AVR-Chat

David VanHorn Wrote
>> >I have put in a "bow thruster", which is a huge 5.0 KW, 12 VDC motor
that
>> >draws about 400 A (which is another story).   This needs to be run from
its
>> >own local 12 V battery (an Optima AGM starting type) because to run it
from
>>
>> Maybe not your best choice of battery.  What's your on time and frequency
>> look like?
>
>12V?  I^2R losses will eat you alive!  48V would be better, but I'll
> assume you're stuck with it.

With a single 12V starter battery, I expect so.  Won't be very good for the
battery either.

Duty cycle and frequency would be interesting to know.  I can think of
approaches that would avoid or at least reduce islands of energy.

Yeah, higher voltages sure would be nice but I made the same assumption as
you.  Changing at this point would probably be a lot of work anyway.

> Turning off this monster will be interesting.

Might not be too bad, I've certainly dealt with higher draws.


>> You've forgotten your local capacitor an/or buffer op-amp.  You could
>> easily run a 10M resistor divider and follow it with a voltage follower
to
>> bring the effective impedance down.
>
>You need to check the opamp's input offset before using such large
>input resistors too.
>The input offset current into 10M could yield a large error.

Good point.

Robert


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