Variant 01-A

Off-grid / Backup (Philippines)

Battery-based system with no grid connection: panels, battery, MPPT charge controller, inverter, wiring and protection, with costs in pesos.

By techhardy team

Not yet Reviewed

System24 V · 900 W of panels · 200 Ah battery

Voltage your system runs on

12 V24 V48 V

Total wattage of your devices

About 2,760 Wh a day.

Start-up surge: 100 W. Required: enter the inverter's surge rating in 05 Inverter.

Solar panels
MPPT charge controller
Busbar (+ and −)
Battery
Inverter
Your devices

Panel frames, metal cases and both surge protectors connect to a ground rod.

Legend

Solar panels
Charge controller (DC to DC)
Busbar
Battery
Inverter (DC to AC)
Your devices
Fuse
Circuit breaker
Disconnect switch
Surge protector to ground
Ground (earth)

Standard electrical symbols (IEC 60617).

Parts at a glance

Part	Amount	Rating
	9	100 W each · 900 W total
	3	at least 9.3 A · buy 10 A · ≥ 74.3 V DC
	1	≥ 74.3 V DC
	1	at least 27.7 A · buy 32 A · ≥ 74.3 V DC
	20 m	10 mm² (≈ 8 AWG)
	1	50 A, 24 V battery
	1	at least 62.5 A · buy 63 A · ≥ 30 V DC
	3 m	22 mm² (≈ 4 AWG)
	1 pair	≥ 70 A
	1	at least 62.5 A · buy 70 A · ≥ 30 V DC
	1	≥ 70 A · ≥ 30 V DC
	1 pair	≥ 70 A
	1	24 V · 200 Ah
	1	at least 19.9 A · buy 20 A · ≥ 30 V DC
	3 m	3.5 mm² (≈ 12 AWG)
	1	300 W · surge ≥ 100 W needed
	1	at least 1.7 A · buy 10 A · 30 mA
	1 set	2 mm² (≈ 14 AWG)
	1	2-pole, ≥ your house main breaker
	1	230 V
	16 m	14 mm² (≈ 6 AWG)
	1	—

Checks

0 to fix5 to check13 OK

Check thisBuy a battery whose maximum continuous discharge current (BMS limit) is at least 16 A: the inverter's draw when the battery is nearly empty.05 Inverter
Check thisRequired: enter the inverter's surge (peak) rating from its label. Needed: at least 100 W for a few seconds (everything running at once).05 Inverter
Check thisCheck the controller's manual for the largest wire its terminals take. This design uses 22 mm² (≈ 4 AWG), too thick for many controllers.04 Charge controller
Check thisEnter the main Class T fuse's DC breaking capacity (kA, on its label) and the battery's short-circuit current (datasheet or seller) to check it can stop a battery short.07 Fuses, breakers & grounding
Check thisAsk your electrician whether your local code also needs: ground-fault protection for the panels (NEC 690.5), and a quick-shutdown switch for panels on a roof (NEC 690.12). Many charge controllers and inverters include ground-fault protection; check the manual.07 Fuses, breakers & grounding
13 checks passed
- Battery: 3,840 Wh usable, 3,174 Wh needed.
- Panels: 3,240 Wh a day, 3,174 Wh needed.
- Charging at up to 50 A, within what a typical 200 Ah lithium battery accepts (about 100 A). Enter the battery's maximum charge current to check it exactly.
- Controller 50 A: 46.9 A needed.
- Panels on a cold morning: about 74.3 V, under the controller's 150 V limit.
- Fit each panel row with its own 10 A fuse in a combiner box: a faulty row could get 14.8 A, more than the panel's 10 A rating.
- Panels on a hot day: about 47.7 V, enough to charge (32.0 V needed, rule of thumb).
- Inverter 300 W: 150 W needed.
- Panels → controller wire: 10 mm², loses 1.26%, safe up to 41 A.
- Controller → battery wire: 22 mm², loses 0.46%, safe up to 79 A.
- Battery → inverter wire: 3.5 mm², loses 1.40%, safe up to 20 A.
- Main Class T fuse: 70 A covers the 62.5 A in or out of the battery.
- Panels stay under 80 V (up to 74.3 V): no arc-fault protection needed (NEC 690.11).

