What a Battery Pack RFQ Actually Needs: A Buyer's Checklist

Send the same "custom battery pack" RFQ to three suppliers and you can get back three quotes that can't be compared. Not because the suppliers are wrong: because the RFQ never specified the cycle life you need, the communication protocol your system expects, or which certification applies to your use case, so each supplier filled in the gaps with their own assumptions.

That gap costs more than a confusing spreadsheet. Every field left vague turns into a follow-up email, a revised quote, and a week added to a program that was already tight. For a team that's "burning cycles on battery iteration," the RFQ is where that iteration either gets contained or gets started.

What a Vague RFQ Actually Costs You

Most battery pack RFQ checklists you'll find online are a list of field names: voltage, capacity, current, certifications. That's not wrong, it's just not enough. A field name tells a supplier what box to fill in. It doesn't tell them what happens if the answer is wrong.

"Certifications" as a bullet point doesn't tell a supplier whether you need UN 38.3 for air shipment or IEC 62133-2 because the pack ships inside a certified end product. "Cycle life" as a bullet point doesn't tell them whether you need 300 cycles for a low-duty prototype fleet or 1,000 cycles because the pack runs a daily duty cycle for three years. Both RFQs look identical on the checklist. The quotes that come back from them should not be identical, and if the supplier has to guess, they won't be.

The fix isn't a longer checklist. It's a checklist where every line item carries the reasoning behind it, so you fill it in with your actual requirement instead of a placeholder. That's what the rest of this post covers, organized by category, with the trade-off behind each one.

The Electrical Brief

Voltage, capacity, and current show up on every RFQ template. The part buyers skip is the one that determines whether the quoted pack will actually survive your application: cycle life at a stated depth of discharge (DoD) and C-rate.

At minimum, your RFQ needs:

• Nominal voltage and cell configuration (series count) your system's power electronics expect.
• Capacity in Ah, tied to the runtime or range your product needs to hit.
• Peak vs. continuous discharge current. These are different numbers for a reason: a motor controller's stall current or a robotics arm's peak torque draw is not the same as its cruising draw, and a pack sized only for continuous current will sag or cut out under peak load.
• Charge current and cutoff voltage, especially if your product supports fast charging or has a duty cycle that leaves little time to recharge between uses.
• Required cycle life, stated at a specific DoD and C-rate. This is the line item buyers most often leave blank, and suppliers most often fill in optimistically. Cycle life numbers vary hugely with the depth of discharge and discharge rate they're measured at. A cell rated for 1,000 cycles at 70% DoD will not deliver 1,000 cycles at 100% DoD: the deeper the discharge on each cycle, the fewer cycles the same cell delivers before it fades past the useful capacity threshold. If your program needs 500 cycles over two years at 80% DoD, say that in the RFQ. Don't accept "long cycle life" as an answer and don't quote a cycle-life number back to a supplier without checking what DoD and C-rate it was measured at.

Dan-Tech's own catalog gives a sense of the real range: cells built around NMC and silicon-anode chemistry in Dan-Tech's catalog run up to roughly 1,000 cycles at 70-90% DoD, and Dan-Tech's own Drone Series A packs are rated at 1,000 cycles at 80% DoD. That's a useful benchmark for what NMC and silicon-anode chemistries can deliver. If a quote comes back citing a much higher number for a similar chemistry and duty profile, ask what DoD and C-rate it was tested at before you take it at face value.

For the full picture on what drives cycle life beyond the RFQ line item, see what actually determines Li-ion cycle life.

Mechanical and Enclosure Requirements

The mechanical brief is where "it fits" turns into a redesign three weeks later. Your RFQ needs:

• Envelope and weight budget, not just a maximum, but the actual space you're designing around, including clearance for connectors and cabling.
• Mounting method: bracket, strap, adhesive, or a custom enclosure feature.
• Cable and connector orientation, which matters more than most buyers expect once the pack is actually installed in a chassis.
• IP rating, if the pack sees dust, moisture, or outdoor exposure at all.
• Connector type, named specifically. "A connector" is not a spec. Dan-Tech's catalog uses XT60 and XT90 for lower-power connections, AS150U on Smart BMS configurations, and Harting Han MPC30 or MPC60 for higher-pin-count or higher-current industrial integrations. If your system needs a specific connector family for compatibility with existing harnesses, name it in the RFQ. If you don't know which one fits your current draw and pin count, say what your current draw and pin count are and let the supplier recommend one.

