1. Loads
List each device, running watts, startup surge and hours per day.
LITHVOLT LITHIUM ACADEMY
Size the system before you buy the battery.
A practical, application-led guide for choosing battery energy, voltage, inverter power, solar charging and protection. Start with your loads—not a product name.
START WITH 6 INPUTS →01 / INPUTS
A correct specification starts here.
Collect these inputs before comparing batteries. Missing one can create an undersized inverter, slow charging or unsafe DC current.
2. Autonomy
Define hours or days without grid, engine or solar charging.
3. Charging
Grid, alternator, generator and available solar roof/ground area.
4. Electrical platform
Required DC voltage, AC voltage, frequency and phase.
5. Environment
Temperature, water/dust exposure, vibration, altitude and ventilation.
6. Project constraints
Space, weight, connectors, communications, destination and quantity.
02 / CALCULATOR
Planning calculator
Use this for a first estimate. Final cable, fuse, BMS and equipment settings must follow the exact component manuals and local code.
Daily energy
3.00 kWhMinimum nominal battery
4.17 kWhBattery capacity
326 AhEstimated solar energy/day
2.02 kWhSolar recovery time
9.3 hPlanning method: load × time; battery size includes usable-depth and efficiency allowances. Solar output includes a 75% planning factor for conversion and field losses.
Four formulas worth knowing
Energy
Wh = watts × hours. Battery nominal Wh = volts × amp-hours.
Runtime
hours ≈ nominal Wh × usable depth × efficiency ÷ load W.
DC current
amps ≈ AC watts ÷ (battery volts × inverter efficiency). Higher system voltage reduces current.
Solar yield
daily Wh ≈ array W × peak-sun-hours × 0.75. Use site-specific data for final design.
03 / RV
RV and camper power
RV body size alone does not determine the battery. Appliance list, simultaneous load, air conditioning, roof area and alternator capability matter more.
| Use profile | Battery energy | Inverter | Solar | Typical loads |
|---|---|---|---|---|
| Van / light camper | 0.8–1.6 kWh | 1–2 kW | 200–400 W | Lighting, fan, router, laptop, small fridge |
| Towable / medium RV | 2.5–5.1 kWh | 2–3 kW | 400–800 W | Daily essentials, microwave in short bursts, coffee maker |
| Large motorhome | 5.1–10.2 kWh | 3–5 kW | 800–1,600 W | Multiple appliances and limited air-conditioning runtime |
| Long-stay / high load | 10–20 kWh+ | 5–8 kW | 1–2 kW+ | Extended off-grid use; requires a full thermal and charging study |
How long does charging take?
Approximate 10–100% times shown below include a 10–25% allowance for taper and losses. The battery/BMS maximum charge current is always the limit.
| Battery | Energy | Standard charge | Fast charge | Solar planning |
|---|---|---|---|---|
| 12.8 V 100 Ah | 1.28 kWh | 20 A ≈ 5–6 h | 40 A ≈ 2.8–3.3 h | 400 W solar ≈ 4–6 sun h |
| 12.8 V 200 Ah | 2.56 kWh | 20 A ≈ 10–12 h | 40 A ≈ 5.5–6.5 h | 600 W solar ≈ 5–7 sun h |
| 25.6 V 200 Ah | 5.12 kWh | 40 A ≈ 5.5–6.5 h | 80 A ≈ 2.8–3.3 h | 1 kW solar ≈ 6–8 sun h |
| 51.2 V 100 Ah | 5.12 kWh | 50 A ≈ 2.2–2.6 h | 100 A ≈ 1.1–1.4 h | 1 kW solar ≈ 6–8 sun h |
04 / SOLAR + MPPT
Solar panels and MPPT
Panel wattage is its rated peak under standard test conditions. Real energy depends on location, orientation, temperature, shade and system losses.
Pmax / Wp
Rated maximum power. Use it to total array size, not as guaranteed continuous output.
Vmp / Imp
Voltage and current at maximum power. Their product is approximately Pmax.
Voc / Isc
Open-circuit voltage and short-circuit current. These set controller safety limits.
Efficiency
Power per panel area. Higher efficiency helps when roof space is limited.
Temperature coefficient
Voc rises in cold weather; power usually falls as cells get hotter.
Bifacial
Can collect rear-side light when mounting and surface reflectance allow it.
Series, parallel and controller selection
Series
Adds voltage; current stays similar. Cold-corrected total Voc must remain below the MPPT absolute limit.
Parallel
Adds current; voltage stays similar. Check controller input current, connector and combiner/fuse requirements.
MPPT
Best general choice for variable solar voltage. Its output current is roughly array watts ÷ charging voltage; retain engineering headroom.
PWM
Suitable only for small, voltage-matched systems where lower harvest and limited flexibility are acceptable.
Mixed panels
Avoid mixing different Vmp/Imp in one string. If shading or orientations differ, use separate MPPT inputs/controllers.
Battery compatibility
Use the battery maker’s charge voltage, current and temperature limits; enable low-temperature charge protection for LFP.
05 / HOME STORAGE
Home solar and storage
Begin with 12 months of bills or a measured load profile. Separate “energy per day” from “instantaneous power” and decide which circuits truly require backup.
| Profile | Daily use | Battery | Inverter | Outcome |
|---|---|---|---|---|
| Essential backup | 3–8 kWh/day | 5–10 kWh | 3–5 kW | Lights, router, fridge, electronics |
| Typical home | 8–18 kWh/day | 10–20 kWh | 5–8 kW | Essential circuits plus selected kitchen/office loads |
| Large / electric home | 18–35 kWh/day | 20–40 kWh | 8–15 kW | High simultaneous loads; split-phase/three-phase study |
| Weak-grid / off-grid | Measured load × autonomy | 2–3 days reserve | Peak + motor surge | Add generator or controlled load shedding |
Typical installation architecture
- 01Survey roof/ground, shade, structure, local utility rules and earthing system.
