RL-3331 Emergency Light

RL-3331 is a cheap emergency light from a company with a strange web address http://www.yxdz88.com/

It has 30 LEDs although versions with 60 and 90 LEDs with slightly different model numbers exist.

The package lists specifications as:

Name of Product: Emergency Light
Item No.: RL-3331
Recharging Voltage Rate: AC220V-240V
Battery Voltage Rate: DC 4V
Battery Capacity: 1100mAh
Lighting Source: 30 LED
Duration time: >= 5 hours
Standard No: Q/STLM 0016-2011

As usual for cheap items from AliExpress. Not all these specifications are correct.

Some sellers also sell this item as "with lithium battery" and it is not true. Some list this device as 6W and it is also not true. The item has lead acid battery and LED power is much less....

General Construction

The general construction quality is quite high. The case is very tight and difficult to open even after removing the screws. The board inside has good solder joints, although it looks like it was made by hand. Therefore the quality can vary between units. There are not many component and it is a simple 4.82V transformer with a transistor to switch LEDs ON/OFF.

Charging voltage is 4.82V when the switch is at OFF position, it goes down from 4.82V to 4.76V if the control switch is set to Low or High modes.

Battery

Some sellers advertise this product as with lithium rechargeable batteries. However this is not true. It simply has a 2 cell lead-acid battery. Battery dimensions are 35mm 22mm 96mm

The small black cap can be removed to expose the rubber caps (valves) for this type of battery. It use a mat between the plates so no liquid can leak. After years of use, if the battery becomes weak, you may try to add some distilled water. Usually battery loses some liquid slowly in this type of simple construction.

Based on the 1100mAh specification. I first ran a 1A discharge test from full 4.8V voltage to empty 3V voltage

The battery did go from full to empty in about 42 minutes which totaled to 706mAh capacity. It could have given different results with different discharge currents. However it took over 24 hours to charge back 706mAh back into the battery!

After this test, I have tested the high power mode on the lamp. It took about 1h50m until it dipped under 3V

It is quite visible from the drop on the curve to see when battery was totally empty. However I continued this test much longer just to see what will happen. This also shows that clearly the lamp is much less than 6W as the 1A discharge test resulted in average 3.62V which makes a 3.62W usage. But it was much much more lighter load when you compare the graphs.

The voltage becomes more stable after the first drop but this is the deep-discharge territory and probably harm the battery in the long run.  It is not good to use the lamp over 2 hours on high power mode as this will damage the battery.

The charging back to 4.82V took over 55 hours! Yes, the recovery was really really slow.

The discharge of the light with low power mode results in a much more sensible discharge graph and it achieves about 4h30m before dipping under 3V. So the >=5 hour rating is also imaginary.

I ran the test for an extended period of 7 hours. I do need to get it to recharge for 2+ days for the lead acid battery to recover.

Conclusion

RL-3331 is a cheap product with cheap components. It will probably last about 2-3 years before the liquids inside the lead-acid battery vaporize. The seals are not always 100% airtight. Overall, it is a good product when the price is considered.

Once the battery is empty, you can change it with an actual lithium battery using a lithium BMS. With about 4.8V maximum voltage, you should be able to charge a 4.2V lithium battery fully. Perhaps an 18650 battery with 3000mAh can be installed to improve the performace dramatically. However it is sad that the charging back can take several days with such slow speeds.