BESS Passive Components: Zero of Walsin’s 2,014 High-Voltage MLCC Reach 1 µF

We measured all 24,026 Walsin MLCC rows at 1,000 Vdc or above: 2,014 clear it, and the ceiling is 220 nF — zero reach 1 µF. BESS passive components above 1,000 V split hard: ceramics handle EMI and snubbing, resistors carry the signal path, and bulk storage is a different part number entirely.

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Venatech Limited, an authorised Walsin distributor in Hong Kong, measured this from four of Walsin Technology (Walsin)’s own parametric exports: 00_ALL_MLCC_parts_combined.xlsx (24,026 rows), Metal_Low_Ohm_Current_Sense_Chip_Resistor__1of1.xlsx (1,188 rows), Thick_Film_Low_Ohm_Current_Sense_Chip_Resistor__1of1.xlsx (10,428 rows) and the eight populated Thin_Film_Precision_Chip_Resistor_WF_Series files (58,314 rows). A battery energy storage system string sitting above 1,000 Vdc — increasingly the Spanish utility-scale norm as inverters push past the old 1,500 Vdc ceiling — touches all four families on one BOM: the DC-link ceramics, the string current-sense shunt, the precision divider feeding the BMS, and a safety-rated cap across the bus. We counted each one separately and the answer is not the same shape twice.

What does a BESS DC link above 1,000 V actually find on Walsin’s MLCC shelf?

Not much capacitance. We parsed all 24,026 rows and grouped everything at 1,000 Vdc or above: 2,014 rows, and the highest capacitance among them is 220 nF, on 2225B224K102 in the Big Sizes series. We have not seen this ceiling stated anywhere — most discussion of high-voltage MLCC stops at case size or AEC-Q200 status and never asks how far short of a microfarad the whole catalogue actually falls.

Rated voltage	Rows ≥ this voltage	Highest capacitance at this exact rung	Holding part number
1,000 Vdc	2,014	220 nF	2225B224K102
1,500 Vdc	61	100 nF	SH56B104K152
2,000 Vdc	511	56 nF	2220B563K202
3,000 Vdc	315	18 nF	2220B183K302

A microfarad-class bulk DC-link capacitor does not exist in this catalogue above 1,000 Vdc at any case size, any series, any dielectric. The 220 nF ceiling is roughly 4.5 times short of 1 µF, and every row we checked above that voltage is smaller still. That is not a shortage story — Walsin never designed this ceramic range for bulk link duty — but it is a fact a spec sheet that simply says “MLCC, 1,000 Vdc” will not tell you, and a selector that filters on voltage alone will hand you a snubber-sized part and call it a DC-link candidate.

How much of that shelf is AEC-Q200, and what does it cost in capacitance?

Thirty-six rows, and we have already published that count. Re-measured today against the same 24,026-row export: 36 of the 2,014 rows above 1,000 Vdc sit in MT or ST, the two series Walsin qualifies to AEC-Q200 — 20 in MT, 16 in ST, none in the 3 MG rows because Walsin’s own series title reads Without AEC-Q200 Certification. Twenty-nine of the 36 are at 1,000 Vdc, two at 1,250 Vdc, five at 3,000 Vdc, and nothing at 1,500, 2,000 or 2,500 Vdc — a gap we flagged in full detail in our 800 V traction-bus measurement and will not repeat here.

What has not been stated before is the capacitance ceiling inside that qualified shortlist specifically: the highest capacitance among all 36 AEC-Q200 rows above 1,000 Vdc is 100 nF, held by exactly two part numbers, ST46B104K102 and ST46B104M102, both 1825 case, both ST soft-termination. Everything else in the 36 sits at 22 nF or below. For a BESS integrator who wants automotive-grade qualification on the high side of the link, the honest shelf is two part numbers deep at its best capacitance point, not 36.

Where does a low-ohm current sense resistor fit, and does it carry a voltage rating at all?

