Better Batteries, Same Price

Lithium-ion made the news when three pioneers of this battery technology were jointly awarded the Nobel Prize. And they deserved it. Without lithium-ion batteries, your smartphone would be the size of a brick, and Teslas would have a range of maybe 50 miles. As compared to older types of batteries such as lead-acid or NiCad chemistries, lithium-ion batteries pack a lot more juice into a smaller package, have a longer life, can accommodate much deeper discharges, and are faster charging.
Seems like something you'd want on your boat. Especially if weight matters. For a given amp-hour capacity, lithium-ions weigh in at less than half the heft of traditional batteries. Heavier batteries aren't a concern on our N series trawlers, as these full-displacement boats run at hull speed whether light on cargo or loaded to the scuppers. But it's a different story on the TT35, where weight reductions can further enhance efficiency in the 9 to 16 mph cruise speeds where these boats shine. And there's more. Because lithium-ion batteries can be drawn down much farther than lead acid varieties, you can get the same number of usable amp-hours from a smaller battery.

Lithium batteries are lighter, last longer
and aren't damaged by deep discharges
After looking over currently available options, we've settled on a battery upgrade for the TT35. The current 600 amp-hour array can be replaced by a single 300 amp-hour lithium-ion battery. Because it can be discharged below 10 percent —as opposed to the recommended 50 percent for lead acids — you end up with about the same 290 usable amp hours as the lead acids. The lithium--on battery pack is much lighter, weighing in at 120 pounds as compared to over 400 for the lead acid pack. This shaves 280 pounds off the dry weight of the boat, and provides a number of additional benefits. The new batteries have about three to four times the life span of lead-acid batteries, accept faster recharge rates, and have the capacity for more rapid discharge, which is important if situations that require a strong current surge. Other noteworthy features include an integrated management system to prevent overcharging, and a 10 percent reserve feature, which protects the final 60 amps from discharge until the reserve is overridden.This feature could be a life saver, providing that final surge of power to get the engines started in a worst-case scenario.
All these advantages do come at a price, and that price is around three times the cost of conventional batteries. But since lithium-ion batteries have a significantly longer service live than other battery technologies, it's not hard to justify the added cost as an up-front investment in long-term benefits.
The lithium-ion battery has been added as an option for TT35 buyers, but since we would like our owners to benefit from this amazing technology, we're footing the bill for the upgrade for our next TT35 buyer. It's a great deal, but the real bonuses are weight savings, significantly greater battery capacity and years of trouble-free operation.