Bidirectional DC Power Supply: Source and Sink in One Unit

Two quadrants, one channel

A conventional power supply works in a single quadrant: positive voltage, positive current out. A bidirectional unit operates in two quadrants, so the same terminals can push current into a device or pull current out of it while voltage stays positive. The transition through zero current is seamless and fast, with output settling within ≤5 ms of a command.

That single behavior collapses a whole test rack. Where you once needed a source, a load, contactors to switch between them and software to coordinate, you now have one instrument that follows a continuous charge-discharge profile. The N35500 platform from Ultra Power Systems delivers this from 0-2250 V at up to 42 kW per 3U chassis.

Who buys a bidirectional supply

• Battery pack and cell test engineers who need clean charge/discharge cycling without swapping hardware between phases.
• EV and BOBC developers validating 400 V and 800 V traction buses and on-board chargers.
• PV and ESS inverter labs that must both feed and absorb on the DC link to test PCS/BESS converters.
• Fuel cell and aerospace/ATE groups needing precise, programmable bidirectional power inside automated racks.

If your test plan has a discharge or absorb step, a bidirectional unit usually pays for itself in bench simplification alone, before counting the energy it recovers.

Core specification at a glance

Add the programmable control feature set and it becomes a fully scripted ATE instrument.

Smooth crossover is what makes it a test instrument

The quality of a bidirectional supply lives in the zero-current crossover. A real device under test does not announce when it stops charging and starts discharging, the supply has to follow it continuously, with no glitch, dead-band or current spike as it reverses direction. A clean crossover is what lets you emulate a battery's full charge-rest-discharge behavior, ride through inverter transients, or sweep a motor drive from motoring into regeneration without the test logic ever switching hardware.

The N35500 platform holds 0.02% F.S. accuracy through that transition and reacts within ≤5 ms, so even fast dynamic profiles stay faithful. Pair that with the NS81000 battery-simulation firmware (7 model libraries plus custom curves, with SoC tracked against OCV) and a single channel can stand in for a real cell or pack across its whole operating window, sourcing on charge and sinking on discharge from the same terminals.

Configure and quote

Bidirectional systems are specified to the job, not sold off a shelf. Decide your maximum bus voltage, your continuous and peak power, and how many independent channels you need, then let the manufacturer size the rack. Start with the Ultra Power Systems quote request, or send specs directly to Ultra Power Systems.

Frequently asked questions