
- cookies used to remember your last settings
- separate batteries page for more information
- cleaned up number formatting
- updated battery list
Things to do:
- ability for you to add your own vehicle along with new batteries, motors & controllers
- nicely formatted printing
- more formatting to clean up
- only remembers popup selections (vehicle/motor/controller/battery), none of the additional hand entered data
- add battery cost to summary
- add tool-tip help text
- add battery dimensions
- use the battery data for the battery layout tool
- compute more battery related statistics, much like those in the battery spreadsheet posted awhile back
- add graphs, blinking text, dancing badgers!
This will be part of my slowly growing EV toolkit. Here’s what we have so far:
- EV Calculator – helps in evaluating components and design choices
- EV Batteries – the batteries used in the calculator, with more details and tools to add new batteries (that part is coming soon)
- EV Battery Layout – simple gizmo I made to help experiment with battery box layouts
Give them a try and then leave a comment or drop me an email with your thoughts, feature ideas, and any bugs you find.
Some other points that I should make a note of. The other EV Calculators default to low rolling resistance tires (0.0015 tire resistance) and perfectly flat terrain. This makes your range look REALLY nice. But it’s not very realistic for most of us so I’ve changed this calculator to default to normal tires and a modest 1% grade.
If I had all of the time in the world (and a few more brain cells) I’d make it so you could upload a GPS tracklog, correlate that with digital elevation models, and compute the range for your exact driving conditions.