Rugged Tablets in Summer: Heat, Sun and Operating Temperatures

Cold slows a tablet battery down for a few hours. Heat does lasting damage. A device left on a van dashboard in July can sit well above the top of its operating range, and unlike the winter problem, the capacity it loses does not come back when it cools. This is the summer counterpart to our winter guide: what an operating temperature means, where UK summer heat really comes from, how to read a screen in sun, and the charging habit to drop in a heatwave.

Heat Is the Bigger Risk, Not Cold

In winter a lithium ion battery delivers less current than it should, the percentage drops fast, and the device may switch itself off early. Warm it up and most of that capacity returns. The chemistry has slowed down, not broken.

Heat works the other way. A warm battery delivers power happily, so nothing seems wrong on the day. Underneath, high temperatures speed up the reactions that age a cell, and that wear is permanent. A battery that spends every summer afternoon hot will hold less charge by autumn than one that was kept in the shade, and no amount of cooling brings it back. A processor that gets too warm also slows itself down to protect itself, so the device feels sluggish just when you are trying to finish a form.

Rugged tablets cope better than consumer ones, and the manufacturers publish an operating range. But the range is a limit, not a promise, and the way most devices overheat in Britain has little to do with the weather forecast.

What the Operating Temperature Actually Means

An operating temperature range is the span of ambient temperatures the manufacturer says the device will function in. Two things about it are easy to miss.

First, it is about the air around the device, not the device itself. A tablet in 28°C air with the sun on its back glass can be far hotter inside. Second, the top of the range is where the device will still work, not where it is happy. The comfortable zone for a lithium ion cell is a good deal lower than the figure on the box.

Here is what our range lists, from products.json, nothing added:

• Tuga A6: -20°C to 50°C
• Tuga A10: -20°C to 60°C
• Tuga WH6: -20°C to 60°C
• Tuga W8: -20°C to 60°C
• Tuga A8: no operating temperature listed
• Tuga W10: no operating temperature listed

Where a figure is missing we do not guess at one. If the A8 or W10 is the device you are considering and the upper limit matters to your work, ask us before you order and we will find out from the manufacturer.

A 50°C or 60°C limit sounds generous for a country where 30°C makes the news. It is, if the device is in the air. It is not if the device is on a dashboard.

The Parked Van Is the Real Danger

Air temperature in the UK rarely gets close to a tablet's upper limit. The inside of a closed vehicle does, routinely. The cab of a parked van heats far beyond the outside temperature, and the dashboard, where the sun lands through the windscreen, is the hottest surface in it. Leave a tablet there for a half day on site and it can spend hours above any figure on a spec sheet.

This is also where the two seasons' advice meets. In our guide to mounting a tablet in a van we recommend a locking dock so the device is secure and charged on the road. A dock is for driving. It is not somewhere to leave the tablet parked in the sun with the engine off.

The habits that matter:

• Take it out of the dock when you park, or at least move it off the dashboard into a footwell, a door pocket or a bag out of direct sun. A padded case helps here; the Rugged Carry Case at £34 fits the A8, A10, W8 and W10 and keeps the glass out of the light.
• Park in shade when you have the choice, and crack a window if the van is secure.
• Never leave it on the dashboard overnight in a heatwave. The cab cools slowly and the tablet cools slower.
• If it has been baking, let it cool before you use it hard. Switching on, uploading a day's photos and charging all at once on a hot device adds heat to heat.

The same applies to a windowsill in a site cabin, a toolbox lid in the sun, and the back of a pickup. A tablet lying on hot metal takes heat in from below as well as above.

Do Not Charge a Hot Device

The winter rule is never charge a frozen battery. The summer rule is the mirror image: do not charge a battery that is already hot. Charging generates heat of its own, and a cell that is both hot and charging ages fastest of all. Many devices sense this and slow or pause charging until the battery cools.

In practice: if the tablet has come out of a hot van or spent the morning in direct sun, let it come down to something like room temperature before you plug it in. Charge in the shade, in the cab with the air conditioning running, or back at base in the evening. The 12V DC Car Charger at £26 is handy between jobs, but not when the device is already warm to the touch.

