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Old 08-08-2012, 10:47 AM   #65 (permalink)
bwilson4web
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Join Date: Mar 2009
Location: Huntsville, AL
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17 i3-REx - '14 BMW i3-REx
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Hi,
Quote:
Originally Posted by Daox View Post
Is there a reason you have decided to split your pack into two parts? I've seen people do this before and the results have been less then stellar vs just running 2 cells in parallel and 15 in series.
I'm building two, independent, 48V (actually 49.3V) strings:
  • Primary - used on the out-bound trip.
  • Reserve - return to home pack.
These will be symmetrical packs and with both charged, either can be used as the primary. But when its voltage falls too much, the isolation MOSFET will begin a 'duty cycle', reduced power, as the per cell voltage hits 3.0V. The driver will know 'time to switch.'

Right now, I'm thinking stop and move a plug but I may rig up a rider accessible switch, similar to a motorcycle reserve valve, that can be flipped on the fly. The rider then knows to 'head home ... while the reserve pack is still good.'

Bob Wilson
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2019 Tesla Model 3 Std. Range Plus - 215 mi EV
2017 BMW i3-REx - 106 mi EV, 88 mi mid-grade
Retired engineer, Huntsville, AL
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