Battery Runtime Calculator
Before you buy a battery, wire a battery bank, or plan an off-grid weekend, you need one number: how long will it actually run your gear? Guessing gets expensive fast — an undersized bank leaves your fridge warm at 2 a.m., and an oversized one wastes money you didn't need to spend. This battery runtime calculator does the math for you in seconds, factoring in voltage, amp-hours, battery chemistry, efficiency losses, and safe depth of discharge, so the number on your screen is the number you'll actually get in the field.
Runtime math looks simple on paper — multiply voltage by amp-hours and divide by your load — but real batteries never deliver their full rated capacity. Heat, age, wiring losses, inverter inefficiency, and how deeply you're willing to drain the battery all shrink that number. Homeowners sizing a home backup system, RV owners planning a week off-grid, solar users balancing panels against storage, campers running a cooler and lights, and anyone setting up emergency backup power all run into the same problem: the runtime a battery is rated for and the runtime it actually delivers are two different figures. A proper battery backup time calculator closes that gap, turning a rough guess into a number you can plan a purchase — or a power outage — around.
Calculate Your Battery Runtime
VOLTS × AH × EFFICIENCY ÷ WATTSEnter your battery specs and load below. Defaults are pre-filled with common values — adjust anything you know precisely for a tighter estimate.
The calculator above updates the moment you click Calculate Runtime, and every field is editable so you can model a 12V, 24V, or 48V system, mix in reserve capacity, and compare a single deep cycle battery against a full bank in series or parallel.
How Battery Runtime is Calculated
The calculator runs three formulas in sequence. Understanding them is genuinely useful — once you know the math, you can sanity-check any battery listing in seconds without opening a calculator at all.
Step 1 — Total Energy in Watt-Hours
Energy (Wh) = Battery Voltage (V) × Battery Capacity (Ah)
A 12V, 100Ah battery stores 12 × 100 = 1,200 watt-hours. This is the battery's full, unadjusted energy content — the number printed on the label, before any real-world losses are factored in.
Step 2 — Usable Energy
Usable Energy (Wh) = Total Energy × Efficiency × Depth of Discharge
No battery delivers 100% of its stored energy. Efficiency accounts for internal resistance, wiring, connectors, and inverter conversion loss — typically 80–90%. Depth of discharge (DoD) is how much of the battery you're willing to drain before recharging; draining a lead-acid battery past 50% regularly shortens its life dramatically, while lithium iron phosphate tolerates 80–100% DoD without the same penalty. Multiply both together and you get the energy you can actually pull from the battery in normal use.
Step 3 — Runtime
Runtime (hours) = Usable Energy (Wh) ÷ Load Power (W)
Divide the usable watt-hours by the wattage of everything you're running. A 500Wh usable battery powering a 100W load runs for 5 hours; the same battery powering a 50W load runs for 10 hours. The calculator also subtracts your chosen safety margin from usable energy before this final division, because published wattage ratings on appliances are often optimistic and batteries lose capacity as they age.
Quick variable reference: V = battery voltage, Ah = amp-hour capacity, Wh = watt-hours (energy), W = load power in watts, DoD = depth of discharge, and Safety Margin = a buffer percentage reserved for real-world losses like temperature swings, wiring resistance, and aging cells.
Worked Examples
Numbers are easier to trust once you've seen them applied. Here are six real scenarios using the exact formula above, with an 85% efficiency and typical depth-of-discharge assumptions.
Example 1 — 12V, 100Ah, 100W Load (Lead Acid)
1,200Wh × 0.85 efficiency × 0.50 DoD = 510Wh usable. 510Wh ÷ 100W ≈ 5.1 hours runtime, roughly enough to run a laptop, router, and a few LED lights through a short outage.
Example 2 — 24V, 200Ah, 500W Load (AGM)
4,800Wh × 0.85 × 0.50 = 2,040Wh usable. 2,040Wh ÷ 500W ≈ 4.1 hours, a realistic figure for a small chest freezer plus a few circuits during a power cut.
Example 3 — 48V Solar Battery, 300Ah, 1,500W Load (Lithium)
14,400Wh × 0.90 efficiency × 0.90 DoD = 11,664Wh usable. 11,664Wh ÷ 1,500W ≈ 7.8 hours — enough to carry a home through an evening on stored solar power alone.
