Vehicle Power · Volume 1
What the Truck Has to Power, and How Much It Actually Needs
Introduction
🔴 THE ARCHITECTURE IN THIS DIVE WAS NOT BUILT. Corrected 2026-08-30. 🔴 There is no house battery, no DC-DC charger and no distribution block. It is an EcoFlow River 3 Max Plus, 858 Wh, 24 lb, with a Renogy 200 W portable panel. The Anker SOLIX F3000 and the 200 Ah bank are both permanently out of the build. The load arithmetic below still stands and is what sized the replacement; the DC-DC charger, the bank capacity and the distribution design are being re-derived. ⭐ The CPAP gate is still met — 3.9 nights at the worst case against a two-night requirement. → Weight and Balance vol 3.
Five dives in this project end by pointing here. The cockpit needs fused, switched and constant supplies. The radios need clean power away from control modules. The cellular gateway, if bought, needs 9–36 V DC. The fridge needs to run overnight without killing the truck. And a CPAP has to run every single night, in the tent, without fail, which turns out to be the requirement that reshapes the whole design.
This volume does the arithmetic that turns those into one system.
1.1 The loads, honestly measured
Table 1 — The loads, honestly measured
| Load | Draw | Duty | Daily energy at 12 V |
|---|---|---|---|
| Fridge | 4–5 A while the compressor runs | Cycles; ~20–35% duty | 30–40 Ah/day |
| CPAP, humidifier OFF | see below | 8 h/night | ~7–14 Ah/night (must be measured) |
| CPAP, humidifier ON | ResMed typical 51–53 W | 8 h/night | ~34 Ah/night |
| Cellular gateway | <14 W, ~1.2 A | Continuous when used | ~10–15 Ah/day |
| Tablet, phone, eTrex charging | 1–3 A intermittent | A few hours | ~5–10 Ah/day |
| VHF/UHF radio, receiving | ~0.5–1 A | Continuous when on | ~5–10 Ah/day |
| VHF/UHF radio, transmitting | 8–12 A at 50 W | Seconds at a time | Negligible in energy |
| Scanner | ~0.3–0.5 A | Continuous when on | ~4–6 Ah/day |
| Camp lighting, LED | 1–2 A | A few hours | ~5 Ah/day |
Two loads dominate and everything else is noise: the fridge and the CPAP. That is the single most useful fact in this volume, and it is a different fact from the one this dive originally recorded — the CPAP was added to the requirement after the first pass, and it roughly doubles the overnight demand.
1.2 The fridge number deserves care
Manufacturer lab data for a fridge of this class is around 0.269 kWh per 24 hours — 269 Wh, or roughly 22.5 Ah at 12 V. Real-world reports consistently land at 32 to 40 Ah per day. The gap is not dishonesty; lab figures are measured at moderate ambient with a closed lid, and real use is neither.
Three factors move it, and all three apply here:
- Ambient temperature. A fridge in a hot bed in full sun can draw 50% more than the same unit in shade.
- Setpoint. Running as a freezer at 0 °F rather than a fridge at 38 °F roughly doubles the work.
- Lid openings. Ten or more an hour pushes draw up 30 to 50%, because cold air falls out of a chest fridge every time the lid lifts.
Design against 40 Ah per day, not 22.5.
1.3 The CPAP number, from ResMed’s own documents
The ResMed AirSense 10 with the Air10 90 W DC/DC converter (model 370003) is the relevant combination, and ResMed publishes real figures for both halves:
Table 2 — The ResMed AirSense 10 with the Air10 90 W DC/DC converter (model 370003) is the relevant combination, and ResMed publishes real figures for both halves
| Source | Figure |
|---|---|
| AirSense 10 user guide, 90 W PSU | Typical 53 W (57 VA), peak 104 W (108 VA) |
| Air10 DC/DC converter guide | Typical 51 W, peak 106 W |
| Converter input rating | 12 V at 13 A (or 24 V at 6.5 A) |
| Converter output | 24 V at 3.75 A |
Those “typical” figures are with the humidifier running, and ResMed says so explicitly in the converter guide: the device with the HumidAir humidifier consumes considerably more than the device alone, and using the humidifier will drain a battery faster.
At 51 W for eight hours that is 408 Wh — about 34 Ah at 12 V, before conversion losses. That is very nearly a second fridge.
Humidifier off is a different machine, and it is the reason the humidifier-off habit is load-bearing rather than a preference. ResMed does not publish a humidifier-off consumption figure in the guides on hand. Blower-only operation at moderate pressure is commonly in the region of 10 to 20 W, giving roughly 7 to 14 Ah over a night — but that is an estimate, and the pressure setting moves it.