It fits in the string current path, and no, the export carries no working-voltage column for it, a fact Venatech has already measured and published across the whole 234,815-row chip resistor catalogue. We re-checked it here on the two series a BESS shunt actually uses: 1,188 rows in Metal_Low_Ohm_Current_Sense_Chip_Resistor__1of1.xlsx and 10,428 in the thick-film low-ohm series — 11,616 rows between them, and neither file has a voltage field of any kind. The nine columns on both files are Part Number, Series Group, Series, Size, Resistance, Tolerance, TCR, Rated Power and Packaging. Voltage is absent, not blank.

Series	Rows	Lowest resistance	Rated power range	Voltage column present?
Metal low-ohm current sense	1,188	0.0005 Ω (WW25AR0L5FTL)	1/3 W to 3 W	No
Thick film low-ohm current sense	10,428	0.005 Ω (WW15WR005FTL)	1/16 W to 3 W	No

On a BESS DC link above 1,000 Vdc the shunt itself typically sits on the low-side return or inside an isolated measurement block, so the part’s own voltage withstand is not the number that matters — the isolation around it is. But a buyer who assumes a current-sense export will tell them a working voltage, the way the MLCC export does, will not find one here on 11,616 rows. We checked all of them.

Does Walsin’s precision thin film resistor export carry a voltage field either?

No, and it is the same nine-column shape as the current-sense files, a pattern we confirmed across the whole WF series rather than assuming it from one case size. For a BMS voltage-divider stack that measures a 1,000 V-plus bus down to a safe ADC input, the resistor side of that divider is Walsin’s thin film precision WF series. We summed the eight populated WF export files — 0201 through 2512 — and counted 58,314 rows, already published as the series total in our divider-accuracy post. None of the eight carries a voltage column. A ninth file, the AEC-Q200-grade Thin_Film_Professional_AEC_Q200_Chip_Resistor_WF_Q_S.xlsx, returns zero rows — also already flagged, in our nine-empty-exports post.

Case size file	Rows	Resistance range	Voltage column present?
WF 0402	6,359	10 Ω – 255 kΩ	No
WF 0603	7,562	4.7 Ω – 1 MΩ	No
WF 1206	8,427	1 Ω – 2.49 MΩ	No
WF 2512	7,823	1 Ω – 3 MΩ	No

The practical consequence for a divider feeding an isolated measurement IC is that element voltage withstand has to be computed from V = √(P × R) off the datasheet’s rated power, not pulled from a filterable field — and the maximum element voltage figure Walsin publishes per case size is in the WF datasheet, which is in our 451 pages and sent on request, not in any of these 58,314 rows.

What does the safety-certified MLCC series actually tell you about working voltage?

Nothing you can use without the datasheet, and this is also a fact we have already flagged rather than a new one: the S2 safety series’ Rated Voltage field holds the impulse voltage on all 173 rows — 5,000 Vdc or 6,000 Vdc — not the working voltage. We re-opened 15_Safety_X1Y2_S2.xlsx to confirm it still reads that way: 173 rows, 87 NPO and 86 X7R, in case sizes 1808, 1812, 2211 and 2220, every single one tagged 5,000 or 6,000 Vdc in the column a buyer would naturally filter on.

A BESS DC link using an X1/Y2-rated cap across the bus for line filtering needs the datasheet’s actual working figures — X1 310 Vac, Y2 250 Vac, 1,500 Vdc — none of which appear in the export. Three named high-voltage soft-termination and safety series we also checked for this post — SH High Voltage, SG High Voltage and the X2/Y3 S3 series — each carry a datasheet reference but return zero searchable part numbers, a gap we have already counted and published in detail elsewhere. We are not re-counting it here; we are telling a BESS buyer specifically that this is where the safety-cap answer stops being a spreadsheet question and starts being a “send us the datasheet” question.

So what can actually serve a DC link above 1,000 V, field by field?

A short list, and we will show you where every candidate differs rather than call any of them a drop-in match.

