One of the most overlooked and under-appreciated elements of a cycle light is its battery pack. Selecting a light is often based only on price and lumens. The price is significantly influenced by the quality of the battery pack. Up to 2/3 of a light’s cost can be attributed to the battery pack. For this reason, the quality of the battery pack is compromised to accomplish price cuts. Regardless of how good the light is, if its battery pack is unable to provide sufficient power, the light is useless. Therefore the quality of the battery pack should not be overlooked. In our opinion, the battery pack is even more important than the lumen rating.

We have taken the time to test a few readily available battery packs. At this stage, we have only compared 4 cell configurations, but the results should also be representative of 6 and 8 cell configurations.

Test setup

We have an analogue timer and a Lux sensor that are modified to turn on the power to the timer when a pre-set Lux measurement is reached.  We aimed to have the timer stop running when the light output dropped below half its max. All the batteries were charged using the same charger. We used an Extreme 1400 cycle light as our test unit. It was connected to a fully charged battery pack and the test system, in a dark room to represent real world results.

The Extreme 1400 has the latest Cree XM-L2 U2 LED, but power wise it is about the same as most single LED Cree XM-L’s. The test should be representative of other Cree XM-L lights in regard to run times.  It should be noted at this stage that most over claimed lights which are supplied with the cheaper, lower capacity battery types, do not power the LED to its full capacity. This is done to fool the user into thinking the extended runtimes are due to the quality batteries.

Test subjects

In total seven batteries were tested. It was interesting to note that all of them were sold claiming to be waterproof. We seriously doubt that the cardboard end caps of Type A will stand up against South African rain. Type A,B, and C are covered with PVC heat shrink which will provide a minimal amount of waterproofing.

The battery cost ranges from R150 to R700. This is a very large jump and we were interested to know if the high-end battery packs were worth 4.5 times more.

Weight does not vary much due to the battery configuration being the same.  The lightest battery pack is 209 g and the heaviest is 288 g. The 80 g weight difference can be attributed to the difference in the quality of the battery housings.

All Li-ion batteries should have some protection against over-charging. Shockingly, though, Type A had none and Type B’s was not functioning. The risk of setting your house on fire with Li-ion batteries are real. For the supplier to provide batteries that are not protected is very irresponsible.

Test results

Measured test results
Weight Cost Expected lifetime Safety system Runtime Capacity*
Type A** 209g R150-R200 1-3month none 1h25 1626mAh
Type B** 212g R150-R200 3month none 2h34 2947mAh
Type C** 213g R200-R400 +3month basic high cutoff 2h48 3214mAh
Type D 227g R300-R500 3m-1y basic high low cutoff 3h17 3769mAh
 Cycle Light 8.4 V Battery 4400mAh (MKII) 287g R550  1-3 years  Full. Over current, high low cut off.  3h49  4382mAh
High Density Samsung 8.4V 5200mAh 287g R845  +3 year  Full. Over current, high low cut off.  4h37  5297mAh
 Super High Capacity Panasonic 6800mAh 289g R1350 +3 years  Full. Over current, high low cut off. 9h24 10785mAh

* Capacity was calculated based on runtimes and is estimations, not actual. The runtime is determined by the built-in protection of the battery and the lower limit set on the timer. Therefore the calculated capacity should just be used as an indication.

**These batteries did not have a low voltage cut-off protection. The light was capable of running for much longer due to this, but the output of the light dropped to below the preset Lux level and the timing stopped. It is detrimental to run Li-ion batteries below 30% of their capacity. The protection circuitry should prevent this.

 Summery

The results clearly show  that not all Li-ion batteries are equal. But due to the false advertisement, it will be very hard to choose. Taking into consideration that the first 5 types all claim the same capacity and waterproofing, but the results prove differently. At the end, it is clear that cost does affect performance. As can be seen with this test a 4.6 times increase in cost results in a 6.6 times increase in performance. That is if you ignore the improved pouch, waterproofing and battery protection circuitry.

The incredible runtime of the Panasonic cells confirmed its fantastic reputation. We found it hard to believe and thus repeated the test 3 times to verify only to confirm its honest performance.

Very alarming was the missing protection circuitry in the cheaper battery packs. This is very dangerous and irresponsible. Li-on batteries are very unstable at high voltage levels. To rely on the charger’s ability to prevent overcharging is very risky. Overcharging Li-ion batteries can explode or spurt out a flame jet. Easily setting alight any flammable material in close proximity. 

How do one know what to look for in a battery pack?

If you are dealing with a reputable dealer it should be easy to compare based on capacity(mAh and Voltage) values. Unfortunately, unethical advertisers easily overstate their specification to make their product more attractive.  This makes it nearly impossible to compare. At the end price and appearance are very good indicators. It is highly unlikely that the supplier will choose to drive up the cost by providing high-quality pouches with waterproofing, without addressing the quality of the batteries to the some extend.

Cycle lights that come standard equipped with Panasonic cells are:
Extreme 1400 1000 lumen for 9h weighing 416g
Extreme 2k 1800 lumen for 4h weighing 399g
Extreme 3K 3000 lumen for 3h weighing 616g