Why "It Just Needs to Fit" Isn't a Spec

A pack that fits the envelope on paper can still fail the application if the connector points the wrong way for your cable routing, or the enclosure lacks the IP rating your product's duty environment actually requires. Mechanical fit and mechanical suitability are two different questions, and an RFQ that only asks the first one gets an answer to the first one.

BMS, Communication Protocol, and System Integration

The battery management system (BMS) is where "integration is becoming a nightmare" usually starts, and it's the section most buyer checklists gloss over.

At minimum, specify:

• Protection functions required: over-current, over-voltage, under-voltage, short-circuit, and temperature protection are standard, but confirm which ones and at what thresholds if your application has unusual conditions.
• Balancing method: active or passive. Passive balancing is simpler and lower cost; active balancing recovers more usable capacity in packs with cell-to-cell variance, which matters more as pack size and cycle count grow.
• NTC thermistor placement and fusing, if your system monitors pack temperature independently or has its own fusing requirements.
• Communication protocol. This is the line item that decides whether your pack talks to your system on day one or needs firmware work after delivery. If your system expects CAN, RS485, UART, or a specific protocol variant, put it in the RFQ explicitly. Dan-Tech's Smart BMS packs support CANBUS, RS485, and UART; a supplier that doesn't ask which one you need, or doesn't offer a choice at all, is a signal to dig deeper before you commit.

For a deeper look at how these protocols actually behave in a pack, see BMS communication: CAN, SMBus, DroneCAN in pack integration.

Certifications and Regulatory Requirements to Name in the RFQ

Most RFQ checklists list "certifications" as a single bullet point. That's not specific enough to get a comparable quote, and it's not specific enough to know what you're actually asking for. Two standards come up most often for custom Li-ion packs:

Name the standard, name the use case it applies to, and ask the supplier what test reports back up their claim. Because every custom pack is built to order, a real supplier answer is scoped per project, not pulled off a shelf: Dan-Tech's own packs are designed to meet CE, UN 38.3, RoHS, and IEC 62133 requirements, with the actual certification scope, testing, and cost confirmed per project rather than assumed at the catalog level. If a supplier's RFQ response claims a finished pack "is certified" without a project-specific test report behind it, ask to see the report.

A forward-looking item worth putting in the RFQ now, especially for European buyers: the EU Battery Regulation's digital battery passport requirement takes effect 18 February 2027 for industrial batteries above 2 kWh, along with EV and light-transport batteries. It requires a QR-linked digital record covering identification, chemistry, and key technical data, and a battery without one can't legally be placed on the EU market or put into service from that date. Most single custom packs sit below the 2 kWh threshold today, but larger industrial and aerospace packs may not. If your program timeline runs anywhere near 2027 and your pack could cross that threshold, ask your supplier now how they plan to handle it rather than finding out during a later production run.

For the fuller picture on certification scope and timing, see battery pack certification in Europe.

Application-Specific RFQ Requirements: Drone vs. Robotics/AGV vs. Aerospace and Defense

A single generic RFQ template misses what actually changes between applications. The checklist categories above stay the same, but the numbers behind them, and which ones matter most, shift by application.

If you're specifying a drone pack, see the custom UAV battery pack guide for the full electrical and mechanical brief. For AGV and robotics sizing, see the AGV battery pack sizing guide. For programs with MIL-STD requirements, see battery packs for aerospace and defense. And if you're not sure which category your program actually falls into, robotics vs. drone battery pack design walks through where the two genuinely diverge.

Cell Sourcing: Specify Dan-Tech's Cell, or Bring Your Own

Most RFQ templates assume the supplier picks the cell. That's fine when you don't have a preference, but it's not the only option, and it's worth putting in the RFQ explicitly either way.

Dan-Tech's catalog sources cylindrical cells from Molicel, Reliance, and Samsung, and both cylindrical and pouch cells from Amprius, covering a range of energy density, discharge rate, and cycle life. If you already know your application well enough to have a target energy density or discharge rate, name it and let the supplier recommend a specific cell from a specific manufacturer, not a generic "high energy density cell." If you already have a cell qualified for your application, whether from prior testing, an existing supplier relationship, or a program-specific requirement, say so in the RFQ. A customer-supplied cell path lets a pack builder design the mechanical, thermal, and BMS architecture around a cell you've already validated, instead of re-qualifying a new one. Not every supplier offers this path. It's worth asking about explicitly if it matters to your program.

