You could try a 1-2 Farad car audio capacitor, basically it's there to try to reduce the voltage sag when a bass note hits etc... would work the same for your application, it would be best to hook it up near the offending device. If there is more than one offender then mount it close to the output of the chennic... this would work well for an always on dc/dc converter, however if the cap was allowed to drain when you turn off the car it would be an insane load on the chennic and probably blow it up. It basically needs a pre-charge sequence just like the controller. Otherwise a small battery, since your a lithium user now, 4 series 10ah headways would be small and provide enough power.
in my upgrade from 96v to 120v I changed from a Curtis 1400 series dc-dc to an inexpensive but higher watt rated one from Chennic. It seems to be working pretty well EXCEPT it seems to not handle in-rush loads very well.
The old Curtis seemed to show no voltage sag when the vacuum pump came on for instance, but the Chennic does.... the headlights dim for a half-second, and the radio power blinks!
I am thinking this evidence of unsteady output voltage is not a good thing for my 12v system components. So, I am wondering what the easiest/cheapest solution is.
Would it work to put a small 12v battery in-line just after the dc-dc before my connection to main 12v system? Basically using the dc-dc as a 'always on' charger and drawing my 12v power from the battery to smooth out the delivery?
If this is the way I need to go, what is the smallest 12v battery that would do the job? A little motorcycle, or toy battery? A little series of rechargable AAA batteries?