Electric Sprayer Battery Capacity: How Buyers Should Verify mAh, Wh and Real Runtime

A sprayer product listing says “2000 mAh battery, 2–3 hours runtime.” The buyer repeats this claim in their retail listing. A customer buys the sprayer, uses it for 45 minutes, and the battery dies. The customer leaves a negative review: “Runtime is less than half of what was claimed.”

The problem is not necessarily that the battery is defective. The problem is that “2000 mAh” and “2–3 hours” are two different measurements that are not directly comparable without additional information.

Why Voltage × Ah = Wh Is the Starting Point

Battery capacity is commonly quoted in mAh (milliamp-hours). This number tells you how much charge the battery can hold, but it does not tell you how much energy the battery stores. Energy depends on both charge and voltage.

The formula is: Voltage × Ah = Wh (watt-hours)

A 3.7V battery rated at 2200 mAh stores: 3.7V × 2.2Ah = 8.14 Wh

This is the nominal energy — the theoretical maximum. Two batteries with the same mAh rating but different voltages store different amounts of energy. For buyers comparing sprayers, Wh is the number that matters for runtime comparison. mAh alone is misleading because it does not account for voltage differences between products.

Motor/Pump Power and Duty Cycle

Knowing the battery’s nominal energy capacity (Wh) is only half the equation. The other half is how much power the pump draws.

A sprayer with a 3.5W pump running continuously from an 8.14 Wh battery has a theoretical maximum runtime of: 8.14 Wh ÷ 3.5 W = 2.33 hours.

But this is a theoretical maximum that assumes:

• The battery delivers its full rated capacity (it rarely does)
• The pump runs continuously at full power (intermittent spraying uses less energy)
• There are no losses in the circuit
• The battery voltage stays above the pump’s minimum operating voltage throughout

This is why the same sprayer can produce different runtime numbers in different tests. The duty cycle (ratio of spray time to total time) is the variable.

Full-Charge Continuous vs Intermittent Spray Tests

To verify runtime claims, the buyer should run two tests:

Continuous spray test: Fill the sprayer, charge the battery fully, lock the trigger on, and time how long the pump runs before the battery is depleted. This is the worst-case runtime.

Intermittent spray test: Simulate typical use — spray for 10–15 seconds, release for 5–10 seconds, repeat. This more closely represents how a home gardener actually uses the sprayer.

Both numbers are valid. The question is which one the supplier used to generate the runtime claim. Both tests must record the pump model, nozzle, liquid (water), ambient temperature, and the test method used.

Low-Voltage Cutoff and Usable Capacity

A lithium-ion battery does not deliver its full rated capacity in use. The BMS cuts off power when the voltage drops below a safe threshold. The exact cutoff voltage depends on the BMS design and cell chemistry — verify with the supplier or by measuring during testing. Do not assume a specific cutoff voltage or usable capacity percentage without confirming it for the specific product.

The buyer should ask the supplier for:

1. The cutoff voltage setting
2. The discharge conditions under which the rated capacity was measured
3. Cycle life data — how capacity degrades over use, based on the specific cell used

Battery Indicator Accuracy

(Content merged from a previously separate article on battery indicators.)

A 3-bar or 4-bar battery indicator typically works by measuring the battery voltage and mapping it to display segments. A Li-ion battery’s voltage does not drop linearly during discharge — the voltage stays relatively flat for most of the discharge, then drops steeply near the end.

This means a 3-bar indicator may show “full” for a large portion of the battery’s discharge, then drop suddenly near the end. To evaluate whether the indicator is useful:

1. Run the system through a full discharge cycle, recording the indicator display and the battery voltage at regular intervals.
2. Note whether the indicator provides meaningful information throughout the discharge.
3. Check whether the indicator flickers under pump load.

The instruction manual should manage customer expectations: “The battery indicator shows approximate charge level. The indicator may show full for an extended period and then drop quickly near the end of the charge. This is normal for lithium-ion batteries.”

What Runtime Claim Can Be Printed After Testing

After running the continuous and intermittent tests, the buyer has two runtime numbers. The conservative approach: print the continuous spray runtime with a qualifier. (Illustrative wording — actual numbers must come from your test results: “Up to X minutes of continuous spraying, or up to Y hours of intermittent use.”)

The runtime claim is a promise that the buyer will have to answer for if it does not match the customer’s experience. Test it, document the method, and print what you can defend.

The key sourcing action: specify the battery capacity, the pump power, and the test method (continuous or intermittent) in the RFQ. A supplier who quotes “2000 mAh, 2–3 hours runtime” without specifying the test conditions is giving you a number you cannot verify or defend.