Connecting an Unregulated Blanket to charge my caravan batteries through the Grey Anderson Plug

Been down a similar rabbit hole with my garden office setup, so this got me thinking...

I've got a Victron 75/15 MPPT handling my panel array, but I started wondering about daisy-chaining charge sources when I occasionally run a secondary battery bank. The whole "what happens when two charge sources meet" question is genuinely murky territory.

For anyone considering running an unregulated panel directly into a caravan battery bank through an Anderson plug — the short answer is don't. Lithium batteries especially will not thank you for it. Without a controller sitting between the source and the battery, you're essentially gambling with your cells every sunny afternoon.

What I'd actually suggest exploring:

• Run a dedicated MPPT on the caravan side rather than trying to share the tow vehicle's controller
• Something like a Renogy Wanderer or a small Victron SmartSolar would sort this cleanly
• The Anderson plug can work brilliantly, but use it to pass regulated DC rather than raw panel output

The trickier question — which I'd love to hear others weigh in on — is what happens when you disconnect the tow vehicle's solar mid-charge and then reconnect the caravan. Does the MPPT on the ute side see a voltage spike from the caravan lithiums backfeeding? I've read conflicting things and my own testing has been inconclusive.

Anyone running a dual-battery setup with a proper DC-DC charger (Victron Orion, Sterling, etc.) between the two banks? That feels like the cleaner solution to me, but curious what others have actually wired up in practice.

@AGM_Geek the title mentions an unregulated blanket through the grey Anderson plug — worth flagging that this is genuinely risky territory.

The grey Anderson (50A) on most static caravans connects directly to the leisure battery bank with no regulation whatsoever. Plug in an unregulated source and you're essentially doing bulk charging with zero voltage ceiling — AGMs especially will gas and cook.

Your Victron 75/15 is the right tool here, but it needs to sit between the blanket/panel and the Anderson, not after it. Run the blanket output → Victron input, Victron output → Anderson. The 75/15 handles absorption and float correctly.

One pedantic but important point: check your blanket's Voc doesn't exceed 75V on a cold morning — the "75" in 75/15 is the absolute PV input limit, not a suggestion.