Example 4 — RV Battery: 12V, 100Ah AGM, 250W Load
1,200Wh × 0.85 × 0.50 = 510Wh usable. 510Wh ÷ 250W ≈ 2 hours of full-load runtime — a reminder that boondocking loads (fridge, fans, water pump) should be spread across a larger bank or paired with solar charging.
Example 5 — Marine Battery: 12V, 80Ah, 60W Load
960Wh × 0.85 × 0.50 = 408Wh usable. 408Wh ÷ 60W ≈ 6.8 hours, comfortably covering a trolling motor on low or a livewell pump for a full day on the water.
Example 6 — Home UPS Battery: 12V, 150Ah, 300W Load
1,800Wh × 0.85 × 0.50 = 765Wh usable. 765Wh ÷ 300W ≈ 2.5 hours, enough to keep a modem, a few lamps, and a desktop PC alive through most short grid outages.
What Is Battery Runtime?
Battery runtime is the length of time a battery — or a bank of batteries — can power a given load before it's discharged to its safe minimum. It's the single most practical figure in any backup power, solar, RV, marine, or emergency power setup, because it answers the question everyone actually cares about: how long do I have before the power goes out? A battery's amp-hour rating tells you how much energy it stores; runtime tells you what that energy is worth in the real world, against your actual appliances.
Runtime isn't fixed — it changes with every variable in the system. The same 100Ah battery can run a phone charger for days or a space heater for minutes. That's why a static spec sheet number is far less useful than a calculator that lets you plug in your own voltage, capacity, and load.
Understanding Amp Hours
An amp-hour (Ah) measures how much current a battery can supply over time. A 100Ah battery can, in theory, deliver 100 amps for one hour, 50 amps for two hours, or 10 amps for ten hours. In practice, discharge rate affects total capacity — pulling current faster than the battery's rated rate reduces the effective Ah delivered, an effect known as Peukert's Law, most pronounced in lead acid batteries and far less significant in lithium chemistries. For runtime estimates, amp-hours matter because they set the ceiling on total stored energy once multiplied by voltage.
Understanding Battery Voltage
Voltage is the electrical "pressure" pushing current through a circuit. Common battery bank voltages are 12V, 24V, and 48V, with 36V, 60V, and 72V appearing in specialty applications like electric bikes and industrial equipment. Higher voltage systems move the same amount of power using less current, which means thinner wiring, lower resistive losses, and better efficiency at scale — one reason larger solar and home backup installations favor 24V or 48V battery banks over 12V.
Voltage also determines how batteries combine. Wiring batteries in series adds their voltages together while capacity stays the same as a single unit; wiring in parallel keeps voltage the same while amp-hour capacity adds up. Both change total watt-hours identically, but they change the wiring, fusing, and equipment requirements very differently.
Battery Capacity Explained
Capacity, expressed in amp-hours, is the total charge a battery can store. It's usually rated at a specific discharge rate (commonly a 20-hour or 100-hour rate for lead acid batteries), and the number printed on the case assumes ideal lab conditions: a fresh battery, moderate temperature, and a slow, steady discharge. Real-world capacity is almost always lower once you factor in age, temperature, and discharge speed — which is exactly why the battery capacity calculator math above applies an efficiency factor rather than taking the rated Ah at face value.
Battery Efficiency
Efficiency describes how much of a battery's stored energy actually reaches your load after accounting for internal resistance, cable and connector losses, and — if you're running an inverter — DC-to-AC conversion loss. A well-maintained system with short, correctly-sized cables and a good inverter might reach 90% efficiency. A system with long thin wiring, loose terminals, or an aging inverter can drop closer to 75–80%. The default of 85% used in this calculator reflects a typical, reasonably well-installed system; if you know your inverter's rated efficiency or have measured your own losses, adjust the field accordingly for a more precise result.
Depth of Discharge
Depth of discharge (DoD) is the percentage of a battery's total capacity you're willing to use before recharging. It exists because chemistry, not just convenience, sets a practical limit on how far you should drain most batteries:
- Lead acid (flooded): 50% DoD is the standard recommendation; discharging deeper on a regular basis accelerates plate sulfation and shortens lifespan significantly.
- AGM and Gel: Slightly more forgiving, typically rated for 50–60% regular DoD, with occasional deeper discharges tolerated better than flooded lead acid.
