Battery Backup Input Form
Example Data Table
| Load |
Battery Bank |
Efficiency |
Usable Depth |
Estimated Use |
| 900 W |
24 V, 400 Ah |
90% |
50% |
Home backup |
| 450 W |
12 V, 300 Ah |
88% |
60% |
RV essentials |
| 1500 W |
48 V, 400 Ah |
92% |
80% |
Larger inverter bank |
Formula Used
Bank voltage: volts per battery × batteries in series.
Bank amp hours: amp hours per battery × parallel strings.
Nominal watt hours: bank voltage × bank amp hours.
Usable AC watt hours: nominal watt hours × depth of discharge × age derate × temperature derate × reserve factor × inverter efficiency.
Runtime: usable AC watt hours ÷ running watts.
DC current: running watts ÷ bank voltage ÷ inverter efficiency.
Peukert factor: reference current ÷ actual current, raised by exponent minus one.
Required amp hours: target watt hours ÷ bank voltage, after losses and reserves.
How to Use This Calculator
Enter the running watt load first. Add the startup surge if motors, pumps, or refrigerators are included.
Enter the AIMS inverter continuous and surge ratings. This lets the calculator check practical load limits.
Enter battery voltage, amp hours, series count, and parallel count. These values define the battery bank.
Adjust depth of discharge, efficiency, age, temperature, reserve, and Peukert values. Use manufacturer data when available.
Press the calculate button. Review runtime, usable energy, current draw, required batteries, and recharge time.
Reliable Backup Starts With Correct Sizing
A backup battery bank should match the load, inverter, and expected outage length. AIMS inverters can support many home, office, RV, marine, and off grid needs. Still, the battery bank decides how long the system can run. This calculator helps you compare available watt hours, usable watt hours, discharge limits, and inverter losses. It also checks surge demand against the inverter rating.
Why Usable Energy Matters
A battery label shows nominal capacity, not always usable capacity. Lead acid batteries should often keep a reserve. Lithium batteries usually allow deeper discharge. Temperature, age, and wiring losses also reduce the real output. The calculator combines these factors into a practical usable energy value. It then divides that value by the running load. The result is a clear runtime estimate in hours and minutes.
Advanced Battery Bank Checks
Series batteries raise voltage. Parallel strings raise amp hour capacity. The calculator handles both arrangements. It estimates bank voltage, bank amp hours, DC current, AC current, and inverter load percentage. It also gives a target amp hour estimate when you enter a desired backup time. This helps you decide whether one battery string is enough, or whether extra parallel strings are required.
Peukert And Recharge Planning
High current can reduce usable capacity, especially with lead acid batteries. The Peukert option gives a better estimate during heavy discharge. Use a lower exponent for lithium and a higher exponent for flooded lead acid. The recharge estimate uses charger current and charge efficiency. It gives a rough recovery time after an outage. Real charging can take longer during absorption stages, so keep a margin.
Safe Use And Practical Limits
Do not size a system only from ideal numbers. Leave room for startup surges, future loads, battery aging, and hot or cold locations. Confirm cable size, fuse size, ventilation, and the actual AIMS inverter manual. This tool is for planning and comparison. Final installation should follow electrical codes and manufacturer instructions.
For best results, measure real appliance wattage with a meter. Enter continuous loads, not only nameplate guesses. Test the system under supervision before relying on it. Keep records of runtime, battery voltage, and recharge behavior after each outage. Adjust for new loads.
FAQs
What does this AIMS backup battery calculator estimate?
It estimates battery bank voltage, amp hours, usable watt hours, runtime, current draw, inverter load percentage, required bank size, and recharge time.
Can I use this for lithium batteries?
Yes. Set a higher allowed depth of discharge and a lower Peukert exponent. Always follow the lithium battery manual and BMS limits.
Why is runtime lower than nominal battery capacity suggests?
Runtime drops because of inverter losses, discharge limits, battery age, temperature, reserve margin, and high current effects.
What Peukert exponent should I enter?
Lithium may use about 1.03 to 1.08. AGM often uses about 1.10 to 1.20. Flooded lead acid can be higher.
Does series wiring increase amp hours?
No. Series wiring increases voltage. Parallel wiring increases amp hour capacity. The calculator handles both parts separately.
Should surge watts be included?
Yes. Motors, compressors, pumps, and refrigerators can need high startup power. Compare surge load with the inverter surge rating.
Why is recharge time only an estimate?
Charging slows near full capacity. Battery chemistry, charger settings, temperature, cable loss, and absorption stages can extend actual recharge time.
Can this replace an electrical design?
No. It is a planning tool. Confirm cable size, fuses, ventilation, grounding, and code requirements before installation.