Every day, folks fire up a 5000 watt inverter to run power-hungry tools, fridges, or even tiny homes. Then comes the head-scratch: “How big a battery bank do I need so the lights don’t flicker out?” If you’ve ever stared at a pile of specs and felt lost, you’re in the right place.
A simple rule of thumb says you’ll want around 400–500 Ah at 48 V (≈ 20–24 kWh) to deliver one full hour of continuous output from a 5000 watt inverter—then scale up from there based on how long you need the power to flow.
In the next few minutes we’ll break down battery math, demystify volts and amp-hours, compare lithium versus lead-acid, toss in safety tips, and answer the questions most people ask after wrestling with inverter specs.
5000 Watt Inverter: Why Internal Resistance Matters
A reliable battery bank starts with three core ideas you can’t skip. Think of internal resistance as friction inside the battery. The lower it is, the less energy turns into useless heat when current flows. Lead-acid cells often sit around 8 mΩ, while quality LiFePO₄ cells drop to 2 mΩ or less. That small difference means cooler cables, higher inverter efficiency, and longer runtimes—especially when your 5000 watt inverter kicks on a big load like an air-compressor. Keep terminals clean and bolts tight; corrosion cranks resistance upward and steals precious watts.
Voltage Explained
Voltage is pressure—think of it like water behind a dam. A 48-volt bank keeps current low and cable sizes thin, which means less heat and higher efficiency. Most 5000 watt inverter models love 48 V for this very reason.
Amp-Hour Rating
Amp-hours (Ah) tell you how much water sits behind that dam. Double the Ah, double the runtime. For a 5000 watt inverter you’ll quickly see numbers north of 400 Ah if you plan to run more than quick bursts.
Depth Of Discharge
Batteries hate being emptied to zero. Lead-acid prefers 50 % depth of discharge (DoD); lithium is fine at 80–90 %. Factor DoD into sizing or you’ll replace batteries sooner than planned.
Calculate Your Power Need
Grab pen, paper, and coffee. List every device you’ll run, add up watts, and multiply by the hours you need. If you plan to drive the 5000 watt inverter at full tilt for two hours, that’s 10 kWh. Allow for inverter efficiency (≈ 90 %), so budget 11 kWh from the battery bank. Divide by your system voltage (48 V). Result: about 230 Ah—then adjust for DoD. For 50 % DoD on lead-acid, double it to 460 Ah; lithium needs roughly 290 Ah at 80 % DoD.
Quick Tip: Always add 15 % wiggle room for future gadgets you’ll inevitably plug in.
Match Voltage Between Inverter And Battery
Running a 48 V inverter on a 12 V battery string? Disaster. Match voltages or the magic smoke escapes. Series wiring lifts voltage; parallel adds capacity. Four 12 V batteries in series give 48 V. Easy math, safer setup.
Info: Check the inverter’s manual first—some 5000 W units accept 24 V or 48 V, but never both at once.
Choosing Lead-Acid Or Lithium
Lead-acid costs less up-front, weighs a ton, and dislikes deep discharge. Lithium iron phosphate (LiFePO₄) is light, cycles 3-5× longer, and delivers stable voltage. For a mobile rig where pounds matter, lithium wins. Stationary off-grid cabins might start with lead-acid and upgrade later.
Fact: A typical 48 V, 100 Ah LiFePO₄ module weighs ≈ 30 kg, while a similar lead-acid bank tips the scale at 120 kg.
How Temperature Affects Capacity
Cold batteries sag. At freezing, lead-acid loses up to 40 % capacity; lithium drops 10–15 %. Warm climates flip the script—heat ages batteries faster. Place your bank in a temperature-controlled space or size larger for winter.
Suggestion: Insulating a battery box is cheaper than buying extra capacity you’ll only need on icy nights.
Parallel Vs Series Connections
Series raises voltage; parallel raises amp-hours. Need both? Build strings in series, then parallel those strings. Two 48 V × 200 Ah strings in parallel equal 400 Ah total.
| Connection | Result | Example (4 × 12 V, 100 Ah) |
|---|---|---|
| 4 in series | 48 V, 100 Ah | Series string |
| 2 series strings in parallel | 48 V, 200 Ah | Typical for a 5000 W load |
| 4 in parallel | 12 V, 400 Ah | Not for 48 V inverters |
Sizing For Off-Grid Homes
Off-grid dwellers often pull 8–12 kWh nightly. A 5000 watt inverter paired with an 800 Ah lithium bank at 48 V (≈ 38 kWh usable) covers a cloudy day and a movie marathon. Add solar or a generator to recharge before breakfast.
Success: Design for three sun-less days, then sleep easy when storms roll in.
Sizing For RV And Van Life
Road warriors usually need shorter bursts—microwaves, AC, power tools. A compact 300 Ah LiFePO₄ bank at 48 V (≈ 14 kWh) keeps the 5000 watt inverter happy for an evening cook-off and morning coffee, then recharges via alternator or solar by noon.
Protecting Your Battery Investment
Install a battery management system (BMS) for lithium or a low-voltage disconnect (LVD) for lead-acid. They shut things down before damage. Fuse positive leads, size cables correctly, and route them away from sharp metal.
Danger: Never bypass the BMS “just to test”—that’s how fires start.
Safety First When Wiring
Wear safety glasses, use insulated tools, and disconnect chargers before tinkering. Start with series connections, double-check polarity, and finish with parallel links. A mistake at 48 V can arc like a welder.
Warnings: Tape your wrench handles—one slip across terminals equals fireworks.
Maintenance Tips For Long Life
Lead-acid needs equalization charges and water top-ups. Lithium prefers leaving 20 % buffer when stored. Keep terminals clean, monitor state of charge weekly, and record monthly readings to spot trouble early.
Conclusion
Picking the right battery inverter and charger bank for a 5000 watt inverter isn’t wizardry—it’s a mix of simple math, honest runtime goals, and respect for DoD limits. Start by totaling your watt-hours, convert to amp-hours at your system voltage, then adjust for chemistry and weather. Treat your batteries well and they’ll power your projects, road trips, or homestead for years.
FAQs
How long will a 5000 watt inverter run on a 100ah battery?
At 48 V that’s only 4.8 kWh gross, about half usable with lead-acid. Expect roughly 30 minutes at full load before voltage sags.
Can I connect solar panels directly to the inverter?
No. Panels feed a charge controller, which charges the battery bank. The 5000 watt inverter then draws from the batteries.
What wire size do I need for a 5000 watt inverter?
For 48 V systems pull ≈ 105 A. Use at least 2/0 AWG copper for runs under 2 m to keep voltage drop below 3 %.
Is lithium always better than lead-acid?
Not always. Lithium costs more upfront. If you rarely discharge deeply and weight isn’t an issue, lead-acid may suffice.
Do I need a generator backup?
If blackout tolerance matters or solar is unpredictable, a small generator provides peace of mind and faster recharging.
