to aĬoastdown: 25-28% duty-cycle, approximately equiv. Main discharge: 41-42% duty-cycle PWM, approximately equiv. ![]() So, a simpler rule of the thumb here is that if you can find alkaline batteries at 0.15€ or less per cell, this is alreadyĪ pretty good deal, even if the capacity isn't that great. The effective unit price can be significantly lower (e.g., see the Panasonic Evolta). Note: most of the tested brands do offer larger packs - 8, 12, 16 cells - which are a more cost-effective package,Ĭonsidering that the total price is not scaled proportionally upwards. Results (in descending order by capacity):Īnd with respect to performance-to-price ratio: ![]() to 30Ω load,Ĭoastdown: 50-60% duty-cycle, approximately equiv. Main discharge: 90-91% duty-cycle PWM, approximately equiv. This drains out whatever's left in the cells. ![]() Then I subject them to a more gentle discharge (termed coastdown/„last will“ here) at less current, ≤50%. After the main discharge (which consumes 90-95% of the energy), I leave the cells to restįor a few hours. With AA/AAA cells, the discharge is split into two phases. The meter's accuracy should be within 1-2% - it's been tested several times. This accounted for in the capacity calculations and keep that in mind when interpreting the discharge curves. Note that the battery pack isn't discharged with constant current, but is more like a constant-resistance load (~30Ω when using theĪforementioned settings). The described scenario with AA cells takes 12-14 hours to do a discharge. This cycle is repeated until the voltage drops below the desired threshold. 1.15s rest and an open-circuit voltage measurement at the end of it.4.8s discharge through a 22Ω resistor, at 90% duty-cycle PWM (this is specifically for AA cells įor others, the settings are listed in the respecive subsections).The discharge cycle has the following timings: What follows is another open-circuit voltage measurement, and after that the real test begins. Then, a heating phase - 30s at 300 milliamps - is performed I measure the momentary initial open-circuit voltage and write it down. I unpack the batteries and connect them to my battery tester. For this reason, I determined three types of tests: „one-hour“ (charging is done, the batteries are put to rest forĮxactly one hour, then they are discharged), „five-days“ (with a waiting time of five days) and „monthly“. Since the batteries lose some charge with time, it is important how much exactly do you wait after the charging is completed, before theĭischarge commences.All batteries are tested in equal conditions, in an air-conditioned room, away from sunlight. ![]() For AA/AAA sizes, a coastdown discharge (termed „the last will“) at smaller current isĪlso employed after the main one, to evaluate the capacity after draining to complete flat.
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