This guide follows Busbar Comparison Guide by DavidPoz, a six-minute teardown that has aged well: about 110,000 views, 2,785 likes, and 214 comments from people who have actually cooked one of these bars. David bought two busbars with his own money — a Pike Industries unit rated 400 A and a $40 red-and-black kit rated 250 A — took them apart, measured them, and explained why one of those ratings is fiction. His context is a stack of four batteries that can each discharge 100 A, which is exactly the arithmetic most DIY banks get wrong.
Why the busbar decides how your bank fails
A battery bank has one component that carries the sum of every current in the system and gets touched by nobody after commissioning. That is the busbar. Fuses protect a wire, a BMS protects a cell, a breaker protects a circuit — but the bar that all the positives land on sees the whole load, all the charge current, and every surge, with no protection of its own. When it gets hot, nothing trips. It just gets softer, and then it gets loose, and then it gets very hot.
That is why a busbar is a poor place to save forty dollars. The failure mode is not a blown fuse you replace in the dark; it is a connection that slowly stops being a connection while the plastic around it softens.
Two bars, measured
David's cheap kit is a pair of red and black bars in a plastic housing with wing nuts, four studs each, sold as a set for around $40. The listing claims 250 A. The bar inside measures 19.1 mm wide and 2.4 mm thick, and the colour under the plating is yellow — it is brass, and the listing says so.
The Pike Industries bar costs more, is rated 400 A, and is solid copper under a zinc or stainless fastener set. It is wider, thicker, and the base is a different shape entirely, which matters because the base is what keeps your lugs and cables from touching each other when the bank is crowded.
His own verdict on the 400 A rating: conservative. On the 250 A rating of the cheap bar: bogus, and he would not run it past 100 A.
Brass versus copper, and the 4x rule
Brass is roughly a quarter to a half as conductive as copper for the same cross-section, depending on alloy. So a brass bar needs something like four times the copper cross-section to carry the same current at the same temperature rise. That $40 bar is not four times bigger — it is thinner, narrower and shorter than the copper one. Which means the honest rating for it is not 250 A and not 150 A; David puts it nearer 45 to 50 A if you want it to stay cool.
The extra holes make it worse. Every drilled hole removes copper from the path between the studs, and those holes sit exactly where the current has to pass. A bar with six studs and four unused holes has less conductor than its dimensions suggest, which is why nameplate numbers and thermal reality diverge so far.
The fastener stack is where plastic enters the circuit
This is the part worth watching twice. On the Pike bar, the studs pass through the plastic housing, so when you torque a lug down you are also clamping the bar against the housing. That is not a favour — it means the joint's clamping force depends on a polymer that softens when the joint warms up. Warm joint, softer plastic, less clamp, higher resistance, hotter joint.
The cheap bar avoids that particular trap and lands in a different one: the bar is held to the housing by two small screws, so the plastic is doing mechanical work rather than being clamped, and the fasteners do not hold the bar at all. Either way, plastic is in the load path of an electrical joint, which is the thing several commenters objected to independently.
The practical fix on the Pike-style bar is to stop torquing through plastic: put a nut against the housing to take the clamping load, then land the cable on top and tighten a second nut against the lug. That gets metal-to-metal compression on the conductor without crushing the housing.
Reading amp ratings honestly
A busbar rating should answer three questions: at what continuous current, at what temperature rise, and with how many connections made. Almost no hobby listing answers any of them. The 400 A figure on a copper bar with a decent cross-section is plausible for a bank; the 250 A figure on a thin brass bar is a number someone typed into a form.
A working rule from the comments, and one we would endorse: at 48 V, above roughly 5 to 6 kW of inverter capacity, stop buying hobby busbars and move to solid copper bar, a Lynx distributor, or a marine-grade busbar with a published interrupt and continuous rating. A 12 kW inverter at 48 V pulls about 250 A continuous before any surge, and surge is where these joints die.
