I have been monitoring the battery evolution for the past 25 years including primary (disposable) and secondary (re-chargeable) batteries. At Sea Data we were using primary alkaline and lithium stacks of 100’s of ampere hours; and when we had to drive GOES transmitters we were using NiCd booster batteries which were charged very carefully from the primary batteries. A similar design is currently used by URI for their Inverted Echo Sounder (IES) instrument to avoid the passivation effect of primary lithiums; it involves two Coulomb charge gauges under microprocessor control, consuming under 25uA of operating current.
A specific point of interest has been the price cross-over point of the Lead Acid batteries versus the Lithium Ions. Lead Acid batteries are used in cars, alarm systems, telco backup systems – they are very rugged, easy to use, inexpensive but also very heavy and include environmentally hazardous materials. The Lithium Ion batteries are used in laptops, PDAs, mobile phones and recently in electric cars; they are lightweight, do not include hazardous materials but they are mechanically and electrically delicate.
If you watch the evolution of the lead acid technologies over the past 25 years, nothing has changed much; in contrast, LiIon technologies have evolved at least by a factor of 20 in terms of cost per kWh.
In a recent article from Electronic Design (June 1, 2012) titled “Here Comes Electric Propulsion”, I noticed the following chart indicative of the technological growth of the Li-Ion batteries
Chart of battery improvements (Courtesy of Panasonic). Energy density DOUBLES every 10 years, i.e. 8% increase every year
An excerpt from Ultralife Corp also highlights that Li-Ions have additional advantages:
But with respect to cost, we have the following points:
- The best deal I could get for a 35AH Lead-Acid battery (which we use at netBlazr for our home brewed UPS systems) is $67 (weight is 27lbs!). 35AH at 12V is equivalent to 0.420 kWH; therefore, lead-acid batteries cost about $160/kWH as of mid 2012
- As reported by Bloomberg New Energy Finance, the cost of Li-Ion batteries in 2011 was about $800/kWH, and in Q1 of 2012 decreased to $689/kWH (14% decrease); it is also expected that use of the Si-Alloy anode material will improve the densities by another 18% without significant increase of the cost. It is also reported by Envia that the cost of the battery pack will be reduced to $125/kWh.
Compiling the Discharge Tolerance and the cost estimates two estimates, we can assert that
- the cross-over point for new designs is NOW
- ignoring the Discharge Tolerance, the cost of Li-Ions batteries will be roughly twice than the Lead Acid batteries by the end of 2012 and parity in 2014; by that time, Li-Ions will be 2-4 times BETTER than Lead-Acids in every aspect!
One final point: the evolution of electronics relating to power management (gauges, conditioning, chargers, protection etc) of Li-Ions has been explosive – just take a look at Linear’s Technologies, Maxim’s and Texas Instrument Data Books!