Stuart Lennox – CTO

At SimpliPhi Power, we know that our innovative energy storage technologies sometimes leave people wondering, “How do they achieve such performance results?” So we sat down with our Founder and CTO, Stuart Lennox, for some insights into how he built such an impressive energy storage solution.

1. Why did you stop using cobalt and switch to LFP in your battery chemistry?

When we started the company in 2002, there was only one lithium-ion (LI) chemistry, Lithium Cobalt Oxide (LiCO). Its cycle life was limited to only three to five years for 600 cycles in some cases. Additionally, it was developing a reputation for bursting into flames if misused, known in the industry as ‘thermal runaway’. This is why today you now see so many different LI chemistries that contain cobalt. Each iteration is an attempt to mitigate the performance dangers of the cobalt itself.

Even though we were not experiencing thermal runaway with our products, customers were becoming skeptical about LiCO technology and resisted using it due to safety concerns. Because we were always looking for state-of-the-art battery cells, by 2008 we had begun developing prototypes with the first Lithium Ferrous Phosphate (LFP) chemistry that were coming into the market. Also known as Lithium Iron Phosphate, this iteration eliminated the risks of thermal runaway, as it could provide large amounts of power at low temperatures. With our proprietary combination of LFP cell selection, battery management system (BMS), and battery architecture, our plug-and-play power packs and larger energy storage systems were able to outperform our competitors’ lithium-ion cobalt-based batteries. This was achieved in multiple ways, such as: eliminating expensive and bulky cooling and ventilation to prevent heat build-up, operating at an unparalleled 98 percent efficiency for more than 5,000 cycles, up to 100 percent depth of discharge, and the ability to cycle daily for 10 years. With LFP, we were able to design a more robust, safe, and efficient delivery of energy storage.

2. You mentioned SimpliPhi’s Power Technology reaching an unparalleled 98 percent efficiency without showing a heat signature. What is it about the way you designed the batteries that allows this to be possible?

Most people think cell chemistry is all that matters. It’s actually only one component in a larger puzzle of how you enable or impede the flow of electrons through the whole system; we call this the efficiency of the battery. You can think of electrical impedance like turbulence during airline travel. The rougher the air a plane has to fly through, the more fuel that plane will have to use to keep it at the proper altitude. The smoother the air, the more efficiently the plane will fly.

The electrical impedance of any energy storage battery is affected greatly by the methods of construction, circuits, and other electronic characteristics. Utilizing the principles discovered by electromagnetic studies at our nation’s top universities, our engineering team designed and redesigned the SimpliPhi battery architecture and electronic circuitry to bring impedance to a minimum and eliminate the production of heat.

3. Some people think if they can get 5,000 cycles out of a battery, they cannot also discharge it fully and vice versa. How do you explain how the SimpliPhi technology can indeed be fully discharged and also offer a very long cycle life?

Operating our batteries within their recommended parameters and voltage ranges, while easily being controlled by our BMS and the settings of system components, will extend the cycle life beyond the intrinsic cycles of the chemistry itself. Combined with our proprietary methods of assembly, we optimize the LFP lifetime.

Battery cells we use have been tested under certain conditions and have shown consistent results, both real-time and in the laboratory. Since we use a particular cell types and know that our battery architecture is better than most other systems, we are confident in their long cycle life.

The concept of full discharge damaging the battery comes from lead acid chemistries, where you can ruin the battery in a short period of time when you fully discharge them. If you want to discharge a SimpliPhi battery to 100 percent, it will not necessarily affect our batteries. What may have an effect on them is if you discharge them to zero and then attempt to charge them to 100 percent very quickly, while at high temperatures.

We do have recommendations in place for our customers to only discharge batteries to a certain voltage range, around 94%. These parameters are in place because we don’t want our customers to harm their ancillary devices that work with them, such as inverters. If you operate our batteries at 94% depth of discharge you will avoid this risk. That level is where inverters, chargers and other devices, which normally rely on battery current to operate would automatically shut down. If you are running off your battery and you discharge it all the way to zero, the current will run out and those devices will automatically shut down.