Put wiring in parallel ? What about solar panels with active electronics (out)

[RJSV]

   I was telling the roommates;   "You've got to use caution if your solar panels have normal active d.c. output (when attempting a parallel hookup).
   Is that correct ?  Raw panels I could see how that would increase the current supplied.  But my (several) little solar trickle automobile battery 'keep alive' top off chargers each have active control electronics, or at least an LED, and so might not operate in expected parallel.
   Maybe that caution would only apply if my solar panels have an active voltage controlling circuit...Now, I'm not sure, if simple parallel of two trickle chargers is safe, and works, to speed up an update of battery charge.   Certainly would be considered a low-power fault in any case, which wouldn't hurt anything ?

Thanks

[NiHaoMike]

If you're using optimizers, check the directions for how they're supposed to be wired. Most are intended to be connected in series. But I suspect what you have are simple PWM controllers and will work fine in parallel.

[RJSV]

   The automobile trickle chargers are intended for placing them, temporarily, on dashboard or whatever, and plug the little panel module into std. cigarette lighter socket.  That way it can trickle charge.
Purchased at popular auto parts retail store, or some big box retailers.
   
   My question would be more straightforward if each of several of those units had a VOLTAGE output regulator. Obviously, in that case the multiple units (when wired in parallel) would fight each other's controlled output, given that the units don't match perfectly.
Thanks

[NiHaoMike]

PWM controllers in parallel work just fine, if one turns off before the others, all you get is a more gradual ramping down in average output current.