01 Loads

Variables

Device	Watts	Qty	Hours/day	Has a motor	Wh/day	Remove
Device name	Starlink watts	Starlink quantity	Starlink hours per day	Starlink has a motor	2,400

Inverter no-load power

Motor start-up draw

Result

Your devices: 2,400 Wh
: 360 Wh
: 2,760 Wh
: 100 W
: 100 W

06 Wiring

Most voltage the wire may lose

Run	Length, one way		Current			Result
Panels → controller	Panels → controller one-way length m	Panels → controller wire size	16.2 A @ 55.5 V	1.26%	41 A ≥ 32 A	OK
Controller → battery	Controller → battery one-way length m	Controller → battery wire size	37.5 A @ 24.0 V	0.46%	79 A ≥ 63 A	OK
Battery → inverter	Battery → inverter one-way length m	Battery → inverter wire size	15.9 A @ 21.0 V	1.40%	20 A ≥ 20 A	OK

07 Fuses, breakers & grounding

Main battery protection

Main fuse or breaker at the battery

Rating of the one you buy

Breaking capacity (DC)

Battery short-circuit current

Result

Minimum: biggest battery current × 1.25: 62.5 A
Recommended: next size sold: 70 A
Used in this plan: 70 A
Battery cables and busbars: cables ≥ 70 A · busbars ≥ 70 A

Can't find a Class T fuse? Alternatives

Minimum 62.5 A. Best first; size for you is the next size each type is sold in.

Type	Use it?	Size for you	Ask for	Caveats
Class T fuse	Recommended	70 A	"Class T fuse", Bussmann JJN / JJS, Littelfuse JLLN, with holder	Made for battery shorts; very high breaking capacity. Scarce in the Philippines: mostly online, pricier.
HRC (NH) fuse for DC	Good alternative	63 A	"DC HRC fuse", "gPV fuse", "NH00 fuse" with an "NH fuse base"	Electrical supply shops (Chint, Schneider, ABB). Must be marked DC or gPV: a plain gG fuse is usually AC only. High breaking capacity. Needs a separate disconnect switch.
DC breaker (DC MCCB or DC MCB)	Alternative, with checks	63 A	"DC MCCB" or "DC breaker", 2-pole, voltage marked DC	Easy to find; also the battery on/off switch. Small ones are often only 6 kA: check against the battery’s short-circuit current. If marked + and −, put the battery on the marked side and switch the panels off first. Sizes jump (32 → 40 → 63 A).
MRBF terminal fuse	Alternative, with checks	next size above 62.5 A	"MRBF", "terminal fuse", "battery post fuse"	Bolts onto the battery post; common on small lithium batteries. Lower breaking capacity than Class T: check its kA at your voltage and that it fits the battery terminal.
ANL or car-audio fuse	Not as the main fuse	—	"ANL fuse"	Easy to find, but usually rated only 32 V DC, with a low or unstated breaking capacity and variable quality. Use only as an inverter-branch fuse on small systems, never as the main battery fuse on lithium.
AC breaker or AC-only fuse	Not as the main fuse	—	—	Never on the battery. DC never passes through zero, so an AC device may not stop a DC arc.

Any choice: rated at least 30 V DC, with a above the battery's short-circuit current, fitted right at the battery + terminal. The battery's BMS is not a substitute.

Ratings: minimum · size to buy

: at least 9.3 A · buy 10 A, each, in combiner
: at least 27.7 A · buy 32 A
: ≥ 74.3 V DC
Controller breaker (DC): at least 62.5 A · buy 63 A
: at least 62.5 A · buy 70 A
: ≥ 70 A DC
Busbars: ≥ 70 A
Inverter fuse (DC): at least 19.9 A · buy 20 A
Battery-side parts rated for: ≥ 30 V DC
: at least 1.7 A · buy 10 A, 30 mA
AC cable: 2.0 mm²
: 14.0 mm²

Safety notes

Use breakers and fuses marked for DC. AC-only ones may not stop a DC fault.
Fit the main fuse or breaker right at the battery + terminal, before anything else.
Switch off the panel breaker before the battery breaker or fuse holder, and switch the battery on last.
Check the battery's BMS allows more current than the inverter draws.
Keep battery-to-busbar cables as short as possible.
Mount the battery and inverter on a non-flammable wall with air around them.

