Backyard shed office 600W 12V
12V system, designed for a -20C (-4F) cold snap - saved 2026-09-06
Compatibility checks
11 passing checks - expand to see the math
passBattery matches the 12V systemSystem voltage coherence
LiTime 12V 230Ah Plus LiFePO4 (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
Renogy 1000W 12V Pure Sine Wave Inverter (RNG-INVT-1000-12V-P2) DC input is 12V-class.
inverter DC input 12V is in the 12V class == system 12V
passCharge controller supports 12V banksSystem voltage coherence
Renogy Rover 60A supports 12/24/36/48V battery banks.
controller battery voltages [12, 24, 36, 48] include 12V
passString Voc stays at 91.2V at -20C - safe down to -235.1C (-391.3F)Cold-temperature string voltage
3 x Renogy 200W 12V Monocrystalline Solar Panel (RSP200D) in series stays below the Renogy Rover 60A max PV input voltage at your design low temperature. The string would not reach the 140V limit until the temperature drops below -235.1C (-391.3F).
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))
= 27.00V x 3 x (1 + (-0.28%/100) x (-20 - 25))
= 27.00V x 3 x 1.1260 = 91.2V
Controller max PV input: 140V
Crossover: string Voc reaches 140V at T = 25 + (140/81 - 1) x 100/-0.28 = -235.1CpassString Vmp 67.8V has healthy margin over the 12V bankMPPT voltage margin
Clears the start floor cold and the hot-weather floor with sag included.
Vmp_string = 22.60V x 3 = 67.8V Start floor = V_batt + 5V = 12 + 5 = 17V Hot Vmp (~11% sag) = 67.8V x 0.89 = 60.3V vs hot floor 20V
passController can pass the array's full output (46.9A of 60A rated)Array size vs controller charge output
No clipping at rated conditions.
Array = 200W x 3 panels = 600W Potential charge current = 600W / 12.8V = 46.9A Controller rated charge current: 60A
passArray 600W is within the controller's 800W rating at 12VMax array wattage for battery voltage
Within the published maximum array wattage.
Array = 200W x 3 panels = 600W Controller max array wattage at 12V: 800W
passRenogy Rover 60A 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 200A 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 = 200A x 1 batteries = 200A Headroom band starts at 80% of limit = 160A
passBank BMS peak 600A covers the inverter's 156.3A surgeInverter surge vs battery peak limit
Surge loads within the bank's published peak rating.
Surge draw = 2000W / 12.8V = 156.3A Bank BMS peak = 600A x 1 batteries = 600A
passCharge current 60A is within the bank's 200A capacityCharge current vs bank capacity
Charge rate within limits.
Controller rated charge = 60A Bank max charge = manufacturer max charge 200A x 1 = 200A
1 check not run (missing published specs)
not checkedNot checkedArray current vs controller input limit
Renogy Rover 60A does not publish a PV input current limit in our data. MPPT controllers generally current-limit safely, but verify against the manual.
Parts list
Wire and fuse guidance
| Segment | Continuous | Run (one way) | Copper wire | V-drop | Fuse/breaker |
|---|---|---|---|---|---|
| Array to charge controller | 9.7A | 25 ft | 14 AWG | 1.80% | 15APV-rated (gPV) fuse or DC breaker |
| Charge controller to battery bank | 60.0A | 5 ft | 4 AWG | 1.16% | 80AClass T |
| Battery bank to inverter | 78.1A | 4 ft | 3 AWG | 0.96% | 100AClass T |
Array to charge controller: show the math
Continuous current = 9.7A Design current = 9.7A x 1.25 (NEC continuous) = 12.1A Wire: 14 AWG copper (75C ampacity 20A); voltage drop 1.80% over 50ft round trip at 67.8V (target <= 3%) Fuse/breaker: 15A - two criteria, both required: carry the load: fuse >= design 12.1A -> 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 = 60A Design current = 60A x 1.25 (NEC continuous) = 75A Wire: 4 AWG copper (75C ampacity 85A); voltage drop 1.16% over 10ft round trip at 12.8V (target <= 3%) Fuse/breaker: 80A - two criteria, both required: carry the load: fuse >= design 75A -> next standard size = 80A protect the wire: fuse 80A <= 4 AWG ampacity 85A - OK bank BMS continuous 200A >= fuse 80A: 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 0.96% over 8ft 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 200A >= 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 | ~60 ft total (25 ft one way, round trip + slack) - Array to charge controller |
| 15A PV-rated (gPV) fuse or DC breaker | 1 | Array to charge controller |
| 4 AWG copper wire | 1 | ~15 ft total (5 ft one way, round trip + slack) - Charge controller to battery bank |
| 80A Class T | 1 | Charge controller to battery bank - include the matching fuse holder/block |
| 3 AWG copper wire | 1 | ~10 ft total (4 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
The backyard office is the quiet common case of off-grid solar: a shed too far from the house to trench a line at reasonable cost, and a workday's loads that are genuinely modest - laptop, monitor, lighting, a fan, chargers. This build runs all three panels in one series string, which keeps current low over the longish run from the shed roof or ground mount to the controller, at the cost of the whole array dimming together if it shades.
The oversized-sounding battery is the point of the design. A workday draws steadily but lightly, so a 230Ah bank cycles shallowly, rides through a dark day or two without drama, and will age gracefully doing it. The compact inverter is matched to the real loads rather than to ambition - office electronics never come close to its rating - and a cold-climate design temperature keeps the string honest against the controller's input limit on clear winter mornings, exactly when a home office still has to work.
Common questions
Why not just run an extension cord from the house?
For a shed near the house, a properly installed line is often the right answer and this build is unnecessary. Solar wins when trenching is expensive or impossible, when the shed is far from the panel, or when you want the office independent of the house entirely. It is an economics question before an electrical one.
Can this run a space heater in winter?
Electric resistance heat is the classic off-grid budget killer - a small heater running through a workday would dwarf every other load combined. Insulate the shed, heat the person rather than the room, or use a fuel heater; spend the solar budget on the loads electricity is good at.
What happens on a string of cloudy days?
The oversized bank is the buffer: light office loads draw it down slowly, and a couple of dark days leave room to spare. Deeper overcast stretches mean rationing the discretionary loads or topping up from the house. The builder's checks size the recharge chain so a clear day afterward refills the bank quickly.
Why 12V for this build?
The loads are small, the wire runs inside the shed are short, and 12V accessories - LED lighting, USB power, fans - plug straight in without a converter. The long run is on the solar side, where the series string keeps current down. At this scale the simplicity of 12V beats the efficiency argument for 24V.