Transfer Switch/Battery Charger Question

[Secular_Sam]

I am looking to be able to power my 6 LiFePo4 battery bank (6 Dakota Lithium 12v 100Ah) with shore power until my wife and I decide what solar setup we want to go with. I would also like to be able to power my sisters RV if she ever comes over. I have been going off of this chart below and these are the amazon items I have found that I am looking to potentially purchase.



Trek Power 30A for our Skoolie shore power


Go Power! TS-30 30 Amp Transfer Switch


Leisure Cords 25' Cord with Male Standard Adapter


Renogy 12v 40A On Board Battery Charger


Would all this work together/work for my sisters RV that requires a typical 30amp connection?


If anybody has any experience with these items, sees a conflict I am missing (electricity noob still), or has better suggestions I would love to hear from you!

 

[Rucker]

Looks like you have the DCDC charger in the wrong spot-it would be between your chassis battery/isolator and the battery bank. That charger is for DC only, not AC. I'm guessing that's just an error on the plan.

I have that same DCDC device, btw (though not yet connected). I also have the GoPower autotransfer, works very well.

What is missing is a shore power charger for the LiFePo's. I have a NoCo 20A charger. It has LiFePo mode but occasionally errors out if left on. It works well if I need to top off the batteries but I have it on a switch, not left plugged in all the time.

You would need some charger like that-it would be powered off of shore power but BEFORE the autotransfer (otherwise your inverter will try to run it off the battery to charge itself).

I bet a diagram would help, but here's my setup: shore power -> Autotransfer #1, whose other input is a second shore power receptacle (where the generator plugs in). It outputs to the NoCo battery charger and AC, both things that cannot run off the inverter, and also outputs to Autotransfer #2, whose other input is the inverter. Circuits that can only run on shore power or generator are handled by the first GoPower Autotransfer box, and everything else is powered from the output of the second autotransfer.

 

[flattracker]

I have similarities in my electrical systems in my "new Crown". I use an RV charger good for 65 Amps of charging current, and it has a DC distribution panel in it. The distribution panel has fuses also. This charger will handle the lithium batteries.
The RV charger will work without any switching needed, but I protect it with a circuit breaker in my electrical panel.
I also have 1 Kw of solar panels mounted on the roof.

I have a 50 Amp connection for outside power installed.
I have a 3 kw sine wave inverter in the system.

I use mechanically ganged circuit breakers in a Siemans electrical panel vs. a transfer switch.
Using the mechanically ganged circuit breakers one cannot have two sources of power connected at the same time as the breakers can only be both off or only one side on. It takes a total of 4 dual breakers to do this. I can select either outside power or generator with one pair, or gen/outside or inverter with the second pair. There are circuits that only get power when connected to outside power or generator but they are isolated from the circuits that get powered from the inverter.
I have two electrically isolated bus bar circuit breaker panels in one box. There is a couple ways to do that or just have two panels.


I have a second alternator mounted to the engine of the bus that also supplies power when the bus is running. I have kept the Crown's electrical system separate from the RV electrical systems.
I installed a main DC electrical bus using saved battery cables from a Crown that I parted out years ago (2/00 gauge)


One thing to remember about lithium batteries is that they have different charging requirements than the alternator in your bus is designed for. I would recommend a second alternator designed for charging lithium batteries. I decided against the lithium route for now based on feedback from the forum.


My current systems are automatic for keeping the batteries up. My way is not the only way.

 

[Albatross]

Well, for starters, I would only use 8-gauge wire for any 30A connection. The voltage is irrelevant, it's the current that heats up a wire and is a fire-hazard. Adding length (and thus, resistance [==heat]) to the equation only makes using a larger gauge more paramount.

Using a 30A-15A adapter is, IMHO, asking for trouble, too--especially if you're looking to hook up a high-amp battery charger on top of it all. This is because battery charging is, ultimately, a chemical process, which requires that voltages be supplied at particular constants (Volts/Amps) throughout the different stages of the chemical reaction. Trying to use something like that will eventually cause a breaker to trip, or cause a fire--especially since most 'modern' households only use 14-gauge wire for most 15A receptacles.

Any time I wire something up, I try to use 12-ga for any 15A circuits, 10-ga for anything that's got a 15A/20A receptacle, and 8-ga or 6-ga for anything that's got a 30A.

 

[Rucker]

I remember your setup Flatracker! Agreed, a mechanically controlled set of circuit breakers is possible but even before that I'd recommend a rotary switch-they're pretty cheap, and foolproof.

Regarding DCDC charging from the alternator I like your suggestion of another alternator but I decided to run off the existing alternator and just limit charging to 20A max. I'm expecting to be driving several hours at a time so there's no need for fast charging from the alternator, and bonus, it is not stressed as would be the case with a bigger DCDC charge controller.

 

[Secular_Sam]

So since we aren't looking to charge off the alternator at the moment, I can nix that DCDC charger, get a charger for the Lithium batteries, and an inverter. If I do that, do I still need another transfer switch? Rucker, I guess essentially don't understand the part about the inverter trying to power itself off the battery. Isn't that what it's supposed to do?

 

[Rucker]

If one of the inputs to the autotransfer is the inverter, and if downstream from the autotransfer is a receptacle that the battery charger is plugged into, the battery is powering the charger that is in turn charging the battery.

Perpetual motion machine?

[edit]
So you need to have a separate branch from the shore power to run the battery power-cannot come from the inverter.

The first autotransfer provides that shore power source for the battery charger, only from either the generator receptacle or the shore power receptacle. The second autotransfer takes the input from the first autotransfer (generator or shore power) and the inverter.

With this setup the battery charger is powered only if you have either generator or shore power; and, you still have 120VAC power from your battery, if there's no power coming from the first autotransfer.

Yeah, I know-a picture is worth a thousand words.

https://www.skoolie.net/forums/members/35340-albums2040-picture28230.html