How each danger is handled

Danger	What protects you	How
Too much current in a wire (it overheats and can start a fire)	A fuse or breaker on every cable: 10 A on each panel row, 32 A for the panels, 63 A for the controller, 20 A for the inverter.	You buy it
Short circuit at the battery (a lithium battery can release thousands of amps)	70 A Class T main fuse right at the battery + terminal, able to break more than the battery's short-circuit current. Sized for the larger of charging and inverter current.	You buy it
Battery drained too low (undervoltage), which damages it	Set the inverter's low-battery cutoff to the battery maker's voltage. The BMS cuts off as backup. If anything runs from the controller's load terminals, set its low-voltage cutoff too. No separate part.	You set it
Battery overcharged	Use a charge controller that supports a 24 V battery, and set it to 24 V if it doesn't detect it. Choose the lithium (LiFePO4) profile and the battery maker's charge voltage. The BMS cuts charging off as backup.	You set it
Battery too hot or too cold	The BMS stops charging or discharging outside safe temperatures. Buy one with temperature protection. Keep the battery out of direct sun, with air around it.	Check when buying
Battery cells out of balance	The BMS balances the cells. Buy a LiFePO4 battery with a built-in BMS.	Check when buying
Inverter overloaded	The inverter shuts down on overload. Check it has overload protection.	Check when buying
Panel voltage too high for the charge controller (on cold mornings)	Panels in each row add up to at most 74.3 V on a cold morning. Keep it under the controller's maximum PV voltage (checked in 04 Charge controller).	You set it
Arcing in a loose or damaged panel connection (fire)	Crimp MC4 connectors with the proper tool and check them yearly. Below 80 V, no arc-fault device is required (NEC 690.11).	Check when buying
Current leaking from a panel cable to the frame or ground	Ground-fault protection, often built into the charge controller or inverter: check the manual. Ask your electrician whether your code requires it (NEC 690.5).	Check when buying
Live panel cables on a roof during a fire	A quick-shutdown switch, if your code requires one for roof panels (NEC 690.12). Ask your electrician.	You buy it
Lightning spikes on the panel cables	DC surge protector rated for at least 74.3 V, connected to the ground rod.	You buy it
Lightning or grid spikes on the 230 V side	AC surge protector at your breaker panel.	You buy it
Grid voltage too high or too low (if the house is also on the grid)	An over/under-voltage protector on the grid side of the changeover switch: it cuts power until the voltage is safe again. The inverter regulates its own output.	You buy it
Electric shock from a fault in a 230 V appliance or wire	10 A RCBO with 30 mA shock protection on the inverter output. Compares hot and neutral current, so it works on Philippine two-wire circuits.	You buy it
Neutral left floating on the 230 V side	Ground the neutral at one point only: the main terminal at the inverter output or your breaker panel, to the ground rod. Follow the inverter manual for where.	You set it
Feeding power back into the grid lines (if the house is also on the grid)	A 2-pole changeover switch: the house runs from the grid or the inverter, never both. Without it, the inverter can electrocute a lineman working on a line thought dead, and the grid can destroy the inverter.	You buy it
A metal frame or case becoming live	All panel frames and metal cases connected to a ground rod with 14.0 mm² ground wire.	You buy it
Working on the system while it is live	Switch off the panel breaker and the battery disconnect first. Label every part that carries DC.	You buy it
Connecting + and − the wrong way round	Check polarity with a meter before connecting. Prefer a controller and inverter with reverse-polarity protection. The fuses limit the damage.	Check when buying
Fire	Mount the battery and inverter on a non-flammable wall with air around them. Keep an extinguisher for electrical fires nearby.	You buy it

08 Parts & cost

Include labor (15%)

Bare minimum vs recommended

Bare minimum: what the calculation strictly needs. Recommended: adds this plan's margins, rounded up to a size that is sold. Safety items have no minimum below the safe one.

Part	Bare minimum	Recommended	Yours	Why
Battery	165.4 Ah	200 Ah	200 Ah	Your devices' use over 24 h of backup × 1.15 for losses, using 80% of the battery.
Solar panels	9 panels (882 W)	9 panels, full rows of 3	9 panels	Refills a day’s use in your sun hours. Recommended rounds up to full rows.
MPPT charge controller	37.5 A	50 A (+25%)	50 A	The panels’ current. Smaller only limits charging on bright days (not a safety risk). Headroom: common rule of thumb.
Inverter	100 W	300 W (× 1.50)	300 W	Everything on at once. Headroom keeps it from running flat out.
Inverter surge (required)	100 W	100 W	not entered	Safety: everything running plus the biggest motor starting. No margin added; the inverter label must cover it.
Panel cable	10 mm²	10 mm²	10 mm²	Minimum: safe for its 32 A fuse or breaker (safety). Recommended: also under 3% voltage drop (efficiency).
Controller cable	22 mm²	22 mm²	22 mm²	Minimum: safe for its 63 A fuse or breaker (safety). Recommended: also under 3% voltage drop (efficiency).
Inverter cable	3.5 mm²	3.5 mm²	3.5 mm²	Minimum: safe for its 20 A fuse or breaker (safety). Recommended: also under 3% voltage drop (efficiency).
Main battery fuse or breaker	62.5 A	70 A	70 A	Biggest current in or out of the battery × 1.25 (code: a fuse should run at no more than 80%). Recommended: the next size sold. Other fuse and breaker types: see 07.

