Sparrow / NmG
Sparrow >> Modifications >> Other Batteries
The achilles' heel of Sparrow ownership is having to so carefully nurture the batteries. The death of a battery pack can be the most expensive repair a Sparrow or NmG owner will ever face. And we all know that, depending on the vicissitudes of electrochemistry or owner distraction, it might only be months away.
Therefore, the holy grail of Sparrow ownership is the Ideal Battery Pack: one that will carry you 40 miles (or 60, or 100, we all have our magic range number) with ease, one that fully charges in thirty minutes flat, one that won't degrade while you're on sabbatical, never overheats, never becomes unbalanced, never leaves you stranded... and one that our spouses will gladly buy us for Christmas this year, it's so reasonably priced.
Those batteries do not exist. (As soon as they do, we'll link to them here!) While the alt.energy alchemists fuss about creating them, we must make do with what we can find. This will change from time to time, so please check the date on this page to judge its relevance, and update it when you discover more current data. Or a whole new option worth considering.
One option worth watching is lithium iron phosphate, or LiFePO4, batteries. (Richard at RCEV posts occasionally on ev_sparrow about his experiments with LiFe batteries in his Sparrow, pairing them with Optimas, experimenting with charging and battery management.) LiFe batteries are significantly lighter than lead-acid, with higher energy density, and without the lithium-family habit of dangerous overheating. There are three significant drawbacks to using them in a Sparrow, however:
That price includes a "VMS" (Voltage Management System, aka Battery Management System- usually "BMS") with embedded GlobeTRAC microchip-- but at nearly $1400 per battery, it had better come with fancy BMS. And to use the GlobeTRAC function (seems to be a clever way to feed battery info to your home computer wirelessly) you have to buy their bluetooth box and pay them a monthly service fee.