knurf said:
I plugged it in before the original regulator, so that it would receive 12v from the new one (maybe this is a bad idea), this was to avoid having to remove wiring and other inconveniences.
If you mean that it is connected to the one that has a problem, then the results are unpredictable, and causes of whatever behavior you get are unknown.
To troubleshoot things, you ahve to remove each potential cause of a problem, to ensure it's eliminated.
So I'd remove the problematic one, and use *only* the new one, and see what happens.
(in theory, if the new one regulates the power sufficiently that there's no sag on it's output, then the problematic one shouldn't hvave a problem anymore, if it's issue was caused by voltage sag, so your idea *should* have worked...but since we don't relaly know why it didn't work to start with, we also don't know why it did'n't work this way).
Could it be bad/wrong wiring? I just used some scrap I had laying around, now I'm staring to think it was too thin or something. But it only needs to handle 5-10 watts or so.
How thin is is it? Remember--wiring isn't about watts, its' about amps. Since the input of the converter is at a high voltage, the current needed to make those watts is significantly lower than it is at the output, so it shouldn't take much of a wire to handle it.
And there's not a huge amount of voltage sag when I draw 1-2kw from the battery maybe 3 volts, thought any regulator worth its name would handle that..
It should...but they're not all designed the same, and cheap converters may simply pass any differences in voltage thru to the output. So a 3v sag on the input could get translated directly to a similar sag on the output, and that's a major loss at only 12v starting voltage.
Another possibility is a bad ground, and when more battery power is used, the ground is "saturated" (not a proper term, but...) and can't handle the current from the DC-DC at the same time as the increased current under motor load. This would mean no matter which DC-DC you use, you'd get the same result. What happens in this case is that the ground voltage rises with current thru it, relative to the output voltage, and so the output voltage "appears" to drop (causing dimming, etc). Effectively it's teh same thing as having voltage sag, but it's a different cause, so a different fix.
Check what the voltage ouptut of the DC-DC is under motor load and no motor load conditions, measuring across the DC-DC output wires.
Then check votlage from the DC-DC output *ground* wire to the battery negative is under the same conditions.