New member from Arizona, needing help with first setup

[SolarRat]

Maybe I'm being naive here, but that's seems like a small draw back for having a considerably larger Amp Hour bank with the same amount of batteries. Is this setup I described uncommon? Or down right unusable?

The lower voltage negates any higher AH numbers as either way would equal the same Kwh, which is all that matters.

With new batteries I don't think you'd have a problem doing it the way you said. It's been done that way for years. But if it were me I'd just run all 8 in series for 48v...I like higher voltage systems more than most here though.

880ah x 12v = 10,560wh
220ah x 48v = 10,560wh

 

[Arizona Off-Grid]

4 6VDC in series = 24VDC, 2 of these 4 battery strings would form 2 24v 220AH banks for a total of 440AH. Being these are lead acid chemistry only 220AH @ 24VDC will be available for use.
Added:
440AH @ 12VDC
With 24 volt batteries the amperage will essentially be ½ of 12 volt batteries.
220AH * 24v = 5280Wh
440AH * 12v = 5280Wh

Following that math, it would then make more sense to do 12v rather than 24v in this scenario. Same WH with more AH.

 

[Arizona Off-Grid]

The lower voltage negates any higher AH numbers as either way would equal the same Kwh, which is all that matters.

With new batteries I don't think you'd have a problem doing it the way you said. It's been done that way for years. But if it were me I'd just run all 8 in series for 48v...I like higher voltage systems more than most here though.

880ah x 12v = 10,560wh
220ah x 48v = 10,560wh

Oh I see, despite the plethora of information. I still struggle to comprehend all of this. I do believe I'm understanding most of it. Sounds like what you'd saying is I should forget about my amp hours. And focus on my watt hours. My demand is a little less that 3,400 watt hours per day.

 

[SolarRat]

Following that math, it would then make more sense to do 12v rather than 24v in this scenario. Same WH with more AH.

AH is irrelevant if they are different voltages. WH is the only thing that matters. Running higher voltages means less amps going through your delicate controllers, inverters and wires, which means longer life, better efficiency and less heat. But I'm not a fan of 24v systems...if you are going to stray from 12v you might as well jump straight to 48v, and I believe that will be the future of RV's and even cars (modern non-ev cars are already switching to 48v because a lot of their electronics require it).

 

[SolarRat]

focus on my watt hours...

Using WH makes it simpler to determine capacity AND loads.

If you have 1000wh available, and your load is 100w, you've got a 10 hr runtime. It doesn't matter if that 100w is DC 12v, 60v or 120v/240v AC.

 

[Supervstech]

Maybe I'm being naive here, but that's seems like a small draw back for having a considerably larger Amp Hour bank with the same amount of batteries. Is this setup I described uncommon? Or down right unusable?

It all depends on the desired voltage.

Ah isnt a capacity, it is a PART of a formula for determining capacity.

880Ah at 12v is EXACTLY the same amount of energy as 440Ah at 24v, or 1760Ah at 6v...

You can often perform more tasks at a higher voltage, due to lower ampdraw, smaller conductor needs, and larger availability of inverters...

 

[Arizona Off-Grid]

AH is irrelevant if they are different voltages. WH is the only thing that matters. Running higher voltages means less amps going through your delicate controllers, inverters and wires, which means longer life, better efficiency and less heat. But I'm not a fan of 24v systems...if you are going to stray from 12v you might as well jump straight to 48v, and I believe that will be the future of RV's and even cars (modern non-ev cars are already switching to 48v because a lot of their electronics require it).

Are you familiar with the 48v MPP all in one units? You connect your battery bank and panels and ta da... Done. That's probably the only 48v system I'd ever touch. But I don't know much about their reliability.

 

[SolarRat]

Are you familiar with the 48v MPP all in one units? You connect your battery bank and panels and ta da... Done. That's probably the only 48v system I'd ever touch. But I don't know much about their reliability.

