AC to DC house power redundancy options

[justinm001]

One of my goals in this coach is to have a full N+1 redundancy plan for every system. As I'm working on this I'm trying to figure the best way to switch my DC loads from battery to AC power.

I'm not sure what will happen if I turn on an ac to DC adapter (like the meanwell) while I have my 12v battery system connected. I'm assuming since it's just over 12V (adjustable) it wouldn't do anything and just sit there idle unless my 12v loads drop under actual 12v.

For now I'm just going to run my 48v devices off AC but eventually I'd want to do the same with my 48v lithium batteries.

Also my poe switch and my pepwave router have dual power inputs and both support 12 to 56v. If 12v mode either isn't POE but I'm curious on how I can wire this up to use both the 12v system as well as my 48v system.

So in short I'm looking for redundancy so either 12v source can power the devices with some form of auto transfer switch or something. For now I can just use the switches on the power strip but it'll still backfeed to my batteries. I'm thinking I need to use diodes everywhere and just make sure all power flow is one way. I'm surprised there aren't fuse panels and tons of other devices with built in diodes. I did notice that my Prevost electric bay has a ton of diodes so it uses them for everything.

Don't judge my panel it's a work in progress, still waiting on relays and fuses and more wiring

 

[sunshine_eggo]

I find it much easier to simply treat the off-grid source as on-board shore power, i.e., simply insert the off-grid system between the umbilical (umbilical to inverter AC input) and the AC panel leaving the house converter and 12V intact. If shore or off-grid shore sources aren't available, you still have the 12V system in place. The presence of the existing 12V battery also helps compensate for any surge loads that may be challenging for a 48-12V converter.

Yes, 12V power is only about 75% efficient, but direct DC-DC is typically no better than 85-90%.

 

[DIYrich]

I gave up trying to direct power from the 48v battery. AC to backup DC when I work on the battery was hard. I decided to let things run off AC, put them on a UPS, and direct feed 12v to the UPS using a victron orion tr 48/12 connected to the battery.

 

[justinm001]

I find it much easier to simply treat the off-grid source as on-board shore power, i.e., simply insert the off-grid system between the umbilical (umbilical to inverter AC input) and the AC panel leaving the house converter and 12V intact. If shore or off-grid shore sources aren't available, you still have the 12V system in place. The presence of the existing 12V battery also helps compensate for any surge loads that may be challenging for a 48-12V converter.

Yes, 12V power is only about 75% efficient, but direct DC-DC is typically no better than 85-90%.

The problem is I'm trying to get redundancy for my 12v loads so if my 12v system (battery/inverter) isn't available I can use AC to DC 12v converter to power the electronics. I guess I could just as easily use a 12v battery charger on the battery and call it a day but I like the idea of having that side power all 12v loads and still have redundancy for interior/electronic loads.

 

[justinm001]

I gave up trying to direct power from the 48v battery. AC to backup DC when I work on the battery was hard. I decided to let things run off AC, put them on a UPS, and direct feed 12v to the UPS using a victron orion tr 48/12 connected to the battery.

This is my though for my 48v loads. I blew my starlink dish from a 12v to 48v power spike off the alternator so like the idea of just using ac to DC for the 48v stuff. Plus it seems these meanwells are 90% efficiency.

 

[efficientPV]

Not sure what you are asking. Two diodes can isolate each battery and device will draw from highest voltage.

 

[justinm001]

Not sure what you are asking. Two diodes can isolate each battery and device will draw from highest voltage.

So I can have that meanwell 12v which puts out 12.10v on while I have my lithiums running which are 13v+ without diodes or anything and it'll just work? If my batteries are off or go to 0% where they're below 12v what'll happen?

Also whatll happen if I plug the 12v and 48v to my switch and firewall at the same time?