Parts list

Safety: required never skip · Recommended good practice, not a safety need · Only if needed the name says when

Part	Qty	Subtotal (₱)
PV array
Solar panel, 100 WNeeded	9	—
Panel mounting kitNeeded	9	—
MC4 connector pairNeeded	3	—
PV combiner box, 3 strings, ≥ 74.3 V DCSafety: required	1	—
PV string fuse 10 A (at least 9.3 A, gPV), rated ≥ 74.3 V DC, with holderSafety: required	3	—
PV cable 10 mm² (panels → controller)Needed	20 m	—
DC surge protection device, ≥ 74.3 VRecommended	1	—
DC breaker / PV disconnect, 32 A (at least 27.7 A), ≥ 74.3 V DCSafety: required	1	—
Charging
MPPT charge controller, 50 A rated charge current, for a 24 V battery (label lists 24 V or 12/24 V or 12/24/48 V or 12/24/36/48 V), ≥ 74.3 V PV inputNeeded	1	—
DC breaker 63 A (at least 62.5 A), rated ≥ 30 V DC (controller → busbar)Safety: required	1	—
Battery cable 22 mm² (controller → busbar)Needed	3 m	—
Battery
LiFePO4 battery, 24 V 200 Ah, with BMSNeeded	1	—
Main battery fuse: Class T 70 A (at least 62.5 A) (e.g. Bussmann JJN-70), rated ≥ 30 V DC, with holder, at the battery + terminalSafety: required	1	—
Battery disconnect switch, ≥ 70 A, rated ≥ 30 V DCSafety: required	1	—
Battery-to-busbar cables (+ and −), flexible pure copper (not CCA), rated ≥ 70 A, crimped lugs, as short as possibleNeeded	1	—
Busbar pair (+/−), ≥ 70 ANeeded	1	—
Cable lugs for the battery cablesNeeded	12	—
Inverter & AC
DC fuse 20 A (at least 19.9 A), rated ≥ 30 V DC, with holder (busbar → inverter)Safety: required	1	—
Inverter, 300 W, 24 V DC in, 230 V AC outNeeded	1	—
Battery cable 3.5 mm² (busbar → inverter)Needed	3 m	—
RCBO 10 A, 30 mA (AC breaker with shock protection, inverter output)Safety: required	1	—
AC cable 2 mm², hot and neutral (inverter → your breaker panel and outlets)Needed	1 lot	—
Changeover switch, 2-pole (hot and neutral), rated ≥ your house main breaker: only if the house is also on the gridOnly if needed	1	—
Over/under-voltage protector, 230 V, rated ≥ your house main breaker (cuts power when grid voltage goes too high or too low): only if the house is also on the grid, on the grid side of the changeover switchOnly if needed	1	—
Grounding
Grounding conductor 14 mm² (green)Safety: required	16 m	—
Ground rod with clampSafety: required	1	—
Safety
AC surge protector, 230 V (at your breaker panel)Recommended	1	—
Warning labels: "DC – solar" on breakers, disconnects, busbars and the batterySafety: required	1 lot	—
Fire extinguisher for electrical fires (ABC dry powder or CO₂), kept near the batteryRecommended	1	—
Total (29 parts not priced)		₱ 0

Enter your supplier's prices to get a total.

09 Why these numbers

Code references are to the US National Electrical Code (NEC 2014), which the Philippine Electrical Code (PEC 2017 Part 1) follows closely: NEC 690 = PEC Article 6.90, NEC 240 = 2.40, NEC 250 = 2.50. Check article numbers against your edition. Where they differ, follow PEC. Where no Philippine standard sets a value (losses, efficiency), international guides are used: IEEE 1562 and NREL PVWatts.