Several devices in our range have a removable battery, which changes the sums in summer. The A6, A8, WH6, W8 and W10 all list one; the A10 does not. Carry a charged spare in a cool bag rather than charging a hot device on site, and swap. Our guide to removable batteries covers the detail.

Reading the Screen in Direct Sun

Heat is the long term problem. Glare is the one you notice on the day. The usual response, turning brightness to maximum, both drains the battery and warms the device.

Screen brightness is measured in nits, and our nits guide explains what the numbers mean outdoors. The short version is that a few hundred nits is comfortable indoors, and direct sun rewards much more. As listed in our range: the A8 is rated at 1000 nits, the W8 at 550 nits, the WH6 at 400 nits and the A10 at 350 nits. The A6 and the W10 list no brightness figure. The A10's 350 nits is a fine screen for drawings under a canopy, and you will be looking for shade with it in full sun.

Ways to get more out of whatever screen you have:

• Turn your back to the sun so the screen is in your shadow. It is the single most effective trick and it costs nothing.
• Use dark text on light backgrounds and large type where the app allows it. Light themes are easier to read in glare than dark ones.
• Keep the glass clean. Dust and fingerprints scatter light and make glare worse. A clean screen at medium brightness often beats a smeared one at full.
• Use auto brightness rather than pinning it at maximum. The screen drops back down when you step inside, which saves battery and heat.

If you work in full sun most of the day, that 1000 nit figure is a reason to look at the A8 first. If you need a 10 inch screen, plan on shade.

Sun Cream, Sweat and Dust

Summer brings a different kind of dirt. Sun cream and sweat leave a film that makes touchscreens less responsive and adds to glare, and dry dust gets everywhere. Every device in our range is at least IP65, which means dust tight, so a damp cloth at the end of the day is fine. Do not jet wash any of them; no device in our range carries the IP69K rating that covers high pressure hot water.

Sweaty hands also make a device easier to drop. A Hand Strap at £24 for the A8, A10, W8 and W10, or the Belt Holster at £22 for the A6 and WH6, is cheap insurance when you are working one handed in shirt sleeves.

Battery Life on a Long Summer Day

Summer shifts run long, and heat makes them harder on a battery in two ways: the screen works harder against the sun, and a warm battery that is also charging ages faster. The battery sizes in our range are as listed: 8000mAh in the A8 and A10, 5050mAh in the A6, 5000mAh in the W8 and W10, and 4000mAh in the WH6. We do not publish run time figures because they depend on your brightness, apps and signal, and a sunny day moves all three the wrong way. The practical answers are the ones above: shade the device, use auto brightness, charge when it is cool, and carry a spare where the battery is removable.

A Summer Checklist

1. Out of the dock and out of the sun whenever the van is parked.
2. A case or a bag for the device when it is not in your hands.
3. No charging while it is hot. Cool first, then plug in.
4. Auto brightness on, screen clean, back to the sun.
5. Wipe sun cream and dust off at the end of the day.
6. A spare battery in the cool bag if your device takes one.
7. Know your device's upper operating limit, and if it is not listed, ask.

Which Tuga Device for Summer Work

For work in direct sun most of the day, the Tuga A8 at £379 has the brightest listed screen in the range at 1000 nits, an 8000mAh removable battery and IP67 sealing. It lists no operating temperature, so ask us about the upper limit if your sites get properly hot.

For a 10 inch screen, the Tuga A10 at £449 is listed to 60°C with IP68 and MIL-STD-810H, but at 350 nits it is a tablet for shade or a site office rather than an open roof.

For a pocket device, the Tuga A6 at £349 is listed to 50°C, the lowest upper limit in the range, with a removable 5050mAh battery and IP67 sealing. Keep it out of the dashboard sun and the limit is not an issue for UK work.

On the Windows side, the Tuga W8 at £629 and the Tuga WH6 at £699 are both listed to 60°C and both have removable batteries. The Tuga W10 at £649 lists neither an operating temperature nor a brightness figure, so ask before you choose it for outdoor summer work.

All prices are as listed, with no VAT to add. Every device comes with a 12 month warranty, and delivery is free to UK addresses in 7 to 10 working days.

Compare head to head: A6 vs A8 · A8 vs A10 · A10 vs WH6