duracell-voltage-depression-example-chart

You can often hear people complaining from various problems with their rechargeable NiCd or NiMH batteries and saying that the problem is caused by the so called “memory effect”, however in truth it is mostly because of improper usage and handling of the batteries. The term “memory effect” is not the best one to describe the issue as the “true memory effect” is not something that you can achieve unless in specially controlled conditions, so a more accurate description is “voltage depletion” or “voltage depression”. And while “memory effect” is the most commonly used term usually they all refer to a drop in voltage and thus resulting in a loss of capacity of a battery due to partial discharge and repetitive full charges without going for a full discharge-charge cycle. The problem was first observed with NiCd batteries and NiMH cells do seem to suffer from it as well, but to a smaller extent and the usual problem causing the so called “memory effect” is when user constantly charges his batteries in order for them to be always ready for use with the maximum capacity. Due to the fact that the newer LSD (Low Self Discharge) NiMH batteries do self discharge much slower compared to traditional NiMHs, they tend to be less prone to such problems as there is no need to top them off frequently in order for them to be always ready to be used.

Fortunately, this effect is reversible and all you need to usually do is one or two full cycles of a NiCd or NiMH battery (discharge/charge cycle) down to about 1V (it is not recommended to discharge to 0V!). Doing so should normally restore a NiCd or NiMH battery to its full voltage and thus the full useable capacity. The good thing is that if you handle properly your rechargeable batteries and do a full discharge/charge cycle once in a while you should not have to worry about getting problems with the so called “memory effect”. The reality however is such so that in almost all cases when users are experiencing problems with their rechargeable batteries it is usually caused by improper handling, overcharging/overdischarging or improper storage and is not associated with the “memory effect” at all. Actually the improper use and storage also is the problem that you are unable to fully utilize the capabilities that other rechargeable batteries such as LiIon, LiFe and LiPo batteries offer as these do not have issues associated with “memory effect” that you can blame.

So the next time you have a dead rechargeable NiCd or NiMH battery think about how you handled and used it before blaming it all on the “memory effect” as it probably had nothing to do with the fact that you’ve left the battery cell to get fully discharged to 0V for example. Have in mind that the negative effects caused by the “memory effect” or more precisely said by “voltage depletion” or “voltage depression” such as loss of voltage and thus useable capacity are fully reversible, however the same problems caused by overdischarging or overcharging a battery repeatedly are not!

1-5v-aa-q-lite-alkaline-battery

The 1.5V AA Q-Lite Alkaline batteries we test here are rated with up to 3 years shelf life and are marked for use up to 03-2016. The Q-Lite Industrial’s website does not have detailed specifications about these batteries, so we have to check them out by testing the actual capacity we can get with different constant current loads.


1-5v-aa-q-lite-alkaline-battery-power-profile

Starting with the power profile test of the 1.5V AA Q-Lite Alkaline batteries we can see that they can handle pretty high loads before reaching the cutoff voltage of 1V that we are using for our tests. We’ve managed to reach up to 1.5A current draw before the batteries hit the cutoff voltage and values over 1 Amp are not that common to find with alkaline batteries, so these batteries are handling quite well. The open circuit voltage of the 1.5V AA Q-Lite Alkaline batteries we tested was 1.62V, though of course that value decreases when the battery is under load.


1-5v-aa-q-lite-alkaline-battery-capacity

Time to move on to the constant current draw tests we are performing. Starting with a 0.1A constant current load tests for the 1.5V Q-Lite Alkaline batteries we got 2219 mAh capacity which we consider to be very good. Going for 0.2A constant current draw form the batteries the useful capacity you can expect is 1873 mAh and going even higher the useful capacity gets a bit less than in half at 0.5A and 1.0A load as compared to the previous rate. Nevertheless the 1.5V AA Q-Lite Alkaline batteries still manage to perform very well even under higher constant current draw rates, though as usual for such cases we would still recommend to go for rechargeable NiMH batteries instead.

The performance of the 1.5V AA Q-Lite Alkaline Batteries in our tests:

– 2219 mAh at 0.1A load
– 1873 mAh at 0.2A load
– 1062 mAh at 0.5A load
– 482 mAh at 1.0A load

– 2.763 Wh at 0.1A load
– 2.257 Wh at 0.2A load
– 1.219 Wh at 0.5A load
– 0.532 Wh at 1.0A load

2s-7-4v-250-mah-gens-ace-30c-lipo-battery

The 2S 7.4V 250 mAh Gens Ace 30C LiPo batteries are compact batteries often used in small scale flying radio controlled models such as RC planes and helicopters. These small batteries have a pretty high discharge and charge ratings that we need to confirm in our tests. What is important to note for this particular battery is that it is a 2 cell battery, but there is no balance plug, only a JST discharge one that brings out the combined voltage from the two cells. While this normally should not be a big problem, not having a balance connector may shorten the life of the battery if the cells become more and more disbalanced over time.

Official Battery Specifications:

– Capacity: 250mAh
– Voltage: 7.4V
– Max Continuous Discharge: 30C (7.5A)
– Max Burst Discharge: 60C (15A)
– Weight: 18g
– Dimensions: 38,5mm*25,12mm*10,5mm
– Balance Plug: N/A
– Discharge Plug: JST
– Charge Rate: 1-3C Recommended, 5C Max


2s-7-4v-250-mah-gens-ace-30c-lipo-battery-capacity

Time for the actual tests, starting with a 1C discharge rate (0.25A) for the 2S 7.4V 250 mAh Gens Ace 30C LiPo battery we’ve managed to get 264 mAh as a maximum capacity which is a value a bit higher than the rated 250 mAh capacity for the battery, so definitely a good thing. Furthermore at up to 20C discharge rate the battery still manages to provide more than the rated 250 mAh capacity and at 25C and 30C the capacity you can get is just a bit less than 250, but still quite close to that value. So the 30C constant discharge rate is confirmed, however we’ve decided not to go for tests at up to 60C that the battery is supposedly able to handle. The reason for that is the fact that at 25C discharge rate the battery had a temperature of 65 degrees Celsius and at 30C it got up to 71 which is out of the safety zone for working temperature.

The performance of the 2S 7.4V 250 mAh Gens Ace 30C LiPo Battery in our tests:

– 264 mAh at 0.25A load (1C)
– 263 mAh at 1.25A load (5C)
– 261 mAh at 2.50A load (10C)
– 255 mAh at 3.75A load (15C)
– 255 mAh at 5.00A load (20C)
– 244 mAh at 6.25A load (25C)
– 234 mAh at 7.50A load (30C)

We can conclude that the 2S 7.4V 250 mAh Gens Ace 30C LiPo batteries are performing very good and meet their specs, the only thing to note is that if you are going to be pushing to their maximum you should make sure they are cooled properly (at 25C-30C discharge rates).

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