Before I get into this post, I want to take a moment to acknowledge my father‑in‑law, Kevin, who passed away this week at the age of 97. He was a man I admired deeply, and I’m grateful for the part he played in bringing my beautiful wife into the world. To Michelle and her family — all my love. Kev, you brought joy into my life from the day I met you. You are missed.
Now, back to the journey ahead. We’ve started our nine months of leave and picked up the Ultimate, so it’s time to get some posts done.
Before we hit the road for the big lap, I wanted to understand exactly how our power system behaves in the real world — not in brochures, not in YouTube reviews, but in our Trailblazer, with our gear, in the conditions we’ll actually live in.
So I ran a simple test: a 200Ah lithium battery in the car, a 40L Engel running as a fridge on low, and the vehicle left untouched overnight.
Here’s what I learned.
The Engel barely sips power in fridge mode
Overnight, the battery dropped only 1–2%, which works out to roughly 2–4Ah. For a 40L Engel running as a fridge, that’s incredibly efficient — and a reassuring sign that the system is healthy.
This tells me:
- The fridge is running efficiently
- The battery is behaving exactly as it should
- There are no hidden parasitic drains in the vehicle
For everyday travel, this is the kind of baseline you want.
Freezer mode will use more — but still manageable
When we crank the Engel up to freezer temps and load it close to full, it will naturally draw more power. That’s just physics.
But even then, with a 200Ah lithium, we’ve got plenty of buffer. The freezer will work harder, especially during the initial pull‑down, but once everything is frozen, the duty cycle settles.
The takeaway:
Freezer mode is totally doable — just expect a higher daily percentage drop.
Safe discharge levels for lithium are generous
LiFePO₄ batteries are happiest when you avoid the extremes. A good rule of thumb:
- Try not to go below 20% for everyday use
- 10% is fine occasionally
- Anything above 20% is considered very battery‑friendly
With our usage pattern, it’s unlikely we’ll ever get close to the danger zone.
The 30A DC‑DC charger gives a predictable recharge rate
A 30A charger pushes 30Ah per hour into the battery (minus whatever the fridge is using at the time). On a 200Ah battery, that’s roughly:
- 15% per hour of driving
- Or 13–14% per hour once you factor in the fridge draw
This makes planning simple. If we ever dropped to 50%, a few hours of driving would bring us right back up.
Real‑world conclusion: we’re comfortably off‑grid for days
Based on the numbers, we can safely assume:
- Around 15% battery use per day in fridge mode
- Up to 5 days off‑grid without starting the car
- Even more if we add the solar blanket into the mix
And realistically, we’ll be starting the car every couple of days anyway. Add the solar blanket — which we can swap between the Trailblazer and the camper — and the system becomes even more forgiving.
The system is ready for the lap
This little test gave me exactly what I needed: confidence.
We now know:
- The Engel is efficient
- The lithium is behaving perfectly
- The DC‑DC charger gives predictable recovery
- Our real‑world usage aligns with the trip we’re planning
It’s one thing to read specs. It’s another to see your own numbers in your own setup. And based on this test, our power system is more than ready for the year on the road.
