Testers, cables & accessories

Battery testers, quality cables and adapters: the small accessories that make a daily difference with your cells and batteries.

Around cells and batteries revolves a whole set of small accessories that, well chosen, change the everyday experience. A battery tester saves you from throwing away good cells or being caught out at the wrong moment. A quality charging cable, in the right format and correctly sized, guarantees a fast and reliable charge, where a poor cable holds everything back. An adapter or a voltage converter, finally, gets you out of trouble when you need to switch from one connector or voltage to another.
We have gathered here our selection of these essential accessories. For chargers (mains, USB, battery or vehicle), head to our dedicated Chargers section. · 17 products

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I - Battery testers

You can have the best batteries in the world, they are useless if they are flat. It is not always easy to know a battery's level: that is where the battery tester comes in. This simple device shows you at a glance the charge level of your batteries, so you never throw away a good one again. Here is our selection.

BT-168 battery tester D-FantiX BT-168 universal battery tester
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D-FantiX BT-168 battery tester

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The classic needle-and-dial battery tester, self-powered and dead simple: one glance at the colour-coded scale tells you if a battery is good, low, or done.

  • Formats: AA/AAA/C/D/9V and button cells
  • Display: Analogue needle (colour-coded scale)
  • Power: No battery required
  • Use: Household and button batteries
  • Huge review base, self-powered, budget price
The D-FantiX BT-168 is a compact, self-powered battery tester with no internal battery of its own; it draws just enough current from the cell being tested to move its needle. It covers the full range of household batteries: AA, AAA, C, D, 9V and small button cells. The colour-coded dial makes the reading instant, green for good, yellow for low, red for replace or recharge. With one of the largest review counts of any tester on Amazon, it is a proven, no-frills way to stop guessing which batteries are still worth keeping.
In-depth reviewRead our full review → 3.9/5 This is about as no-frills as a battery tester gets, and that simplicity is exactly why it works so well. Drop in a battery, and the needle swings to green, yellow or red almost instantly, no buttons, no settings, nothing to charge or replace. We keep one in a kitchen drawer specifically to sort through the pile of AA and AAA cells that inevitably accumulates from swapped-out remotes and toys, and it makes short work of separating the ones worth keeping from the ones headed for recycling. It handles button cells too, which covers most of what a typical household needs to check, though it is a generalist rather than a specialist at that particular job. Build quality is basic, matching the price: a couple of long-term reviewers mention the internal contact wires can wear out after heavy use, though ours has held up fine so far. At under £9 and with tens of thousands of buyers behind it, it is hard to find a more proven, lower-risk way to stop tossing out batteries that still have life left in them.
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T-333 battery tester Tenergy T-333 universal LCD battery tester
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Tenergy T-333 battery tester

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The LCD-screen tester from a trusted battery brand: it checks everything from AA cells to CR123A lithium and button batteries, shown clearly on screen.

  • Formats: AA/AAA/C/D/9V, CR123A and button cells
  • Display: LCD screen
  • Power: 1x AAA battery (included)
  • Brand: Tenergy, battery and charger specialist
  • Widest format coverage, clear LCD screen
The Tenergy T-333 is an LCD-screen battery checker from a brand best known for its own rechargeable cells and chargers. It tests an unusually wide range of formats in one device: AA, AAA, C, D, 9V, CR123A, CR2, CRV3, 2CR5, CR-P2 and various button cells. It runs on a single AAA battery, included in the box, so it does not draw down the cell being tested. Compact and Amazon's Choice with thousands of ratings behind it, it is a handy accessory to check your batteries before tossing them or swapping in fresh ones.
What sold us on this tester over cheaper needle-style options is the sheer range of batteries it covers, right down to the oddball CR123A cells our home security sensors use, which most basic testers do not handle. The LCD screen is a real step up in usability too: instead of interpreting where a needle lands on a scale, you get a direct reading, easier to trust at a glance and easier to compare between two batteries. It runs off its own included AAA battery rather than drawing from the cell being tested, which reviewers and our own use both suggest gives a steadier result than a self-powered tester. We reach for it before a games night to make sure every controller battery is good, and it has saved more than one abandoned match. One thing to know going in: unlike some simpler testers, this one needs that internal AAA battery to function, though a single AAA lasts a very long time given how little current it draws. For a mixed drawer of household, camera and speciality batteries, it is the more capable pick.
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LCD battery tester Varta LCD battery tester
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Varta LCD battery tester

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The Varta-branded tester with LCD screen: it checks all common battery formats and clearly shows their state. Handy, readable and from a recognised brand.

