I can imagine a relay system with four batteries which could get 12, 24, and 48 volts without necessarily draining any batteries unevenly.
It would be a little cluttered.
1). 4 batteries in parallel for 12 volts.
2). 2 paralleled batts in series with the other 2 paralleled batts for 24 volts.
3). 4 in series for 48 volts.
In all these configurations the batteries ostensibly would drain evenly. After all the relays were purchased and installed and an intuitive control system for the relays was conceived and implemented an electronic controller starts to seem a logical investment. I do, however, see merit in any system on a boat which is non-electronic/
Hans
--- On Wed, 7/8/09, aweekdaysailor <aweekdaysailor@
From: aweekdaysailor <aweekdaysailor@
Subject: [Electric Boats] Re: Relays to replace a controller
To: electricboats@
Date: Wednesday, July 8, 2009, 11:45 PM
resistors = cheap, relays = expensive, controllers = more expensive... (but not by much - used golf cart controllers are cheap and readily available)
Remember that the increase in torque is nearly instantaneous - a large prop on a small boat and something might tear off - though there is probably some way to introduce a capacitor to slow the current rush down.
I've considered it in the context of systems redundency - I have a brushless but could carry a brushed motor and rig such a setup in a pinch.
Controllers eat about an amp, relays probably much less and so I would think the efficiency would actually be higher - except the loss of fine-grained control means you will burn amps when you don't need to (you are more likely to over-throttle than under) - that could amount to a 20% overall loss in range for example. So now you are carrying more batteries than needed - and where is the savings in that?
-Keith
--- In electricboats@ yahoogroups. com, "dennislarson1939" <dennislarson1939@ ...> wrote:
>
> What does the group think about replacing a controller with relays that reduce the voltage from 24 to 12 volts? What is the efficiency loss and what other problems would be expected? And could the same thing be done with a 48 volt system, reducing it to 36, 24 and 12? There must be some reason why older golf carts used resistors to reduce speed rather than reducing the voltage.
> Thank you
>
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