For light electric vehicle manufacturers
Two battery packs.
One traction bus.
Levy PowerBridge is the power management board that lets a light electric vehicle run two lithium packs in parallel — different states of charge, either one removable mid-ride — without the packs dumping current into each other. It is in production in our own scooters. We are now making it available to other manufacturers.
- packs combined
- 2packs combined
- validated architecture
- 14Svalidated architecture
- mm board
- 100 × 50mm board
- Class 2 build
- IPC-6012Class 2 build
Both packs deliver current at the same time. The controller holds each path at a matched potential, so neither pack carries more than its share.
You cannot just wire two lithium packs together
Two packs at different states of charge are two voltage sources with a potential difference between them. Connect them directly and current flows from the fuller pack into the emptier one, limited by almost nothing — not because anything is broken, but because that is what the physics requires. The packs get to argue about it, and the BMSs get to referee.
The usual workarounds each cost something real. Matching the packs means you can never let a rider carry a spare. A passive diode keeps them apart but burns power as heat every second the vehicle moves. Neither is a good answer for a product that has to ship to consumers, survive weather, and come back under warranty.
Packs never fight each other
Wire two lithium packs directly together and the fuller one dumps current into the emptier one the moment you connect them. The board sits between them and gives each pack its own controlled path, so a full pack and a half-empty pack can share a bus without a damaging inrush between them.
Low-loss combining, not a diode drop
A plain Schottky-OR wastes real power as heat every second the vehicle is moving. Using an actively controlled MOSFET path instead of a passive diode keeps the forward drop and the resulting heat far lower, which matters when the same board has to survive inside a sealed stem or deck.
Hot-swap and ride on one pack
Either pack can be removed while the other keeps the vehicle running. For swappable-battery products that is the whole proposition; for fixed packs it means a single failed pack degrades range instead of stranding the rider.
Independent, protected charge paths
One charger input feeds both packs without letting either pack back-feed the other through the charge port. Each pack still charges behind its own protection.
Fault state the controller can actually see
Per-pack fault status is reported to the motor controller over an optically isolated interface, so the vehicle can respond to a pack dropping out instead of just losing power.
Built for a sealed vehicle, not a bench
Conformal coating, 3 oz copper, IPC-6012 Class 2 workmanship and a keyed nine-connector harness — specified for a production vehicle that ships to consumers, not a prototype.
How the board handles each case
Switch between the three situations the board has to get right.
Both packs deliver current at the same time. The controller holds each path at a matched potential, so neither pack carries more than its share.
What is on the board
A 100 × 50 mm two-layer board with 3 oz copper, conformal coated, on a keyed nine-connector harness. Select a callout to see what each section does.
Illustration is representative — component placement is simplified.
Ideal-diode OR controller. Drives the pass elements so both packs can share the traction bus with a fraction of the loss a passive diode-OR would burn.
Specifications
The shipping board, as built. Anything not listed here is a conversation, not a promise.
- Function
- Dual-pack parallel combiner with independent charge pathsTwo battery packs feed one traction output through a low-loss ideal-diode OR.
- Pack inputs
- 2 × independent discharge inputs
- Validated pack architecture
- 14S lithium-ion, 52 V nominalFull-charge 58.8 V. Other series counts evaluated on request.
- Charge path
- Single charger input split to both packsEach pack keeps its own protected charge port.
- Fault reporting
- Optically isolated status outputs to the motor controller
- Board size
- 100 × 50 mm
- Construction
- FR-4 TG170, 2-layer, 1.6 mm, 3 oz copper, ENIG
- Workmanship
- Built to IPC-6012 Class 2
- Environmental
- Conformal coated
- Interconnect
- 9 connectors, keyed harness
- Production status
- Pilot production
On certification: this board is a component and does not carry an independent safety certificate. Vehicle-level certification — UL 2849, UL 2272, EN 15194 and the rest — is done on the complete system and belongs to the vehicle manufacturer. We will share construction and design documentation to support that work. We will not imply a certificate we do not hold.
“Does this break my UL 2849 listing?”
It is the first question a serious buyer asks, and it deserves a straight answer rather than a logo on a page.
