Truck camper 400W 12V
12V system, designed for a -15C (5F) cold snap - saved 2026-08-16
Compatibility checks
infoArray is oversized for the controller - output will clip at ~384WArray size vs controller charge output
The array can push 31.3A but the controller tops out at 30A. This is common and usually fine: you harvest more in mornings, evenings, and winter, and the controller simply caps peak output. Verify the controller's max array wattage is not exceeded (separate check).
Array = 200W x 2 panels = 400W Potential charge current = 400W / 12.8V = 31.3A Controller rated charge current: 30A
11 passing checks - expand to see the math
passBattery matches the 12V systemSystem voltage coherence
SOK SK12V206P 12V 206Ah Marine (12.8V nominal) is a 12V-class battery.
battery nominal 12.8V is in the 12V class == system 12V
passInverter matches the 12V systemSystem voltage coherence
Victron Energy Phoenix Inverter 12/1200 120V VE.Direct (NEMA 5-15R) DC input is 12V-class.
inverter DC input 12V is in the 12V class == system 12V
passCharge controller supports 12V banksSystem voltage coherence
Victron Energy SmartSolar MPPT 100/30 supports 12/24V battery banks.
controller battery voltages [12, 24] include 12V
passString Voc stays at 48.5V at -15C - cannot reach the 100V limit at any temperatureCold-temperature string voltage
2 x Rich Solar MEGA 200 200W 12V Monocrystalline Solar Panel in series stays below the Victron Energy SmartSolar MPPT 100/30 max PV input voltage at your design low temperature. This string cannot reach 100V at any physically possible temperature.
Why this matters: Panel voltage rises as temperature falls. A string that measures fine in summer can exceed the controller's absolute maximum input voltage on the first cold clear morning, which can permanently destroy the controller - and at these DC power levels, failures can start fires. This is the mistake experienced builders catch most often in DIY parts lists.
Voc_string = Voc x N_series x (1 + tempCoeff/100 x (T_design - 25))
= 21.80V x 2 x (1 + (-0.28%/100) x (-15 - 25))
= 21.80V x 2 x 1.1120 = 48.5V
Controller max PV input: 100V
Crossover: string Voc reaches 100V at T = 25 + (100/43.6 - 1) x 100/-0.28 = -437C (below absolute zero - never reached)passString Vmp 36.8V has healthy margin over the 12V bankMPPT voltage margin
Clears the start floor cold and the hot-weather floor with sag included.
Vmp_string = 18.40V x 2 = 36.8V Start floor = V_batt + 5V = 12 + 5 = 17V Hot Vmp (~11% sag) = 36.8V x 0.89 = 32.8V vs hot floor 20V
passArray short-circuit current 11.60A is within the 35A limitArray current vs controller input limit
Within the Victron Energy SmartSolar MPPT 100/30 published max PV short-circuit current.
Isc_array = 11.60A x 1 parallel = 11.60A Controller max PV short-circuit current: 35A = 35A (manufacturer-specified, compared directly)
passArray 400W is within the controller's 440W rating at 12VMax array wattage for battery voltage
Within the published maximum array wattage.
Array = 200W x 2 panels = 400W Controller max array wattage at 12V: 440W
passVictron Energy SmartSolar MPPT 100/30 supports LiFePO4 chargingBattery chemistry support
Controller has a lithium profile or user-adjustable charge voltages.
battery chemistry = lifepo4; controller lifepo4_profile = true
passBank BMS limit 170A comfortably covers the inverter's 78.1A drawInverter draw vs battery BMS limit
Healthy headroom at full inverter load.
Inverter draw = 1000W / 12.8V = 78.1A Bank BMS limit = 170A x 1 batteries = 170A Headroom band starts at 80% of limit = 136A
passBank BMS peak 200A covers the inverter's 171.9A surgeInverter surge vs battery peak limit
Surge loads within the bank's published peak rating.
Surge draw = 2200W / 12.8V = 171.9A Bank BMS peak = 200A x 1 batteries = 200A
passCharge current 30A is within the bank's 70A capacityCharge current vs bank capacity
Charge rate within limits.
