Battery Ponderings
 

Hey all..

I work at an aircraft company, and recently we have done some R&D into using Li-Ion for ships battery, and it has had some really nice results.


I am not an engineer myself, so I do not know any of the specifics of this sort of design, but has anyone heard of using this type of cell to replace the heavy lead acid ones?

The hardest part to come up with might be a charging system. The battery would be pretty expensive initially, and might even have to be built up.. but the weight savings and inherent high energy would be a nice benefit.

I am sure many will chime in behind me, but the Li-Ion batteries I believe are the latest advance in battery technology. So I would think you're heading in the right direction. But as stated I am sure others will be chiming in soon with relevant facts.

Li-ion have several advantages over lead-acid or even NiHM. They are very adaptable to shape and are much lighter. They don't suffer from battery "memory" and have an extremely low self-discharge rate.

Their main disadvantage is they lose capacity based on age, not charging cycles. Li-ion batts lose about 20% charge capacity every year. Exposure to high temperatures shortens the lifespan even further. As they age the internal resistance also rises, reducing the maximum current that can be drawn.

Li-ion chemistry is not as safe as nickel metal hydride or nickel-cadmium, and a Li-ion cell requires several mandatory safety devices to be built in before it can be considered safe for use outside of a laboratory. These are: shut-down separator (for overtemperature), tear-away tab (for internal pressure), vent (pressure relief), and thermal interrupt (overcurrent/overcharging). The devices take away useful space inside the cells, and add an additional layer of unreliability. Typically, their action is to permanently and irreversibly disable the cell.

So, while it seems they would be ideal in an aviation environment, due to reduced weight and space conformity ability, they look like poor long term choices for things like electric cars unless the manufacturers are able to tackle the longevity problem.

Voltphreaks - Home
This is the lightest and most "cutting edge" battery I have come across, but it comes at a pretty heavy premium.

Short of that you might want to look into Braille, who make lighter weight traditional batteries at regular prices.