Time for another Eneloop battery comparison between different generations, namely the latest 5th generation Panasonic Eneloop Pro AA size NiMH batteries rated at 2500 mAh minimum capacity that we have just recently tested and the older 3rd gen 2550 mAh Sanyo Eneloop XX NiMH AA batteries that we have tested a couple of years ago. Specifications wise and performance wise both the older generation and the latest generation high-end Eneloop Pro/XX batteries do seem very similar to each other (like their smaller AAA version), but let us take a closer look at the results we got in our tests…


It seems that the newer Panasonic Eneloop Pro batteries manage to perform slightly better in terms of usable capacity in all of our tests at constant current loads of 0.2A, 0.5A, 1.0A and 2.0A, though the difference isn’t that big if you take a closer look at the numbers. It seems that the newer generation might be handling a bit better higher currents as the performance at 2.0A seems to be the only one with more significant difference between the 3rd generation Eneloop XX and the latest 5th generation Eneloop Pro AA NiMH batteries we have tested. Still, the good news is that the newer Panasonic Eneloop Pro batteries do manage to keep up with the expected good performance we are used to wit the Eneloop brand of rechargable batteries.

mAh Capacity – Eneloop XX – Eneloop Pro
— 0.2A load – 2452 mAh – 2472 mAh
— 0.5A load – 2423 mAh – 2453 mAh
— 1.0A load – 2385 mAh – 2388 mAh
— 2.0A load – 2200 mAh – 2322 mAh

Wh Capacity – Eneloop XX – Eneloop Pro
— 0.2A load – 3.096 Wh – 3.080 Wh
— 0.5A load – 2.999 Wh – 3.015 Wh
— 1.0A load – 2.856 Wh – 2.870 Wh
— 2.0A load – 2.436 Wh – 2.601 Wh

We got a pack of the latest generation Panasonic Eneloop Pro AA NiMH batteries with 2500 mAh capacity to check out and see what you can expect from what are considered as one of the best rechargeable NiMH batteries out there. These batteries come pre-charged with solar energy and are low self discharge, meaning that they are capable of retaining up to 85% of their capacity in a year. The Eneloop Pro are great choice for use with devices that require higher current and are also suitable for use in low temperature conditions of up to -20 degrees Celsius with good performance. According to the specifications they should be good for 500 recharge cycles. Looking back a couple of years back when we have tested an earlier generation Sanyo Eneloop XX AA NiMH batteries it seems that things have not changed that much in terms of rated capacity or battery specifications.

The 1.2V AA 2500 mAh Panasonic Eneloop Pro NiMH batteries are rated at minimum 2500 mAh capacity and our discharge tests have shown really good results with very close to that capacity usable at constant current loads of 0.2A and even 0.5A. Going for a higher discharge load of 1.0A and even 2.0A and the batteries still manage to perform surprisingly well at over 2300 mAh usable capacity in both cases. We remind you that these batteries are intended to be used for high drain devices, so we expected to see good performance with higher current loads, but we are also going to be testing them at even higher loads in a separate test to see where is the limit. So it seems that not only the specifications, but also the usable capacity of the newer Panasonic Eneloop Pro is very similar to that of the older generation Sanyo Eneloop XX that we have tested a couple of years ago. The good news is that there is no drop in quality and the new Eneloop Pro rechargeable batteries are still one of the best NiMH AA batteries you can currently get on the market.

The performance of the 1.2V AA 2500 mAh Panasonic Eneloop Pro NiMH batteries in our tests:

– 2472 mAh at 0.2A load
– 2453 mAh at 0.5A load
– 2388 mAh at 1.0A load
– 2322 mAh at 2.0A load

– 3.080 Wh at 0.2A load
– 3.015 Wh at 0.5A load
– 2.870 Wh at 1.0A load
– 2.601 Wh at 2.0A load

The 4000 mAh ASUS ZenPower Slim Power Bank (ABTU015) is a very slim, compact and stylish device for charging your smartphone or other mobile devices on the go from Asus. The 4000 mAh battery is inside a plastic case with a larger matte and smaller glossy surface and that looks pretty nice, however the glossy plastic scratches very easy when touched and very soon it does not look that good anymore. The device also has a single white LED disode that provides “flashlight” functionality that in our opinion is totally useless and the power bank could’ve been better without it anyway. There is an on/off button (used for the flashlight as well) and a small three-LED indicator about the current power bank charge that looks nice and is quite useful. The compact size and weight make the ASUS ZenPower Slim Power Bank perfect to sit in your pocket and save you whenever you need some extra power and cannot use a power charger for your smartphone or other mobile USB gadget and without the glossy plastic part and the LED light it could’ve been a really great small capacity power bank. Do note that ASUS also offers a version of this portable power bank with a smaller 3000 mAh capacity that is apparently with the same specifications as the 4000 mAh version we are testing here, apart from the 1000 mAh lower capacity battery inside it of course.

4000 mAh ASUS ZenPower Slim Power Bank Specifications:
– Battery Type: Rechargeable Li-Polymer Cell
– Battery Capacity: 3.85V/4000 mAh
– Input Power: 5V/1A
– Output Power: 5.1A/1A
– Rating Capacity: 5.1V/2200mAh
– Charging Time: <6 hours with DV 5V/1A standard cable - Dimensions: 115 x 71 x 8.3 mm - Weight: 92 g


We need to see how well the ASUS ZenPower Slim Power Bank manages to perform under our test conditions with a constant current load of 1.0A as per its official rating in order to get a better idea on what to expect in terms of actual usable capacity. In the official specifications Asus rates the useful capacity at 2200 mAh. This was something that we were actually a bit surprised to see mentioned in the official specifications for a power bank as usually manufacturers do not cite these cumbers in their product’s specs. The 2200 mAh rating sounds a bit disappointing for a 4000 mAh battery inside the power bank, but our tests have shown that you will actually be getting more… We managed to get 2574 mAh or 12.11 Wh as usable capacity and that is actually what we consider a very good performance, though the output voltage was a bit lower at about 4.7V, but keeping stable at that value. So good job for Asus for this power bank, but it could’ve been even better without the extra glossiness that easily scratches and the useless LED light “flashlight”.

The performance of the 4000 mAh ASUS ZenPower Slim Power Bank in our tests:

– 2574 mAh at 1.0A load

– 12.11 Wh at 1.0A load

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