On 08/10/12 13:09, boat_works wrote:
> I hope there is something more to this than a busbar and battery taps to control voltage. Unless you're talking about a low power installation, the arcing when making and breaking connections would be impressive.
>
> Perhaps you are referring to a system that uses contactors to switch various combinations of batteries in series/parallel.
>
> I expect that you would find that the cost of suitable contactors and the extensive wiring would be a big percentage of just buying a spare controller and mounting it adjacent to the one in normal operation. If the control circuitry harness and high-power cables are adequate length, I can imagine that the spare controller could be operational in in just a few minutes. Stow the tools required near the controller, and you're good to go.
I've got a spare controller (after I blew one up). While not the spare
isn't mounted anywhere, the 'active' controller is held in with 4 bolts
and has 4 power connections and 4 'control' connections. It would take
me about 15 minutes to swap with the tools I always carry anyway. I've
already ensured the spare controller is programmed with the correct
settings so I don't need a laptop if I ever have to do a swap in the field.
While experimenting when setting up originally I tried to power the
motor with just 12 volts (2 batteries in my string of 6v Trojans). Even
under no motor load (prop spinning in air) the resulting arc took a
chunk out of one of my battery terminals.
A 'bus bar' controller, while simple on paper, will probably burn out
contactors if you are not careful, in particular you may find you can't
'throttle back' when the resulting arcs cause the contacts to weld
together. Suitable contactors to cope with the possible arcing will
probably set you back more than a spare solid state controller.
The heritage 'traction' equipment I drive as a hobby (trams/street
cars, 600v DC, 'line breakers' set for 375amps) have all sorts of tricks
in their 'resistance' controllers to minimise/control arcing.
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