- Lithium (LiFePO4): Commonly rated for 80–100% DoD, since the chemistry doesn't suffer the same degradation from deep cycling that lead acid does — one of the main reasons lithium batteries deliver more usable capacity per rated amp-hour.
A shallower DoD extends battery lifespan but means you need a physically larger bank for the same usable runtime — a trade-off worth weighing when comparing an inverter battery runtime target against upfront cost.
Battery Types
Chemistry has a bigger impact on real-world runtime than almost any other single variable, because it dictates usable DoD, efficiency, weight, and how gracefully capacity fades as the battery ages.
Lead Acid (Flooded)
The oldest and least expensive rechargeable battery chemistry, still common in vehicles, basic backup systems, and budget solar setups. Lead acid batteries are heavy, require periodic maintenance (checking electrolyte levels), and should be limited to roughly 50% DoD for a reasonable service life.
AGM (Absorbent Glass Mat)
A sealed, maintenance-free lead-acid variant that resists vibration and can be mounted in more orientations than flooded batteries. AGM batteries deliver dependable performance for RVs, marine use, and UPS systems, at a moderate price premium over flooded lead acid.
Gel
Another sealed lead-acid variant using a silica-thickened electrolyte. Gel batteries tolerate heat well and self-discharge slowly, making them a solid choice for infrequently-used backup systems, though they're generally less tolerant of fast charging than AGM.
Lithium Iron Phosphate (LiFePO4)
The current standard for serious solar and off-grid battery banks. Lithium batteries are roughly half the weight of lead acid for the same capacity, tolerate deep discharge, deliver 2,000–5,000+ charge cycles versus 300–500 for flooded lead acid, and hold voltage more consistently as they discharge — which is part of why lithium battery runtime estimates tend to be more predictable than lead acid ones.
Nickel Batteries
Nickel-cadmium (NiCd) and nickel-metal hydride (NiMH) batteries are less common in stationary power applications today but still appear in some industrial and portable tool applications. They tolerate wide temperature ranges and abuse well but have largely been displaced by lithium chemistry for new battery bank designs due to lower energy density and, in NiCd's case, toxicity concerns.
Series vs Parallel Batteries
Combining batteries changes your system's voltage, capacity, or both, depending on how they're wired. Getting this right matters — miswiring a bank doesn't just hurt performance, it can damage equipment.
| Configuration | Voltage | Capacity (Ah) | Best For |
|---|---|---|---|
| Series | Adds together (2 × 12V = 24V) | Stays the same as one battery | Raising system voltage for lower current draw |
| Parallel | Stays the same as one battery | Adds together (2 × 100Ah = 200Ah) | Extending runtime at the same voltage |
| Series-Parallel | Increases (per series string) | Increases (per parallel string) | Large banks needing both higher voltage and capacity |
A practical example: four identical 12V, 100Ah batteries wired in series-parallel — two pairs of two in series, then those pairs wired in parallel — produce a 24V, 200Ah bank (9,600Wh total). Wire those same four batteries purely in series and you get 48V at 100Ah (also 9,600Wh); wire them purely in parallel and you get 12V at 400Ah (also 9,600Wh). Total energy is identical in all three cases — what changes is the voltage and current profile your inverter and wiring need to handle.
Battery Runtime Chart
The table below estimates runtime in hours for common battery sizes across a range of loads, assuming a 12V lead-acid battery, 85% efficiency, and 50% depth of discharge — the same defaults used in the calculator above. Use it as a quick reference; run your exact numbers through the calculator for anything you're about to buy.
| Capacity | 50W | 100W | 200W | 500W | 1000W | 1500W | 2000W |
|---|---|---|---|---|---|---|---|
| 50Ah | 5.1 | 2.55 | 1.28 | 0.51 | 0.26 | 0.17 | 0.13 |
| 100Ah | 10.2 | 5.1 | 2.55 | 1.02 | 0.51 | 0.34 | 0.26 |
| 150Ah | 15.3 | 7.65 | 3.83 | 1.53 | 0.77 | 0.51 | 0.38 |
| 200Ah | 20.4 | 10.2 | 5.1 | 2.04 | 1.02 | 0.68 | 0.51 |
| 300Ah | 30.6 | 15.3 | 7.65 | 3.06 | 1.53 | 1.02 | 0.77 |
| 400Ah | 40.8 | 20.4 | 10.2 | 4.08 | 2.04 | 1.36 | 1.02 |
| 500Ah | 51.0 | 25.5 | 12.75 | 5.1 | 2.55 | 1.7 | 1.28 |
Battery Voltage Comparison
Voltage doesn't change total stored energy on its own, but it fundamentally shapes how a bank is wired, fused, and connected to an inverter.
