[ausev] *****SPAM***** Re: Technical Considerations; Battery Pack Replacement 98 Ranger

[jtp]

Engine compartments can reach over 250 degrees at times.  Many batteries have insulator blankets or plastic covers.  These extend the functional life approximately 30 percent. 
The only heat factor which is relevant, then, is your rate of charge in an EV.  The more heat (faster charge rate) the greater the reduction of endlife.  Installing heat sensors or other devices which can monitor heat values during charging may help greatly to study appropriate charge rates for all of the various use, discharge, and battery state conditions.  
 This might be more feasible as part of bench-test studies.
Carefully recording readings with an infrared thermometer taken of all cells (bottom to top) during various recharge rate tests might be easier and cheaper given all that has to be done to replace the pack.   I would contact the battery manufacturer to ask about nominal rates and temperatures.
Also,  what just occurred to me, if heat-up rates are closely comparable to OEM (orig. equip. manuf.), then you may not need to be concerned about extra cooling of some sort. Otherwise, it may be a good idea to get recommendations from the battery manufacturer about possibly needing some additional   active or passive cooling. 
Dan Petit.  
  ----- Original Message ----- 
  From: michael 
  To: 'AustinEV News Announcements and General Discussion' 
  Sent: Thursday, August 10, 2006 8:10 AM
  Subject: *****SPAM***** Re: [ausev] Technical Considerations;Battery Pack Replacement 98 Ranger


  Based on all of this, it brought me to a new question…. 

   

  In cars with engines, heat is the major killer of batteries, I don’t know how many “swelled” batteries I replaced during my grease monkey/tire jockey days.  Is this a concern for Electric cars or is the heat not as much of an issue since it only is sun heat and not engine and sun heat?  

   

  (I hope that last sentence made sense)

   

  Thanks!

   

  Michael Ringer

  Administrative Manager

  GCE, Inc

  512-528-0908

  512-528-9293 FAX

  Your Passport to education and employment

  Member of NACES

  http://www.naces.org

  -----Original Message-----
  From: ausev-bounces at austinev.org [mailto:ausev-bounces at austinev.org] On Behalf Of jtp
  Sent: Thursday, August 10, 2006 11:46 AM
  To: AustinEV News Announcements and General Discussion
  Subject: [ausev] Technical Considerations; Battery Pack Replacement 98 Ranger

   

  Additional technical aspects worth considering in the battery pack replacement may relate to some of the new advanced electrical controls on '99 and later IC's.

    '99 and later DC alternators on GM vehicles, for example, use a computerized all-silicon voltage regulator, which requires a specific sequence in reconnecting the harness, high amp output, and ground, in order to properly "bias" the charging system for it to work.   

     Consideration might be given to the possibility that components of the '98 Electric Drive Ranger may not only have a reconnection sequence as well, but possibly, the question ought to be answered as to the potential need for a disconnection sequence also.  

     When inspecting the Ranger at the "Who Killed the Electric Car" event,  I noticed that the drive motor was manufactured by Siemens.  It might be a good idea to see if Siemens Engineering could provide guidelines about  this

  or anything else in the wiring and controlling.

     Since there is apparently  a very substantial undertaking in the replacement of the batteries,  I recommend that a very high level of working precision be required here.  For example,  an "Inch-ounce" torque wrench in order to record the removal torque required for all bolts and clamps at the batteries, and making a carful decision as to minimal and maximal torque specification at battery connections.  Torque should be rechecked at least three times at differing temperatures (as if you were working on the Space Shuttle).

  Recording torque readings at removal for the main tray bolts also would be important with a foot-pounds torque wrench.

    Since the "Sprung-weight" of the batteries would be off of the suspension, and, an anticipated spring travel will reposition front steering and suspension geometries, then, it may be a good idea to lubricate any available grease fittings in the "extended-travel" positions of the lubricated joints.  This in anticipation of dried-out or thickened lubricants at all of the suspension points. 

    I am very opposed to the use of any kind of grease coating at any battery connection, since grease is an insulator and can melt down between critical contact areas.  While for  IC automotive (easy to access) battery sitiations I use clear acrylic spray paint which keeps corrosion at bay for at least 5 years (and is also of some value in reducing the chance of accidental shorts as it has slight, low voltage insulating value),  I can not say I could recommend that for higher voltage packs at all, but only for the auxiliary voltages at a 12 volt auxiliary battery only. 

     Another consideration which comes to mind, given the difficulty in this endeavor, is to test cycle ALL the batteries at least a minimal number of times in a similar application.  This may sound like a lot of work, but actually using the batteries in a similar load-scenario may be wise, such as installing them (if they will fit), into an EV where the batteries could be performance tested.  Then, if there is one or more which seem unable to perform as well as the rest, then there ought to be an exchange requested for the underperformers. 

     Optional items.  Diamler-Chysler utilizes a datastream called "Battery Temperature".  There is a sensor placed in the tray underneath the battery which provides battery temperature as a function of  "reference voltage" whereby temperature of the battery influences its internal resistance.

  (Allowing for a very nicely accurate decision as to which mixture ratio schedule to process).   This may be a really nice way to remotely monitor battery temperatures, but maybe on an analog basis.   Also,  performing bench testing of cell temps during recharging each battery after a calibrated discharge (of several discharge rates) may be helpful in preventing inadvertent installation of a weak battery. 

   

   Dan Petit. 

     

     

    



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