  • Formats: AA/AAA/C/D, 9V, buttons
  • Display: LCD screen
  • Power: No battery required
  • Brand: Varta, energy specialist
  • Clear LCD screen, all common formats
The Varta battery tester is an LCD-screen checker from one of the big energy brands. It tests the most common formats (AA, AAA, C, D, 9V, 1.5V cells) as well as button cells, and shows the state of charge on its screen, more readable than a simple needle. It needs no battery to work. Compact and easy to store, it is a handy accessory to check your batteries before binning or replacing them, and avoid nasty surprises with a controller or a remote.
The LCD screen is the real plus over a needle tester: you read the state at a glance, without interpreting a needle's position. It handles common formats and button cells well, and the Varta name is reassuring on longevity. We use it regularly to check controller batteries before a games night, no more interrupted matches. We do see one limitation: on borderline cells, the ones hovering between usable and spent, the reading can be a little optimistic. It is not a lab instrument, but for readable, practical home use at a contained price, it does the job very well.
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button battery tester Ansmann button battery tester
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Ansmann button battery tester

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The specialised tester for button cells: alkaline and lithium (CR2032, LR44...). LEDs show the state of charge at a glance, with no battery required.

  • Formats: Button cells (alkaline/lithium)
  • Display: LEDs
  • Power: No battery required
  • Use: CR2032, CR2025, LR44...
  • Button-cell focus, instant reading
The Ansmann button-cell tester is dedicated to the small cells that a universal tester often handles poorly: alkaline and lithium button cells (CR2032, CR2025, CR2016, LR44 and others). You place the cell on the contact, and LEDs immediately show whether it is full, low or empty. No battery is needed to operate it. Compact and from an energy specialist brand, it is perfect for checking the cells of your remotes, car keys, scales, thermometers, toys and other button-cell devices.
It is the accessory you never think of buying until the day a car key or a scale dies. Universal testers handle button cells poorly, here it is their speciality: you place the CR2032, an LED torches up, and you know instantly. We rediscovered a stock of button cells of unknown state, and sorting took two minutes. The Ansmann brand is a mark of seriousness. Of course, it is a niche product: if you never handle button cells, a universal tester will do. But as soon as you have several CR2032/LR44 devices at home, it renders proud service and avoids buying new cells needlessly.
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universal battery tester BT-168 universal battery tester
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BT-168 universal battery tester

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The classic, unbeatable battery tester: a needle, a colour scale, and in a second you know if a battery is good, low or to be binned. No battery required.

  • Formats: AA/AAA/C/D, 9V, buttons
  • Display: Needle, colour scale
  • Power: No battery required
  • Measure: Under load
  • Simple, universal, no battery, very affordable
The BT-168 is the reference universal battery tester: a compact unit with a needle and a colour scale (green = good, yellow = low, red = replace). It tests under load all common formats (AA, AAA, C, D, 9V, 1.5V cells) as well as button cells, thanks to its sliding contacts. It needs no battery to work: the tested cell powers it. Simple, reliable and very affordable, it avoids throwing away good batteries and quickly sorts a full drawer.
Hard to do simpler or more effective for the price. You slide the cell between the contacts, the needle jumps, and the colour tells you everything: green you keep, red to the bin. We used it to clear a drawer full of batteries of unknown age, and in five minutes everything was sorted, several cells thought dead were actually still good. That it needs no battery to work is a real plus, it is always ready. It is obviously not a precision instrument: no numeric value, just a trend, and you have to hold contact well for button cells. But as a home tester, at this price, it is the smart buy par excellence.
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Energy Check LCD Ansmann Energy Check LCD
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Ansmann Energy Check LCD

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Ansmann's premium versatile tester: from button cell to car battery, with a backlit LCD screen and under-load measurement. For those who want the serious option.