🔴 This number must be measured, not estimated, because it is the load the design is built around. The measurement is already scoped: the CPAP project’s AS10-BENCH-SHEET.html worksheet in Tasks/CPAP/ exists specifically to capture the hardware-blocked measurements on this machine, and humidifier-off current at the operating pressure belongs on it. Volume four covers what else to record.
1.4 Sizing the battery
Two scenarios, and the difference between them is the design decision.
Table 3 — Sizing the battery
| Scenario | Fridge | CPAP | Everything else | Daily total |
|---|---|---|---|---|
| Humidifier off | 40 Ah | ~12 Ah | ~25 Ah | ~77 Ah/day |
| Humidifier on | 40 Ah | ~34 Ah | ~25 Ah | ~99 Ah/day |
Against those:
Table 4 — Against those
| Autonomy | Humidifier off | Humidifier on | AGM equivalent (hum. off) |
|---|---|---|---|
| 1 night | ~80 Ah | ~100 Ah | ~160 Ah |
| 2 nights | ~155 Ah | ~200 Ah | ~310 Ah |
| 3 nights | ~230 Ah | ~300 Ah | ~460 Ah |
This is a materially different answer from the one the fridge alone produces. A single 100 Ah LiFePO4 — the obvious starting point for a fridge-only rig — is now roughly one night, not two.
🔴 What actually happened: the fridge came out of the build, and the whole analysis above collapsed with it.
Without the fridge there is only one load that matters, and it is the CPAP. At ResMed’s confirmed 10–25 W with humidifier and heated tube off, a night is 80 to 200 Wh — not the 34 Ah the fridge-plus-CPAP arithmetic produced. ⭐ That is a small enough number that a fitted bank is no longer justified, and the build settled on an EcoFlow River 3 Max Plus, 858 Wh, 24 lb, which gives 3.9 nights at the top of the band and 9.6 at the bottom against a two-night requirement.
⚠ The options below are recorded as the reasoning that led there, not as the recommendation. They were correct for a rig carrying a fridge.
- ~100 Ah LiFePO4 — one comfortable night with the humidifier off. Adequate for a rig that drives every day, and thin if it does not.
- ~200 Ah LiFePO4 — two nights with the humidifier off, or nearly two with it on. This was the recommendation while the fridge was in the build. It weighs roughly 50–60 lb, which is a real payload cost on a truck that is already tight.
- AGM at any of these capacities is impractical. The 50% depth-of-discharge limit means roughly double the nameplate and roughly double the weight again — over 300 Ah and well past 150 lb for two nights. On this truck, lithium is not a refinement, it is the only workable chemistry.
1.5 The design rule a medical device imposes
The CPAP is not a comfort load and it does not get treated like one.
Everything else on this list can be sacrificed. The fridge can be turned off and the food eaten or lost. The gateway, the radios, the lights, the charging — all of it is discretionary. The CPAP is therapy, and running out of battery at two in the morning is a real consequence rather than an inconvenience.
Three rules follow, and they are the reason this volume was rewritten:
- Reserve capacity for the CPAP explicitly. Whatever the bank is, one night of CPAP is spoken for and is not available for anything else. A battery monitor showing 30 Ah remaining with the humidifier off means one more night of therapy and nothing else, not “30 Ah of margin”.
- Humidifier off is the default in the field, on purpose. It is roughly a 22 Ah/night saving — the difference between a bank lasting one night and two. Since the humidifier can be turned off most of the time anyway, this costs almost nothing and buys a great deal.
- There must be a fallback that does not depend on the truck. Covered in volume four; this is the reason the CPAP project’s separate battery-pack build matters to this project.
1.6 The insight that sizes everything: driving is the charger
Solar gets the attention in overland builds and the alternator does the work.
A 30 A DC-DC charger replaces roughly 30 Ah per hour of driving. Against the revised figures:
Table 5 — A 30 A DC-DC charger replaces roughly 30 Ah per hour of driving. Against the revised figures
| Charger | Per hour | Hours to replace a humidifier-off day (~77 Ah) |
|---|---|---|
| 20 A | 20 Ah | ~4 h |
| 30 A | 30 Ah | ~2.5 h |
| 40 A | 40 Ah | ~2 h |
| 50 A | 50 Ah | ~1.5 h |
The CPAP moves the recommendation from 30 A to 40 A. With the fridge alone, two hours of driving covered a day comfortably and 30 A was ample. With the CPAP added, 30 A needs two and a half to three hours, which is more driving than a rig that has found a good campsite necessarily wants to do. 40 A restores the “a couple of hours of driving covers a day” property, and that property is what makes the whole architecture work.
