EnerDel Lithium Titanate Batteries

EnerDel has a busy day today – they cut the ribbon on their Indiana battery plant and signed a deal with Fisker Automotive to possibly supply batteries for the Fisker Karma. So what type of batteries does EnerDel have to offer and how do they stack up?

EnerDel offers two types of batteries – Lithium titanate (LTO) and hard carbon (HC). Their HC batteries work better for plug-in hybrids because of the large pulse power needed from fewer cells compared to an EV. The LTO batteries can work for EVs or HEVs, as their lower pulse power is OK when in a parallel hybrid configuration when you have an engine for a lot of power, or in a pure EV where there are many cells to draw the power from (see my battery primer for more details). Unfortunately their specification sheets aren’t nearly as detailed as Altairnano or A123 (my analysis of their spec sheet coming soon).

The hard carbon batteries are available in an 18Wh cell and the LTO battery is available at 12.5Wh. The cells are the same physical size, so you can see that Hard Carbon has a better energy to volume ratio, which might come in handy when building a full EV and you want a more than just a two seater with a huge battery pack behind you. However, 18Wh and 12.5Wh are both comparatively small to the 28Wh and 116Wh cells Altairnano offers. A larger cell size would allow for less packaging, wiring, cooling, etc. if the battery characteristics remain roughly the same.

EnerDel states that both of their batteries are capable of over 1,000 cycles at high temperatures (55°C or 131°F) while losing less than 10% of their original capacity, which would mean that keeping the battery cooler than 55°C would mean an even longer life. Charts from other battery manufacturers have shown that temperature makes a very large difference in capacity life – a battery that has 5,000 cycles at 25°C might only have 2,000 cycles at 55°C.

The first Fisker Karma cars aren’t due until sometime 2010, and even then its not a sure thin EnerDel’s batteries will end up in the Karma. EnerDel already has the contract for the Th!nk City vehicle, a small 100 mile BEV, though Th!nk has been through financial difficulties.