Where to locate battery switch

[Stuft]

HI all,
I'm renovating the electrics in a little folkboat and first on the wishlist is to move the existing on-/off battery switch from a most inconvenient place.

The plan is to put switches, fuses and associated wiring on a hinged panel on the chart table bulkhead. The panel will be directly above (and slightly forward of) the battery compartment, giving runs of less than 1m for major cables.

Next is installing a second, smaller battery for light domestic duty on the odd overnighter. Reading these forums, a voltage regulator and two-battery switch with the options for either, both and none is the go.

But is it wise (electrically) to put a battery switch on the same panel? Should it be mounted elsewhere for some good reason?

Got some other (dumb) questions too, but I think I should get this bit right first..

Thanks
Dave

[seanform]

From my experience i do not like main switches. It is better to unscrew or screw a fly nut. Takes a little more time but gives peace of mind. My switch malfunctioned and the batteries were not charging ...this leads to alternator problems that might also cause a fire.

[Stuft]

Probably not practical for this boat to disconnect the battery, thanks seanform. She needs a small bilge pump on battery all the time. What happened to your setup?

[Landlubber]

Stuft,

BEP (NZ) make excellent battery switches. Get a copy of the BLA catalogue from any chandler in Australia, they are the distributors in AUS.

It is normal to have a battery switch in a panel, and a fuse in the line as close to the battery as possible. On the other hand, you can use the new electric battery switches that are motor driven, see:
http://www.bepmarine.com/

for more details.

[charmc]

A well made battery switch/isolator will last a long time with complete reliability. Don't scrimp on cost; the quality of the switch is inexpensive insurance. Do some reasearch to find the reliable brands available where you are. Landlubber has good advice on location and wiring.

[Stuft]

Guys, thanks for the replies and the links. Your time is much appreciated.

[Tim B]

A decent relay or MOSFET is the other option. You can then run everything in the switch panel with very light cable. MOSFETs are great, as they're solid state and very low resistance when on. You can also get mosfets suitable for handling VERY large currents. They are also pretty cheap. Since they are basically a solid-state switch (with massive impedance) they can be driven from almost anything.

If I were doing it I'd probably switch all the systems with mosfets, then have a cable interface (likely 37-way D connector) to the switch panel. You could then include a parallel port interface to allow for computer-controlled switching.

Cheers,

Tim B.

[Tim B]

I've knocked up a quick circuit diagram, U2 can be either a 7905 or 7912 depending on what voltage you want at the switch panel. U1 is a 7905 to allow you to directly interface TTL circuits (eg Parallel port). Q1 is capable of handling 200A at 40 volts. Obvously the connections to/from it must be capable of handling this as well.

I have only shown one circuit for clarity. The switch board needs a switch wired between pin 1 and 3, and a 5volt LED wired between pins 2 and 4. And similar connections for the other circuits.

On P1, the main power connector, pin 1 is negative, and pin 2 is positive.

Cheers,

Tim B.

[Stuft]

Thanks TimB. Have to take that away and digest it. It is probably more than I need but an interesting way to do it.

How do you go with these components in marine environments?