L-kougen is a Chiba Japan based company with solutions for both indoor and outdoor lighting. Although L-Kougen makes everything from desk lights to street lights, the products that continually prove to be popular overseas is our line of solar light. So we decided to make English version solar light products information.

Solar street light
《 Middle capa series 》

BT/WT type

BT is installed on existing pole and WT is fixed on wall of existing facilities. Shipping cost is saved.


Popular type for road side light with pole and anchor complete set.

1) Competitive price

Although we purchase battery cells, we do make them battery package by ourselves with our original BMS(battery management system). So compared to the price of using complete built up battery pack, most expensive parts cost is reduced by 50% more.

Cell tap welding

Assembled our original battery pack designed for solar light purpose

2) Long products life of 15years

The battery cells has long cycle life of 10,000 times charge/discharge till down to 70% capacity, which is equivalent to 27 years as the solar street light use. In fact, our first our middle cap installed in Miyazaki Japan in 2008 has been still lighting with keeping original illuminance without replacement by new battery.

Cycle Life

Cycle Life is dependent upon charge and discharge rates, operating temperature, calendar time and state of charge swing or delta SOC.Figure 10 projects cycle life expectations as a function of delta SOC where reducing delta SOC results in greatly enhanced cycle life.

Cycle Life

ANR26650M1B Cycle Life at Various Temperatures

ANR26650M1B Cycle Life at Various Temperatures

Our solar lights have been used at night temperature 20℃ average at DOD rate from 40% to 70% typical (circle in red in the above data). Considering of the above data and our experience, we so far give maxium 10years warranty.

3) The Weather synchronization system

For any solar light, it is necessary to have a countermeasure for less sunshine weather. Many companies tend to use a large battery to address this problem. This way, on a good day they may charge 7 days' worth of electricity, for example, to compensate for days with bad weather. Certainly this way can be one solution for countermeasure for unstable weather, but necessary big capacity battery raise up cost of the products.

On the other hand, our Weather Synchronization System is the control system we use to accurately measure the charge accumulated over the day and adjust the brightness of the LED lights at night. On the days that the battery reaches a full charge, the light will shine at its rated brightness. However, for example, if the battery only charges up to 60% due to continuous inclement weather, the lights will shine at 60% of their rated brightness during the night. By doing this, we are able to minimize the size of the battery.

There is only one downsides to the Weather Synchronization System is that the brightness of the LED lights decrease on days with continuous bad weather. It goes without saying that some customers do not mind this tradeoff, as long as the light does not turn off during the night. Because people, unlike luminometers, will adjust their pupils to take in more light in dim environments. However, for those who think this is still a problem, we perform the necessary adjustments.

Adjustment for the area where weather condition is not good.

We do simulation how often diming brightness days happen based on the average amount of solar radiation data of the area. The bellow are examples, one is Miyazaki city where enough sunlight is available through the year, and Akita city where in winter most of the days are snowy and less sunshine.

Weather synchronization simulation result Year 2020 Apr to 2021 Mar Place:Miyazaki city Solar 50W / Battely 264Wh

[ Miyazaki city simulation result ]
Lighting at 100% rated brightness through the year. No need to add any items. It rather may be reduced power of solar and/or battery capcity.

Weather synchronization simulation result Year 2020 Apr to 2021 Mar Place:Akita city Solar 50W / Battely 264Wh

[ Akita city simulation result ]
Light below the rated days are appeared often for the period of November to February, Then we do following adjustments. Increase solar ppower to 100W from 50W and battery capacity to 528Wh from 264Wh.

Weather synchronization simulation result Year 2020 Apr to 2021 Mar Place:Akita city Solar 100W / Battely 528Wh

[ Akita city simulation result after adjustment ]
The days lighitng less than 50% of the rated brightness is dissapared. Weather synchronization system make it possible to optimize solar and battery use. We do this adjustemnt one by one depending on the each place.

Middle capa in Afghanistan

Installation at off grid area in Bhutan

Training in Bhutan

Middle capa gose anywhere on earth to birng solar light.  CONTACT