Flexible Busbar Design Guide

Version 1.0 · 2026-11-12 · matches drawing OGS-FLEXIBB rev D.

How to put a FLEXIBB insulated flexible copper busbar into a 3D model or a build plan so it can actually be built and ordered. It's written so an AI design assistant can follow it step by step. A machine-readable version of every rule is in the JSON rules file. If the two ever disagree, the JSON file wins.

1. What the part is

A flat stack of thin tinned-copper layers inside a soft insulating sleeve. Each end has 1.0 in [25.4 mm] of bare copper (the tab) with one hole, 0.50 in [12.7 mm] from the end, centered on the width. The sleeve covers everything between the tabs.

2. Pick the size and hole

Max A is a short-term rating. For continuous current, use the size chooser (ogsolarstore.com/pages/flexible-busbar-size). The bolt goes through bare copper only (thickness = copper T), so set screw length from that.

3. Length

• L = hole center to hole center, measured along the bar's centerline through every bend and twist.
• Order length = L rounded up to a whole inch, 2 to 60 in.
• Tolerance: +1/2 / -0 in. The real bar can be up to 1.5 in longer than your routed path (round-up + tolerance). Leave that slack in a bend or an S offset. Never route a bar tight and straight between two fixed points.

4. Routing rules

Think of the bar as a ribbon: it bends easily across its flat face and twists along its length. It cannot bend edgewise (within its own plane).

1. Flat bends only. Bend about the axis across the width. Inside radius at least 8 mm on the copper (centerline radius = 8 mm + copper T / 2). The sleeve outside will be larger.
2. Turning within the bar's plane: fold it flat over a 45° line (a 180° fold that turns the bar 90°), or twist 90° and then flat-bend.
3. Twists: 90° or less (never over 100°), on a straight run at least 2.5 x copper width long (better: 3 to 4 x). That's 39 mm (200) or 60 mm (350/500) minimum. No bend inside a twist.
4. Folds (L or Z fold, flattened with a soft mallet): allowed when the route needs one. For hole alignment, a fold counts as 180° of net bend.
5. Keep-out: no bend, twist or fold within 1.0 in [25.4 mm] of a hole center. That covers the bare tab plus 1/2 in of sleeve.
6. Don't bend over sharp edges. Leave room for the sleeve thickness at every pass-through.

5. Net bend angle (pre-drilled holes)

The copper layers slide past each other as the bar bends, so on a bar drilled straight the holes in the layers drift apart. Opposite bends cancel. Add up the flat-bend angles: positive when face A is on the inside, negative when face B is. A 180° twist swaps the faces, and a fold counts as 180°. An S offset is net 0°, an L is 90° and a U is 180°. The bend radius doesn't change the result.

These limits are calculated from the hole clearance and are deliberately conservative.

If the route's net angle is over the limit, you have two choices: oversize holes (5a) or one end uncut, drilled on site after bending (5b).

5a. Oversize hole option

Order the bar with a hole bigger than the screw. After bending, each layer's hole sits a little off from the next, and the open area becomes an oval window where the holes still overlap. The screw fits as long as that window is at least as wide as the screw.

Requirements: a flat washer under the head and under the nut, at least 16 mm OD for M8 (a fender washer is better), plus a spring or Belleville washer. The bigger hole removes about 4% of the tab contact face, the screw sits off-center in some layers, and the layer ends look slightly staggered. All of this is expected.

5b. One end uncut

For any route over the limits, order the bar with one end left long and undrilled (add "one end uncut" to the order). Bolt the drilled end, bend to shape, then mark, cut and drill the free end in place. Step by step: Flexible Busbar Best Practices.

6. SKU (the BOM line)

FLEXIBB-<size>-<L in>-<hole>, e.g. FLEXIBB-350-16-M10. Regex: ^FLEXIBB-(200-([2-9]|[1-5][0-9]|60)-M6|(350|500)-([2-9]|[1-5][0-9]|60)-(M8|M10))$

Ordering: 2 to 12 in with the standard hole (200 M6, 350 and 500 M8) are on the product page (ogsolarstore.com/products/flexible-copper-busbar). M10 holes, lengths over 12 in, one end uncut, and the field drilling jig are by request (ogsolarstore.com/pages/contact-us). Put the SKU in the message.

7. Checklist before you call the route done

• Size and hole are an allowed pair (section 2).
• Every bend is a flat bend with inside radius 8 mm or more. No edgewise bends.
• Every twist is 90° or less over at least 2.5 x width of straight bar.
• Nothing bends, twists or folds within 1.0 in of either hole center.
• Net bend is within section 5, or the order uses the oversize hole (5a) or one end uncut (5b).
• L is measured on the centerline, rounded up, 2 to 60 in, with up to 1.5 in of slack in the route.
• The SKU matches the regex.

8. Worked example

A 350A jumper from a battery terminal to a fuse whose hole is 4 in over and 2 in up. The route runs 1.5 in straight out of the first hole, bends 90° up, rises, bends 90° back flat, then runs straight to the fuse. Both bends are at the 8 mm inside radius (centerline R = 9.05 mm).

• Net bend 0° (S offset): pre-drilled is fine. The first bend is 1.5 in from the hole, which clears the 1.0 in keep-out.
• Centerline length = straights (101.6 − 2R) + (50.8 − 2R) + two quarter arcs πR = 83.5 + 32.7 + 28.4 = 144.6 mm = 5.69 in, so order 6 in. Up to 0.8 in of extra bar (round-up + tolerance) goes into a slightly looser S.
• BOM: FLEXIBB-350-6-M8.

Disclaimer: For reference only. Do proper engineering to determine your requirements and always follow applicable code.