His eureka moment came the day his laptop got spoilt and after diagnosis by a professional, he was advised to change its battery.
Like clockwork, Waweru's curiosity got the better part of him and he decided to disassemble the battery and study its inner workings. He realised the battery contained lithium-ion cells. "I did some research and found out that if the laptop battery no longer works, it is probably just one cell that has died, and the others are still perfect. Sometimes the cells are in perfect condition, but the charging system has issues," he explained to The Standard.
Waweru then decided to test the cells to determine their state. The test was positive, a sign that they were still usable. He used the cells to power the handwashing device, and they worked. Further, he learnt that the cells could last up to a week before the charge ran out.
The Physics teacher set out to make portable power banks from laptop batteries, which he housed in recycled containers such as UPS (uninterruptible power supply) casings.
"I started by making small power banks, then gradually ventured into larger sizes that could even power computers and TVs. I figured being a physics teacher I could use my knowledge to make these products without any training," says Waweru.
He uses his innovation to light his house and other appliances around the home without needing to rely on electrical power. His power banks also act as backup whenever there is a blackout.
The innovator even recycles laptop screens, which he uses in place of light bulbs. Waweru later bought a motorbike that operated using the conventional lead-acid battery. However, after six months, the battery ceased functioning.
The innovator once again embarked on a quest to find an alternative solution to his problem. "I asked myself, if I was able to make a battery that powered different things, why not try to do it again," he posed.
This time though, he did not do it alone. He sought the counsel of his mentor, Ibrahim Macharia, who he met at a science and innovation exhibition at his alma mater.
"Together we researched the possibility of using lithium-ion cells to move the bike and eventually he was able to produce the first prototype," says Macharia.
Waweru then tested his invention, which, he says, exceeded expectations. The motorbike moved for more than 50km using the power bank.
Macharia now says Waweru's innovation is necessary and an effective means of E-waste management for the sake of cleaner environment.
"What he is doing is the way to go, particularly in this era where current climatic conditions are becoming a nuisance and good waste management is not upheld," says Macharia.
He also feels that the government should be more proactive in its support of innovators to avoid losing brilliant minds to foreign countries.
Besides Waweru's innovation being environment friendly, sustainable and cost effective, it accepts charging by solar power.
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The device also requires only three hours of charging and does not need to charge to full capacity to operate effectively.
Waweru has expanded his innovation beyond his house, venturing into the recycling business. He now heads the Eco-Power Company, which he uses to implement his trials.
The company makes an array of portable power backup devices capable of powering small to large gadgets and appliances such as phones, cameras, lights, music systems and television sets.
His products range from Sh10,000 to Sh25,000.
Waweru advises upcoming innovators to be consistent and persistent. He also believes money should not be the primary motivation for innovation.
"First focus on coming up with something that provides a solution. Once the client is satisfied, the money automatically follows," he advises.