Sizing

Battery voltage24 V: Power = volts × amps, so the same power at a higher voltage needs fewer amps: thinner wires, smaller fuses, less heat. Common choice: 12 V up to about 1,000 W, 24 V for about 1,000–3,000 W, 48 V above. A guide, not a limit: the plan sizes every part for the voltage you pick.; Source Common practice in off-grid design; check the voltages your inverter and battery support.
System loss factor× 1.15: Energy lost between the battery and your devices: the inverter (typically 5–10%), the wiring, and charging and discharging the battery. Guides on off-grid sizing use 10–20% losses; the default 1.15 adds 15%. Replace it with your own figure: 1 ÷ (inverter efficiency × battery round-trip efficiency), both on the datasheets. Wiring is also in the panel efficiency below, so together the two are slightly cautious.; Source IEEE 1562-2007 (array and battery sizing for stand-alone PV), section 9.2: typical losses 10–20% (VERIFY against the standard); inverter and battery datasheets.
Depth of discharge80%: A battery lasts more cycles when never fully emptied. For LiFePO4, 80–90% balances usable capacity against life. Lead-acid: usually 50%.; Source Battery manufacturer's cycle-life data.
Hours of backup24 h: How long the battery alone runs your loads with no sun. Each device is counted for its full hours per day inside the outage (whole days repeat), and the inverter idles throughout, so the battery covers the outage whenever it happens. More hours: a bigger, costlier battery.; Source Design choice.
Peak sun hours4.5 h: The day’s sunlight as hours of full-strength (1,000 W/m²) sun. Philippine averages: roughly 4.5–5. Cloudy and rainy months are lower, and an off-grid system must cope with them.; Source NREL and PAGASA solar resource data (VERIFY for your location).
Solar system efficiency80%: Panels produce less than their label. NREL’s PVWatts counts 14% by default: dust 2%, shading 3%, mismatch 2%, wiring 2%, connections 0.5%, early ageing 1.5%, label tolerance 1%, downtime 3%. Heat costs more in hot climates (about 0.4% per °C above 25 °C, from the panel datasheet), so the default 80% (20% losses) is on the cautious side. Replace it with your own figure.; Source NREL PVWatts default system losses (14%); IEEE 1562-2007 section 9.2 (10–20%); panel datasheet temperature coefficient.
Battery charging current≤ 0.5 × Ah (typical): Too much charging current shortens a lithium battery’s life or trips its protection. Typical limit: about half its Ah rating (100 A for a 200 Ah battery). Check the battery’s datasheet.; Source Battery manufacturer datasheet (typical LiFePO4 0.5C). VERIFY for your battery.
Battery discharge current (BMS)≥ inverter draw: The battery’s BMS cuts the power when more current flows than it is rated for. It must allow at least what the inverter draws when the battery is nearly empty.; Source Battery datasheet: 'max continuous discharge current'.
Days to refill an empty battery: Usable battery capacity ÷ what the panels make beyond the devices’ daily use. If the panels can’t keep up with the devices, the battery never refills.; Source Energy balance: usable Wh ÷ (daily harvest − daily use).
Inverter headroom× 1.5 (bare minimum × 1): Inverters run cooler and last longer below full load, so the recommended size is above everything on at once. Bare minimum: your peak. Motor start-up is a separate, required check against the inverter’s surge rating.; Source This plan’s design (× 1.5); inverter datasheet continuous and surge ratings.

Panels and controller

Controller headroom+25% (recommended 25%): Sunlight can briefly exceed the 1,000 W/m² test condition (at the edge of a cloud, for example), so panels can make more than their label. The code takes panel-side current at 125% for wires and fuses; using the same margin for the controller is common practice, not a code rule. An undersized controller only limits its output: this margin avoids wasted solar power, not a safety risk.; Source NEC 690.8(A)(1) (125% for panel circuits); controller makers’ sizing guides.
Start-up surge3× the biggest motor: Motors draw several times their running power for a moment when they start. The inverter’s surge rating must cover everything running plus the biggest motor starting. Fuses and breakers ride out short surges; a fast fuse may not.; Source Commonly quoted motor starting factor (VERIFY on the device label); inverter surge rating from its datasheet.
Controller terminals: Thick cables often don’t fit a controller’s screw terminals, and trimming strands to fit creates a hot spot. Cables are checked against the largest wire the manual allows.; Source Controller manual.
Voc safety margin× 1.1: Panel voltage rises about 0.3% per °C below 25 °C. The margin keeps a cool morning's voltage under the controller's maximum; above it, the controller can be destroyed.; Source NEC 690.7; panel datasheet Voc temperature coefficient.
Panel maximum system voltagenot entered: Each panel is insulated for a maximum voltage across the whole row (often 1000 V). The row’s cold-morning voltage must stay under it.; Source Panel label or datasheet: 'maximum system voltage'.
Lowest panel voltage to charge24 V × 1.25 + 2 V (rule of thumb): A 24 V LiFePO4 bank charges at up to about 30.0 V. An MPPT controller needs panel voltage well above that, and hot panels lose voltage. The datasheet's 'PV input voltage range' gives the real figure; it is often higher than the rule of thumb.; Source Charge controller datasheet: 'PV input voltage range' for your battery voltage.
Highest panel voltage while chargingnot entered: Above its working range a controller stops tracking or charging, although it is not damaged until the maximum PV voltage. Checked against the panels’ working voltage on a cold morning.; Source Charge controller datasheet: 'PV input voltage range' or 'MPPT range'.
Most panel powernot entered: A controller can only turn about its rated current × battery voltage into charge. Panel power above its limit is wasted, and some makers forbid it.; Source Charge controller datasheet: 'max PV input power' for your battery voltage.
Panel voltage on a hot day× 0.86: Panels lose about 0.35% of their voltage per °C. In Philippine sun they reach around 65 °C, so working voltage drops about 14%. The controller still needs enough voltage then.; Source Panel datasheet temperature coefficient. VERIFY for your panel.
String fusespanel max 10 A: With strings in parallel, a faulty string receives current from all the others. Each string needs a fuse when that current (other strings’ Isc × 1.25) can exceed the panel’s maximum series fuse rating: rarely with two strings, often with three or more.; Source NEC 690.9(A); panel label "Maximum series fuse rating".

