As winter sets in, I’ve really started to notice my radio battery life dropping off a cliff. As you will know, cold weather is brutal on LiPo and Li-ion cells — their internal resistance increases as the temperature falls, which means reduced capacity and shorter operating times.
When we were working on the balloon project earlier in the year, Dave G1JKS solved this problem neatly by using a USB-powered hand warmer to keep the batteries and electronics at a stable temperature. I’d only ever used the old-school chemical warmers before — the little pouches you ‘clicked’ to activate — so I hadn’t realised how good modern rechargeable warmers had become.
I ordered a pair from Amazon for £15.98, just to test the idea, and early results are encouraging. They are tiny and have three heat settings, and even the lowest one is easily warm enough for hands or for keeping gear cosy. They take around 3½ hours to fully charge (each has a 3500mAh internal battery) and they’re rated for 8+ hours of use. So far I’ve run them for over three hours without any drop in performance.
Right now, I’ve tucked one inside a mitt and the other into my LiPo battery case — and both are doing a great job of keeping the cold at bay and the voltage up. For SOTA or any winter field work, this might be one of the simplest, cheapest upgrades you can make.
I could have done with some of those the other week when I activated Pendle Hill. Was a tad cold up there!. We’ve got some battery powered hand warmers at work bit I’ve not seen how much they are. Might invest in a few.
If the problem is keeping a battery warm, it might be possible to use the battery itself to feed a suitable resistive load?
Obviously caution would be required to avoid hotspots, over discharging etc, and maybe the self contained hand warmers are a simpler and safer solution.
He may have a pair of DiLithium crystals on there and an adjustment mechanism to adjust the spacing so he can control the matter/antimatter reaction rate and thus the heat output. It’s how I’d do it.
Add a little camp stove thingy and a Moka pot bubbling away next on it next to the steam thing for extra greatness!
We have a few windmills near here, proper windmills, not wind turbines. We do MOTA up there sometimes. I wonder could you power a MOTA field day with one of the windmills and make a sack of flour at the same time?
… my batteries are a bit big for that. I usually use 2x 5200mAh