What the standard actually covers
UL 2849 evaluates the e-bike electrical system as a combination — drivetrain, battery and charger together. It is not a certificate you can buy for one board and bolt on. That means adding any component between the packs and the controller is a change to the assembly that was evaluated, and it has to be assessed as part of your system.
What that means in practice
If you already hold a listing, adding this board is a modification your certification body needs to review. If you are certifying a new vehicle, it is simply part of the system under evaluation from the start — which is the cheaper path. Either way we are a component in your file, not a shortcut around it.
What we provide
Construction detail, board specifications, schematic-level description of the protection behaviour under NDA, and direct engineering contact with whoever is doing your evaluation. If your certification body asks a question we cannot answer from documentation, we will run the test.
The component route, honestly
There are two credentials a board like this can genuinely hold in its own name — recognised-component status, which comes with published conditions of acceptability your certification body can rely on, and a functional-safety certificate covering the control behaviour and its safety analysis. We do not hold either today. They are real, they cost real money, and they are the kind of thing we would pursue alongside a committed design win rather than speculatively. If that is a gating requirement for you, say so early and we will talk about who funds it.
Why this is tightening
UL certification is already law for sale in New York City, New York State, and — since January 2026 — California. A proposed federal rule published in June 2026 would make the UL standards mandatory nationwide, and its definitions name battery management systems explicitly, including ones external to the pack and part of the vehicle controls. Whatever you specify now should assume the requirements get stricter, not looser.
In Europe
EN 15194 is the equivalent gate for EPACs and explicitly covers power management systems and electrical circuits. The same logic applies — system-level evaluation, component-level support from us. Note also that the EU battery regulation makes removable, replaceable batteries mandatory for light means of transport from February 2027, which pushes in favour of modular multi-pack architectures rather than sealed single packs.
Not yet available — in design review
Regenerative braking — in development
The next revision adds a controlled path for braking energy to return to the packs through their charge ports, with the charger and the regen source reverse-blocked from each other, per-pack current limiting, and a temperature window that inhibits regen when the cells cannot safely accept charge. It is an engineering concept package under active design review, not a released product — the first pilot deliberately caps total regen current well below the packs’ charge rating while the protection scheme is validated.
- Braking energy returned through the pack charge ports, not blindly onto the traction bus
- Charger and regen sources reverse-blocked from one another
- Per-pack branch current limiting and fusing
- Regen inhibited outside the cells’ safe charge temperature window
- High-state-of-charge foldback so a full pack is never overcharged under braking
Worth understanding why this is a redesign rather than a firmware change. Devices that combine two packs work by blocking reverse current — that is exactly how they stop one pack draining into the other. Regenerative braking is reverse current, so the mechanism that makes paralleling safe is the mechanism that rules regen out. The aftermarket combiners say so on their own product pages, and the same constraint applies to our shipping board. Having both in one vehicle needs a deliberate return path and a decision about which pack the energy may enter, which is a different architecture. We wrote up the full problem here.
Design review stage. We are looking for OEM design partners to validate it on real vehicles — talk to us if that is interesting.
Where a two-pack architecture earns its keep
Swappable-battery vehicles
If the rider can pull a pack out mid-ride, something has to keep the vehicle alive on the remaining pack and stop the packs from fighting when the fresh one goes in.
Range-flexible platforms
Ship a base vehicle with one pack and sell the second as an upgrade, without redesigning the electrical system or stocking two wiring harnesses.
Split-pack packaging
Two smaller packs fit in places one large pack cannot — a stem and a deck, a frame triangle and a rack — and each stays under the weight a person can carry.
Service and fleet economics
One degraded pack becomes a single-pack replacement instead of a whole-vehicle teardown, and a failed pack degrades range instead of stranding the rider.
