Re: what is the max bus voltage, 300V?

[Victor Tikhonov <vtikhono@lsil.com>]

Lee Hart wrote:

> 
> > I thought that if you doubled the pack voltage, the current would drop
> > by half, assuming the same power level and series string configuration.
> 
> It does. But the resistance quadruples, putting you back where you
> started.
> 
> > If the current per battery is the same, won't the high voltage string
> > be putting out much more power than the lower voltage string, so how
> > can you compare? That's like saying that the Optima YT 12V stores
> > about the same energy as the 6V, both having ~50Ah.
> 
> You forgot that when you double the voltage, you have to cut the amphour
> capacity of each battery in half; otherwise the pack doubles in size,
> weight, cost, etc.

Lee, in [electrical] theory you are of course right.

There are practical advantage of working with smaller wire - more
flexible and convenient to route. Who cares if you use twice as many
pieces.

Battery terminals are not that stresses because of no force from
inflexible thick cables if only short piece needed to connect
adjacent batteries. Less chance to unseal sealed battery and get
leaks from flooded one.

Screws are (can be) smaller torques are smaller, less stress on
metal. Twice as many is OK, at least bolt heads won't break off
and the bolts bend. Lead doesn't flow as quickly since not squeezed
as hard (for single string).

More forgiving. Once in a while I hear about molten posts because of 
poor contacts. In ACRX I put one of clamps on Optima by hand and
forgot to tighten at all. Drove like this for about 2 month.
No problem. I cruise at 17A (35 mph) or 40A (65 mph)

Try it with the system which draws 300A routinely.

Victor