| Voltage | Typical Current at 1,000W | Common Applications |
|---|---|---|
| 12V | ~83A | RVs, boats, small solar setups, car audio |
| 24V | ~42A | Mid-size solar systems, telecom backup, forklifts |
| 36V | ~28A | E-bikes, some mobility equipment |
| 48V | ~21A | Home solar battery banks, larger inverters |
| 60V | ~17A | Electric scooters, light electric vehicles |
| 72V | ~14A | Electric motorcycles, industrial equipment |
Battery Chemistry Comparison
| Chemistry | Efficiency | Weight | Price | Cycle Life | Maintenance | Best Use |
|---|---|---|---|---|---|---|
| Lead Acid | 75–80% | Heavy | Low | 300–500 | Regular | Budget backup, automotive |
| AGM | 80–85% | Heavy | Moderate | 400–700 | None | RV, marine, UPS |
| Gel | 80–85% | Heavy | Moderate | 500–900 | None | Hot climates, standby power |
| Lithium (LiFePO4) | 90–95% | Light | High | 2,000–5,000+ | None | Solar banks, daily cycling |
| Nickel (NiMH/NiCd) | 70–80% | Moderate | Moderate–High | 1,000–2,000 | Low | Extreme temperature, industrial tools |
Typical Appliance Runtime
Wattage varies by model, so treat these as starting points and check your own appliance's rating label or the power consumption calculator linked below for an exact figure.
| Appliance | Typical Wattage | Estimated Runtime |
|---|---|---|
| LED TV (40") | 60W | ~8.5 hrs |
| Laptop | 65W | ~7.8 hrs |
| Desktop PC | 200W | ~2.6 hrs |
| WiFi Router | 10W | ~51 hrs |
| Refrigerator (compressor cycling) | 150W avg | ~3.4 hrs |
| Chest Freezer | 200W avg | ~2.6 hrs |
| Microwave (in use) | 1,000W | ~0.5 hrs |
| Coffee Maker | 800W | ~0.6 hrs |
| Box Fan | 60W | ~8.5 hrs |
| LED Lights (per fixture) | 10W | ~51 hrs |
| CPAP Machine | 40W | ~12.8 hrs |
| Security Camera System | 25W | ~20.4 hrs |
| Phone Charger | 10W | ~51 hrs |
| Water Pump (small) | 250W | ~2 hrs |
| Medical Equipment (oxygen concentrator) | 350W | ~1.5 hrs |
| RV Appliances (combined) | 400W | ~1.3 hrs |
| Power Tools (circular saw, intermittent) | 1,200W | ~0.4 hrs |
Common Mistakes When Estimating Battery Runtime
- Over-discharging. Draining a lead-acid battery well past 50% to squeeze out extra runtime shortens its lifespan and often damages it permanently.
- Ignoring efficiency losses. Assuming 100% of rated capacity is usable overstates runtime by 15–25% in most real systems.
- Choosing the wrong battery type for the job. A flooded lead-acid battery installed for daily deep cycling will fail years earlier than a lithium battery sized for the same task.
- Underestimating the load. Nameplate wattage often reflects peak, not average, draw — refrigerators and pumps in particular cycle on and off rather than pulling a constant load.
- Forgetting inverter losses. Running AC appliances off a DC battery bank adds inverter conversion loss on top of battery efficiency loss; the two should not be counted once.
- Ignoring temperature. Battery capacity drops in cold weather — often 20% or more below freezing for lead acid — and runtime estimates made in mild weather won't hold in winter.
- Using an old or degraded battery's rated capacity. A battery's usable capacity fades with age and cycle count; a 3-year-old lead-acid battery may only deliver 70–80% of its original rating.
Battery Maintenance Tips
- Keep terminals clean and free of corrosion with a wire brush and a baking-soda-and-water solution.
- Check and top off electrolyte levels on flooded lead-acid batteries with distilled water only.
- Avoid discharging lead-acid batteries below their recommended depth of discharge.
- Store batteries at a partial charge (40–60%) if they'll sit unused for extended periods.
