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Carbon dioxide detectors
Carbon dioxide detectors (or CO2 detectors) measure carbon dioxide, which is very unlikely to reach dangerous levels in any vehicle. High CO2 levels could cause drowsiness, which is a risk especially when driving. Look for an NDIR sensor, which measures CO2 directly; cheap "eCO2" sensors only estimate it from other gases. Don't confuse carbon dioxide detectors with carbon monoxide (CO) detectors; be sure you're buying the kind you want. Products listed here are battery powered or car-outlet powered; plug-in (AC) models are usually cheaper but not as well suited for nomadic living.
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Carbon monoxide detectors
Carbon monoxide detectors (or CO detectors) are important for safety, especially when sleeping in your vehicle or using any appliance that burns fuel. Look for certifications to ensure that it actually detects CO well, such as "USA NIST" calibration for portable meters or UL 2034 for home-style alarms. Note that CO2 detectors (not CO) measure carbon dioxide, which is very unlikely to reach dangerous levels in any vehicle. Be sure you're buying the kind of detector you want. Products listed here are battery powered or car-outlet powered; plug-in (AC) models are usually cheaper but not as well suited for nomadic living. Many products detect multiple gases including CO, so if you want additional protection, consider a gas monitor instead of a CO detector.
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Diesel heaters
Diesel heaters (also called parking heaters or air heaters) burn a small amount of diesel in a sealed chamber and blow the warm air into your living space, while the exhaust goes outside. They use very little fuel, usually about 0.03–0.13 gal (0.1–0.5 L) per hour, and very little electricity once running. They do need a short burst of extra power at startup to heat the glow plug. All-in-one models have the fuel tank and controls built in and sit outside or in a toolbox, while split models are installed permanently. Budget models are often advertised as "8kW", but their real output is usually much lower, so don't rely on the rated number. If you camp at high altitude, look for altitude adjustment. Webasto, Eberspächer (Espar) and Autoterm (Planar) make the premium heaters; budget brands like Vevor, Hcalory and Sunster cost far less, but quality varies more. The exhaust must always be sealed and routed outside, and you should always use a carbon monoxide detector with one.
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LiFePO4 batteries
LiFePO4 batteries (lithium iron phosphate, sometimes written LFP) are the most popular deep-cycle batteries for vehicle electrical systems, mostly replacing lead-acid and AGM batteries. They weigh about half as much, last thousands of charge cycles, and you can use nearly all of their rated capacity, while lead-acid batteries should only be drained about halfway. Capacity is listed in amp-hours (Ah); a 12V 100Ah battery holds about 1,280Wh. A built-in battery management system (BMS) protects the cells. Most LiFePO4 batteries must not be charged below freezing, 32℉ (0℃), so if you camp in the cold, look for low-temperature cut-off or self-heating. Unlike a portable power station, a bare battery has no outlets or inverter, so it needs a charger and a solar charge controller. Popular brands include Battle Born, Renogy, LiTime, SOK and Epoch.
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Portable fridges
Portable fridges (also called 12V fridges or electric coolers) use a compressor, like a home refrigerator, so they keep food cold or frozen without ice. Most run on 12V/24V DC from your vehicle or house battery, and many also plug into a wall outlet. Once they are cold they use surprisingly little power, so a small solar setup or power station can often keep one running. Don't confuse them with cheaper thermoelectric coolers, which can only cool to a set amount below the outside temperature and use a lot of power. Dual-zone models have two compartments, so you can run a fridge and a freezer at the same time. Some models have a built-in battery. Look for adjustable battery protection, which shuts the fridge off before it drains your starting battery. Popular brands include Dometic, ICECO, ARB, BougeRV and Alpicool. Premium models often use a Secop compressor, which has a reputation for being reliable and efficient.
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Portable power stations
Portable power stations are a convenient way to get electricity for your devices and small appliances while camping or on the road. They don't make their own power; they are large batteries that can be charged from an outlet, your car, or solar panels. These are sometimes marketed as "solar generators" (recharged via solar) and can be used in place of fuel-powered generators for some uses. Popular brands include Bluetti, Jackery, EcoFlow, GoalZero, and Anker. Smaller brands often use cheaper batteries and components, and are less likely to provide detailed product specifications, so don't shop on price alone. To appear on this list, a device must have at least 100Wh capacity and at least 1 AC outlet.
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Solar charge controllers
Solar charge controllers sit between your solar panels and your battery, and control the charging so the battery is charged properly and isn't damaged. MPPT controllers turn more of the panel's power into charge than PWM controllers, especially in cold weather or with higher-voltage panels. PWM controllers are cheaper and work fine for small, simple setups. To pick a size, divide your total panel watts by your battery voltage and leave some room to spare (for example, 400W ÷ 12V ≈ 33A, so choose 40A). Also make sure your panels' open-circuit voltage (Voc) stays below the controller's maximum PV input voltage, because Voc goes up in the cold. For lithium batteries, look for a LiFePO4 charging profile and low-temperature charge cut-off. Be careful with very cheap controllers that claim high ratings like "100A MPPT": their real performance is often far lower. Popular brands include Victron, Renogy, EPEver, BougeRV and LiTime. You don't need a separate controller for a portable power station, which has one built in.
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This productFABISENSE Portable CO2 Detector, Indoor Air Quality Monitor with Temperature & Humidity Display, 400-5000 PPM CO2 Meter, Audible Alarm, Rechargeable Battery for Home, Office, Greenhouse (Orange) 
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INKBIRD Smart Air Quality Monitor Ndir CO2 Monitor Bluetooth with App | 3 in 1 Battery Powered Indoor CO2 Detector for Carbon Dioxide & Temperature & Humidity for Home, Office, Grow Tent (IAM-T2) 
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