![]() You could buy readymade 12V Li-Ion power packs and charge units from that, but the weight and cost per Ah is higher than AAs, and you’d need to recharge the power pack itself in the warm. Sadly, rechargeable Li-Ion or Lithium polymer AAs are not available. The very afforable GP Ultras beat the Duracells fair and square, even if neither performances were stellar.įor serious low temperature use, lithiums are the solution. If you have an excellent recharging system, perhaps LSD-NiMH (like Eneloops) have a use, but they will need constant care. ![]() So, with plenty more testing yet to do, the results as I see them are: Energizers don’t tend to do this so dramatically. Whether this is because in series current is being drawn unequally and ‘toasts’ one cell entirely, I don’t know. An oddity I noticed, and have done so when using two GP cells in a GPS, is that occasionally after heavy use the cell will read 0.0V – it dies entirely. On rewarming, both returned to around 1.5V unloaded. After eleven hours, the Energizer was holding on at 1.07V with a dim glow in the bulb. The GP’s results were 1.27V, then oddly, 1.30V for the two and four hour checks. After one hour, it was 1.33V, two hours, 1.32V, and four, 1.30V. From this point, the batteries were left to discharge, with the Energizer holding a higher voltage when tested each hour. In the cold, these only dropped around 0.05V, which is impressive. The lithiums had an unloaded voltage of 1.8V (Energizer) and 1.9V (GP). The batteries were re-warmed and gave a voltage of around 1.14V (Durcell) and 1.37V (GP Ultra). The GPs held out until 0.9V at one hour, whilst the Duracells failed to light the bulb at this point. It is worth saying that a larger drain (from a powerful torch) reduces a battery’s useful capacity (the mAh number) and so are often quoted at currents like 0.05A in order to sound better. AA performance at a volt becomes very poor, and some would say a voltage sub-1.2V is not useful. The GP Ultras fared better at 1.2V and 1.1V. After just 20 minutes the Duracells were at 1.1V, and 1.0V after forty minutes. Then, I let them discharge through the bulbs. Having chilled the whole system down to just below -20 degrees C, it read 1.35V. Once loaded (I used a 0.3A lightbulb per cell) this dropped to 1.5V. For batteries listed as 1.5V (typical for single use AAs – 1.2V is more normal for rechargeables) this is about right. The alkalines had a voltage of around 1.6V without a load. Lithiums are well known to be better in the cold, especially under high load, so there will be little surprise in the results alkaline vs lithium, but the question is by how much? Is the major price difference worth it? And how much to they vary between brand? I tried two traditional alkaline types, GP Ultra (a well-regarded budget brand) and Duracell (their standard cell), and two lithium AAs, again from GP, and the pricier market leader, Energizer Ultimate. I’ve run some tests of a few common AA cells – so a geek alert I’m afraid – but have tried to cut to the useful information pretty quickly. Some are rechargeable, but the NiMH chemistry used for these (even the newer low-self-discharge types) is notoriously impotent once the mercury heads south of zero. They can be used solo in units like GPS handsets, or combined in power packs to create 12V that all sorts of tech can charge from. Having considered the different sizes, chemistries and options on the market, I have found that typical AA batteries are excellent in this role. Instead of having a mess of different battery types, charging systems and the weight they represent, it makes sense to use a single ‘base source’ of power.
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