Hi Ben,
I'm a fan of Thundersky batteries, having had them on my trimaran for a couple of years now, and I'm putting another set into a solar boat right now.
A suitable set of Thundersky (or CALB) cells could be based around the 400ah cell. They 3.2 volts each and you'd need say 24 of them for your target 72 volts. So a much smaller battery farm than the trojans.
24 of these stacked together would be 1560 mm long, 461 mm wide and 285 mm high. And this could be divided into smaller groups of course but that will give you a sense of the space required.
The mass would be, at 13.5kg each cell, a total of 324kg.
Such a string would assume 100% discharge for meeting your needs for range. But these cells can handle deep discharge, and this would naturally reduce their life cycles, but it still seems likely to be much more than lead acid.
There's a nice graph on Jack Rickards Electric Vehicle website evtv.me showing discharge tests on a lithium cells of this type where it was discharged 500 cycles to 100% and at that point the capacity had just declined to the rated capacity. It seems that the cells generally have above the specified capacity. Here's the blog entry http://www.projectooc.com/evtv/index.php?showid=33
Costs of these cells in Australia is around $500 each, and I'd guess its less in the US.
Having said this, there are some caveats about using them. They do require more installation time and mucking about initial balancing and so on. As well you need to consider the options about whether or not to have a battery management system, and if so which one. So they're not a walk in the park.
But compared with flooded lead acid you don't have the 30% losses of putting the power in and getting it back out of the batteries. Which means you get more bang for your buck from he generating sources you plan to have on board.
If you do contemplate using them I recommend you get into comfortable chair and sit back and watch a few of Jack Rickards movies about Electric Vehicle building which has lots about lithium batteries and lots more besides. http://evtv.me
Cheers
Chris
On 24/06/2011, at 8:04 AM, Ben Okopnik wrote:
> On Thu, Jun 23, 2011 at 09:44:41PM -0000, Tom wrote:
>> It's not quite that many batteries, Ben.
>> T-105s are 2225AH at 6V, so you only need 40.
>>
>> Did I just say "only" 40? :)
>
> [grin] A little blasé about those large quantities of lead, are we?
> I'm getting that way myself, actually. :)
>
> I suspect you mean '225AH', but - yeah, it's still pretty much a
> ridiculous number of batteries, so T-105s are not the right answer. I
> guess that would be the other thing to juggle: how to "package" your
> storage so that it's serviceable, etc.
>
>
> Ben
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