Given the choice, 1 limited system or 2 systems?

[chrisski]

Could be your Outback Inverter / CHarger has that pre-charge built in. The inverters I use are stand alone inverters and are not multi-function. The 2000 watt inverter I installed had quite the spark when I had no resistor. My 300 watt inverter was not an issue. I’m installing a 3000 watt inverter and that’s what I got that resistor for.

 

[Wellbuilt]

I have a 3600watt unit , where are you seeing the spark ?
If I try to hook my pos lead to the battery’s with the breaker on that is BAD but I’ve never done that with the out back
I can disconnect the negative lead with out the fire works .
I was told the marine type switches in FG s link where not rated for a 48 v system I see 63volts with temp compensation in the winter time.

 

[Wellbuilt]

Doing some reading over at the out back form and it seam that the inverter can draw more power then
the Lith battery BMS will allow it to supply and kills the battery power .
It doesn’t seam Necessary with lead acid batteries?
Still reading

 

[Wellbuilt]

Will it’s using Lith battery with BMS I don’t think you need to pre charge your inverter
every time you turn it on . I don’t get any spark because I have a breaker / switch in line .
I have seen the contacts on one of the switches that will has on his vid burnt up enough that I changed it .
Thoughts ?

 

[chrisski]

Inverters only need to be pre charged when hooked up the first time. Not every time they are turned on and off.

 

[Wellbuilt]

If I have a breaker on the positive going into the inverter I can just keep it off until I get the wires hooked up .
So I have no sparking ?
What I’m wondering is should I be charge ing the inverter when I turn it back on after a few weeks ?
It sounds loud when I turn the breaker on .
I wondered about this but it said nothing in the manual ?

 

[chrisski]

If I have a breaker on the positive going into the inverter I can just keep it off until I get the wires hooked up .
So I have no sparking ?

I don’t know. I have a 250 amp 48 volt battery switch I could turn off, hook everything up, and then turn it on, THere still would be a large innrush of current. I’m sure some sort of arc would occur inside my switch. I don’t know what would happen in the circuit breaker.

I know the resistor idea works because its the resistance that keeps the capacitors inside the inverter from charging up so quick it sparks and spits molten metal, so I’m still goin to fo the switch.

 

[Wellbuilt]

I’m going to have to work some thing out
I’m not sure what ??‍

 

[Rednecktek]

So y'all have me leaning to a single system with a step-down for the 12v. OK. I was thinking about my last power audit and I had another thought. I need 50a of 12v at full load, 300w for lights/tv/fans, 300w for the coffee pot, and I'd like to add in a 12k BTU 120v air conditioner at about 1100w. By my rough math that puts me at 1700w worst case scenario on the AC line, plus my electric fridge that I got after my last power audit and can't find power info on. Now, the odds of needing all that power at the same time are slim to none since I'm not going to be starting up all 3 heaters and firing up the aircon at the same time, but it gives me a power envelope to work with.

Here's a thought that popped in my head, and please poke holes in it:

MPP LV2424 MSD inverter AIO for about $700
Uxcell 24v -> 12v 70a converter for about $80
2x 120Ah deep cycle FLA batteries for about $200
AiLi Shunt for about $50
125a DC Breaker for about $25
12-slot DC Fuse Block for about $20
1200w-ish of panels to the AIO
400w-ish of panels to old MPPT

Not counting wire and the panels I've got in another budget column, that comes out to $1075-ish which is within margin budget.

I can put 6 panels to the SCC in a 3s2p and an additional 2 panels in series to the old MPPT controller I'll be recycling to keep the batteries topped up while the system is disconnected for the 6-8 months at a time I'm overseas.

I'll use the existing 4 batteries I have and get 2 more of the same in a 2s/3p 24v config which should get me about 180Ah of usable power.

I'm thinking the startup procedure would be something like:
Step 1: Hold Precharge button for (X-time)
Step 2: Turn on battery breaker
Step 3: Turn on Big White MPP Box
Step 4: Party

OK Guys, start poking holes! While yes the 48v system would be smaller wires, I only have physical space for 6 batteries so I can have a 60Ah@48v OR 180Ah@24v. Stupid physics! Same with the panels. I might be able to stick another string of panels out there but the open space I have I'm pretty sure limits me to 3 racks total and my old MPPT can't take a 3s panel set without catching on fire.

 

[Wellbuilt]

O boy, adding new battery’s to old is no good
Really any thing but a RV should be 48v system it’s just so much better .
Really ? AC on 6 battery’s is not really enough power for battery power , for a cabin ,house , home battery power
really starts a 200 ah @ 48 volts .
Your math just dosent really work out , thing are way different when you are charging and discharging battery’s
Running loads .
marine / start battery’s are half the battery a golf cart battery is , these are real deep cycle battery’s .
With 6 battery’s you will have a problem with inverter low-voltage shut off because the battery will get suck down at start up .
You could run on solar power after your battery’s are charged but 1600 watts is not going to be enough power to do it .
1600 watts could give you 1300 watts in good sun at noon but the rest of the time you will get less , a lot less .
In my world AC Cancels out heat power use .
Just a thought , I own 3 3000+ sf houses is a very cold area and I heat with wood , I don’t even own a furnace?

 

[Wellbuilt]

24 volt and 48 volt and the solar panel power is the same it dosent really matter .
The thing is voltage is the speed of power and amps is the amount of power .
When you start a AC or heavy load a 48 volt system can deliver power at twice the speed .
Thicker wires helps but it’s just not as good

 

[Red Squirrel]

Yeah I would avoid mixing batteries. Not just because of age but because they are not made equal especially over the years. You can buy the exact same model number a year later, and it will be different than the one you bought before.

