Electrical

The way we currently travel is 4-5 hours driving or staying in one place for a day or two. Ideally that one place will be shaded in summer, or in winter likely open. Either way, being able to function for 3-4 days on a single battery charge, and recharge batteries quickly when driving or in sunlight is desirable. We are leaning toward Lithium despite the expense, for the rapid charge capability and large capacity for a given volume and weight.

As we sit in Redwoods State Park in NorCal, we have been listening to someone’s generator running for the past 90 minutes. That reinforces our desire not to have a generator - noisy and annoying.

Lithium Reference

Lithium batteries (with various chemistries) have a bunch of advantages over Deep Cycle and AGM Lead Acid:

  • no need for lengthy float charging
  • 80%+ capacity usable vs. 50% for Lead
  • much lighter (and somewhat smaller) for a given capacity

They do have challenges though:

  • charging when below 0C/32F will damage the batteries
  • many solar charge controllers and alternator/battery/shore power chargers do not have appropriate profiles for Lithium
    • even those that do may not be optimal
  • $8-$13 per Ah is much more expensive than Lead Acid ($2-3$3 per Ah ?)

Since we want something usable in winter, keeping the batteries within the van envelope will be necessary, and we may want to add an electric blanket around the batteries to keep them warm in sub-freezing temperatures

Build Overviews

Deciding on an electrical budget and system size is the first step, and there are lots of variables involved. Some builds use extensive battery and electrical, where others rely on propane and/or diesel for cooking. Heating is almost always with propane/diesel/gas unless you’re in fair weather climates and need limited heating. Depending on who’s writing the electrical overview, power requirements are either in Watt Hours (Wh) or Amp Hours (Ah). The Ah values assumes a 12V system generally. 24V and 48V systems do exist, but they’re uncommon on van builds.

Winston has a very large Lithium system using:

  • Elite Power Systems LFP 5x 100Ah batteries and BMS
  • Magnum 2812 inverter/charger with MMP breaker/switch panel
  • 3x 270W Kyocera panels (810W!)
  • Midnight Classic MPPT solar charge controller
  • Nations 280A secondary alternator

He has some extensive commentary about his design, and some detailed photos

Interesting feedback about setting up MS2812 for charging

Speaking of profiles, we are ‘testing’ Magnum’s “Custom” and “CC/CV” (Constant Current/Constant Voltage) profiles. Despite our very favorable reaction to the Magnum 2812, it suffers the same “current follows voltage” limitation of all chargers. In order to obtain a sustained high 125 amp charge rate, the Magnum must be programmed to a voltage (“Bulk” or “Constant Voltage”) well above the desired final “charged” battery voltage. For us, this will require “manual monitoring” while charging, then, when the battery reaches its target charge, a reprogram of the charger.

It seems like it should be possible to use the BMS high voltage disconnect to shut off the charger once an appropriate voltage is reached. We would need to look at what interfaces are available on the BMS and charger, since it’s desirable to still use the inverter/charger as an inverter even when not charging.

Hein’s Sprinter also uses the MS2800 inverter/charger with a 500 Ah AGM bank. Ideas from his build:

  • thermocouple-controlled fan to cool inverter enclosure - it can get hot under load
  • 200A DC out of MS2800 is quite possible, so ensure wires and bus bars are appropriately sized, and positive bus bars insulated or shielded
  • recommends batteries under the floor of the van, lower center of gravity and saves space in living quarters. Not as feasible for Lithium due to challenges with LFP and freezing temperatures.

SD_Charlie is using MultiPlus 12⁄3000 120-50, BlueSolar MPPT 100⁄50, BMS12/200, BMV 700, Color Control GX all from Victron, powered by two 270-watt panels in series. Battery is Victron 12.8⁄200. Initial Schematic

TODO: take a look at http://www.go-modular.com/Traveler/EcVictronComponents.JPG and see if there are more details.

