Silly Question- 12V or 24V system

[theservicegroup777]

Good Morning All,

Let me start of by introducing my self. My name is Tim and run a Alarm and CCTV company in the Midwest. Indiana to be exact. Ive always been into low voltage. Recently have been pondering the Idea of setting up solar for my home.

I have talked myself into going into a 24v system. If anyone has any other opinions feel free to explain.

My question is particular to the power inverter. Is there a 24VDC INPUT to 120VAC power inverter?

If not how to i get my 24V back to 12V?

If so , Am I wrong to think im wasting energy by using a 24V inverter since my AH would be the same as 1 12v battery vs using 12v ah would be double. Either way makes 120VAC i feel like the latter (24V) is wasting AH.

[Robert1234]

Lots of 24v inverters out there. 48v too. Start thinking wattage... volts * amps = watts. Higher voltage is better as it will draw less amps for the same wattage. To quote someone wise on this forum... "12v is for toys" - don't go there.

As you are very new to this stuff, think very VERY hard before trying to do solar "off-grid". It will cost you dearly.... over and over again as you replace batteries. Do your research. It will save you tons of $$$.

[Naptown]

There are many 24v inverters out there.
When comparing power available from batteries don't necessarily look at AH
Instead look at available watt hours.
A 100 AH 48v battery = a 200AH 24v battery = a 400AH 12v battery.

The difference comes in in charging and discharging amps required and used. Sizes of cabling etc

[theservicegroup777]

Makes Perfect Sense! Thanks for both of the above answers I have been researching this for about 6 months pricing everything and obviously came to the conclusion to go completely off grid at once is impo$$ible . We just bought a house that we will probably die in...lol and Were have the Prepper / Independant bug in us. Were dropping in a bunker next spring as well as maintaing and aquaponics system here at our property. I feel that this will benefit is in the long haul. Hey, better put my money toward something worthwhile NOW while I have it...

[thastinger]

If you're just looking for some indepenance from the utility grid and some emergency power just add up the kWh of the things you would want to power. If you had to survive on it, I think you would be surprised about what you can do with 2-4Kwh/day. I converted an 8.8 CuFt chest freezer to funtcion as a fridge, it uses .5Kwh/day etc. There are lots of ways to reach your end goal (say refridgeration was it) without burning the power level of traditional home appliances. If you wanted to be able to run, say a circular saw, you would want to consider that in the design phase, which would mean you would have an oversized inverter but you would want to limit yourself to only using it for very short durations. Your goal is definately obtainable but it does cost a bit of money, I found alot of unexpected expenses while I was building mine. I had not factored in the core charge for my battery bank (had no turn in batteries) and I had not factored in that the racking cost as much as the panels, you could eleminate the majority of the racking cost for a survival type system. Disconnects/fusing etc also added up quick. You could probably do a pretty capable 2+Kwh/day system for around 4-4.5K without the racking. I spent a good portion of mine on the charge controller and inverter, the panels themselves are pretty cheap.

[Guliver]

When comparing power available from batteries don't necessarily look at AH
Instead look at available watt hours.
A 100 AH 48v battery = a 200AH 24v battery = a 400AH 12v battery.

The difference comes in in charging and discharging amps required and used. Sizes of cabling etc

There is an advantage for cabling and lower losses as you say, there really isn't a difference in battery size or price between A 100 AH 48v battery = a 200AH 24v battery = a 400AH 12v battery.

Your 12V battery will consist 8 X 100Ah batteries in series, 400Ah X 12V = 4800 Watt hours.

Your 24V battery will consist 8 X 100Ah batteries in 4 strings of 2 X series with the strings in parallel, 200Ah X 24V = 4800 Watt hours

Your 48V battery will consist 8 X 100Ah batteries in 2 strings of 4 X series with the strings in parallel, 100Ah X 48V = 4800 Watt hours.

Same watt hours and cost in each case.

[SunEagle]

There is an advantage for cabling and lower losses as you say, there really isn't a difference in battery size or price between A 100 AH 48v battery = a 200AH 24v battery = a 400AH 12v battery.

Your 12V battery will consist 8 X 100Ah batteries in series, 400Ah X 12V = 4800 Watt hours.

Your 24V battery will consist 8 X 100Ah batteries in 4 strings of 2 X series with the strings in parallel, 200Ah X 24V = 4800 Watt hours

Your 48V battery will consist 8 X 100Ah batteries in 2 strings of 4 X series with the strings in parallel, 100Ah X 48V = 4800 Watt hours.

Same watt hours and cost in each case.

Better check your math. 8 x 100 Ah batteries in series will get you a 96volt 100Ah system.

Now 4 x 100Ah 12 volt batteries in parallel will get you a 12 volt 400 Ah system or 4800 watt hours.

[theservicegroup777]

There is an advantage for cabling and lower losses as you say, there really isn't a difference in battery size or price between A 100 AH 48v battery = a 200AH 24v battery = a 400AH 12v battery.

Your 12V battery will consist 8 X 100Ah batteries in series, 400Ah X 12V = 4800 Watt hours.

Your 24V battery will consist 8 X 100Ah batteries in 4 strings of 2 X series with the strings in parallel, 200Ah X 24V = 4800 Watt hours

Your 48V battery will consist 8 X 100Ah batteries in 2 strings of 4 X series with the strings in parallel, 100Ah X 48V = 4800 Watt hours.

Same watt hours and cost in each case.

Wouldnt this 48V bank have a 200AH ??

[Guliver]

Better check your math. 8 x 100 Ah batteries in series will get you a 96volt 100Ah system.

Now 4 x 100Ah 12 volt batteries in parallel will get you a 12 volt 400 Ah system or 4800 watt hours.

Sorry Parallel, but you get my drift.

Wouldnt this 48V bank have a 200AH ??

Yes the Ah change the Watt hours do not.

[theservicegroup777]

Sorry Parallel, but you get my drift.



Yes the Ah change the Watt hours do not.

Is it not Watts = Amp X Volts Totaling 9600 WH?

[theservicegroup777]

There is an advantage for cabling and lower losses as you say, there really isn't a difference in battery size or price between A 100 AH 48v battery = a 200AH 24v battery = a 400AH 12v battery.

Your 12V battery will consist 8 X 100Ah batteries in series, 400Ah X 12V = 4800 Watt hours.

Your 24V battery will consist 8 X 100Ah batteries in 4 strings of 2 X series with the strings in parallel, 200Ah X 24V = 4800 Watt hours

Your 48V battery will consist 8 X 100Ah batteries in 2 strings of 4 X series with the strings in parallel, 100Ah X 48V = 4800 Watt hours.

Same watt hours and cost in each case.

IM SOOOOOO CONFUSED. Wouldnt this be 12V at 800ah = 9600 Watt Hours Unless your explanations are showing a 50% state of discharge? If so I missed where you mentioned this. Obviously using 100% of a bank is foolish.. Maybe someone can explain where im calculating wrong

[Naptown]

the part in bold is incorrect it would be 8 batteries in PARALLEL

[SunEagle]

the part in bold is incorrect it would be 8 batteries in PARALLEL

Didn't I bring that up a few posts ago?

And 8 x 100 Ah in parallel would be an 800 Ah 12 volt system = 9600 watts not 4800 watts

[Guliver]

Didn't I bring that up a few posts ago?

And 8 x 100 Ah in parallel would be an 800 Ah 12 volt system = 9600 watts not 4800 watts

Sorry about that not sure Watt I was thinking.

[paulcheung]

Sorry Parallel, but you get my drift.



Yes the Ah change the Watt hours do not.

The Ampere hours is like watt hours. it won't change no matter how you arrange the batteries.