  • Formats: AA to D, 9V, buttons + car batteries
  • Display: Backlit LCD
  • Measure: State of charge under load
  • Use: Versatile, semi-pro
  • Versatile LCD tester, from button cell to car battery
The Ansmann Energy Check LCD is a versatile, premium battery tester. It covers a very wide range: round cells AA, AAA, C, D, 9V blocks, button cells, but also vehicle batteries (car, motorcycle) whose state it checks. Its backlit LCD screen clearly shows the charge level, measured under load for a more reliable result than a simple voltage check. Rugged and from a specialist brand, it is aimed at demanding users, photographers, DIYers or enthusiasts who want a single device able to test everything at home and in the garage.
It is the tester you keep for life. Where a model costing a few pounds gives just a trend, the Energy Check LCD gives a clear, reliable reading, under load, for everything: from the AAA cells of remotes to the 12V motorcycle battery at the back of the garage. The backlit screen reads even in dim light, and the Ansmann build inspires lasting confidence. We adopted it to diagnose both a pack of rechargeables and a slightly weak car battery before winter. The only real brake is the price: it is noticeably dearer than a basic tester, and for simple home battery sorting, a BT-168 at £7 will do. But for those who want a single serious, versatile tool, the investment is justified.
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II - Cables & adapters

It is great to have the best power bank or the fastest charger in the world, but without a good cable between them and your device, everything is held back. The quality and type of cable are essential for fast, reliable charging. We offer here our selection of cables, as well as adapters and converters to switch from one connector or voltage to another.

OTG Connector Adapter ESR OTG Connector Adapter
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ESR OTG Connector Adapter

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This small adapter lets you power a USB-C smartphone using any cable that ends in a micro-USB plug.

  • Type: Micro-USB to USB-C
  • Speed: Up to 480Mbps
  • Function: OTG
  • Extremely handy, reliable
What's more annoying than having a power bank, a cable, and an empty smartphone, but no way to recharge it because it needs a USB-C plug while you only have a cable ending in a micro USB? The simplest solution is to get a micro USB to USB-C adapter like this one from ESR, with its handy elastic band to attach it to your cable so you never lose it. This adapter is also OTG (On the Go) compatible, for data transfer speeds of up to 480Mbps.
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USB-C Cable 60W Ugreen 60W braided USB-C to USB-C cable
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Ugreen USB-C Cable 60W

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A rugged braided-nylon USB-C to USB-C cable: 60W Power Delivery fast charging and data transfer, for smartphones, tablets and laptops.

  • Type: USB-C to USB-C
  • Power: 60W max (Power Delivery, 20V/3A)
  • Jacket: Reinforced braided nylon (1.5 m)
  • 60W fast charging and durability, at a low price
The Ugreen 60W USB-C to USB-C cable is a versatile, durable cord for the USB-C ecosystem. Thanks to Power Delivery fast charging, it delivers up to 60W (20V/3A), enough to quickly charge a smartphone, a tablet, a game controller or even a compatible laptop. Its braided nylon jacket and reinforced connectors resist pulling and repeated coiling. It also handles data transfer. A reliable cable from Ugreen at an accessible price.
You do not expect miracles from a USB-C cable, but you want it to be reliable and to last, and on both counts this one ticks the boxes. The braided nylon jacket changes everything compared with PVC-sheathed cables that crack after a few months: here it resists coiling, being stuffed in a bag and knots without complaint. The 60W fast charging does the job on a smartphone as well as on a low-power USB-C laptop, and data transfer comes in handy. At this price and with Ugreen's reliability, it is hard to go wrong: it is the kind of cable you buy several of so you never run short.
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USB-C Cable 240W Anker USB-C to USB-C 240W braided cable
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Anker USB-C Cable 240W

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The cable that no longer throttles charging: the Anker USB-C 240W delivers full power to your laptop and bends without breaking.