Mojogoat listed a bunch of tips and tricks on both sprinter-forum and promasterforum:

  • Just finished installing the battery heater in my lithium bank. I used a 12v seat heater kit, 60watts made from carbon mesh. I tested it and it started transferred heat through the bottom of of my battery box, 3⁄4” plywood within in 2 minutes. Cheap and easy.

Electrical

Vendors and suppliers

There are a limited number of vendors for Lithium batteries and components, most are targeted at the Electric Vehicle market, and aren’t necessarily that well suited to RVs. There are a few suppliers targeting RVs, and some crossover from the marine world, where Lithium is becoming more popular on cruising sailboats.

  • Starlight Solar in AZ sell Elite Power Solutions LFP and Relion “smart” Batteries with built-in BMS. EPS LFP ranging from $12 / Ah (100Ah) to $8.40 / Ah (500Ah) including BMS
  • AMSolar has started selling Victron LFP batteries and components, along with their own customized relay system to control high/low voltage cutoffs and temperature cut-off. Pricy though - $1150 for the base kit, and ~$12 per Ah for the Lithium batteries. Looks like a thorough and complete DIY system design though.
  • Peter Kennedy Yacht Service / PKYS is another Victron dealer, with similar pricing to AMSolar - a bit cheaper in some cases, more expensive in others.
  • Electric Car Parts Company sell Bright-star aluminum-shell LiFePO4 batteries. Recommend Orion Jr BMS

Batteries

  • Battle Born Batteries have 100 Ah 12V LFP battery with integrated BMS for $899 - $9/Ah in Group 27 case 12.75x6.85x9
  • Stark Power has 12V 100Ah and 12V 125 Ah batteries ($899, $1270 = $9/Ah, $10.08/Ah) in Group 31 case (12.4x6.5x8.5)
  • Bright Star aluminum shell LFP 220Ah ($1280 + $510 Orion Jr BMS = $8.13/Ah - cheaper at 400Ah - $6.97/Ah) dimensions 5.1x12.4x11.9 + BMS - CALB are marginally cheaper 180Ah @ $230 = 7.94/Ah with BMS
  • Victron - $12/Ah + BMS - see above
  • Lithionics
  • Stark Power

Solar

Attaching solar panel cables so they don’t bounce around

  • adhesive cable tie mounts tend to fall off
  • Orton “I bolted a piece of aluminum flatbar across the panel from each side aluminum extrusion. Tie wrapped the cables to that to get to the panel perimeter aluminum extrusion. Did not try to bond anything to under side of the panel.”

Roof rack for solar

  • Mojogoat has a custom rack for 4x100W panels. Based off Vantech mounts with custom aluminum welding?
  • If I want more than 2x300W panels on the roof, it will be necessary to build a slider (or omit the maxxfan) One approach for a slider is L-channel or C-channel plus a drawer slide. See example That works for smaller panels, but finding a 60”+ full extension slide in stainless steel that isn’t huge is a challenge. Perhaps use 80⁄20 in two layers and sliding door glides?
  • for roof rack layout the Body Builder Guide has dimensions for the roof pins - see Measurments for roof rack mounts
  • WeatherGuard roof rails look promising - about the same price as 6x vantech mounts, and more flexible

System Layout

  • Progression through a variety of layouts
  • separate circuit for non-esential loads
  • wire choices
  • Anchorless electrical plan
    • Layout for Transit with Lifeline AGM, Small Magnum inverter/charger, CTEK alternator/solar

  • Use ropes to determine cable length and tag with wire size and connector.

    The first picture shows the ropes that were taken to the local Interstate Battery store to get the cables made. They cost $111.50. Each rope has a red or black tape denoting the color, a tag that gives wire size and a tag at each end that states if connector is straight or a 90 and what diameter hole is required. There were a couple more samples in addition to those shown in the picture.

Solar panel vendors

https://pinboard.in/u:dttocs/t:solar/t:rv/

Sliders for solar panels

Tesla batteries

Monitoring