You could add power diodes when connecting the batteries in parallel to prevent cross-charging, but then you get slightly higher loss, however in a pinch it would work. But then who's ever been in a pinch such that they can afford to slap five 9V batteries + 5 diodes on something but not 6xAA's? :D

Hi, I know this is an old question but what did you end up doing in the end? I have exactly the same question as you, similar distances involved and minimum 100kHz clock rate. I'd be interested to know what worked for you, thanks.

Hmmmm, interesting I hadn't seen that before. Are you using the same onStep value for all channels (preferably 0)? Which method are you calling to change the duty? Another thing I noticed was that some channels flicker more than others, presumably because they are off for longer during the cycle reset while others don't seem to flicker much at all. Are you noticing that?

Totally agree about the strobe effect at night, it's immensely distracting for at least some people with high sensitivity to flicker, myself included.

Found some more info and managed to solve my problem by turning off phase balancing. This may have other implications, but for now it suits my purposes. See my new answer below.

@Mangist hmm, thanks for that. I just found this post which seems to suggest that it's actually a flaw in the PCA9685 itself with certain LEDn_ON and LEDn_OFF values leading to missed cycles. Which PCA9685 library did you use? I'm using this one, perhaps there's something that can be tweaked there.

I'm having this exact problem right now, same PWM board but using MOSFETs to drive 3W LEDs. Did you find out what the problem was or come across a solution?

Yeah, I was trying to keep this side simple, but FETs are another option, you're right.

+1 for removing power source ASAP. The longer current is flowing the more damage can occur. I've also used methylated spirits (rubbing alcohol) on some circuits to wash out the corrosive water. It evaporates quickly and leaves little residue. However there are probably other risks to some components, YMMV.