Flexible Busbar Best Practices: How to Bend, Twist and Fold for a Clean Install
A flexible busbar is a flat conductor made from a stack of thin copper sheets inside a soft insulating sleeve. Ours have 1 inch of bare tinned copper and one hole at each end. You shape them by hand and bolt them on: no lugs, no crimper, and a lot less bulk than cable.
They're forgiving, but a few habits make the difference between a clean, cool-running joint and a bar that fights you at the last bolt. Here are the six that matter, then what to do when your route needs a sharp turn.
The Six Rules
1. Bend gently
Bend across the flat face, around a dowel or your thumb. Keep the inside radius at least 8 mm (5/16 in), and never fold it over the sharp corner of a bench or a terminal.
2. Keep bends off the tab
Start every bend or twist at least 1 inch from the hole center. The bare tab has to sit flat on the terminal, and the sleeve right next to it needs to stay straight.
3. Twist slowly
A twist changes which way the flat face points. Keep it to 90° (never past 100°), spread over a straight run at least 2.5 times the bar's width: 60 mm (2-3/8 in) on our 350A and 500A bars, 40 mm (1-5/8 in) on the 200A. Don't put a bend inside a twist.
4. Fold to turn a corner
A flat bar can't bend sideways in its own plane. To turn a corner while the bar lies flat on a panel, fold it back on itself over a 45° line, then flatten the fold with a soft (plastic or rubber) mallet. The other way to turn is to twist 90° and then bend.
5. Prefer S offsets
An S offset (two opposite bends, also called a Z bend or joggle) is the friendliest shape for a pre-drilled bar. The next section explains why an L, a U or a fold needs a little planning.
6. Leave a little slack
Measure hole center to hole center along the bar, and round up to the next whole inch. We make bars up to 1/2 in long, never short. Put that extra length into a gentle bend, not a tight straight run between two fixed terminals.
Why Bend Direction Matters for the Holes
Imagine a deck of cards. Square it up, then bend the whole deck into an L. At the far end the cards no longer line up: the card on the inside of the bend travels a shorter path, so it sticks out further.
A flexible busbar does the same thing. Its copper sheets slide past each other as it bends, which is exactly why it bends by hand at all. Bends in opposite directions cancel each other, so an S offset ends with the sheets lined up again. An L, a U or a fold doesn't, and on a bar drilled straight the holes in the sheets drift apart until the bolt won't pass.
How much bend a pre-drilled bar can take
Add up your bends, counting one direction as plus and the other as minus. That's the net bend: 0° for an S offset, 90° for an L, 180° for a U or a fold. Keep it within these limits:
| Bar | Standard hole | M10 hole + M8 screw |
|---|---|---|
| 200A | 20° (M6) | not offered |
| 350A | 20° (M8), 15° (M10) | 100° |
| 500A | 5° | 33° |
Within the limit, order a standard bar. Over it, use one of the two options below.
Option 1: Oversize Holes (350A)
Order the bar with the M10 hole and bolt it with an M8 (or 5/16 in) screw. After bending, each sheet's hole sits a little off from the next. Looking down the stack, the open area is no longer a circle but an oval window where the holes still overlap. As long as that window is wider than the screw, it goes through and every sheet lies flat. That's enough for an L bend on the 350A bar.
What to know:
- Use a big flat washer under the screw head and under the nut, at least 16 mm across for M8 (a fender washer is better), plus a spring or Belleville washer to keep it tight.
- You lose about 4% of the tab's contact face. In a clean, tight joint you won't notice it.
- The screw sits off-center in some sheets, and the sheet ends at the tip look slightly staggered. Both are expected.
- It isn't enough for a U bend, a fold, or an L on the 500A. Use Option 2.
Option 2: One Uncut End, Drilled on Site
For any route, shape first and drill last. Ask us for a bar with one end left long and undrilled. Bolt the drilled end, make your bends, then mark and drill the free end exactly where it lands. Every sheet is drilled in its final position, so the hole lines up no matter how many bends you add.
- Fit the bar. Bolt the drilled end, bend the bar to shape, and lay the free end on its terminal.
- Mark the hole. A transfer punch through the terminal hole is the most accurate.
- Mark the end 1/2 in past the hole center, and cut there if needed (a shear, or a fine hacksaw with the bar clamped between blocks).
- Slide the sleeve back about 1-1/2 in.
- Clamp the sheets tight between two scrap blocks, center punch, drill a 1/8 in pilot, then the final size: 1/4 in for M6, letter Q for M8, 13/32 in for M10.
- Deburr both faces and check that no chips are trapped between the sheets.
- Slide the sleeve back so 1 inch of copper is bare, and bolt it down.
Need a field drilling jig? Contact us to buy a hand-held jig for drilling holes on site.
Designing With an AI Assistant?
If you plan your battery or panel in CAD or with an AI design tool, point it at our FLEXIBB design guide. It lists every size, hole and length, the bend, twist and fold limits above, and how to turn a route into an order code. For example:
Follow the FLEXIBB design guide at ogsolarstore.com/pages/flexible-busbar-design-guide. Route a flexible busbar from the battery positive terminal to the fuse, check every rule, and give me the SKU to order.
Quick Checklist
Ordering
The flexible copper busbar comes in 200A, 350A and 500A max sizes. Not sure which size you need? The size chooser works it out from your current and how the bar is installed. For an uncut end, an M10 hole, a length over 12 in or a field drilling jig, contact us.
Disclaimer: For reference only. Do proper engineering to determine your requirements and always follow applicable code.