- 02Group compatible panels into strings; verify cold Voc and Isc before selecting PV isolators, protection and MPPT.
- 03Connect battery through a correctly rated DC fuse/breaker and disconnect close to the source; size cable for ampacity and voltage drop.
- 04Use an approved inverter/charger whose battery voltage, AC output, surge, communication and grid mode match the project.
- 05Configure BMS/inverter charge limits, commissioning tests, emergency shutdown, labels and monitoring.
- 06Grid-connected and high-voltage work must be designed, permitted and commissioned by qualified local professionals.
Fishing boat and marine power
Choose the bank
Keep engine-start and house/trolling banks separated unless the approved architecture explicitly combines them.
Match the motor
Trolling motors commonly use 12, 24 or 36 V. Match nameplate voltage and verify maximum current against BMS, cable and breaker.
Estimate runtime
Runtime ≈ usable Wh ÷ average motor watts. Propeller, hull, wind, current and speed can change consumption sharply.
Charge safely
Use shore, alternator or solar chargers with an LFP profile and galvanic/corrosion-aware marine installation.
Install for water
Secure the battery against movement; use protected terminals, suitable enclosure/IP level, ventilation and ignition requirements for the compartment.
Plan redundancy
Navigation, bilge, communications and engine starting should not depend on one unprotected consumer circuit.
Golf cart and low-speed vehicle
Voltage first
Match the existing 36/48/72 V controller and charger. Never substitute a different nominal voltage because the connector fits.
Power capability
BMS continuous and peak current must cover controller demand, hill starts, passengers and accessories without nuisance trips.
Energy and range
Range depends on usable kWh, vehicle mass, tires, speed, terrain and temperature; validate with a route test.
Mechanical fit
Measure tray, hold-downs, terminal clearance and axle loading. A conversion may need a new mounting kit and state-of-charge display.
Charging
Use an LFP-compatible charger with correct pack voltage and communication/interlock behavior.
Fleet planning
Size around the longest duty cycle and available overnight/shift charging window, then keep reserve for aging and cold.
Portable power stations
300–500 Wh / 300–600 W
Phones, router, lights, camera and a laptop; not heating appliances.
700–1,200 Wh / 1–2 kW
Mobile office, TV, CPAP and efficient fridge; short bursts of kitchen loads if surge allows.
1.5–3 kWh / 2–3 kW
Longer backup and heavier appliances; weight and recharge time become decisive.
Above 3 kWh
Treat as a wheeled/modular energy system with dedicated protection and transport planning.
Check ports
Verify AC voltage/frequency, USB-C PD rating, regulated DC output and solar input voltage/current window.
Runtime rule
Use measured appliance energy when possible. Compressors cycle; heaters draw near nameplate continuously.
LithVolt technical library
Advanced guides for buyers, engineers and channel teams
Battery–inverter compatibility: what must match
A practical checklist for matching LiFePO4 batteries with hybrid and off-grid inverters.
Low-voltage vs high-voltage home batteries
How installers should compare architecture, current, expansion, service and inverter choice.
UN 38.3 vs IEC 62619: different evidence for different risks
Understand transport testing and industrial battery safety evidence before requesting documents.
How to audit a lithium battery PACK supplier
A buyer-focused audit framework for engineering, traceability, process control and after-sales readiness.
OEM battery development from brief to controlled production
A stage-gate path for private-label and custom battery projects.
BMS communication: CAN, RS485 and the protocol behind the connector
Why matching the plug is not enough for a safe battery–inverter integration.
EU battery compliance starts with the economic operator and exact model
A practical framework for brands, importers and distributors to organise evidence before market entry.
Non-negotiable design checks
- Fuse or breaker each energy source and branch for the conductor and fault current.
- Provide a service disconnect; prevent accidental short circuits and exposed live terminals.
- Confirm BMS continuous, peak, charge current and series/parallel permissions.
- Do not mix chemistry, capacity, age or state of charge unless the manufacturer approves it.
- Respect operating/charging temperature limits; many LFP batteries must not charge below 0°C without protection.
- Use torque values, crimp tools, cable lugs and enclosure ratings specified for the installation.
- Verify inverter surge, neutral/earth behavior, RCD/GFCI and local grounding rules.
- Final design must use exact datasheets, local electrical/fire rules and qualified installation.
Documents and market access
Transport
The exact cell/battery design must meet applicable UN 38.3 requirements; packing, labels, state of charge and paperwork depend on mode and configuration.
Industrial / motive
IEC 62619 covers safety for industrial lithium cells and batteries, including stationary, golf-cart and marine examples; end-use rules still apply.
Stationary ESS
North American projects may require evaluated batteries, inverters and the complete system under standards such as UL 1973, UL 1741 and UL 9540; local fire/electrical code controls installation.
Portable products
Requirements differ by product architecture and market. Confirm battery, charger, EMC, radio and mains safety for the exact model and destination.
Educational planning guidance—not a final electrical design, compliance declaration or installation instruction. Local rules and exact manufacturer data take precedence.
Turn your load list into a buildable system.
Send the application, country, loads, hours, charging sources, dimensions and quantity. LithVolt will return a configuration brief for technical confirmation.