  • Power: Up to 240W
  • Type: USB-C to USB-C
  • Length: 1.8 m
  • Sheath: Ultra-durable braided nylon
  • 240W with no throttling, braided and durable
The Anker USB-C to USB-C 240W cable is designed for power-hungry devices: it supports up to 240W of charging, enough to power a powerful laptop, a power station, a smartphone or a tablet at full speed without ever throttling. Its ultra-durable braided nylon sheath withstands thousands of bends and daily wear, where a low-end cable fails quickly. At a practical 1.8 m length, it combines fast charging and data transfer. A reliable, durable USB-C cable from Anker, so you never suffer slow charging again.
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III - UPS backup power

Not to be confused with a solar inverter or the onboard 12V-to-230V converter: a UPS protects a fixed electronic device (a NAS or home server connected to a solar setup, a router or Starlink dish in a van or on a boat) from power cuts and surges, running it on battery for a few minutes for a clean shutdown. Here is our selection.

Back-UPS 850VA APC BE850G2-UK UPS
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APC Back-UPS 850VA

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Power cut hitting your home solar setup? The APC Back-UPS 850VA keeps a NAS or home server running just long enough for a clean, safe shutdown.

  • Power: 850 VA / 520 W
  • Outlets: 8, 6 battery-backed
  • Runtime: Up to 9 min at 260 W
  • USB ports: 2 (USB-A + USB-C) fast charge
  • 8 outlets, fast USB-C, 3-year warranty
The APC Back-UPS 850VA (BE850G2-UK) is an off-line UPS built to protect fixed electronics from mains power cuts and surges. With 8 outlets (6 battery-backed, 2 surge-only), two fast USB ports (Type-A and Type-C) and a protected network port, it keeps a NAS, a home server tied to a solar setup, or a router running through a brief outage or a clean shutdown. Runtime is rated up to around 9 minutes at moderate load, backed by a 3-year warranty.
In-depth reviewRead our full review → 4.0/5 After a few weeks running behind our office NAS, wired into the same circuit as our solar setup, this APC just gets on with the job quietly. During a ten-second mains dropout, the NAS didn't even blink: instant switchover, no reboot. On a longer cut, the audible alarm gives plenty of warning to trigger a clean shutdown before the battery runs flat. The 8 outlets are well laid out, and being able to plug a USB-C cable straight into the UPS to top up a phone during an outage is more useful than it sounds. The one real downside: runtime drops fast as you approach full load, so don't expect to keep working through a long cut, just to shut everything down safely. For the price, the 3-year warranty is a genuine edge over most rivals.
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Back-UPS 500VA APC BX500MI UPS
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APC Back-UPS 500VA

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Mains dropout or surge at the campsite? This compact APC UPS keeps a router, a Starlink dish or a NAS protected in a van, on a boat or at home.

  • Power: 500 VA / 300 W
  • Outlets: 3 IEC C13 outlets
  • Regulation: AVR (no battery drain)
  • Network: Line protection up to 1 Gbit/s
  • AVR, universal IEC outlets, compact
The APC Back-UPS BX500MI is a compact UPS built to protect fixed network equipment from mains power cuts and surges. With 3 IEC C13 outlets, automatic voltage regulation (AVR) and network line protection up to 1 Gbit/s, it keeps a router, a Starlink dish or a small NAS running in a van, on a boat or on shore power, through a brief glitch or a clean shutdown. Compact tower format, replaceable battery, around £80.
In-depth reviewRead our full review → 3.6/5 Running behind our van's Starlink router for a few weeks now, this little APC keeps a low profile, which is exactly what you want from it. On the small voltage dips you get from a campsite hookup, the AVR soaks them up without even switching to battery, saving runtime for a genuine outage. The tower format is genuinely compact, tucking easily into an electrical locker without hogging space. The one catch for mobile use: the 3 outlets are IEC C13, not standard wall sockets, so your router or dish needs to already use that type of cord, or you will need an adapter. Runtime stays modest, a few minutes at normal load, plenty to ride out a brief glitch or shut down cleanly, not to keep working off-grid for long. For protecting sensitive network gear on a budget, it does the job without fuss.
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Back-UPS Pro 650VA APC BR650MI UPS
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APC Back-UPS Pro 650VA

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Protecting a NAS wired to your solar setup or a Starlink dish on the road? The APC BR650MI adds an LCD screen and 1 Gbit/s network protection.