Protection

Arc-fault protectionfrom 80 V: A loose or damaged connection in a high-voltage panel cable can arc and start a fire without blowing a fuse. Panel wiring on or in a building at this voltage or more needs a device that detects arcs and cuts the circuit; many charge controllers have one built in.; Source NEC 690.11 (VERIFY against PEC Article 6.90).
Over/under-voltage protectoronly if also on the grid: Grid voltage can surge or sag far from 230 V and damage appliances. The protector cuts power until the voltage is back in range. Off grid, the inverter regulates its own output and shuts down on faults, so it isn’t needed there.; Source Common practice; set its limits to your appliances’ rated voltage range.
PV fuse and breakerIsc × 1.25 × 1.25 (= 1.5625): 1.25 for sunlight above test conditions, times 1.25 because a fuse or breaker should carry no more than 80% of its rating continuously.; Source NEC 690.8(A)(1) and 690.8(B).
Battery-side fuses and breakers× 1.25: 125% of the current they carry (same 80% continuous-duty rule), rounded up to the next standard size.; Source NEC 210.20(A) and 240.6 (standard ratings).
Inverter current at a nearly empty battery0.875 × battery voltage (typical): An inverter draws more current as battery voltage falls. It draws the most just before its low-battery cutoff (about 21 V on a 24 V lithium battery). The fuse, cable and battery protection are sized for that current.; Source NEC 690.8(A)(4) (lowest input voltage); inverter datasheet. VERIFY the cutoff voltage for your inverter.
Main battery fuse size: Every amp in or out of the battery passes the main fuse: the controller’s full rated charge current one way (it can deliver it on a bright, cool day), the inverter’s draw at its low-battery cutoff the other. Sized for the larger, × 1.25, then the next size sold.; Source NEC 240.4 and 690.9; battery manufacturer guidance.
Busbars: Rated for the biggest fuse or breaker connected to it, since it carries current between all of them.; Source Busbar manufacturer rating.
DC voltage ratings≥ 1.25 × battery voltage on the battery side: A fuse, breaker or switch rated below the highest DC voltage it sees may not break the circuit safely. Panel side: the cold-morning panel voltage. Battery side: the full-charge voltage.; Source NEC 690.9(D) and 690.13; device ratings.
Main fuse or breaker at the battery: A LiFePO4 bank can deliver thousands of amps into a short circuit. The main protection’s DC breaking capacity (kA) must exceed the battery’s short-circuit current. Class T fuses are made for this but are hard to find in the Philippines; a DC-rated HRC (NH) fuse or a DC breaker works if its kA rating is enough. Ordinary fuses, car fuses and AC breakers may not.; Source UL 248-15 (Class T); IEC 60269 (NH/HRC fuses, gPV for DC); IEC 60947-2 (DC breakers). Breaking capacities differ by maker: read the label.
A bigger main breaker than needed: Allowed if the battery cables and busbars are rated at least as high, and the controller breaker and inverter fuse stay to protect their thinner cables. Breakers come in steps (32, 40, 50, 63 A), so the next step up is often bigger than a fuse would be.; Source NEC 240.4 (protecting conductors).
Polarized DC breakers: Many DC breakers are marked + and − and only stop a fault safely when current flows the marked way. Battery current flows both ways: put the battery on the marked side (it drives any short), and switch the panels off first so the breaker never opens against charging current.; Source Breaker manufacturer wiring diagram (printed on the breaker).
Battery cable: Flexible, fine-stranded pure copper with crimped lugs. Copper-clad aluminium (CCA) carries much less current and runs hot. Big battery cable often won’t fit controller terminals: check the largest wire the manual allows.; Source Cable and controller manufacturer data.
DC-rated breakers only: AC passes through zero 120 times a second, which helps an arc go out. DC never does, so an AC-only breaker may fail to break a DC fault.; Source Breaker manufacturer's DC rating.
Battery disconnect: Isolates the battery for maintenance or emergencies. Rated at least as high as the main fuse. A DC main breaker does this job too: no separate switch needed.; Source NEC 690.13 and 690.71.
Surge protection: Long panel cables on a roof pick up surges from nearby lightning. A surge protection device diverts them to ground before they reach the controller.; Source IEC 61643-31 (PV surge protective devices).
AC output breaker(inverter W ÷ 230 V) × 1.25: Philippine household supply is 230 V. Sized at 125% of the inverter's full output current, then the next RCBO size sold (IEC: 10, 16, 20, 25, 32, 40 A…), to protect the AC wiring to your loads.; Source PEC 2017; NEC 210.20(A).
Hot and neutral, grounded at one point: Philippine 230 V circuits use two wires, hot and neutral. Ground the neutral at one point only, the main terminal. Grounding it in more places puts current on the ground wire and can stop the RCBO working.; Source PEC 2017 Art. 2.50; inverter manual for where its neutral is bonded.
Changeover switch: If the house is also on the grid, the inverter and grid must never connect at the same time. A 2-pole changeover switch makes that impossible.; Source NEC 702.5 (transfer equipment); PEC 2017.
Grounding conductor: Gives fault current a safe path, so a breaker or fuse trips instead of a frame becoming live. Sized from the largest fuse or breaker in the system.; Source NEC 250.122 (PEC Art. 2.50).