- Keep batteries in a temperature-controlled space when possible; extreme heat and cold both shorten lifespan.
- Use a smart charger or charge controller matched to your specific battery chemistry.
- Torque terminal connections to the manufacturer's spec — loose connections cause resistance heating and voltage drop.
- Equalize flooded lead-acid batteries periodically per the manufacturer's schedule to prevent stratification.
- Never mix old and new batteries, or batteries of different capacities, in the same bank.
- Size cables correctly for your amperage to minimize resistive losses and heat.
- Fuse every battery bank appropriately to protect against short circuits.
- Avoid fully draining any battery chemistry to 0% — even lithium benefits from stopping at a small reserve.
- Inspect for swelling, corrosion, or cracked cases regularly, especially after deep cycling.
- Recharge promptly after use rather than leaving batteries in a discharged state.
- Ventilate flooded lead-acid battery compartments to prevent hydrogen gas buildup.
- Track cycle count or age on a label so you know when a battery is approaching end of life.
- Use a battery management system (BMS) with lithium banks to prevent over-charge and over-discharge automatically.
How to Increase Battery Runtime
If the calculator's number is shorter than you need, there are a handful of practical levers to pull, roughly in order of cost-effectiveness:
- Reduce the load first. Switching incandescent bulbs to LEDs, running a fridge on eco mode, or turning off idle electronics often buys more runtime than any hardware upgrade.
- Add batteries in parallel. Doubling amp-hour capacity roughly doubles runtime at the same voltage and load — the most direct lever available.
- Switch to lithium. A lithium battery rated for 90% DoD delivers close to double the usable energy of a same-capacity lead-acid battery limited to 50% DoD.
- Tighten up wiring. Shorter runs and properly sized cable gauge cut resistive losses, improving effective efficiency.
- Right-size the inverter. An oversized inverter running a small load operates well below its efficiency curve; matching inverter size to typical load improves overall system efficiency.
- Add solar charging. Even modest solar input during the day extends effective runtime by replenishing capacity you'd otherwise pull straight from the bank.
Frequently Asked Questions
How do I calculate battery runtime?
Multiply battery voltage by amp-hour capacity to get total watt-hours, apply your battery's efficiency and depth-of-discharge percentages to find usable energy, then divide by your load in watts. The calculator above runs this formula automatically.
How long will my battery last?
It depends on capacity, voltage, chemistry, and your load. A 12V 100Ah lead-acid battery running a 100W load lasts roughly 5 hours; the same battery on a 1,000W load lasts around 30 minutes. Enter your own numbers above for an exact figure.
What is the formula for battery runtime?
Runtime (hours) equals usable energy in watt-hours divided by load in watts, where usable energy equals voltage times amp-hours times efficiency times depth of discharge.
How many amp hours do I need for 8 hours of runtime?
Divide your target watt-hours (load in watts times 8) by voltage, then divide by your efficiency and depth-of-discharge percentages to find the rated amp-hours needed. The calculator's "Recommended Bank Size" output does this automatically.
Does battery type affect runtime?
Yes. Lithium batteries typically allow 80–100% depth of discharge and 90%+ efficiency, while lead-acid batteries are usually limited to about 50% depth of discharge and 75–80% efficiency, so a lithium battery delivers noticeably more usable runtime per rated amp-hour.
What is depth of discharge and why does it matter?
Depth of discharge is the percentage of a battery's capacity you use before recharging. Staying within the recommended DoD protects battery lifespan; exceeding it regularly, especially on lead-acid chemistry, accelerates degradation.
Why is my actual runtime shorter than the calculated runtime?
Battery age, cold temperatures, undersized wiring, and appliances drawing more than their rated wattage are the most common causes. Building in a safety margin, as the calculator does by default, helps close this gap.
What's the difference between series and parallel battery wiring?
Series wiring adds battery voltages together while capacity stays the same as a single unit. Parallel wiring keeps voltage the same while amp-hour capacity adds together. Total stored energy is identical either way.
How many watts can a 100Ah battery run?
A 12V 100Ah battery stores about 1,200Wh. At 85% efficiency and 50% depth of discharge, that's roughly 510Wh usable — enough to run a 100W load for about 5 hours, or a 500W load for about an hour.
How long does a 12V battery last?
