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Replacing some Rubber and an Interim Battery



As spring gave way to summer, I started to prioritize getting this Electr02 rolling.  My first trips on the car involved using the existing battery and equipment as it was purchased.  Although I did have some very successful cruises around town, it was clear that the batteries were past their prime and needed to be replaced.  For most of the Electr02's life, it was driven without a BMS, so cell voltages varied enough during use and charging to be suboptimal, maybe long enough to stress some of the batteries in the pack, especially those which were at the ends of packs which were connected via long cables where voltage sag was the worst.  This is not a criticism of the build as it was bought, these are glorified forklift batteries and at the time they were installed many forklifts ran these very unregulated and although often safe and reliable, they can live a much shorter lifespan.  






Regarding the drivetrain, currently and moving forward.  Sitting it has a Netgain Warp7 attached to the factory manual 4 speed via the factory clutch.  Powering the motor is a 100amp 300+v Soliton 1(der Senior) by Evnetics.  The Warp motors are great, this one is well cared for, but they are not 'modern' they are a well timed forklift motor with ultra high quality windings with very high temperature epoxy coatings.  They are the best of brushed, but I have never owned a brushed EV, and my limited drives with an aging battery didn't sell me, I needed more voltage to know how having shifting would benefit the cars driving experience. 


Before going into the motor/choices it makes sense to go over my philosophy on this build.  I want to keep steering geometry front/rear near standard outside of mild factory performance fitments, no flares, no stance, max mph need not even near 3 digits.  185 tires might be on for an Autocross, but 165's on steelies on cn36 is preferable.  I think a car has to work from the tire and car mass backwards to drivetrain/power needs.  With that in mind, there are a few options:

  1.  Transmission with Diff - Update to modern brushless and keep a transmission or shifting capability but keep the diff/ring/pinion arrangement.  This could be keeping stock transmission, or switching to a 2 speed with reverse planetary gearbox with synchro's and internal clutch for a switch between a high torque max speed of 45mph and low torque max speed of XXmph.  
  2.  Transaxle replacing Diff - Update to modern brushless and use an existing transaxle mounted to the stock subframe with custom axles and subframe modifications including chassis modifications to the trunk floor between final bulkhead.   This would be a tesla small drive unit, or Leaf motor, or i3 motor if the controller is figured out.  
  3. Engine/Kers - Bring an engine back into the mix and relegate the electric motor to be KERS so leaving the neighborhood is silent, but the remaining time is 8,500 magnesium blocked bmw k motorcycle powered fun with 50hp of torque fill and a Sequential gearbox.  

Before I take any steps, I want to test how this drivetrain feels with the max v and amps it is supposed to be able to accept.  Even if for low range.  To do that I found the quickest cheapest method of doing so while investing in components that I know could be usable in any of the above future builds.  I chose a123 Cells in 26s3p 72v Configuration with about 5kw each to be run 3 in series for 15kw.  These cells communicate via can bus to the Thunderstruck MCU which acts to enable and manage the onboard BMS the cells come with. They weight 300lbs and should have enough peak discharge and voltage to max my setup and then use the knowledge and experience to plan further. 


I don't expect to move fast on any given path, I prefer to keep the car operational and make choices after technology continues to mature.  I do not want to be forced to carry more motor/transaxle or motor/transmission than is required and I prefer the higher density battery tech come down a bit in price.  The current motor may stay in its current location many years of fun depending on the cost and packaging of more modern technologies.  I have started 3d scanning the trunk and doing some light layout work to see how existing motor and battery systems may be packaged, images of those concepts are shown below. 
















Edited by joshgoreworks

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This should be fun to follow. Most of us here are knowledgeable with ICE terms so abbreviations are fine, but can you explain and give more information using simple language when discussing the electric part of the build? 

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