Wiring

Wire rated ≥ its fuse: The fuse protects the wire. A wire rated below its fuse can overheat before the fuse blows.; Source NEC 240.4.
Small wires have a fuse limit2.0 mm² ≤ 15 A · 3.5 mm² ≤ 20 A · 5.5 mm² ≤ 30 A: The smallest wires need a smaller fuse than their rating suggests. This plan never puts them behind a bigger fuse.; Source NEC 240.4(D) (14, 12 and 10 AWG).
Hot air lowers what a wire can carry× 0.82 on the roof, × 0.94 indoors: Wire ratings assume 30 °C air. Cables on a sunny roof sit in 41–45 °C air and a Philippine room is often 31–35 °C, so each rating is reduced.; Source NEC Table 310.15(B)(2)(a), 75 °C column. VERIFY against the PEC table.
Metric wire sizes: Philippine mm² sizes don’t exactly match US (AWG) sizes. Where a metric size is smaller than its nearest AWG size, its rating is reduced in proportion.; Source PEC 2017 Table 3.10.1.16 (metric sizes). VERIFY every value against it.
Ampacity at 75 °C: Breaker and lug terminals are usually rated 75 °C, so wire ratings come from the 75 °C column even for 90 °C insulation.; Source NEC 110.14(C); PEC 2017 Table 3.10.1.16.
Voltage drop limit3%: Keeps losses low and charging accurate. On low-voltage DC, a fraction of a volt is a large share.; Source NEC 210.19(A) Informational Note (a recommendation, not a requirement).
Copper resistivity0.0216 Ω·mm²/m: Copper's resistance at 75 °C, the temperature of wires under load. With length and size, gives the voltage drop.; Source NEC Chapter 9, Table 8 basis.

