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eliminate double inverters
#1
i am starting a diy powerwall and solar setup to run aquarium lighting for growing corals and possibly some other dc powered items.

so far most items that will be powered via powerwall are 19-36v dc range max 5amps. different brands/size equipment using a different voltage, not a range of voltage.

Im trying to figuire out the best method to elimate using 2 inverters. so im not scaling from 48vdc-120vac then from 120vac-24vdc via inline inverter.

current plan for system
solar panels
mppt controller
18650 powerwall @48v (collection phase)
inverter for some 120vac equipment

i know you can use buck converters to step down to specific voltages. not all equipment using same voltage
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#2
(02-23-2019, 10:59 AM)sk8ter20 Wrote: i am starting a diy powerwall and solar setup to run aquarium lighting for growing corals and possibly some other dc powered items.

so far most items that will be powered via powerwall are 19-36v dc range max 5amps. different brands/size equipment using a different voltage, not a range of voltage.

Im trying to figuire out the best method to elimate using 2 inverters. so im not scaling from 48vdc-120vac then from 120vac-24vdc via inline inverter.

current plan for system
solar panels
mppt controller
18650 powerwall @48v (collection phase)
inverter for some 120vac equipment

i know you can use buck converters to step down to specific voltages.  not all equipment using same voltage

You would typically need a suitably rated buck converter for each different voltage you need. 
You might also think about the wiring to each device - ie if all the gear is close together it's less of an issue, but if you have to run new DC cables everywhere vs standard mains cables there's some extra cost & thought needed.
Don't forget to use some fuses/DC breakers!
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#3
i have yet to start wiring the room, so im trying to plan ahead before drywall goes up.

could i wire a circuit just like regular 120vac from battery bank to dc marked outlet boxes. so it would be a 48vdc grid and add bucks where needed?
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#4
If you use buck converters, they should be close to the device in which it's powering. Especially if the voltage is down to 24V. Otherwise, you'll have voltage drop issues. There's no reason to install heavier cable if it's not needed.
There are several buck converters that can handle 5A available on ebay and aliexpress. If you get the open pcb versions, make sure to get the ones with the 2 trim pots as they are usually more robust, less likely to be faked out, and don't cost that different. The other one are the ones with red, yellow, black wires and the whole unit is in an aluminum housing and potted (sealed) which is also good. Some of these go up to like 10A or 20A I believe.
You "can" parallel bucks together, however it's advisable to put diodes on the Pos output sides of each so they don't back feed into each other (this is more of an issue when the load is turned off)

You can wire using standard romex house wire, yes. However, it "must" be marked in the wall that it is not AC. I don't know the actual color coding, but if you spray paint the wire a different color (like blue or green or such), it'll stand out if someone ever goes into the wall again for what ever reason. You wouldn't need to color the whole length of wire, though.

Just remember there will be voltage drop between batteries and outlets. So make sure to run your wire as short as possible, and don't daisy chain like AC wiring would be done.
Example: If wiring a room, it might be better to put a junction box at the first point entering the room and have 1 run to left, and 1 run to the right, instead of running the wire all the way around the room in a circle like AC would be wired up. However, make sure the connections are super secure in this case.

Hopefully someone will know the code sections for this and clear the mud up a bit more.

Also, sk8ter20, where are you located? That will help a lot in what is allowed and not allowed.
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#5
i am located in georgia (USA). we are closing in the garage (250 sq ft).

already have a subpanel installed from main panel for regular wiring needs.

so technically the solar portion and powerwall will be off grid
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#6
Creating a ring circuit can increase the current handling better if it is run from and back to the battery and not created from a Tee point. House wiring in the UK has "ring mains" for the socket circuits which is a ring with sockets connected in and the reasons are to increase the current handlling for a given socket point (twin) and even out the volt drop. Source and end is in the fuse box. As Korishan say, don't tee off a ring.

Having a 48V circuit in wall would then allow any bucks to be connected up... would make it quite a good install. Fuse per buck (input side and output side). Fuse for the ring at the battery.
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#7
I have run over such "direct supply" concepts many times now, some i wanted to do by myself.
In the end in most cases the AC Variant, 2 Inverters, proves to be the most flexible one. Otherwise you have a plethora of Inverters, Wires, wire losses and whatever, which money should have been just invested for more panels and Storage, instead spending it for some equipment.

Just my 2 ct.
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#8
(02-23-2019, 04:33 PM)completelycharged Wrote: Creating a ring circuit can increase the current handling better if it is run from and back to the battery and not created from a Tee point. House wiring in the UK has "ring mains" for the socket circuits which is a ring with sockets connected in and the reasons are to increase the current handlling for a given socket point (twin) and even out the volt drop. Source and end is in the fuse box. As Korishan say, don't tee off a ring.

Having a 48V circuit in wall would then allow any bucks to be connected up... would make it quite a good install. Fuse per buck (input side and output side). Fuse for the ring at the battery.

I guess the UK likes to make giant ac transformers , you can get a current from the ground wire doing that or a adjacent set of wires or even an aluminum chair to ground, DC loads do it also on a surge.
Ring circuits in the US are not to code
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