Solar, by contrast, is sized around 200 W for a 100 Ah lithium bank by the usual rule of thumb, yielding perhaps 60–80 Ah across a good summer day — comparable to two hours of driving, but only in sun. Under the forest canopy that characterises most of the Upper Peninsula, solar should be treated as a bonus rather than a plan. With a CPAP on the bus, that distinction stops being academic.
The correct framing: the DC-DC charger is the primary source, solar is the stationary backup, and the CPAP is the reason there must also be a third answer.
1.7 Re-examining the Anker SOLIX F3000
The equipment list carries an Anker SOLIX F3000: 3,072 Wh, 3,600 W AC output, 2,400 W solar input, four AC outlets, a 30 A RV plug, a 12 V car socket, an Anderson port, USB-C and USB-A, expandable to 12 kWh — and just over 91 lb, with a wheeled suitcase design.
It is a good product and it is a home-backup product. The mismatch, stated plainly:
- 3,072 Wh is roughly 256 Ah at 12 V — about three nights of full camp with the humidifier running, which is genuinely useful, but it delivers that in a single 91 lb lump.
- 91 lb is more than half a rooftop tent on a truck whose payload is the binding constraint. It is the heaviest discretionary item on the equipment list.
- Its strength is AC at 3,600 W, and almost nothing here is an AC load. The fridge, radios, gateway, lighting and the CPAP’s DC converter are all natively DC. Running them through an inverter means converting 12 V up to 120 V and back down again, paying an efficiency penalty twice.
- It cannot be charged from the alternator at anything like DC-DC rates. Charging a power station through a 12 V socket is limited to what that circuit allows — a small fraction of what a 40 A DC-DC delivers.
✅ RESOLVED 2026-08-30: the F3000 is permanently out of the build. Its genuine roles are home backup and base-camp AC, and that is where it stays. ⚠ But the conclusion this volume drew from the analysis — build around a fitted 12 V bank and a DC-DC converter — did not survive either. Removing the fridge removed the load that justified it.
But the CPAP does rehabilitate part of the portable-station idea — just not this station. The CPAP has to run at the tent, eight feet up a ladder, and volume four argues that a small dedicated pack is the right answer to that. A few hundred watt-hours at ten to twenty pounds does that job. Ninety-one pounds does not go up a ladder.
1.8 What this volume concludes
⚠ Items 1 to 4 below were written while the fridge was in the build. It is not, and they no longer describe the system. They are kept because the reasoning is what produced the replacement.
The fridge and the CPAP are the loads.🔴 The fridge is out of the build. The CPAP is the only load that matters.Target two nights of autonomy: roughly 155 Ah.⭐ Two nights is still the requirement, but it is now 160–400 Wh rather than 155 Ah.Around 200 Ah of LiFePO4.✅ EcoFlow River 3 Max Plus, 858 Wh, 24 lb.40 A DC-DC.🔴 No DC-DC charger. The pack takes 220 W from the truck’s 12 V socket, which refills a night’s use in under two and a half hours of driving.- ✅ Solar is a bonus under Upper Peninsula canopy, not a plan. Around 200 W is the right scale — and a Renogy 200 W portable panel is what was bought, matched to the pack’s 220 W input.
- ✅ The Anker F3000 is out of the build. The instinct that a small dedicated pack belongs at the tent turned out to be the whole answer rather than a supplement.
- ✅ The CPAP’s humidifier-off draw was settled: ResMed’s own 10–25 W.
⭐ What replaced four volumes of architecture: a 12 V socket, a 24 lb power station, and a folding panel. Removing one load removed the entire fitted electrical system.
References
- ResMed — AirSense 10 user guide, 90 W power supply: typical power consumption 53 W (57 VA), peak 104 W (108 VA). Local copy:
Tasks/CPAP/refs/as10-user-guide-amer.txt. - ResMed — Air10 90 W DC/DC converter guide (model 370003): input 12 V/24 V at 13 A/6.5 A, output 24 V at 3.75 A, typical 51 W, peak 106 W; explicit warning that the HumidAir humidifier consumes considerably more and drains a battery faster. Local copy:
Tasks/CPAP/refs/air10-dc.txt. - 12 V fridge consumption: manufacturer lab data around 0.269 kWh/24 h (~22.5 Ah); real-world 32–40 Ah/day; sun adding up to 50%, freezer setpoint roughly doubling it, frequent lid opening adding 30–50%.
- Battery sizing practice: LiFePO4 requiring roughly 70% of equivalent AGM capacity; lead-acid usable depth of discharge around 50%; solar rule of thumb of roughly twice the AGM Ah in watts.
- Anker — SOLIX F3000: 3,072 Wh, 3,600 W AC, 2,400 W solar input, just over 91 lb.
- GL.iNet — GL-X3000: under 14 W, 9–36 V DC input.
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