Part number	Series	Case, dielectric	Capacitance	Rated voltage	Match / mismatch vs a 1,000 Vdc link position needing ≥100 nF
2225B224K102	Big Sizes, commercial	2225, X7R	220 nF	1,000 Vdc	Match on capacitance and voltage; mismatch — no AEC-Q200 grade
ST46B104K102	ST, AEC-Q200, soft term	1825, X7R	100 nF	1,000 Vdc	Match on voltage and grade; mismatch — less than half the capacitance of the commercial part above
1812B104K102	Middle to High Voltage, commercial	1812, X7R	100 nF	1,000 Vdc	Match on voltage; mismatch — the only Middle-to-High-Voltage row at 100 nF or above in this band, smaller footprint than Big Sizes
SH43B104K102	SH soft termination, commercial	1812, X7R	100 nF	1,000 Vdc	Match on voltage; mismatch — polymer termination adds flex tolerance, no AEC-Q200
WW25AR0L5FTL	Metal low-ohm current sense	2512	0.0005 Ω shunt	not a voltage-rated part	Mismatch by design — belongs in the current path, not the link; no voltage field to compare
S242B103K502	Safety X1/Y2 (S2)	1808, X7R	10 nF	5,000 Vdc (impulse, not working)	Mismatch — the column is impulse voltage; working voltage must come from the datasheet

We counted 26 rows across the whole 24,026-row export that reach 100 nF or above at 1,000 Vdc or higher — 13 SH, 10 Big Sizes, 2 ST and exactly one Middle-to-High-Voltage part, 1812B104K102. That 26 is the entire usable shortlist once the requirement is “100 nF, at least 1,000 Vdc,” and it is the number this post adds to the 2,014 and 36 already on the record.

What should a Spanish BESS integrator do with this?

Split the BOM by function before you touch a voltage filter. A DC link above 1,000 Vdc is not one part category — it is a snubber-and-EMI ceramic position, a current-sense shunt with no voltage spec of its own, a precision divider resistor with the same gap, and a safety cap whose export column needs a datasheet to mean anything.

1. Stop asking the MLCC catalogue for bulk capacitance above 1,000 Vdc. It tops out at 220 nF. Bulk link energy storage at this voltage comes from a different capacitor technology entirely, and Walsin’s ceramic range is not it.
2. Treat the current-sense and thin film resistor voltage question as a datasheet question, not an export filter. Across 11,616 current-sense rows and 58,314 WF rows, there is no voltage column to filter on in the first place.
3. Cross the whole BOM in one pass. Paste up to 500 part numbers or drop your Excel or CSV into the free cross-reference tool. It decodes 18 manufacturers’ part numbers and matches against 800,000+ crossable Walsin part numbers, returning every difference from your original rather than hiding it behind the word equivalent.
4. Check what is physically in Hong Kong on ready stock before committing a build slot. That page is a dated snapshot as at 23 September 2026, not a live feed.

For the full voltage-versus-AEC-Q200 measurement on an 800 V bus, see EV traction inverter passives for Germany. For the current-sense resistor floor and TCR grading, see Current sense resistor TCR: zero of 10,428 reach 50 ppm. The full ranges are on the Walsin MLCC and Walsin chip resistor pages.

The short version

We measured a BESS DC link above 1,000 Vdc against four of Walsin’s own exports. The MLCC shelf is 2,014 rows deep but never reaches 1 µF — 220 nF is the ceiling, on 2225B224K102. Thirty-six of those rows are AEC-Q200, and inside that qualified set the ceiling drops again, to 100 nF on exactly two part numbers. The current-sense shunt (11,616 rows across two series) and the precision thin film divider (58,314 WF rows) carry no voltage field at all — a fact already on the record, confirmed again here specifically for a high-voltage BESS BOM. The S2 safety series’ voltage column is impulse, not working. Twenty-six rows in the whole catalogue clear 100 nF at 1,000 Vdc or above.

Send us your BESS DC link BOM with the function each line performs — link ceramic, shunt, divider or safety cap — and we will come back with Walsin candidates field by field, the AEC-Q200 rows marked, and the Hong Kong position as at 23 September 2026 beside each. If your link needs more than 220 nF above 1,000 Vdc, where is that capacitance actually coming from on your bill of materials right now?

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Frequently asked questions

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