My pickup sits undriven for months at a time. The battery runs down even though I keep it unconnected. I bought a solar battery charger but it doesn’t work, probably because it plugs into the cigarette lighter socket which isn’t connected when the car is off. But even when I turned the ignition switch to a position that powers the cigarette lighter I don’t measure a voltage on the terminals that connect the battery (ground disconnected from the battery), as though there were a diode blocking reverse current. Am I missing something?
I may be misunderstanding you but if the ground is disconnected from the battery, the cigarette lighter won’t have any power regardless of the ignition position. And if that’s the case, you won’t measure voltage anywhere on the vehicle. Are you saying you aren’t measuring voltage on the battery terminals themselves? I think your best bet with the solar charger is to put some clips on instead of the cig lighter adapter and connect it directly to the battery. You may have to extend the wires a bit, then just sit the panel on the windshield on top of the wipers or something.
If you want to see whether there is voltage coming from the charger, you will need to disconnect the positive terminal from the battery, and clip one lead of your multimeter to the battery and the other lead to the cable, so the current flows through the positive cable and into the battery through the meter. Don’t disconnect the ground cable.
I agree that you should probably clip the charger directly to the battery terminals. Turning the key on so that the cig lighter is enabled will turn on other accessories and probably give you a net drain.
Connecting the meter between the cable end and the battery is how you check CURRENT (measured in amps). VOLTAGE doesn’t require this method.
However, I agree with connecting the solar charger directly to the battery and the battery disconnected from the truck. It is the best method to use. T
Quoth rripstop:
‘I may be misunderstanding you but if the ground is
disconnected from the battery, the cigarette lighter won’t have any
power regardless of the ignition position.’
You misunderstand. If the cigarette lighter is connected to
the electrical system then when I apply a voltage to the cigarette
lighter I can measure that voltage on the terminals of the battery. I
want to measure the power from the cigarette lighter at the battery’s
terminals. I disconnect the battery so I don’t have the battery’s
voltage to confuse the issue.
Quoth rripstop:
‘I think your best bet with the solar charger is to put some
clips on instead of the cig lighter adapter and connect it directly to
the battery. You may have to extend the wires a bit, then just sit the
panel on the windshield on top of the wipers or something.’
How would I prevent theft?
Quoth StrongDreamsWaitHere:
'If you want to see whether there is voltage coming from the
charger, you will need to disconnect the positive terminal from the
battery, and clip one lead of your multimeter to the battery and the
other lead to the cable, so the current flows through the positive
cable and into the battery through the meter. Don’t disconnect the
ground cable.’
Why? They should be equivalent, and disconnecting the ground
is safer. I don’t want to measure current, I want to measure voltage.
Quoth StrongDreamsWaitHere:
'Turning the key on so that the cig lighter is enabled will
turn on other accessories and probably give you a net drain.’
I'm not such a fool as to leave my keys in my car, especially
in the ignition. I mentioned that even when I turn the ignition
switch to a position that energizes the cigarette lighter I still
don’t measure the voltage the battery charger generates at the
terminals that connect to the battery. This makes sense only if there
is a diode to prevent current from flowing backwards, a possibility
(people attach all sorts of nonsense to cigarette lighters) the
manufacturer may want to protect against.
Everybody agrees that I should connect directly to the
battery, but this requires getting a new wire through or giving the
charger away to the first dishonest person who happens by. These
things are built to attach to the cigarette lighter: is my situation
odd?
First. Your vehicle dosn’t have a cigarette lighter. Cigarette lighter circuits are hot all the time so they can be used without the ignition switch having to be turned on. What you have is called a power port. A power port is controlled thru the ignition switch So the power port won’t work in this application.
Locate the fuse box in the interior of the vehicle, and with a test light see if there are any empty fuse positions that are hot all the time, or there may be a power tap on the fuse box that’s hot all the time. If you find that, connect the positive output of the solar charger to that connection, and the negative to any good ground in the interior of the vehicle.
Tester
Thanks, Mr Tester. It has one of those heating coils inserted in it that gets hot enough to light a cigarette. The owner’s manual and the shop manual call it a cigarette lighter. It certainly isn’t energized with the ignition off and has a diode that prevents reverse current flow, so it’s worthless for this application. The diode is consistent with the manufacturer being aware that it may be used as a power outlet to protect against reverse voltage.
I already found a wire live without the ignition switch on, attached a cigarette lighter socket I had in my collection of spare stuff, plugged the charger in.