[Brundah1 (David)]

There is a good reason I prefer 13.8V regulated power supplies over batteries whenever 240VAC is available. UPS is an alternative, but again you are dependent on the small battery being in good condition!

Car batteries and OEM long scope leads invariably result in significant voltage drop at the scope end under load. I pulled my new CPC8 long lead (10M) apart and found the + line hanging by 2 strands at the dob of solder - it struggled to get to 10V under load!

I prefer to make my own leads using 3mm twin auto wire, Hela 4914 plugs and 4916 sockets at the PSU or battery end. Make sure you use the correct sized center contact connectors at the scope end - I have seen numerous 2.1mm center contacts - when some scopes require 1.8mm - check your scope specs! An in-line fuse should also be used.

My leads even at 10M vastly reduce voltage drop at the scope under load when a battery source is used, but you are still dependent on the health of your battery and its capacity limits.

BTW Jcar Merit plugs are cheaper than Hela 4914 and are similar quality, Jcar Merit sockets are not Hela quality!

Most 4WDers use Hela plug / sockets for their car fridge, or the small Anderson polarised plugs for higher current load. Hela and Anderson plugs available from Ashdowns and caravan suppliers.

Cigarette plugs just cannot be trusted to maintain good contact.

I now use Manson SPA-8230 13.8V 23A regulated & O/V protected power supplies available from Andrews (were $79 now $99). I discussed these at length with Lee before buying them, he sells lots to hamers, with great reliability reports - few returns. Output from this PSU at 12A is rock solid, no off-on over swing. Should be all Astrophotography rigs require.

No commercial interest yada yada.