The Smart Drive

So I’m not the worlds most diligent blogger, but that doesn’t mean things aren’t going on.  First some explanation.   Last summer I started working at EeTrex, a startup company working on hybrid electric plug-in conversions in Boulder, Colorado.  I work on building battery management systems (BMSs) for lithium-ion batteries. Management systems for batteries is something that I have always been interested in and this is an absolute dream job.  Needless to say, with a job I enjoy, and working like crazy, the electric vehicle and other projects have slowed a little.

I live in Colorado and winters here are pretty cold and snowy, as a result I haven’t been driving the electric vehicle much.  However the winter has started to break and today is a beautiful day, perfect for a top down all electric drive.  Before heading out I decided to check the level of the batteries and add water to ones that were low.  For those who are wondering, when you charge flooded lead-acid batteries the chemical reaction in the cells separates water via electrolysis and the gasses escape.  Thus over time, the water that is in the cells decreases and it must be added back.  Here is a good page on PbA battery basics. Because the water that escaped was pure H2O the only water that should be added back into the cells is pure distilled water.  You can find distilled water at most grocery stores.  One of the best and easiest ways I found to water the cells is to put a gallon of distilled water above the car, then use a length of flexible tube to siphon the water down to the car.  Simply folding the tube over and holding it in one hand allows control of how much water enters each cell.  After the watering I took the car out.  On the drive today and drives over the winter I noticed some degradation in the range of the batteries since I haven’t been driving much.  I think this will improve with a few discharge-charge-equalization cycles.  Check out this page on battery balancing and lead-acid equalization for how to even out a EV pack.

That’s about it for the EV.  The next item on the list is to do the rear brakes on the car as I think they are about at the end of their life.  As things change look for updates!

If you are not familiar with The Smart Drive’s electric car, check out the post on The Electric Car Experiment.

For a quick summary, The Smart Drive’s electric vehicle was built in 2001 and competed in two road rallies in the Northeast in 2001 and 2002. Since 2002 it has been used continuously as a commuter vehicle in New Jersey and an every day vehicle at Virginia Tech.

While the car is at its new home, it isn’t quite ready to use. Over the past 8 years the car has traveled about 30k miles on two traction batteries packs. Electric vehicle lead acid traction batteries have a limited charge and discharge cycle lifetime and the current battery pack, installed in 2005, is at the end of it’s life. This means time for some new batteries! This weekend my father and I spent a good deal of time removing the old batteries, cleaning up the battery brackets and installing the new pack. The new batteries are 6 volt deep cycle golf cart batteries with a capacity of 225 amp-hours. The specification and form factor of the cells almost exactly match the T105 batteries from Trojan Battery however rather than costing $125 and up these batteries cost $71.28 and can be purchased off the shelf at Sam’s Club almost anywhere in the US (The Costco I checked didn’t have them). The model is the GC2 and the new set I got for the car were Energizer branded. The batteries used in the old pack we removed were also purchased at Sam’s Club and performed at the same level as an OEM supplied original pack.

Check out the gallery for some pictures from the upgrade. Take a look at #9 then #8 for a before-and-after under the hood!