(Corrected) Planning the Electrical & Energy System

This build will be all electric, except for the Ford gasoline engine, of course. No fossil fuels for heating, cooling, cooking, fridge, hot water, etc. The goal is to have at least 1 week of autonomy in winter and unlimited time on location in summer in North America's latitudes
 
  Update (Feb'23)   Not true anymore. A gasoline heater is now being installed, based on the experience from the 1st winter test trip described here: ice climbing in Ouray !


 
Achieving this will require a very large battery system. Spit balling daily energy use in winter in -4°F / -20°C weather, assuming only 2 days of sunshine:
  • 300W air heating x 8 hours
  • 1000W cooking x 0.5 hours
  • ~1000Wh hot water (hindsight: 1400W for 10' is enough for 1 shower)
  • 100W fridge+lights+wifi+computer+misc x 12hours
  • 30W night x 12 hours
  • - 200W x 6 hours solar power x 2/7 days
  • = 5120Wh/day 🠚 36KWh total battery capacity for a week
Not unrealistic, as that kind of capacity can now be found in most EV cars. However, I will only be using a 30KWh Nissan Leaf battery pack, which depletes in 5.5 days in this scenario.
 
  Correction (1st pack attempt)   the battery comes from a salvaged 24KWh 2015 Nissan Leaf pack, that I was using in a 48V configuration as part of the house's PV system. However, configured to 12V for the van, only 3/4 of its capacity can be used because of each Nissan module's 2S2P construction (1 module =  2 pouch cells in Parallel forming a pair, 2 pairs in Series. Total: 2 + 2 = 4 pouch cells). Details:
  1. 2S2P prevents arranging cells in an optimal 3S mechanical & electrical setup for 12V. Instead, it forces a 4S mechanical stacking (4S2P), but using only 3S electrical out of that.
  2. Leaf modules in 4S can not be used for a 12V application. It would result in 15.2V nominal and 16.8V peak voltages, which would fry many devices as most are designed for 14.4 to 14.8V max.
  3.  So only 3S can be used out of the 4S stacking, thus providing only 3/4 of the capacity, i.e. 18KWh.
Worse, for 110V use, with 3S even less capacity can be used because of the Victron Multiplus inverter's 12.1V minimum low cutoff. That is completely inadequate for Leaf cells in 3S, as their end-of-discharge knee is much lower, at ~10 to 10.5V. So only ~10% of the capacity could be used before the inverter cuts off, at least with that Victron inverter.
Bottom line: lithium manganese oxide (LMO, early Nissan Leaf), lithium nickel cobalt managanese oxide (NCM, Leaf 2017) or lithium nickel cobalt aluminum oxide (NCA, Tesla) chemistries are just not optimal for 12V applications. Unlike Lithium-Iron-Phosphate (LiFePo4, i.e. LFP) which has a lower nominal voltage of ~3.2V. That allows for 4S configurations with Max & Min voltages compatible with most loads, and provides access to the full battery capacity.
 
  Update (Nov'22)   Consequently, the Leaf pack went back to the house's PV system, and LFP cells were procured. More on that saga in the posts starting here: Why LiFePo4 for 12V ?
 
 
So, insulation will be critical. All metal surfaces will be covered, thermal bridges must be minimized, and all openings will require thick thermal covers.
 
And, oh well, compromises will have to be made, like wearing a beany & moonboots inside to cut down on heating, and eating our cereals cold 😂

Electrical diagram (click to enlarge):
Design priorities
  • Safety - compliance with regulations (Transportation, RV, NEC Home & Solar. Whichever is the most stringent standard)
  • Safety - emergency dumping-outside mechanism for the Lithium battery trays (accident or electrical issues)
  • Minimal use of 110v to minimize inverter ON time & losses (only for microwave, AC, induction cooktop, outlets)
  • Maximal use of 12v direct from battery pack (air heating, floor warmer, bed & rack motors, USB, etc)
  • Ease of access / maintenance (no quick disconnect, control, fuse, component stuck behind walls or gear in the garage...)
  • (*) Simple automation / control architecture (no computer / software)
User priorities
  • Lower vehicle weight + mountain bike space in summer (cut battery pack in half)
  • 4 charging sources (solar, shore, alternator, EV charging stations)
  • USB & 110v outlets everywhere
  • 2 drawers with integrated 12v & 110v outlets to charge gizmos
  • Most fixed loads on timers & dimmers (set-push-forget to limit consumption, noise, etc)
In later posts I'll cover some of the intricacies and safety aspects of this electrical build. Starting with cabling, how thrilling ! 😴

(*) the impetus is that most future owners should be able to maintain the system via simply replacing / repairing basic and readily available devices (individual timer boards, relays, switches...). So, although it would have been cheaper and much more fun to automate the fans / sensors / timers / heating / etc via an Arduino or Raspberry Pi, those are not a long term viable solution for most people due to skill gaps and HW + SW obsolescence.
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>>> next post: Sizing Cables

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