Controller rated charge = 30A Bank max charge = manufacturer max charge 70A x 1 = 70A
Parts list
| Part | Qty | Est. price | Where to buy |
|---|---|---|---|
Rich Solar MEGA 200 200W 12V Monocrystalline Solar Panel | 2 | $340 | |
Victron Energy SmartSolar MPPT 100/30 controllerdatasheet | 1 | $220 | |
SOK SK12V206P 12V 206Ah Marine batterydatasheet | 1 | n/a | |
Victron Energy Phoenix Inverter 12/1200 120V VE.Direct (NEMA 5-15R) inverterdatasheet | 1 | $393 | |
| Estimated total | $953(some prices unknown) |
Wire and fuse guidance
| Segment | Continuous | Run (one way) | Copper wire | V-drop | Fuse/breaker |
|---|---|---|---|---|---|
| Array to charge controller | 11.6A | 12 ft | 14 AWG | 1.91% | 15APV-rated (gPV) fuse or DC breaker |
| Charge controller to battery bank | 30.0A | 4 ft | 8 AWG | 1.18% | 40AClass T |
| Battery bank to inverter | 78.1A | 3 ft | 3 AWG | 0.72% | 100AClass T |
Array to charge controller: show the math
Continuous current = 11.6A Design current = 11.6A x 1.25 (NEC continuous) = 14.5A Wire: 14 AWG copper (75C ampacity 20A); voltage drop 1.91% over 24ft round trip at 36.8V (target <= 3%) Fuse/breaker: 15A - two criteria, both required: carry the load: fuse >= design 14.5A -> next standard size = 15A protect the wire: fuse 15A <= 14 AWG ampacity 20A - OK construction: PV-rated (gPV) fuse or DC breaker
Charge controller to battery bank: show the math
Continuous current = 30A Design current = 30A x 1.25 (NEC continuous) = 37.5A Wire: 8 AWG copper (75C ampacity 50A); voltage drop 1.18% over 8ft round trip at 12.8V (target <= 3%) Fuse/breaker: 40A - two criteria, both required: carry the load: fuse >= design 37.5A -> next standard size = 40A protect the wire: fuse 40A <= 8 AWG ampacity 50A - OK bank BMS continuous 170A >= fuse 40A: the bank can hold the fuse's rated load construction: Class T (interrupt rating matters on battery mains)
Battery bank to inverter: show the math
Continuous current = 78.1A Design current = 78.1A x 1.25 (NEC continuous) = 97.7A Wire: 3 AWG copper (75C ampacity 100A); voltage drop 0.72% over 6ft round trip at 12.8V (target <= 3%) Fuse/breaker: 100A - two criteria, both required: carry the load: fuse >= design 97.7A -> next standard size = 100A protect the wire: fuse 100A <= 3 AWG ampacity 100A - OK bank BMS continuous 170A >= fuse 100A: the bank can hold the fuse's rated load construction: Class T (interrupt rating matters on battery mains)
Mount the fuse close to the battery positive terminal - it protects the wire run, so the unprotected stub should be as short as possible.
Sized for 75C copper ampacity with the NEC 1.25 continuous factor and a 3% voltage-drop target. Round up when between sizes and verify against local code.
Balance of system - shopping list
| Item | Qty | For |
|---|---|---|
| 14 AWG copper wire | 1 | ~30 ft total (12 ft one way, round trip + slack) - Array to charge controller |
| 15A PV-rated (gPV) fuse or DC breaker | 1 | Array to charge controller |
| 8 AWG copper wire | 1 | ~10 ft total (4 ft one way, round trip + slack) - Charge controller to battery bank |
| 40A Class T | 1 | Charge controller to battery bank - include the matching fuse holder/block |
| 3 AWG copper wire | 1 | ~10 ft total (3 ft one way, round trip + slack) - Battery bank to inverter |
| 100A Class T | 1 | Battery bank to inverter - include the matching fuse holder/block |
Derived from the wire and fuse guidance above. Wire lengths include round trip plus slack - verify against your actual layout, and verify ratings against local code. Buy fuses and wire from reputable electrical suppliers; marketplace listings for these items are a common source of counterfeit or mislabeled parts.
About this build
Slide-in truck campers fight for every pound and cubic inch: the electrical bay is tiny and everything counts against the truck's payload rating. This build keeps the system on 12V - matching the camper's native wiring - and picks components for weight and footprint first. The marine-grade battery is built for the vibration and moisture a camper actually sees.
The compact 1200VA inverter class is a deliberate ceiling: phone and camera charging, a laptop, small appliances. Bigger inverters invite bigger batteries and bigger wire, and the payload budget disappears fast. The roof pair of 200W panels wires in series to keep current low through the roof entry. If you camp mostly where you drive, a DC-DC charger from the truck alternator is the natural next addition - check your alternator's rating before adding one.
Common questions
Rigid or flexible panels on a truck camper?
Flexible panels save weight and follow a curved roof, at some cost in efficiency and lifespan. Rigid panels last longer but need racks and sealed penetrations. On a payload-limited camper the weight argument often wins - this example uses rigid panels, so swap them in the builder if your roof disagrees.
Will the truck's alternator charge this battery?
Not properly on its own - lithium wants a charging profile a raw alternator connection does not provide, and a big lithium bank can work an alternator hard. A DC-DC charger solves both problems and is the standard answer for charge-while-driving.
Why a marine battery in a truck camper?
Camper batteries live a rough life: vibration, temperature swings, occasional moisture. A marine-rated LiFePO4 is built for exactly that environment, and its BMS ratings leave comfortable headroom for this inverter class.