RE: I need help

["Roger Stockton" <rstockton@delta-q.com>]

> -----Original Message-----
> From: owner-ev@listproc.sjsu.edu 
> [mailto:owner-ev@listproc.sjsu.edu] On Behalf Of Jon "Sheer" Pullen
> Sent: November 29, 2001 4:48 PM
> To: ev@listproc.sjsu.edu
> Subject: Re: I need help

[snip]

> High voltage has a few good points
> 
>     1) The interconnects can be thinner, lowering the total 
> weight of the car. [by maybe 50 lbs ;-)]

Although thinner, there will typically be more interconnects in the high
voltage system, so weight savings may not be realised.  Also, suitable
batteries tend to be available in limited sizes (weight/battery), so the
higher voltage pack could end up heavier.

>     2) certain types of power electronics tend to be more 
> efficient at higher voltages.
>     3) a high voltage series string of batteries is likely to 
> give less headaches than a buddy-paired low voltage string. 
> [this is my opinion anyway]

However, it is worth noting that a low-voltage string does not have to
be composed of buddy pairs.

>     4) in my case, my drive gives me a set number of amps no 
> matter what the voltage, so the higher the voltage I use, the 
> more watts I can pump into the load - i.e. the faster the car 
> gets up to speed. If you've driven a 'lead sled', you know 
> that being able to dump watts in the drive to get out of the 
> way of other cars is really nice. ;-)

This tends to be true for DC and AC systems alike; the controllers offer
a set maximum current over some input voltage range - crank up the
voltage for more power.  The traffic I experienced in Lima gives me the
impression that a lead sled is far less of a liability in Peru than in
the US... just make sure you can dump watts to the HORN ;^>

5) Higher voltage systems typically force you to use smaller batteries
to keep the pack weight reasonable, and the smaller batteries tend to be
expensive VRLA types rather than the less expensive, more forgiving
(maintenance wise) flooded lead-acid types available to the low(er)
voltage crowd.  Associated with these batteries are more sophisticated,
more expensive chargers and charging systems.

6) Worse yet, the expensive VRLA lead-acid batteries that the
high-voltage AC systems end up using (e.g. Optima YTs) are the sort that
are well-suited to delivering the high currents required by powerful
lower-voltage DC systems, but available AC controllers tend to have peak
current limits well below the capabilities of these batteries (i.e. you
end up paying for something you can't take advantage of).

Cheers,

Roger.