Parasitic draw test for batteries on the truck?

That's a picture of one like I have,Mine is at the house in North Pole,I'm in Houston now.

 

You get what you pay for with meters and Fluke has an excellent reputation for a reason. Buy one if you're a young'n because you will have it for life and can trust the results.

For most low voltage ac/dc something like this is just dandy: Low Priced CSI830 Digital Multimeter

It will be back in stock eventually and sell out again. The cats out of the bag i'm afraid about Circuit Specialists.

I would still advise you to buy a Fluke if you can afford it. I've seen those things dropped, left out in all sorts of elements and downright abused and still remain operational. The mid $300 units will provide you with a wider range for testing microfarads, useful for testing caps and will have a temperature port.

 

this meter is about 15 years old and live in a can coozie
it has had 3 9v batteries and cost about $15
it is nowhere near as precise as a Fluke but is still functional

 

If you google for current draw you will find a picture that shows direction of current with a load.

Dc current on automotive is reverse dc current in the practical world.

You will see arrow goes from negative to positive to load back to negative.

Current starts from mass electrons to lack of electrons. Positive being mass and negative being lack.

By checking only negative. All you're seeing is the return. Positive pulls more. Goes to load. What doesn't get used returns to negative.

So you check Positive first. Negative second. Subtract negative from positive and that's your current draw.

Current flows from mass to lack. Positive meter goes to positive battery. Negative meter goes to positive cable. On the negative side. Positive meter connects to cable and negative meter goes to negative battery. Reversing the connection shows a negative reading on the meter.

The clamp meters have an arrow on the clamp for current direction. Arrow points away from battery on positive. Towards battery on negative. Reversing the arrow will show negative reading.

If you have dirty batteries. Dirt also acts as a conductor. Put one meter on the battery terminal. Negative or positive. Doesn't matter. Run the other meter along the top of battery. You will see voltage reading on the meter. That's the voltage seeping between positive and negative. Dirt shorting the battery.

 

Well of course they will, the parisitic draw is not the problem, the sitting with the load is.

Get a solar charger that you can throw into the windshield when it is parked, or disconnect the batteries altogether.