Lots of people here are using them. I'm not, so I'll let them hopefully chime in. But I have thought about using them for my upcoming boat modifications.

 

[new off grid]

Hello all!! I'm a new member here but I've enjoyed reading a plethora of information posted on this site. So I've decided to join and get involved.
Let's jump right in, shall we!?

I've got a 1990 Coachman Classic 30ft travel trailer.
She's going to become my off-grid baby. I'm going to be living in it full time. My off grid site is at 3,400ft elevation. Annual Temp high is only 95* F, pretty great for western Arizona.

So I've done lots of research and planning. But would really like to run things by the Pros before I get my dollars involved. I've estimated my average use to be about 14Kwh per day right now. I'd like to stay close to that if possible, I'm sure I could simplify and get lower if needed. Here we get 8.5 hours of sunlight according to the Insolation maps. So I've done my math to come up with 7,344 watt hours per day based on the information listed below. And keeping my 14Kwh in mind I've calculated my average consumption to be 2,058w per day. I'll show my math below.

Im planning to use:
(4) 270w 24v panels. They are Talesun TP660p-270
A 60a MPPT controller
Pure sine wave Inverter (Help me here does it need to be over 2000 watt or over 3000 watt?)
Circuit Breaker (how many amps?)
Wire gauges and fuses?

And now onto battery banks... Pros please advise
A. (1) Renogy 12v 200ah Gel
B. (2) Trojans 6v 225ah (wired in series to 12v)
C. Any other recommendations? Not $950 lithiums lol

-Solar Panels information:
Cell type - Poly
Voc = 38.5V
Isc = 9.09A
Vmpp = 31.3V
Impp = 8.63A
So with this information, how should these be wired? Please advise.

Math Corner:
-Consumption
14 kwh per day
8.5 average sunlight hours
{watts = (14 kWh × 1,000) ÷ 8.5 hrs}
=1,647w
x 80% loss for efficiency (inverter loss)
= 2,058w

-Solar array
4 panels. 270w each.
8.5 average sunlight hours
80% loss for efficiency
4 x 270 x 8.5 x 0.8 = 7,344 watt hours per day

If you read all of this I appreciate you!

Hi,
Just finished my 48v Off Grid system, using 48v/200ah Lifepo4 ( 10 Kwh ) battery with full function BMS, good for up to 6000 Cycles @80% SOC, for the price of $2600 USD + $ 800 door to door shipping ( I'm in San jose, CA ) AND a 10 years warranty. It's been running for about 10 days now, super nice so far. You should think about Lithium Battery , more money first but way better on the long run, but not like 10 Grand, or even 5k, just 3k for 10000w, very good deal !!

 

[new off grid]

Some pix, Pls check them out, thanks

 

[SolarRat]

How is this transfer switch working out for you? I've been thinking about getting this...

 

[new off grid]

Works as designed, fast transfer, so far so good.

 

[Arizona Off-Grid]

So I recently purchased some of my equipment. I got a 48v 3000w all in one unit. It has many features built in. I also bought 6 polycrystalline 270w panels. Giving me a 1,620w array (before loss of course) that's about 10kw per day where I'm located. Next I'll be buying 8 of the 220ah 6v batteries. Wired to 48v. So 10,560wh battery bank and 10kw solar array. Thoughts?

 

[Arizona Off-Grid]

Forgot to mention details of the all in one unit.

2019 Beawindhog-mhp split phase compatible charge controller inverter

Max PV array open circuit 145V
Max PV array power 4500W
Operating voltage MPPT range 60-115Vdc
Max solar charge current 80A
Max AC charge current 40A
Max charge current 120A

 

[SolarRat]

So 10,560wh battery bank and 10kw solar array. Thoughts?

All looks good, but i wouldn't charge that size battery bank with more than about 30 amps. Hopefully your CC can be limited?

Edit: Ahh the solar array is only 1620w...so the max it could charge is about 32a...good to go.

 

[Arizona Off-Grid]

All looks good, but i wouldn't charge that size battery bank with more than about 30 amps. Hopefully your CC can be limited?

