The Sun on Mars

01 Jun 2022 back to blog

This is a quick overview of what we learned and what I’d propose we consider on the next go for our (entirely off grid) solar power system on Mars. Many thanks to all who were involved with the power system this year!

The 22 Approach

Many systems, many arrays

• Earth: 2500w PV + 9.6kw Battery
• Water: 2500w PV + 9.6kw Battery
• Air: 1000?w PV + 9.6kw Battery
• Internet: 1000?w PV + ~2kw Battery

The 22 Results

Initially seemed to work OK, but unbalancing tanked our reliability

• System initially handled okay, though was high in maintenance (many thanks to Flo for leading this!)
• Feb 15: Disaster strikes when a solar charge controller fails, killing an inverter with it. The frankensteined remaining system overdraws every day for two weeks, unbalancing the batteries, before…
• March 2nd: Replacement hardware arrives, but doesn’t have enough extra amperage to refill, let alone rebalance, its battery array
• Trailer batteries struggle to refill themselves, BMS safety open circuits every night from here on out, load is unevenly distributed

Lessons Learned

• Battery banks need rebalanced, particularly when fully discharging
• Battery monitors and load monitoring needs to be implemented on all systems from day 1
• Easy and fast ways to bring in generator power to fill up the system need to be built in from day 1
• The cost of losing power to any given building is low, the cost of losing power to refrigerators is high, the cost of losing power to internet is unbearable
• Our battery banks were too small: the 4x200ah48v only gave us 9.6kwh, enough to run the 1kw load for only 9 hours - not enough margin for error (also hard on the batteries)
• Lost significant PV generation capacity to systems that did not use the power

What about 2023?

Proposal: the Power Room

3 systems based on criticality, colocated in partially dust protected space:

• Primary: Largest system, handles main load, chargers, trailers
• Secondary: refrigerators, hydroponics, also able to step in for short stints in the event of primary failures
• Critical: Very small system for internet only

This room could house the solar charge controllers as well - while maintaining our solarpunk #a e s t h e t i c of having our panels at the top of the various buildings, we can send the power down at 120v before transforming it to battery voltages.

Additional details / changes

• Built in AC power selector for effortless changes between generator and inverter supply - allows non technical users to begin recovery by simply turning on a generator, immediately the entire system has functioning AC power
• 4x small (cheap) 12v chargers to rebalance the 48v battery banks
• A large dedicated 48v battery charger to allow a generator to charge the 48v system ( would be very nice and vastly improve recovery post full discharge)
• Using 24v for the two smaller systems would reduce the amount of rebalancing, using 48v for the main system reduces voltage loss to wire inefficiency - there is a case to be made for for going all 24v or all 48v though
• Allocating an extra 24v inverter + 2 100ah batteries for a art car would be optional, removes generator noise

posted by: Atin Octavia