Charge a battery with a bench power supply: when to stop

The crocodile clips are already on the pack and the constant-current lamp is lit. Charge a battery with a bench power supply is the search that usually follows a lithium pack that went to sleep, or a starter battery that looked flat. The box holds the voltage and the current you set for as long as the output stays enabled. A charger built for that chemistry decides when the charge is finished. If you cannot stand there and watch, the clips come off.

This page is from Peter F., editor for DIY & tools. Prices, stars, and review lines are amazon.co.uk figures stored on 16 October 2026 for our laboratory power supply comparison. We did not charge a cell, wake a pack, or lab-test these units. A qualifying purchase through our links can earn a commission at no extra cost to you.

In short

A bench supply gives you a voltage and a current limit. It does not finish a charge, balance a pack, or notice that a cell is hot. One UK review that woke a LiFePO4 battery management system is a single owner's outcome. If the pack is lithium, swollen, unknown, or you would leave the room, unclip it and use a charger made for that battery.

What the supply will do on a battery

You set a voltage and a current ceiling. With the output on, the supply holds that voltage while the load stays under the ceiling, or it holds the current and lets the voltage fall when the load asks for more. The Institution of Electronics calls the handover the joint result of the settings and the load. The lamp shows which rule is winning, not whether the pack is full or safe to leave.

The Jesverty SPS-3010V is the top pick for a general 30 V bench: £50.99, 4.6 from 915 amazon.co.uk reviews, and a 0–30 V, 0–10 A switching title. An OUTPUT button keeps the rail off while you set the numbers, unless OPN is enabled, when the listing says the output comes on with the mains switch. Clips already on a pack would see that rail at switch-on. The bullets say 115/230 V selectable and the attribute table says 115 V, so confirm the rear panel. BS EN 61010-1:2010+A1:2019 covers laboratory equipment for shock, burn, fire, and live terminals. The knob order for a circuit sits on how to use a bench power supply. On a 300 W unit, 30 V and 10 A meet at the ceiling.

A current limit is not a charger

A constant current battery charge feels familiar because current comes first, then voltage, once the battery climbs into the setpoint. A bench supply will pass through those two modes if the load allows it. A charger stops, tapers to a defined end, or moves to a maintenance stage, against rules for that chemistry. The supply holds the last setpoint until you change it or you disable the output.

Lithium charging safety is where that gap bites. This page will not give a cell voltage, a series count, or a lithium procedure. If you are asking whether you can charge a lithium battery with a bench power supply, use a charger made for the pack. A lithium pack can be harmed by a voltage it was never meant to sit at, by current it cannot shed as heat, and by a management board that has already opened. Over-current protection watches the current you set, and only when it is armed.

Raising the knob so the CC lamp goes out removes the only ceiling you had. The lamp means the limit is active, which is the point of the note on a CC lamp on a bench supply. Some Nankadf listings tie a long press to the over-current alarm. An alarm you have not armed will not trip, and an armed alarm still does not know state of charge.

A review is not a recipe

A UK review of the Nankadf WPS3010H, listed at £59.99 with 4.4 from 1,517 reviews, says the owner woke a LiFePO4 BMS and tried 12 V vehicle electrics. It records no voltage, no current, no duration, and no later state of the pack. Sleep can mean the board opened because something was already wrong. If the wrap is swollen, hot, or the chemistry is unknown, it stays disconnected. A board that then allows current is not proof the cells are inside their limits.

The OWON SPM6103, at £143.99 with 4.6 from 70 reviews, names battery experiments beside phone and laptop repair. That line is marketing. A UK review of a Wanptek unit mentions diode blockers just in case, because current can flow back when the battery sits above the output. This page will not name a diode, and a diode would not end the charge. The Wanptek 30 V 10 A, at £50.92 with 4.5 from 379 reviews, is a repair bench. A set rail for a board is the job on bench power supply for electronics repair.

Signs to stop

Stop on heat, shape, or smell. Swelling, a hiss, a sweet or solvent smell, or a case you cannot hold means the output off, the clips off, and the pack on a non-flammable surface.

Stop when you would leave the room, or when you cannot name the pack. The supply will not shut itself down because the current became small, and a small current into a lithium pack can still be the wrong current. An unmarked wrap, a salvaged tool battery, or a chemistry you would guess from the plug all fail that test. Lead-acid, lithium-ion, and LiFePO4 do not share a profile. A 12 V label is not a setpoint.

Lead-acid, the USB port, and work

A lead-acid charger eases off and holds a maintenance level. A bench supply stays where you left the encoders. This page will not print a voltage for a car, leisure, or gel battery. If the battery lives in a vehicle, use a charger sold for it and follow that manual. A supply you then turn down can sit below the battery, so current flows back into the output. Do not leave the clips on while the two voltages equalise.

The USB socket ignores the current limit on the main terminals. Listings claim about 18 W on the Nankadf units and about 20 W of USB-A and USB-C on the Jesverty. A review of a Wanptek 5 A unit says that USB current is fixed, and on the OWON SPM6103 the USB socket is for communication. It is the wrong outlet for a tool pack or a starter battery.

At work, the Electricity at Work Regulations 1989 require maintenance where people are employed. The Health and Safety Executive does not demand a PAT test on every item every year. A supply used as a charger on a workplace bench can injure someone, so it still has to be looked after. A hobbyist who employs nobody is outside that duty. One UK review of the Wanptek 30 V 5 A, at £49.98, describes a magnetic plug and fuse. The plug check is on check the UK plug.

When you still want a bench supply

Buy the supply for a circuit, a motor inside the watt ceiling, or a repair where a battery was only the original source. The best bench power supply page names the Jesverty SPS-3010V for that general 30 V bench after you confirm the mains selector. Skip it for a second rail or a linear supply with a stated noise figure. The best value is the Nankadf WPS305H at £49.99, 4.5 from 1,045 reviews, when 5 A is enough. Skip that one when the work needs 10 A. Neither pick is a charger.

The bench power supply buying guide keeps the order: the voltage you will use, the watt ceiling rather than the title, an output switch, and a BS 1363 plug you have looked at. A 400 V listing is a shock hazard on a first bench. Set the output off, set the voltage for the circuit, set a current you can justify, then connect plus and minus. The centre or green post is mains earth. If OPN is enabled, leave the board unclipped until you know the rail comes on with the mains. When the load is a battery you mean to replenish, use a charger that matches the label on the pack.