I'll have to look into this. The system has many settings and can be configured in many ways. What's the best way to calculate what amperage I SHOULD be charging at? Or does an expert here just want to tell me what my number should be? (That would be great! Haha).

 

[SolarRat]

I'll have to look into this. The system has many settings and can be configured in many ways. What's the best way to calculate what amperage I SHOULD be charging at? Or does an expert here just want to tell me what my number should be? (That would be great! Haha).

See my edit above, you should be fine.

Lead acids usually want to be charged somewhere about C/10 to C/7. For a 220ah battery that would be 22-33 amps. But check the specs on those batteries to see if they say much different.

 

[SolarRat]

Copied from another forum for those Duracell batteries from Sams:

"The Sam's East Penn made Duracell GC2 is a Deka GC-10 with a Duracell Sticker. The Sam's EGC2 is a Deka GC-15 with a Duracell Sticker.

The recommendations from East Penn, for that battery, in a cycling / off-grid application are. (Note: floats are higher in off-grid than typical golf cart use).

At 12V:

Max Charge Current = 30% or less of Ah capacity (20 hour)

Absorption Voltage = 14.4V - 14.7V
Absorption End Point = Current change over 1 hour period of less than 0.1A
Max Absorption Time = 12 Hours

Float Voltage = 13.8V - 14.1V
Float End Time = No Limit

Equalization = 15.0V to 15.3V
Equalization End Point = Current change over 1 hour period of less than 0.1A
Max Equalization Time = 12 Hours

Temp Compensation = -.018V for every degree °C rise above 25C

Note:

For dock charging you may want to compensate float down to 13.4V to 13.6V the guidance above is for off-grid or deep cycling applications where the batteries are cycled daily.

Stick to the 14.7V end of the absorption range and the batteries will do much better "


..............................................................................................


So they say the max is 30% which is higher than normal (C/3), and would be a 66a max charge. Not bad. But I'd play it safer if you want to get the most life out of them.

 

[Arizona Off-Grid]

Copied from another forum for those Duracell batteries from Sams:

"The Sam's East Penn made Duracell GC2 is a Deka GC-10 with a Duracell Sticker. The Sam's EGC2 is a Deka GC-15 with a Duracell Sticker.

The recommendations from East Penn, for that battery, in a cycling / off-grid application are. (Note: floats are higher in off-grid than typical golf cart use).

At 12V:

Max Charge Current = 30% or less of Ah capacity (20 hour)

Absorption Voltage = 14.4V - 14.7V
Absorption End Point = Current change over 1 hour period of less than 0.1A
Max Absorption Time = 12 Hours

Float Voltage = 13.8V - 14.1V
Float End Time = No Limit

Equalization = 15.0V to 15.3V
Equalization End Point = Current change over 1 hour period of less than 0.1A
Max Equalization Time = 12 Hours

Temp Compensation = -.018V for every degree °C rise above 25C

Note:

For dock charging you may want to compensate float down to 13.4V to 13.6V the guidance above is for off-grid or deep cycling applications where the batteries are cycled daily.

Stick to the 14.7V end of the absorption range and the batteries will do much better "


..............................................................................................


So they say the max is 30% which is higher than normal (C/3), and would be a 66a max charge. Not bad. But I'd play it safer if you want to get the most life out of them.

Very informative. Thank you!

 

[Arizona Off-Grid]

So I've been off the grid for a week now.
With eight 6v Duracell GC2 batteries wired series to 48v.
Six 270w polycrystalline panels, two parallel sets of 3 in series.
And my 3KW Mppt solar charger/Inverter box

I'm loving it, plenty of power. And the LCD screen has loads of live numbers. I love playing with this thing. Very easy to setup and get going. On average I bring in about 100v and 135w. But the computer changes that depending on load. I've seen 935w come in at around 65v

All n all very happy. Thanks for everyone's part in helping me make Informed decisions.