Commercial Terms to Put in the RFQ From the Start

Technical specs get most of the attention in an RFQ, but commercial terms left for a later conversation are exactly what turns a promising quote into a stalled negotiation. Put these questions in the RFQ itself:

• Payment structure. Sample and low-volume orders are typically handled differently from production-volume orders: expect payment due on receipt for small sample quantities, and a deposit-plus-terms structure once an order moves into production volume, NRE, or certification scope. Ask which applies to your quantity before you're deep into a quote.
• Sample-to-production transition. Ask explicitly how the supplier handles the step from a validated sample to a production order: does pricing change, does lead time change, is there a minimum order quantity at that stage. A supplier who can answer this clearly in the RFQ response is signaling they've done it before.
• Lead time. Ask for a real number, not a range that spans months. Dan-Tech quotes lead times as short as 3 weeks for standard catalog-based configurations; a custom build with new certification scope will run longer, and a straight answer to this question in the RFQ response tells you a lot about how the rest of the relationship will go.

Generic RFQ hygiene, like BOM detail, revision control, and drawing formats, matters too, but it's already well covered by manufacturing RFQ guides in general. The three items above are the ones specific to battery packs that a generic template won't prompt you for.

Summary: The Battery Pack RFQ Checklist

• Voltage, capacity, and configuration, tied to your system's actual power electronics, not a rough estimate.
• Peak vs. continuous discharge current, because a pack sized only for continuous current will sag under peak load.
• Cycle life at a stated DoD and C-rate, because "long cycle life" without those two numbers can't be verified or compared across quotes.
• Envelope, weight budget, and named connector type, because "it fits" and "it fits and works in your system" are different questions.
• IP rating, if the pack sees dust, moisture, or outdoor exposure.
• BMS communication protocol (CAN, RS485, UART, or your system's specific requirement), so the pack talks to your system without post-delivery firmware work.
• Named certification standards (UN 38.3 for transport, IEC 62133-2 for cell/battery safety), with the use case that applies to your program, plus a request for the test reports behind any claim.
• EU Battery Passport awareness, if your program timeline or pack size puts you near the 2027 deadline and the 2 kWh threshold.
• Application-specific priorities: energy density and weight for drones, cycle life and duty cycle for robotics/AGV, traceability and documentation for aerospace and defense.
• Cell sourcing path: specify a cell from the supplier's catalog, or bring your own qualified cell.
• Payment structure, sample-to-production transition, and a real lead-time number, asked in the RFQ itself, not left for a later call.

FAQ

What's the single biggest mistake in a battery pack RFQ?

Leaving cycle life as "long" or "high" instead of a number tied to a specific depth of discharge and C-rate. Two suppliers can both answer "long cycle life" honestly and mean completely different things.

Do I need to specify a cell brand, or can I leave that to the supplier?

Either works, but say which one you're doing. If you want the supplier to recommend a cell, give them your target energy density, discharge rate, and cycle-life requirement so their recommendation is grounded in your actual application, not a generic pick.

What's the difference between UN 38.3 and IEC 62133-2?

UN 38.3 is a transport safety standard: it governs whether a lithium battery can legally ship by air, sea, or road. IEC 62133-2 is a product safety standard for the cell or battery itself, often required to integrate into a larger certified end product. Most shipped packs need UN 38.3; whether you need IEC 62133-2 depends on where the pack ends up.

Does the EU Battery Passport apply to every custom pack?

Not yet, and not to every pack. The requirement, effective 18 February 2027, applies to industrial batteries above 2 kWh along with EV and light-transport batteries. Many single custom packs sit under that threshold today, but it's worth flagging in the RFQ if your program is large enough or timed close enough to 2027 that it might not.

Can I send an RFQ with a cell I already have, instead of picking from a catalog?

Yes, and it's worth stating explicitly in the RFQ rather than assuming the supplier will ask. A customer-supplied-cell path lets the pack be designed around a cell you've already validated.

What if I don't have an RFQ template to start from?

Email Dan-Tech directly. Ask for a ready-made RFQ template to fill in yourself, or just describe your application and requirements in the message, and Dan-Tech's team will build the RFQ from what you send.

Every one of the line items above turns a vague RFQ into a quote you can actually compare, and a quote you can compare is a quote that doesn't come back for a second round three weeks later. Don't have an RFQ template to start from? Reach out to Dan-Tech directly, ask for a ready-made template to fill in yourself, or just describe your application and requirements in the message and Dan-Tech's team will build the RFQ from what you send. If you're ready to put a real RFQ together, start with Dan-Tech's Tool Box to configure your pack's electrical and mechanical requirements directly, or browse Dan-Tech's battery pack catalog to see the cell and configuration options available before you write the first draft. Lead times run as little as 3 weeks once your RFQ is complete.