Compared with the other ways people do this
| Approach | Cost | What actually happens |
|---|---|---|
| Wire the packs straight together | Effectively free | Works right up until the packs are at different states of charge. The fuller pack drives current into the emptier one through nothing but wire resistance, and the BMSs are left to sort it out. Gets worse as the packs age apart. |
| Passive diode OR | Very low | Safe in the sense that the packs cannot back-feed each other, but every amp pays a diode drop as heat, continuously, inside a sealed enclosure. Fine on a bench, expensive on a vehicle. |
| Aftermarket combiner modules | Roughly $60–100 retail | A real category — sold through forums and marketplaces for retrofits, and several of them work. But they are consumer parts: no documented workmanship standard, no conformal coating, no fault reporting to the controller, no safety certification, and nobody to call when a field failure shows up in your warranty data. Note also that vendors use "parallel" loosely — some of these switch between packs rather than combining them. |
| A closed drive ecosystem | Whole-system commitment | Bosch, Yamaha and Specialized all solve this inside their own platforms. It works well, but the capability is captive — you buy the entire drive system, and the combining electronics are not available as a component you can design into your own architecture. |
| PowerBridge | Component pricing on request | Actively controlled low-loss combining, independent protected charge paths, isolated fault reporting to the motor controller, IPC-6012 Class 2 build with conformal coating — designed for a consumer vehicle that ships at volume. |
Questions engineers ask
Can I just wire two battery packs in parallel myself?
Physically yes, safely no — not unless the packs are matched in chemistry, age, capacity and state of charge, and even then it is fragile. Connect a full pack to a depleted one and the potential difference drives a large current between them, limited only by wiring resistance and whatever the BMSs decide to do about it. Over time the packs age at different rates and the mismatch gets worse. A combiner exists so the two packs never see each other directly.
How is this different from a BMS?
A BMS protects the cells inside one pack — cell balancing, over-voltage, over-current, temperature cutoff. This board sits one level up, between two already-protected packs and the vehicle, and decides how those packs share a single traction bus. You still need a BMS in each pack; this is not a replacement for one.
Do the two packs have to be identical?
They should be the same chemistry and series count, but they do not have to be at the same state of charge — handling that mismatch safely is the point of the board. In the Levy vehicle the two packs are different physical form factors with different housings.
Is the regenerative braking version available now?
No. The shipping board does not do regen. The regen revision is an engineering concept package in design review, with the protection architecture still being validated. We are talking to OEMs who want to be design partners on it, but nobody can buy it today and we would rather say that plainly than take an order we cannot fill.
Is the board certified to UL 2849 or UL 2272?
Not today. The board is a component, and those standards certify a complete system — pack, charger, controller and vehicle together — which makes vehicle-level certification the manufacturer’s responsibility. There are two credentials a board like this can hold in its own name (recognised-component status, and a functional-safety certificate covering the control behaviour); we do not hold either yet, and we would rather say so than let the ambiguity sit in your file. We will share design and construction documentation to support your certification work, and if a component credential is a gating requirement for you, that is a conversation worth having early.
What series counts and current levels are supported?
The released design is validated around a 14S lithium-ion architecture at 52 V nominal. The underlying approach is not specific to 14S — if your architecture is different, the practical answer depends on your continuous and peak current, your controller’s maximum input voltage, and your thermal envelope. That is the first conversation we would have.
Can you build a variant for our vehicle?
That is the most likely way this starts. The board was designed for a specific vehicle with a specific motor controller and pack set, so some adaptation is normal — connector and harness changes are straightforward, and changes to voltage class, current rating or the status interface are a design conversation.
Does adding your board affect our packs’ UN 38.3 transport classification?
A fair question and one most component suppliers will not raise with you. The short version: the board contains no cells, so it needs no transport testing of its own. Your packs are also unchanged internally — we sit between them, not inside them. What does deserve a look is how your two packs plus the board are treated as an assembly, because the transport rules care about changes to protective devices and about how cells are connected. Where it lands depends on your pack energy and how you ship. We will work through it with your dangerous-goods people rather than hand you a blanket assurance.
What volumes and lead times are realistic?
Current builds are pilot-scale through an established PCBA partner, with lead times measured in weeks rather than days. Tell us your annual volume and your design-freeze date and we will be straight with you about whether we can support it.
Tell us about your vehicle
We are a small hardware company, not a component distributor — so the useful first step is a real conversation about your pack architecture, your controller, and whether this is even the right answer for you. If it is not, we will say so.