Cordless Tool Battery Guide — How to Get the Most from Your Batteries

Cordless tool batteries are the heart of your cordless tool system — and they're not cheap to replace. With proper care and the right charging habits, a quality lithium-ion battery should last for hundreds of charge cycles and several years of regular use. Here's everything you need to know.

Understanding Battery Specifications

Voltage (V): Voltage determines the power output of the tool. Higher voltage generally means more power. The entire TEH professional cordless range runs on 20V lithium-ion batteries — meaning all batteries are interchangeable across drills, grinders, saws, impact wrenches, jigsaws, sanders, and more.

Amp Hours (Ah): Ah determines how long the battery lasts per charge — it's the capacity of the battery. Think of voltage as the pressure of water in a pipe and Ah as the size of the tank.

A 4Ah battery lasts approximately twice as long as a 2Ah battery on the same tool. For professional use always buy 4Ah — the extra runtime more than justifies the small weight increase.

Always buy kits with 2 batteries: When one runs out, swap to the second while the first charges. No downtime on site.

Lithium-Ion vs Older Battery Technologies

All TEH 20V batteries use lithium-ion technology — the same technology used in smartphones and electric vehicles. Compared to older NiCd (nickel cadmium) batteries:

• No memory effect — you can charge at any time without fully discharging first
• Higher energy density — more power in a lighter, smaller pack
• Low self-discharge — holds charge for months in storage
• Consistent power delivery throughout the charge cycle

Charging Your Batteries — Best Practices

Do charge:

• Charge before the battery is completely flat — lithium-ion batteries prefer partial discharge
• Charge at room temperature — cold batteries charge more slowly and incompletely
• Use the TEH 20V charger supplied with your kit — it's designed specifically for TEH batteries

Don't charge:

• Don't leave on charge indefinitely — remove from the charger once fully charged
• Don't charge immediately after heavy use — allow the battery to cool for 15-20 minutes first
• Don't charge in very cold conditions (below 5°C) or very hot conditions (above 40°C)
• Don't use a damaged charger or one with a frayed cable

How long does charging take? The TEH 20V fast charger typically charges a 2Ah battery in approximately 45-60 minutes and a 4Ah battery in approximately 90 minutes.

Storing Your Batteries

If you're not going to use your tools for a while, proper battery storage prevents degradation:

• Charge to approximately 50-60% before storage — storing at full charge or completely flat degrades lithium-ion cells over time
• Store in a cool, dry place — away from direct sunlight and heat sources
• Store at room temperature — avoid garages and outbuildings in winter where temperatures drop below freezing
• Check charge every 3-6 months — lithium-ion self-discharges slowly over time, top up if below 30%
• Store separately from the tool — reduces accidental discharge

Getting Maximum Runtime from Each Charge

• Use the right battery for the job — a 4Ah battery on a heavy tool like an impact wrench lasts significantly longer than a 2Ah
• Keep batteries warm — cold batteries deliver less runtime. In winter keep spare batteries in a pocket or warm van rather than leaving them in a cold toolbox
• Don't over-discharge — stop using the tool when the battery indicator shows low. Running batteries completely flat repeatedly shortens their lifespan
• Match the tool to the task — using a powerful tool for a light job wastes battery. Use the smallest appropriate tool for the application

The TEH 20V Battery Indicator

TEH 20V batteries feature a battery indicator — press the button on the battery to see remaining charge at a glance:

• 4 lights — full charge
• 3 lights — approximately 75%
• 2 lights — approximately 50%
• 1 light — approximately 25% — charge soon
• Flashing — critically low — charge immediately

Signs Your Battery Needs Replacing

Even with perfect care, batteries degrade over time. Signs that a battery needs replacing:

• Noticeably shorter runtime than when new — less than 50% of original runtime suggests significant cell degradation
• Tool loses power under load — healthy batteries maintain voltage under load, degraded ones drop
• Battery gets very hot during normal use — some warmth is normal, excessive heat indicates cell problems
• Battery won't hold charge at all — a battery that discharges within minutes of charging has failed

TEH 20V replacement batteries are available individually at tehtools.co.uk — you don't need to replace the whole tool kit when a battery wears out.

The TEH 20V Battery System — One System, Every Tool

The biggest advantage of the TEH 20V system is that every battery works with every TEH 20V tool:

• Cordless drills and impact drivers
• Cordless angle grinders
• Cordless jigsaws and circular saws
• Cordless reciprocating saws
• Cordless impact wrenches
• Cordless sanders
• Cordless planers
• Cordless multi-tools
• LED work lights
• And more

Buy once, use everywhere. As you add more tools to your kit, your existing batteries work with everything — no need to buy new batteries for each new tool.

Browse TEH 20V batteries, chargers and the full cordless tool range at tehtools.co.uk