10 Words used in this plan

AC surge protector: Surge protector for the 230 V side: sends voltage spikes to ground before they reach your appliances.
Amp-hour (Ah): Charge a battery holds. × battery voltage = watt-hours: 200 Ah × 24 V = 4,800 Wh.
BMS (battery management system): Protection circuit built into a lithium battery. Cuts power if the battery is overloaded, overcharged or too empty.
Breaking capacity (kA): Biggest short-circuit current a fuse or breaker can safely stop, in thousands of amps. Must exceed what the battery delivers in a short (ask the battery seller).
Busbar: Metal bar with several bolts for connecting many cables to the battery, instead of stacking them on one terminal.
Cable lug: Metal end crimped onto a thick cable for bolting to a battery, fuse or busbar.
CCA (copper-clad aluminium): Cheap cable that looks like copper but is aluminium with a thin copper skin. Carries much less current and runs hot. Scratch a strand: pure copper is copper all the way through.
Changeover switch: Connects the house to either the grid or the inverter, never both. Required if the house is also on the grid.
Charge profile: Charge controller setting for battery type and charge voltage. Choose lithium (LiFePO4) and the battery maker’s voltage.
Class T fuse: Main battery fuse: a heavy-duty fuse that safely stops the huge current a lithium battery releases in a short circuit. Fit it right at the battery + terminal; all charging and discharging current passes through it.
Combiner box: Box where the panel rows join, with a fuse for each row.
DC and AC: DC (direct current) flows one way, as from a battery or panel. AC (alternating current) comes from a wall socket.
DC breaker: Switch that turns off by itself when too much current flows and can be switched back on. Must be rated for DC.
DC breaker (DC MCCB): Breaker made to switch off direct current. Trips like a fuse and works as an on/off switch. AC-only breakers may not stop a DC fault.
Depth of discharge (DoD): Share of the battery used before recharging. Using 80% a day makes it last many more years than emptying it fully.
Disconnect switch: Big switch that cuts the battery off completely, for repairs or emergencies.
Fuse: Melts and cuts the circuit if too much current flows, before the wire overheats.
Grounding (earthing): Wire from the metal frames to a rod in the ground, so a fault trips the breaker instead of making the metal live.
Hot and neutral: The two wires of a Philippine 230 V circuit. Hot carries the voltage; neutral is the return path, grounded at one point (the main terminal).
HRC fuse (NH fuse): High Rupturing Capacity fuse: a blade-type industrial fuse (sizes NH000, NH00) that fits a fuse base. Easier to find in the Philippines than Class T. For the battery, use one marked for DC (gPV).
Idle draw: Power the inverter uses when switched on with nothing plugged in.
Imp (maximum power current): Panel current at full power. On the label.
Inverter: Turns the battery’s DC power into 230 V AC, the same kind of power as a wall socket.
Isc (short-circuit current): Most current a panel can push, if its wires touched. Used to size fuses. On the label.
LiFePO4: Lithium iron phosphate: a safe, long-lasting lithium battery common in home solar.
Low-battery cutoff (undervoltage protection): Switches the load off before the battery drains far enough to be damaged. Here: an inverter setting, with the battery’s BMS as backup. Not a separate part.
MC4 connector: Standard waterproof plug on solar panel cables. A Y-branch joins two panel rows into one cable.
MPPT charge controller: Box between the panels and the battery. Turns the panels’ higher voltage into a safe battery charge and gets the most power from the panels.
Parallel: Rows of panels joined side by side, plus to plus and minus to minus. Currents add; voltage stays the same.
Peak sun hours: The day’s sunshine counted as hours of full, strong sun. A sunny day with 12 hours of light gives about 5.
Polarized breaker: DC breaker marked + and −; stops a fault safely only when current flows the marked way. Connect the battery to the marked side.
RCBO (breaker with shock protection): Breaker for the 230 V side that also switches off in a split second if current leaks to ground, such as through a person touching a faulty appliance. "30 mA": the leakage it reacts to.
Series: Panels joined end to end, plus of one to minus of the next. Voltages add; current stays the same.
Start-up surge: Extra power a motor (fan, pump, fridge, power tool) draws for a moment when it starts, often 3× its running watts. The inverter must handle it for a few seconds or it shuts off.
String: One row of panels joined in series.
String fuse: Small fuse on each panel row, so the other rows can’t feed a fault in one row.
Surge protector (SPD): Sends voltage spikes from nearby lightning to ground before they damage the controller.
System voltage: The battery bank’s voltage: 12, 24 or 48 V. Higher voltage: lower current, thinner and cheaper wires.
Vmp (maximum power voltage): Panel voltage at full power. On the label.
Voc (open-circuit voltage): Highest voltage a panel makes, with nothing connected. On the panel label.
Voltage drop: Voltage lost along a wire as heat. Longer or thinner wires lose more. Keep it under 3%.
Watt (W): Power used at a given moment. A 60 W laptop charger draws 60 W while charging.
Watt-hour (Wh): Energy used over time: watts × hours. A 60 W charger used for 3 hours uses 180 Wh.
Wire rating (ampacity): Most current a wire can carry all day without overheating. Must be at least the rating of the fuse or breaker protecting it.
Wire size (mm²): Copper cross-section in square millimetres. Bigger number: thicker wire, more current. AWG is the American system, where a smaller number means thicker wire.

These numbers are estimates. Check them against your own measurements and product labels before you build. Performance depends on weather, temperature, equipment and installation. Have a licensed electrician check the design. Follow the Philippine Electrical Code.