A battery circuit can change its operating role between charging and supplying a load. A breaker quotation that says only “DC suitable” leaves an important purchasing question unanswered: does the offered device support the required current directions, terminal connections and fault conditions?
Buyers should request an operating-state review linked to the exact breaker and its manufacturer's diagrams. This guide develops that evidence package. Use the DC breaker trip-curve and interrupting-rating guide for the separate protection-performance assessment.
Define the direction question in the RFQ
Use three distinct descriptions so bidders answer the same questions.
Connection polarity concerns the manufacturer's required relationship between marked terminals, circuit potentials and current direction. Have the manufacturer interpret its markings on the proposed circuit diagram.
Line/load direction identifies a required source-side and load-side connection where the device specifies one. In this guide, reverse feeding means supplying the device from the opposite side of that arrangement.
Bidirectional use means that the proposed, unchanged connection must support the specified operating and fault cases with current potentially flowing in either direction. State those cases explicitly; a broad “bidirectional” claim can otherwise leave its intended scope unclear.
Do not identify terminals solely by wire color, physical top/bottom position or a similar-looking product photograph. Request the exact manufacturer's terminal designations, complete diagram and applicable limitations.
Read manufacturer statements within their product scope
Schneider Electric states that C60H-DC is polarized, requires its marked polarity to be respected and should not be used where current direction may change momentarily. That is a specific restriction for the named range. Schneider C60H-DC polarity FAQ.
ABB's S300P page, by contrast, identifies polarity-independent operation within its stated DC voltage, pole-connection and breaking-capacity conditions. This establishes a different design approach for that range, not a universal rule for miniature breakers. ABB S300P DC application information.
Reverse-feed guidance also contains exceptions. Schneider's published list distinguishes particular trip-unit, accessory and DC variants. Read the exception list with the offered catalogue number rather than applying a family name alone. Schneider reverse-feed FAQ.
These examples support model-specific review. They do not recommend either product for a SINAWATTS assembly or establish permission for an unidentified substitute.
Build an operating-state matrix before requesting a quote
Give the designer and bidders a marked one-line diagram. Identify the proposed breaker location, terminals, source connections and operating modes. Use conventional-current arrows consistently and label the assumptions so every reviewer can interpret them.
For each relevant state, record the voltage envelope, current direction, source availability and required protection function. Ask the responsible engineer to identify fault cases and any transitions that the normal operating description omits.
On small screens, swipe or scroll sideways to read every column. Keyboard users can focus the table and use the arrow keys.
| State or question | Buyer information | Evidence needed before release |
|---|---|---|
| Normal supply | Source, load and expected current direction | Diagram and operating permission for the exact connection |
| Charging or regeneration | Whether current reverses through the same device | Written applicability to the specified reverse-current duty |
| Mode transition | Switching sequence and credible temporary states | Coverage of the relevant transient direction changes |
| Fault on either side | Engineer-defined fault locations and contributing sources | Direction-specific protection and interruption evidence where applicable |
| Alternate source connection | Proposed change to source-side terminals | Explicit reverse-feed permission for the complete variant |
| Maintenance arrangement | Required isolation function and possible source connections | Separate isolation assessment and approved operating procedure |
Only include states that apply to the project. The table is a procurement framework, not a wiring diagram or authorization to test a live circuit.
The resulting matrix should let a reviewer trace each “permitted” response to a document, an exact configuration and an accountable technical decision. Record each applicable row as supported, excluded or unresolved, with its document reference and engineering disposition. Release the specified duty only when every applicable row is supported and accepted; an unresolved row stays open even if the normal operating case is covered.
Ask what “non-polarized” actually covers
A polarity-independent statement answers one question. Ask separately whether the offered arrangement permits the proposed line/load connection, carries the required current in each operating direction and provides the required protection for the assessed faults.
Keep voltage, pole arrangement, earthing topology and accessories attached to the response. If a document covers one configuration, do not extend it to another by adding pole voltage figures or changing jumpers.
Similarly, ask whether any attached sensing, residual-current, electronic-trip or auxiliary equipment introduces a restriction. Schneider's reverse-feed list includes accessory and trip-unit exceptions, illustrating why the complete configuration belongs in the review. Schneider variant and accessory exceptions.
Any ambiguous statement should remain an open technical item. Ask the breaker manufacturer to resolve the precise application question and obtain the responsible engineer's acceptance before releasing the configuration.
Compare hypothetical supplier replies
The following replies are invented examples for evaluating quotation quality; they are not reports about actual suppliers.
Reply A: “It carries the same DC current, so either direction is fine.” Hold the direction decision. Request the manufacturer, full part number, terminal diagram and supported operating states. A current figure alone does not answer the stated polarity and connection questions.
Reply B: “Our model is non-polarized; the datasheet is attached.” Check whether the attachment identifies the offered variant and configuration. If it establishes polarity independence but does not address a proposed alternate source connection or other unresolved operating case, request clarification rather than filling the gap with an assumption.
Reply C: “The quoted breaker and accessory list correspond to drawing revision B. The attached manufacturer documents cover the listed operating states; the unresolved regeneration case is identified separately.” This is a more useful response because it exposes the remaining boundary. The open case still requires resolution before approval of that duty.
Compare the completeness of the evidence and the stated deviations alongside price. A clearly disclosed limitation is actionable; an unexplained assurance is not a substitute for documentation.
Freeze the terminal map and approval record
Once the engineering review is complete, include the accepted breaker reference, accessory references and manufacturer instruction revision in the controlled bill of materials. Attach the accepted operating-state matrix and a terminal map that can be checked against the actual sample.
For first-article inspection, define observable checks: correct identity, legible markings, terminal numbering, supplied accessories and agreement with the released documents. Compare the sample to the approved record without performing improvised reverse-current or high-fault tests.
Record discrepancies with photographs and the affected lot or sample identity. Missing markings, a different suffix or a changed instruction should trigger review of the relevant approval evidence.
Use the quality control process page when discussing document and inspection records. The battery disconnect specification guide provides related questions about switching and isolation duties.
Include unresolved scope in the commercial request
Request separate confirmation of component quantities, accessories, samples, engineering documents and any additional evaluation. Identify which approval milestones affect the required delivery schedule.
An alternative offered after quotation should include a comparison against the accepted direction matrix. Require advance notification if a substitution changes markings, terminal arrangement, trip-unit version, accessories or applicable manufacturer instructions.
The purchasing record should distinguish a confirmed commercial offer from an approved electrical application. Do not infer certification, availability, price or lead time from a general product-category description.
Buyer FAQ
Can a polarized breaker be used where a battery charges and discharges?
Only if the exact manufacturer's documentation permits the actual directions and configuration. If the required duty conflicts with the product's restriction, select a supported arrangement through the responsible engineer.
Does the absence of visible plus/minus markings prove bidirectional suitability?
No. A photograph may omit information, and the complete variant can have other restrictions. Verify the manufacturer's instructions and the required operating-state matrix.
Does reverse-feed permission prove the same interruption performance in every case?
Do not assume that. Request the applicable DC ratings and conditions for the proposed arrangement and the engineer-defined fault cases.
What should be included when requesting price, MOQ and lead time?
Specify the breaker and accessory references, quantity, sample requirement, direction evidence and approval milestones. Ask for written commercial terms and clearly identify unresolved technical items.
Send a direction-specific breaker inquiry
Review the fuse-box and protection-component category, then Send a DC breaker RFQ with the diagram, operating-state matrix and exact questions about polarity, reverse feed and bidirectional duty.
Technical sources checked on 10 September 2026.