Drone Battery Procurement: What to Specify in an RFQ (A Field Engineer’s Checklist)
When a procurement team asks me to “quote a drone battery,” the request almost always lacks the details that actually decide whether the pack flies well. After fifteen years specifying lithium packs for UAV platforms — from agricultural sprayers to fixed-wing survey airframes — I have learned that the RFQ (request for quotation) is where projects win or lose months. A vague RFQ produces a vague pack that fails flight testing. A precise RFQ gets you a custom battery solution that matches your mission, clears certification, and ships on schedule.
Start With the Mission, Not the Volts
Before you write a single number, describe the flight. Endurance target in minutes, payload mass, cruise and hover duty cycle, and the operating temperature range tell an engineer more than a nominal voltage ever will. I have watched buyers specify “22.2 V 6S” and then wonder why the pack overheats on a heavy-lift mapping mission. The pack must be sized to the power profile, not just a cell count. A drone lithium battery that is perfect for a cinematic quad may be completely wrong for a long-endurance fixed wing, and the RFQ is exactly where that distinction gets locked in. In my experience the best RFQs open with a one-page mission summary, not a parts list.
Think about duty cycle, not just peak draw. A survey drone that climbs once and then cruises for forty minutes is a very different load than a racing quad that pulses to maximum C-rate every few seconds. When a buyer hands me the actual flight log instead of a guess, I can usually shave 8-12% off pack mass while holding endurance — pure savings that come from the RFQ being specific.
Electrical Specifications to Lock Down
These are the numbers a supplier will quote against, so they must be exact and unambiguous:
- Nominal and cutoff voltage, plus the cell configuration (for example 6S, 12S, or 14S).
- Capacity in ampere-hours and the C-rating for both continuous and peak discharge.
- Maximum charge current and the recommended charge protocol (CC-CV, balance current, termination current).
- Internal resistance target and the communication bus (SMBus, CAN, or DroneCAN).
- Allowed voltage sag under peak load, because sag — not just capacity — is what drops your motors out of spec.
For a heavy-lift quadcopter I typically specify a continuous 15C with a 25C peak for ten seconds. For a long-endurance fixed wing, a 5C continuous pack with low self-discharge matters far more than raw C-rating. Getting these wrong is the single most common reason a lithium battery underperforms in the field, and it is almost always traceable to a thin RFQ.
Mechanical, Thermal and Environmental Limits
Mass budget is brutal on a drone. Every gram of battery is a gram stolen from payload or flight time. Specify the maximum mass, the envelope dimensions, and the connector type — XT60, EC5, or an industrial aviation connector for harsher environments. Then define the environmental envelope: IP rating for dust and water ingress, operating temperature (we regularly design for -20 °C cold-start), and shock and vibration tolerance aligned to MIL-STD-810 methods. Buyers who omit these clauses end up with a pack that fits the airframe on the bench but fails on the first cold dawn sortie.
Why Connector Choice Shows Up in the RFQ
The connector is not an afterthought. A flimsy connector adds resistance, heats under high discharge, and becomes the failure point on a drone lithium battery. Specify the connector family and the crimping standard so the supplier cannot quietly substitute a cheaper part that passes on the bench and melts in the air.
Temperature Envelope and the Cold-Start Problem
Below 0 °C, lithium cells lose available capacity and charge acceptance drops sharply. If your drone flies in winter, the RFQ must state the cold-start temperature and the allowable capacity loss, otherwise the supplier will quote a pack tuned for 25 °C lab conditions that collapses the moment the airframe meets real weather.
Certification and Compliance: UN38.3, IEC 62133, FAA and EASA
This is where vague RFQs get dangerous. A drone battery shipped by air must clear UN38.3 transportation testing, and the cell or pack should carry IEC 62133 (or the newer IEC 62619 for industrial packs). For air transport, FAA and EASA rules limit lithium content and require the UN markings plus a test summary. I always ask buyers to state the destination markets and the transport mode up front so we build the documentation into the project instead of bolting it on after the fact. Skipping this clause is how otherwise good packs get held at customs or refused by the carrier.