What I would personally do with oddball mixed batteries is use them for smaller sub systems throughout the property. They can simply be on a small charger powered by main system. Great for important loads like fridge etc so they get a bit more run time.

 

[Wellbuilt]

Hmmmmm what type of charger are you thinking about ?

 

[Red Squirrel]

Honestly not sure, stuff like that can be kind of hard to find, I would look for just a power supply that has a variable voltage setting that you can set, then set it to whatever float voltage is for the battery. Usually 2.25v per cell. Ideally a power supply that can do current limiting so if the load takes more current than power supply can handle it won't just blow up. Been meaning to learn more about SMPSes so I can design my own stuff like this actually. I want to eventually get into lithium ion but that requires more electronics knowledge for balance charging the cells etc. I kind of have an idea in mind but I want to test it with super capacitors first as the charging profile would probably be similar.

 

[Wellbuilt]

Most power supply’s I’ve seen use a lot of power.
Seams like running the power thru a inverter to charge a small battery bank is not very productive .
Maybe a dc to dc power converter
Or a mppt charge controller hooked up to the 48 volt bank . ??‍

 

[Red Squirrel]

Yeah if you can do a DC DC converter that works better, but may be harder to find unless you design your own. Depends what voltage to what voltage you are trying to get to. A proper power supply should not use THAT much power though. There are some conversion losses going from AC but modern ones are quite efficient, like 90%.

The charge controller idea might work too actually...

 

[Rednecktek]

My thoughts on going to 24v were the physical limitations of only having 6 batteries. I can get more watt-hours out of 6x@24v than I can out of 4x@48v so longer run time. Even at 6 batteries I suspect I'll have one of them hanging over the edge of the shelves a little.

Running the air con would have a sticker saying to have the generator running first to offset the draw.

I'm hoping I can add more panels in later, measuring tape time is required first and taking down some trees I'm sure.

This is only Phase 1, getting the infrastructure in. Phase 2 will be buying some high quality AGM batteries and getting rid of the FLA's. I'm not planning on ever going to Lithium for numerous reasons. Space and budget allowing I'll be adding in more panels in Phase 2 or it'll be part of Phase 3 where I actually install the air con system.

I know the standard argument of "Spend now or spend later" but in my case it works MUCH better to spend later due to time and budget constraints, hence doing everything in phases.

While I would love to spend more money, I also have budget set aside for bulk panel buys, tools, consumables, and an on-demand hot water heater so I can have a warm shower. All the utility power work, the shower revamp, and the solar revamp have to happen in about 5 days also.

Simplicity is rule #1... gotta make it idiot err... Family friendly to use.

 

[Wellbuilt]

It’s your system at the end of the day .
The best way to get a good working system is to go to 48v the only time I would recommend AGM battery’s is for a Mobile installation .
Stick to the rules and flood battery’s work great .
You can put the batterys any where
Reconfigure your shelf so you can get 8 6v
Battery’s there , is my experience that your 6 battery’s won’t start a ac Reliably unless the sun is out.
All the math Dosent matter when you hit the power button and nothing happens .
All I can do is give you my opinion baced on years of experience .

 

[Short_Shot]

Gotta say I hard disagree with 48v just because "its not an RV".

If the max is 2000w 12v is absolutely fine.

Just means a bit extra money in larger wiring, which is negated if your system already handles it. No sense in spending far more.

24v would be viable of course but there's no need for 48v just because you have the opinion that stationary applications should be 48v.

Also you can run a small mini split off 2kw inverter, but it'll be most of the capacity until it brings the temps down and settles at a lower output.

 

[Rednecktek]

Well, it DID start out as a RV, or at least a 1972 travel trailer which is where my 12v infrastructure comes from. The previous property owners drug it up there in 1988 (according to the tabs) and put it on posts & blocks. After that they tore off the tip-out and expanded the main room, added a second bedroom, and built a small utility room in the back. Grand total, less than 380sq ft.

Since I bought the place 4 years ago, I've un-clusterf%#ked the 120v wiring, added in 2 diesel parking heaters, replaced the propane heater that died, replaced the broken fridge with a 120v version, rebuilt the well and water system, new pump house and wiring/plumbing for the 315ft between the cabin and the pump house, rebuilt the outdoor shower, insulated the living room floor, replaced all the lighting with LED, replaced the toilet, cleaned and repaired the stove, replaced both beds, etc.

Considering I only get to be out there for 1 week in early spring and 1 week in late fall, it's been coming along nicely. I have to do everything in stages planning on only having a week to work and about $3000 total budget for everything I want to do, gas, food, etc. each time. 8 months a year (6 on, 2 off) on a ship and a month between the time I get home and the time I have my last paycheck to get parts shipped really slows things down.

This time around I've got a few projects I want to get done (pass my utility power inspection, get a new water heater on the outdoor shower, the entire solar rebuild, etc) during my late fall week which leaves me with my $1,000-ish budget to work with. Since I have limited time, limited budget, and limited space I am looking to utilize them all most efficiently.

I posted this thread hoping to get input on the best bang for the buck system working within my limitations, I can't print and spend money I don't have, I can't make metal frame shelves just magically wider unless I want to give up the hot water heater, I can't put in more panels than I physically have available, I can't give up the 12v system already running critical systems like heat.