12v battery charge socket Yaris mk4

12v socket eBay

12v accessory socket £4.30

Voltmeter eBay

Voltmeter with switch £9.60

Instructions:

Take off the battery cover.  Look on the reverse and drill a hole between the strengthening ribs.  I used a stepped drill.  About 2" along, on the same line, drill another hole.

Insert the voltmeter and tighten the fixing ring, making sure the meter stays aligned (straight).

Push the spade connections onto the back of the voltmeter (red to + and black to -).  Cut off the spades and bare the ends about 1cm of wire. Twist the wire.

Insert the accessory socket and, like the voltmeter, tighten the ring making sure the cover flap is straight, tab pointing down.

On the accessory socket rear, feed the red voltmeter wire through the hole in the positive terminal of the accessory socket.  Bring the wire up over the spade and whilst holding it, push the red wire spade terminal of the accessory socket on the spade, trapping the voltmeter wire, ensuring there are no bare wire showing.

Repeat for the negative, black, wire of the two items.

On the wires for the accessory socket, cut a bit out of the brass ring terminal making it U shaped instead of O

Remove the negative battery terminal.  Keep it out of the way.  Loosen the + battery nut a few turns and insert the red accessory socket terminal behind the washer.  Tighten the nut.  10mm spanner.

Reattach the negative terminal.  Insert the black accessory socket terminal behind the washer.  Tighten the nut.

Press the "on" button on the voltmeter and see the voltage.  Press again, see % charge.  Long press turns it off.

NOTE: Do not shorten wires, leave them long so that if you have to remove the battery cover again, there will be enough slack to allow it to be simply taken off and placed in the footwell.