Remote control of battery switch

[Manfred Amoureux]

After some discussions with Roy and Craig, I am investigating the possibility of using a relay to command the DC switch of the battery, in order to :

• give the possibility to Utah to switch off the system from ground level (without climbing on top of the bathroom)
• keep the length of cable between the battery and the inverter as short as possible (to avoid resistive losses).

I am summarizing here what I found so far.

Specifications :

• in case of interrupted power (i.e. cable disconnected), the relay must be open, not close to avoid accidents
• the relay must work at shorter voltages than the load disconnect voltage of the inverter
• it must operate at low dc voltage 
• the inner power consumption of the relay must be low (< 5W) and it must withstand currents over 70A (the rating of the DC fuse)

Using standard abreviations, that would be : NO / Form A (Normaly Open), SPST (Single Pole SIngle Throw).

From my Wikipedia readings, it seems we should look for a Contactor relay ( http://en.wikipedia.org/wiki/Contactor ). Eventualy a solid state relay as well ( http://en.wikipedia.org/wiki/Solid_state_relay ).

Again, there should be some automobile components that match our needs. The point is which ones and where ?

A first gave me some examples :

•  http://www.aecsensors.com/html/automotive_relays.html   see the DG85 (rated 100A, 6 /12 / 24 Vdc )
• Or searching here , I found also several models complying with these specifications.  One example.

The prices seem very reasonable (under 10€).

Roy, we'll have to see if the shop close to the ISET in Kassel sells that.

Manfred.