Lithium Battery for Borehole Pumps: Off-Grid Water Supply
Lithium Battery for Borehole Pumps: Off-Grid Water Supply
A borehole pump is one of the few loads that genuinely justifies a dedicated battery bank: water is non-negotiable, the grid may not reach the site, and the pump only runs for short windows each day. Farms, lodges, and remote work camps are replacing diesel gensets and lead-acid banks with lithium packs charged from solar. An experienced lithium battery manufacturer can size the bank to the pump’s starting surge rather than its running current, which is where most undersized systems fail.
Why Pumping Suits Lithium Chemistry
Submersible pumps draw a large inrush — commonly four to six times running current for two to five seconds — and then settle into a steady draw for 20 to 60 minutes. Lithium cells deliver that surge without the voltage sag that collapses a lead-acid bank, so the pump’s motor controller does not trip on undervoltage. Depth of discharge is the second advantage: a lithium bank can be cycled to 80 or 90 percent of nameplate capacity every day, while a lead-acid bank rated at the same amp-hours delivers roughly half that in service. Self-discharge below 2 percent per month also means a seasonal borehole still holds usable charge after weeks of standby.
Sizing to the Surge, Not the Average
Start from the pump’s locked-rotor or starting current, not its nameplate wattage. A 1.5 kW submersible on a 230 V supply may pull 4 kW or more for the first seconds, and the inverter and BMS must both sustain that peak for the specified window. Multiply running current by daily pumping hours to get amp-hours, then divide by usable depth of discharge and add 15 percent for aging. A typical 1.5 kW pump running two hours daily needs about 6 kWh of usable energy, which a 7.5 kWh lithium bank covers comfortably where a 12 kWh lead-acid bank would be marginal.
Borehole Power Comparison
| Attribute | LiFePO4 | Lead-Acid | Diesel Genset |
|---|---|---|---|
| Usable depth of discharge | 80–90% | 50% | n/a (fuel) |
| Surge capability | Excellent | Poor (sag) | Good |
| Cycle life | 3000–6000 | 300–500 | Overhaul ~5000 h |
| Routine maintenance | None | Watering, equalizing | Oil, filters, fuel |
| Cost per delivered kWh | Low | Medium | High |
Solar Pairing and Charge Control
Most borehole systems pair the bank with a solar array and an MPPT controller, because pumping demand correlates with sunshine in irrigation and livestock use. Size the array to replace the daily draw plus losses in the worst month, not the annual average; a winter-dimmed array is the most common reason a system works in July and fails in January. Where the site has grid or genset backup, an automatic transfer switch lets the charger top the bank during long cloudy spells without anyone driving out to start an engine.
Installation Notes for Remote Sites
Mount the battery in a ventilated, shaded enclosure rated IP65 or better, and keep cable runs from bank to inverter short so voltage drop does not eat the surge margin. Low-temperature charging is a hard constraint: standard LiFePO4 cells must not be charged below 0 °C, so specify internal heating or a cold-weather charge cutoff if the borehole sits in a freezing climate. Remote monitoring over RS485 or a cellular gateway lets an operator check state-of-charge and pump cycles without a site visit.
What to Ask a Supplier
Bring the pump nameplate, starting current, daily run hours, and site temperature range. Ask for the sustained surge rating in seconds, the usable capacity after depth-of-discharge limits, the low-temperature charge strategy, warranty terms in cycles as well as years, and whether the BMS talks to your inverter brand. Request a written sizing calculation rather than a catalogue recommendation.
People Also Ask
How big a battery do I need for a borehole pump? Multiply running watts by daily run hours, divide by usable depth of discharge, add 15 percent for aging — then confirm the bank and inverter cover the starting surge, which is usually the binding constraint rather than total energy.
Can a lithium battery run a 230 V submersible pump? Yes, through an inverter sized for the starting current. Most residential and light-agricultural borehole pumps run well on a 3–5 kW inverter paired with a 5–10 kWh lithium bank.
Do I still need a generator? Only as seasonal backup. If the array is sized for the worst month and the bank carries two to three days of autonomy, most sites retire the genset entirely.
How long will a lithium borehole bank last? Typically 10–15 years at one cycle per day, versus 2–4 years for a lead-acid bank cycled to the same depth.
Written by Karl at China Battery Technology. Request a quote.