Sizing for a real bank
Do the arithmetic in amps, not watts. David's stack is four batteries at 100 A discharge each, so the bar sees 400 A in the worst case, and a 400 A copper bar is the minimum. If you have six 280 Ah rack batteries at 30 A continuous each — the conservative figure a commenter cites for server-rack units — that is 180 A nominal with peaks well above it, and a 200 A class bar is defensible only if the peaks are short.
Then add the inverter. The busbar carries battery discharge to the inverter and charge current back from it, and those can overlap when one inverter is charging while another is loaded. Size for the sum, not the larger of the two.
| Cheap brass kit | Pike Industries bar | |
|---|---|---|
| Listed rating | 250 A | 400 A |
| Bar material | Brass (yellow under plating) | Solid copper |
| Cross-section | 19.1 mm × 2.4 mm | Wider and thicker (not published in the video) |
| Realistic continuous | ~45–50 A, or 100 A with heat accepted | 400 A, described as conservative |
| Fastener stack | Bar held by two small screws | Studs clamp bar against plastic housing |
| Indicative price | ~$40 for a red/black pair | Medium-priced, single unit |
Figures from the measurements and statements in the video, not from manufacturer datasheets.
What the video does not measure
No thermocouple, no torque wrench, no load bank. David is honest about comparing construction rather than performance, which is why the comments fill the gap with failure stories instead of lab numbers. If you want to qualify a busbar yourself, the cheap test is a 30-minute run at your expected continuous current with an infrared thermometer on the stud, then re-torque to spec and see whether the fastener moved.
The other missing measurement is contact resistance at the lug interface. That is where most hot joints actually live — oxide on the lug, insufficient torque, a washer in the wrong place — and no busbar, however thick, survives a bad crimp.
Alternatives worth pricing
Solid copper bar, drilled and tapped, is what several commenters moved to. One built a 30-inch bar, half an inch thick and 1.5 inches wide, with enough holes for four inverters and six 280 Ah banks. It costs less than a branded busbar of the same capacity and it removes plastic from the joint entirely — but you have to make your own shrouds, because a bare copper bar at 400 A is a live part with no fingers allowed near it.
At the other end, Victron's Lynx distributor and Blue Sea's 250 A class busbars are the buy-once options. People who run them describe no detectable warmth at rated current, which is what you are paying for: a published rating, a fuse holder built in, and covers that were designed rather than moulded.
Install checklist
Torque to the fastener spec with a wrench, not a wrist. Keep the bar's plastic out of the clamp path, or pre-load a nut against the housing first. Use one cable per stud where possible and avoid stacking three lugs on one stud. Cover the bar — a 48 V bank at 400 A with exposed metal is a tool-drop away from an arc. And put a fuse or breaker between the bar and the inverter, because the busbar itself is the one part of the bank that nothing else protects.
If you are building the bank around a specific inverter, our guide library covers pack assembly, BMS wiring and series versus parallel layouts; the product range includes rack and wall-mount packs whose busbar and terminal hardware is already rated for the continuous current, which is the part most DIY builds underestimate.
What Viewers Are Asking (Top Comments on the Video)
The comment section under this video is the most useful part of it: builders describing bars that melted, bars they machined themselves, and the conductivity maths behind why a thin brass bar cannot carry a 250 A label. All quotes below are as posted, with like counts at the time of writing. David did not reply in these threads, so the answers are ours.
If you would rather not machine your own copper, we build the packs that sit behind the busbar. Dajiu Energy has manufactured LiFePO4 batteries since 2017 — drop-in replacements, EV and golf cart packs, wall-mounted home storage, portable stations, commercial cabinets and swap units — and the rack and wall-mount lines ship with terminals and internal buswork rated for the continuous current rather than a label. Take a look at the product center, or read the build and buying guides on pack assembly, BMS wiring and bank layout. Tell us the inverter and the battery count and we will size the busbar and cabling to match.