Quality, Traceability and Production Controls
Specify grade-A cells with a documented cycle life — at Horizon Power we commit to 80% capacity at 500 cycles for most packs — full traceability of cell batches, and formation and aging procedures. Require a capacity test report per pack and a defined acceptable mAh tolerance. These clauses are what keep a fleet consistent across a 1,000-unit order. A custom battery solution without traceability is just a gamble at volume, and the RFQ is the only place you can force the discipline before the line is running.
A Practical RFQ Template and the Mistakes I See
Here is the skeleton I recommend sending to any supplier:
- Mission profile: endurance, payload, duty cycle, temperature range.
- Electrical: configuration, capacity, C-rating, charge limits, communication.
- Mechanical: mass, dimensions, connector, mounting method.
- Environmental: IP, shock, vibration, altitude ceiling.
- Compliance: UN38.3, IEC 62133, destination transport rules (FAA/EASA).
- Quality: cell grade, cycle-life target, test reports, traceability.
- Commercial: quantity, lead time, sample policy, warranty terms.
The three mistakes I see most often: forgetting the thermal envelope, omitting the communication protocol, and leaving the certification destination blank. Any one of them can add six weeks to a program and a few thousand dollars in unplanned requalification. I tell every new buyer the same thing: if you can fill this seven-line template from real flight data, your supplier will respect the RFQ and your program will move.
Incoming Inspection: Accepting the First Batch
A good RFQ does not stop at the quote — it defines acceptance. State that the first production batch is subject to incoming inspection: a sample is discharged to cutoff, weighed, and X-rayed for internal defects. I have caught mislabeled capacity and off-spec internal resistance this way before a single unit reached a customer. Put the inspection method in the RFQ and the supplier knows you will measure, not trust.
Balancing, Construction and the Watt-Hour Ceiling
Specify how the pack is built: spot-welded nickel versus ultrasonic-welded busbars, the balancing strategy (passive during charge or active), and the separator and vent design. For high-discharge UAV packs I insist on ultrasonic-welded busbars because they hold resistance stable across the full 500-cycle life instead of creeping up as the nickel joint fatigues. Also state the air-freight parcel limit — a single drone battery above 100 Wh must be declared as dangerous goods, and that changes both the packaging and the freight price. Putting the watt-hour ceiling in the RFQ keeps the logistics team off the critical path and prevents a nasty surprise at the dock.
How a Custom Battery Solution Speeds Time-to-Market
When the RFQ is complete, a good supplier returns a validated pack faster than you can iterate on off-the-shelf parts. The right lithium battery partner treats your RFQ as a specification, not a guess, and that discipline is what protects your launch date when the schedule is already tight.
Frequently Asked Questions
What capacity should I request for a 30-minute flight?
It depends on the airframe and payload, but a typical 30-minute multirotor at 5 kg takeoff mass needs roughly 10,000-16,000 mAh at 6S. Always size from measured power draw, not from a rule of thumb, and validate with a discharge test before bulk ordering.
Do I need UN38.3 for domestic shipments?
Yes. UN38.3 is a transport safety standard, not a border rule. Any air shipment of a drone lithium battery — domestic or international — requires the test summary and UN marking. Ground domestic may differ by carrier, but most buyers ask for it anyway to keep one qualification across all channels.
Can one pack serve multiple drone models?
Sometimes, if the voltage, connector, and mass envelope overlap. But mixing missions usually means compromising endurance or C-rating. A custom battery solution per airframe is almost always the better engineering call when flight time is the selling point.
How do I verify real capacity before a bulk order?
Order a pilot batch, then run a constant-current discharge to cutoff and compare against the quoted mAh. Require the supplier to attach a per-pack test report. If you cannot measure it, do not buy 1,000 of it — the RFQ should mandate this test up front.
What does a custom battery solution cost versus off-the-shelf?
Unit cost is usually 10-30% higher at low volume, but you save on integration labor, returns, and delayed launches. At volume the gap closes, and the consistency of a graded, traceable lithium battery pack pays for itself in fleet reliability.
How long does a drone battery RFQ take to fulfill?
A complete RFQ gets a quote in days and samples in two to four weeks. An incomplete one drags for months through clarification loops. The quality of the RFQ is the single biggest lever on your schedule, so spend the hour to write it well.
