Power Banks and cold weather

We all use mobile phones when we are out and about and more and more often we take battery packs or power banks with us for recharging. If you are wild camping, backpacking or on a campsite without an electric hookup then you will most likely have one of these handy devices.

We are not here to discuss which are the best power banks for your money, that will be a matter for another article. What we are here to find out is how well a typical battery pack performs at recharging your mobile phone and other devices when the temperature drops.

By now I am sure we all know that mobile phone battery life can be affected by the cold weather, but does this also apply to the power banks or battery packs we use recharge our tech?

Recently Mrs TentLife went camping to Pembrokeshire, Wales and although the temperature wasn’t extremely cold it did drop down into low single figures overnight. It was the middle of November and she was testing some sleeping bags for their warmth and comfort.

One issue that she did mention upon her return from this camping trip, was how quickly the power bank had drained down whilst recharging her mobile phone. We discussed the possibilities that it may be down to it being a rubbish battery pack or perhaps that it had been affected by the cold temperatures. During it’s normal usage, the power bank would have gotten cold in her backpack, and was also placed on the tent floor overnight whilst recharging her phone.

Anything that has a lithium ion battery inside it will be affected by extremes of heat and cold, so how much of a problem is this really? We’ve all heard stories of the cold weather turning off mobile phones, but what about these power banks?





EXPERIMENT
So we decided to do a simple experiment whereby we would test how long the battery bank lasted in warm and cold temperatures.

For this test we are using a power bank that we own a couple of. We like these as they have a percentage readout on them instead of just some LEDs. We purchase these from amazon as they always seem to have the best prices. The battery pack is a brand called Imuto, 20000mAh, costing about £20.

We rigged up a large LED torch bulb to drain the power down and replicate having a phone or other device attached. These power banks do have a small torch built into them, but just leaving the torch on and timing it could take days. We are aware the torch LED would drain the power bank faster than a mobile phone, but the comparison between the 2 tests needed to be identical and the ratio of the 2 timings is the key factor (and I didn’t want to stick my phone in the fridge).





We tested the power bank whilst it was warm (sat on my office desk), then we recharged it and tested in the cold (stuck it in our fridge). Both discharges were timed and the details/results are set out below.

TEST 1.
The first test is the ‘fair weather’ benchmark.

We made sure the power bank was fully charged to 100%, then attached a temperature probe to the outside of the power bank and recorded a constant temperature of 20 degrees C.

 

We started the timer, attached the torch LED and began to drain down the power bank. The test was started at 7.49 am and we would run the test until the power bank was completely empty (0%).

By 12 noon the battery bank charge was down to 50%, and by 2:50pm it was down to 30%. By 4:30pm the power bank was fully discharged, reading 0% and the LED had gone out.

TIME - It took 8 hours and 40 minutes to drain the power bank from 100% to 0%.

TEST 2.
The ‘cold weather’ test.
Time to put it in the fridge. Our fridge is set to run at 4 degrees C down in the chiller draw, I checked this with the temperature probe and it was accurate.

The battery pack was recharged to 100% overnight and dropped into the chiller draw for 30 minutes to let it cool down sufficiently before we started testing.

At 6:50am, with the pack cooled and reading 100%, we attached the torch LED and started the timer. Within just one hour, the power reading had dropped dramatically to 70%. That is a lot quicker that we were expecting.

I kept a close eye on the torch LED and the battery pack readout, and by 8:50 it was completely dead. The LED had gone out and the battery bank was at 0%, we were amazed.

TIME - So at 4 degrees C, the power bank lasted just 2 hours (6.50am to 8.50am).

WOW
That’s quite some difference. We were expecting worse results for the cooler temperature, but not that extreme. At a constant rate of discharge, the battery bank at 20 degrees C lasted over 4 times longer than when it was cooled down to 4 degrees C.

That can be a very important issue to deal with if you are out in cold weather for a few days.

WHAT CAN BE DONE?
So what can you do to minimise the problems this may cause? Keeping that power bank warm is the key, not letting it’s temperature drop too much – but how do you do that?

Well with mobile phones, people recommend you keep them in an inside pocket so you body heat keeps it at a reasonable temperature. Also, taking it out for short periods of time before returning it back into that inside pocket is good advice too. You could do the same with your battery pack, but you may not have enough pockets. Also these power banks can be heavy and bulky and could impact on your activities such as hiking, scrambling or climbing.

Normally our power banks are dropped into the bottom of our rucksacks, or even stored in an outside pocket of a bag. OK for the fair weather trips, but now we will have to find ways in which to prevent the power banks temperature from dropping. This could possibly be achieved by wrapping them inside your spare clothing (pair of socks maybe), but certainly away from the outside of your bag. I am not aware of any insulating jackets for power banks, but I’m sure you people could come up with some ingenious solutions (we would love to hear them).

When recharging overnight you should also try to keep your tech off the floor, either on your sleeping mat or even inside your sleeping bag with you. Be careful of condensation though, common sense must prevail.

This forward planning should be done before you leave the house, when you are preparing your gear. Surely it’s much better to prevent the power banks temperature from dropping, instead of finding out you have a problem and need to warm it back up when you desperately some power.

Anyway, I’m off to the fridge again – there is a bacon sandwich with my name on it.

Enjoy your travels,

TentLife xx