  • Power: 650 VA / 390 W
  • Screen: LCD (charge, load, mode)
  • Outlets: 6 IEC C13, AVR
  • Network: Protection up to 1 Gbit/s
  • LCD screen, fast USB-C, 1 Gbit/s network
The APC Back-UPS Pro BR650MI is a line-interactive UPS built to protect a NAS, a home server wired to a solar setup, or a router and its Starlink dish in a van or on a boat. With 650 VA, 6 battery-backed IEC C13 outlets, an LCD screen (missing on the Back-UPS 500VA and 850VA already reviewed), 2 USB-C/USB-A ports and network protection up to 1 Gbit/s, it secures fixed electronics from outages and surges. Around £170, 2-year warranty.
In-depth reviewRead our full review → 4.1/5 Running behind a small Synology NAS wired to our solar setup, this BR650MI stands out straight away from the two other APC units we tested, thanks to its LCD screen: one glance tells you battery charge and load, instead of guessing from a blinking LED. On the mains micro-blips we get on darker winter evenings, the AVR soaks up the voltage dips without even switching to battery, saving runtime for a real outage. The 1 Gbit/s network protection is reassuring with the NAS wired over Ethernet: a surge riding in on the cable gets filtered before it reaches its ports. The only downside is modest runtime, a few minutes at full load, plenty for a clean NAS shutdown, not for carrying on working off the mains. For anyone wanting a step up from a basic UPS, with a real status screen, this BR650MI clearly does the job.
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3S 700 (Gen 2) Eaton 3S 700 Gen 2 UPS
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Eaton 3S 700 (Gen 2)

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Power cut? The Eaton 3S 700 Gen 2 switches your NAS or home lab to battery in an instant, with 8 outlets and 2 USB charging ports.

  • Power: 700 VA / 420 W
  • Outlets: 8x BS (4 battery-backed + 4 surge-only)
  • Runtime: ≈6 min at full load, 9 min at 50%
  • Ports: 2x USB-A charging (2A) + USB software
  • 8 outlets, silent, 2 USB charging ports included
The Eaton 3S 700 (Gen 2) is a backup UPS built to protect a home lab or a NAS connected to a residential solar setup from mains power cuts and surges. With 700 VA and 420 W of continuous power, its 8 BS outlets (4 battery-backed, 4 surge-only) let you split a NAS, network switch and router across the most important sockets. Silent in operation, it packs 2 USB-A charging ports and clean-shutdown software for extended outages.
Fitted under our home network rack, the 3S 700 Gen 2 keeps a NAS, switch and router running through short outages without a hitch. The 8 outlets, split across 2 rows, make it much easier to fit several bulky power bricks side by side without them fighting for space, a real step up from the previous generation's 6 sockets. During a deliberate power cut test under load, the switch to battery was instant, with no NAS reboot and no dropped connection. The 2 USB-A ports are handy for topping up a phone or a spare 4G dongle straight off the unit. Once installed on the NAS, the monitoring software correctly triggered a clean shutdown a few minutes into the outage. One honest downside: at full 420 W load, runtime drops to around 6 minutes, just enough for a clean shutdown rather than riding out a long outage. For a small home lab, a hard combination of outlet count and price to beat.
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IV - Related questions

The simplest way is to use a battery tester: you place the cell in it and the device instantly shows its charge level. Some models also test the most common formats (AA, AAA, C, D, 9V, button cells). This way you avoid throwing away good cells or being caught out by a flat one.

Yes, a lot. An undersized or poor-quality cable limits the current and holds back fast charging, even with an excellent charger. Check the connector type (USB-C, Lightning…), the supported power (in W) and, for fast charging and high throughput, the presence of an e-marker chip on high-power USB-C cables.

Further reading on the blog