Runtime depends entirely on capacity and load — a 12V battery isn't one fixed runtime. A 12V 50Ah battery and a 12V 400Ah battery behave completely differently under the same load, which is why capacity and load must always be entered together.
How long does a 24V battery bank last?
A 24V bank's runtime follows the same formula as any other voltage: total watt-hours (24V × Ah) divided by load, adjusted for efficiency and depth of discharge. Doubling voltage from 12V to 24V at the same Ah roughly doubles stored energy and runtime.
How long does a 48V solar battery last?
A typical 48V, 300Ah lithium battery stores about 14.4kWh. At 90% efficiency and 90% depth of discharge, that's roughly 11.7kWh usable — enough to run a 1,500W load for close to 8 hours.
Do deep cycle batteries last longer than regular batteries?
Deep cycle batteries are built for repeated partial discharge and recharge cycles, unlike starting batteries designed for a brief high-current burst. For runtime applications like solar, RV, or backup power, deep cycle batteries hold up far better over time.
Does inverter efficiency affect battery runtime?
Yes. Converting stored DC battery power to AC through an inverter typically loses 5–15% of the energy as heat, which is why efficiency is included as a separate factor in the runtime formula.
How does temperature affect battery runtime?
Cold temperatures reduce a battery's effective capacity, sometimes by 20% or more below freezing for lead-acid chemistry, while high heat accelerates aging. Runtime estimates should be treated as best-case in extreme temperatures.
What size battery do I need for my appliances?
Add up the wattage of everything that will run at once, decide how many hours of runtime you want, then use the "Recommended Bank Size" output above, which reverses the runtime formula to solve for the amp-hours needed.
Is it safe to fully discharge a lithium battery?
Lithium batteries tolerate deeper discharge than lead acid, but regularly draining to 0% still stresses the cells. Most manufacturers recommend stopping around 10–20% remaining, which is reflected in the 90% default depth of discharge used above.
How accurate is a battery runtime calculator?
A calculator that includes efficiency, depth of discharge, and a safety margin is far more accurate than the simple watt-hours-divided-by-watts math alone, though real-world results still vary with battery age, temperature, and true appliance draw.
Can I use this calculator for a solar battery bank?
Yes. Enter your bank's total voltage and amp-hour capacity, select lithium or your specific chemistry, and enter your expected household or off-grid load to estimate how long stored solar energy will last without additional charging.
What's a safe amount of reserve to keep in a battery?
Most guidance suggests keeping at least 10–20% capacity in reserve beyond your chemistry's recommended depth of discharge, which the calculator's safety margin field applies automatically.
Why does my battery's actual capacity seem lower than its rating?
Ratings are measured under controlled lab conditions at a specific discharge rate. Faster discharge, cold temperatures, and battery age all reduce the amp-hours a battery can actually deliver compared to its printed rating.
Related Calculators on Inverter110
Battery runtime is one piece of a larger power-system puzzle. These related tools help you size the rest of your setup:
- Power Consumption Calculator — total up your household or appliance wattage
- Solar Battery Calculator — size a battery bank for solar charging
- Generator Size Calculator — pick the right generator for your loads
- Wire Gauge Calculator — match cable size to your amperage
- Solar Panel Calculator — estimate panel wattage needed to recharge your bank
- UPS Calculator — size backup power for sensitive electronics
- Inverter Calculator — match inverter capacity to your battery bank
- Voltage Drop Calculator — check cable runs for excessive loss
Final Thoughts
Battery specs on a box or a listing page tell you what a battery is rated for; they don't tell you what it will actually do for your fridge, your CPAP machine, or your RV's water pump on a real night off-grid. Chemistry, efficiency, depth of discharge, wiring configuration, and load all shift that number — sometimes by more than half. Running your exact setup through a battery runtime calculator before you buy, wire, or rely on a battery bank turns a guess into a plan, whether you're building a home backup system, outfitting an RV, sizing a marine battery, or designing a solar storage bank from scratch. Adjust the fields above with your real numbers, compare a few battery types and configurations side by side, and size your system around the runtime you actually need — not the one printed on the label.
Battery chemistry and efficiency figures referenced above are consistent with general guidance published by organizations such as the U.S. Department of Energy, the National Renewable Energy Laboratory (NREL), Battery University, and IEEE standards for stationary battery systems. Always consult your battery manufacturer's datasheet for exact specifications on any specific product.