Battery Forumla?

We'll opinions are like A-Holes, everyone has one and they all stink. But, for your stated use of 140AH/day that means an absolute minimum of 280 AH battery bank and assuming you want to go 2 days without recharging then 560 AHs. The closest to this would be 6, 6volt bank for 675 AHs and your 880 watts solar would recharge that in most cases in 1 day of full sun.

So using your numbers and my assumptions I would go with 6 6volts.

400 to 1600 amp hours, JMHO.
(50% to 200%)

KJINTF,
Thanks for the info,

IIRR, when I started figuring out to go to solar , I figured I had a total useage of about 140a and the average sun time was about 5 hrs, per day during the winter time use, when we use the most power.

I have since changed all inside lights to LED's, so the useage will be less, this year we experienced a low of -(MINUS)22* for a couple weeks and the average temps was 20-30*, cold and clear, 4-6" of snow on the ground.

What I don't know about is this COLD weather info, and how to figure/allow for these spec's etc.

I am NOT worried about the summer time useage as I know I will have more power than I can use, etc.

Tia,
Don

KJINTF wrote:
I do not believe a "correct" or "proper" ratio exists
The amount of battery you need depends on your loads and how quick you want to get it recharged
For me 550watts and two 6Vdc GC batteries works just fine

I do not believe a "correct" or "proper" ratio exists

The amount of battery you need depends on your loads and how quick you want to get it recharged

For me 550watts and two 6Vdc GC batteries works just fine

Thanks for the info, guys.

What I am asking is,
I have 880 watts in panel size,using a MS MPPT-60a CC,
Do I need 2 or 4, or more of GC batteries 220+a types,
to have the correct/proper ration of panels to batteries, for charging the batteries etc.

IIRR, I think,
I was advised to have 1-220w panel per 220a of battery???

Tia,
Don

If you are asking how any amps can you expect from 880 watts of panels, the answer is, it depends.

Battery SOC
Type of Controller (PWM or MPPT)
Line and connection losses
Panel alignment with sun
Ambient temp

Optimal conditions: 60 to 70 amps

P=IxE to solve for current I=P/E So if you know the power in watts and the Voltage you can find "I" the current.

In electronics it is known in transformers that the power in watts in the primary will be the same as the power developed in the secondary even though the voltages are different. It works the same in other places. The power in watts being used in your 12 volt system will equal the power in watts being consumed in the RV. The above formula will allow you to solve for all three if you know two of the three.

If you know the voltage and current being used by your inverter you can find the power in watts your inverter is producing, or if you know the power in watts you can find the current being used. This will match what your 12 volt system is doing by adding up all the appliances using current or power, you can measure the voltage and with the right connections, the current also.

I've seen from 1x to 1.5x your storage capacity.

Of course the right way to do it is figure up your total average daily draw, etc - but generally these 'rules of thumb' are pretty accurate.

I hope Pianotuna chimes in here. Going by my not too reliable memory, I believe the ratio is something like 50 to 160 watts of solar power per 100 AmpHours of battery capacity. I know I'm close, but can't guarantee that I'm dead on.

We're running 420 Watts of panel to 484 AH of battery. We could use another 100 watts or even a bit more.