Mechanics

TOYOTA COROLLA TERMINAL PROBLEM

2009 Toyota Corolla • 11,000 miles

I want to install a solar battery charger in my Corolla but wire it permanently, not through the cigarette lighter socket, which is controlled through the ignition.
Is there a connection point that will go directly to the battery but disconnect when the ignition key turns on?
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Casemaker
November 15, 2012.



Not aware of anything that turns off when the ignition switch is on but you can do what you want by adding a diode in series with the solar cell. That's a one-way valve for electricity that will allow current to flow from the solar cell to the battery any time. You do not have to disconnect the solar cell just because the engine is running but system voltage does go up a little from 12.6 volts to as high as 14.75 volts. If that 14.75 volts is higher than what the solar cell produces, the diode will prevent current from flowing backward through it.

If you really want the solar cell to be disconnected when the ignition switch is on, you can use a relay. When the ignition switch and relay are off, you use the "normally closed" (NC) contact to connect the solar cell to the battery. Turning the ignition switch and relay on makes that contact go "open circuit" which disconnects it. I can draw you a diagram if you want to do it that way. Relays like that are real common and you can find them in lots of cars in the salvage yard. I used a lot of Chrysler relays for my radio display at old car show swap meets. The relay must have 5 terminals. Those are more common than those with only the four terminals that are always needed.


Caradiodoc
Nov 15, 2012.
Thanks for the quick reply. The manufacturer of the solar cell seems to want a mechanical disconnect so that's why I didn't go for the diode.
I was hoping there might be an existing relay on board, with some unused contacts but if not, I will have to get one.


Tiny
Casemaker
Nov 15, 2012.
One way of setting this up is with the installation of an "A" relay. When the relay is not powered, you have continuity and when relay is powered, it turns off the circuit.


KHLow2008
Nov 15, 2012.
That's the fifth terminal on the common five-terminal relays.

I'm very familiar with Chrysler's automatic shutdown (ASD) relay. They have five terminals but only four wires in the socket. When that relay is off, as in the engine is not rotating, the common contact is connected to the unused terminal, and it is connected directly to the battery positive cable. If you have something similar on your car, or a fuel pump relay with a fifth terminal, you might be able to add a terminal and wire to the socket and use that. Otherwise just say the word and I'll draw a picture of how to wire in a separate relay.


Caradiodoc
Nov 16, 2012.
Well, since you offered: I haven't worked on the Corolla before so if you could point out the best fused location to tap into a direct positive connection (other than the battery) where I can connect the relay.


Tiny
Casemaker
Nov 17, 2012.
Sorry for the delay. Just got back from deer hunting for the first time.

This is the very common 1" cube relay used on many Chrysler and Ford vehicles. Terminal 87A is rarely used. In the diagram, the relay is shown in the at-rest, or turned-off position. Terminals 30 and 87 are making contact. 80 goes to the battery positive post, (or to anything in the fuse box that is always live). 87A goes to the positive wire of the solar cell. Current will flow from the solar cell into terminal 87A, to terminal 80, and to the battery positive terminal.

When the ignition switch is turned to the "run" position, the magnetic field from the coil pulls the movable contact from 87A to 87, (shown in red). 87 is what is used normally to turn something on, but in this case, since it's not connected to anything, it is turned off. No current will flow to or from the solar cell.

On many relays the ground and 12 volt feed wires to terminals 85 and 86 can be switched and it will work just fine, but these have a spike suppression diode added across the coil to short out those spikes that occur when the coil current is switched off, just like in an ignition coil. Diodes are one-way valves for electrical current and these are in the circuit backward so they conduct no current. Reversing the two wires will cause unlimited current to flow and the diode will instantly overheat, short, and smoke. The diode will either burn open, at which time the relay will work normally, or it will draw high current and blow the fuse for the circuit feeding the 12 volts to it in the "run" position. You may be able to pop the cover off and see the diode inside, and cut one or both ends of it, or just fetch another relay and wire it correctly. You'll find a half dozen in every car in the salvage yards.

You don't need a socket for this relay. Just use four crimp-on solderless terminals on the end of the wires, or you can just solder the wires to the terminals.


Caradiodoc
Nov 19, 2012.