Parallel Amps Question

I deleted my earlier post as I have not been able to repeat the results, which I now doubt. I do not know what is going on.

I am back after evening out the wiring after the Y split, to getting fractions of an amp on the controller I put the ammeter on, whether the pos or neg wire to the battery or on which controller.

I think maybe what is happening is that with the 10a mulitmeter on as part the path on one side, this sends almost all the amps along the other controller's fatter wires (than the meter's) since it now has the better path. No clue, of course :(

This could show why you might need a clamp- on ammeter to measure the amps on each side of a Y, so it does not disturb the thing being measured.

( I do remember in science class that in Lab, they said you can't measure anything without changing it so your measurement was dubious. Something about Empirical something or other, IIRC. This was in 1960, so sorry I can't remember it better! :)

Anyway, never mind my earlier report---all is in doubt, and I have no measurement of how many amps go on each side of the Y. All I know is the overall result is working great, and I have not fried any of the two 20a controllers.

Hello all. If I remember my electronics 101 that would be Kirchoff's current Law even if there is some relationship to Ohms law involved.
Happy camping nm1oqrz

smkettner wrote:
Ohm's law will divide the amps.

I'm not quite sure of your installation, but if you are using two controllers in parallel, the currents could differ more because of subtle differences in the thresholds of the controller operation. The wiring resistance if different would make a variation, but might not show up because of controller variations.

As you said, like in horse shoes, real close is good.

deleted

The Trimetric will only show what is going into or out of the batteries. The power going directly from the controllers to equipment will not show. What you are seeing makes sense, 1.2 to the batts, ~8 to the other loads. Did you try putting the ammeter on the wire supplying the 12-volt system?

In this situation I do not need to evenly balance resistance to get half each amps. I only need to get the most any one controller does nominally is 16a out of its 20a rating.
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I wish Mr Ohm were here now to help me un-confuse myself taking these readings.

I wanted to wait until total amps fell below 10 so it would be safe to use my 10a accurate ammeter part of the multimeter. I would then check amps on the Trimetric and subtract the amps on one controller and get both controller's amps to the battery.

Wrong! Total amps was down to about 2 by the time I got started, so I turned on some lights and a fan with solar disconnected to get minus 8.1a on the Tri.

Since the batts were taking almost nothing, I figured solar would be under 10 running the loads. Connected up solar , amps jumped to plus 9.7 but quickly tapered to plus 1.1a steady state with loads running.

So I figured solar was doing about 9 amps and half that would be 4.5a
But ammeter on one controller said 0.83a and the other controller was 1.30a. (put ammeter between controller pos and battery) Meanwhile the stupid Trimetric was still showing plus 1.2 with loads on.

Something is goofy including me, but anyway, whatever the reason is for the numbers seen, it seems the split is something like 0.83 on Y(b) vs 1.3 on Y (a) ratio ?

So you would think the higher amps went with the fatter wiring of the Y split. Nope. Y (a) is 12 ft of #6 cu booster cable plus 2 ft of #8 stranded. Y(b) is 14 ft of #2 cu clad al piece of booster cable plus 6" of #8
So that must mean Y (b) has worse connections than Y(a) to have more resistance even though fatter?

The coarse ammeter readings taken earlier showed approx. half each, so this shows at least they split 1/3, 2/3, whatever. Good enough split for me to keep either controller at 16a or below when total is 20. I will try for a better measurement when conditions allow so I don't have to run a load and get so confused :(

smkettner wrote:
Ohm's law will divide the amps.

You forgot to add what could be important: Ohm's law will divide the amps according to the resistance (Impedance actually) in the circuits.

Current (amps) will follow the path of least resistance. If you want to control the flow of current you will need to add balancing resistors to the circuit.

To follow up, mid-day got 20.2a in clear blue, with no 12v loads in the trailer except LP alarm/stereo clock. So the wiring zoo is ok.

Same losses as when I had them in two arrays anyway.

Isc on the 130w is 8.2 and Isc on the 100s is 6.3 so I should see 12.6 plus 8.2 = 20.8 I am losing about half an amp along the way, which is what I have been seeing all summer doing it this way.

Not enough to justify the PITA it would be trying to improve on it.

Good to know BFL. Thanks for the test.