Battery bank : lead acid

[Hedges]

My fence-mount array is facing East. Purpose is to make some power during the new peak-rate time of 4:00 to 9:00 PM.
My ground-mount arrays (only one visible) is SW, aimed at 2:00 PM sun.
One array is heavily shaded by a big bush. I plan to reassemble it aimed at morning sun (now that early afternoon isn't worth more than morning anyway.

Did you need year-round power, or is your system grid-tie?
You don't want shade on the panels. Whatever angle, South, SW, straight up, ideally have no obstructions head-on to the panel or 45 degrees off left and right, and better to point up at the sky than tilt steeply South and have it shaded during it's highest producing hours by trees.
But if you need power in the winter, then whatever orientation gets the most winter production.
If watts is watts and doesn't matter what season, then 20 degrees off horizontal, almost straight up, could be good.

 

[cisumma]

Still deciding, I will probably try to follow your design once the panels arrive I will have to go with what works. The angle you are using is probably going to be the most effective now that I think about it.
Thanks, take care.

 

[cisumma]

Have you ever evaluated or come to terms with the east facing PV array.
Because, from 07:00- 10ish I get intense unadulterated sun.
Likewise, the front yard is due West with intense PV potential from 16:00 - 19:30.ish
The south facing array shares a couple of hours of the morning and evening sun and fair to partly cloudy tree line sunshine.
Maybe, I should split the arrays up.

 

[Hedges]

There are areas of my yard with South and West exposure. There is a hill to the East, so sun comes up a bit later.
Some tall trees to the South, and one big bush on the West side.

I originally placed all my panels aimed at 2:00 PM SW, tilted for Spring/Summer/Fall (due to time of use rates.) 3:00 PM would have been centered in Noon-6:00 PM, but less sun late in the day, especially during winter.
Now (17 years later) a small bush blocks two arrays, one even at 2:00 PM. I plan to orient it more SE and less tilted, so it catches more morning and summer overhead sun.

I'm also paralleling strings of multiple orientations onto the same MPPT input. There is a small (2%) expected reduction due to not quite maximum power voltage for the arrays, but it lets me put 50% more panel wattage on the controller (or inverter in my case.)

Look at Insolation websites which consider your latitude (some your actual location, for weather). You can enter orientation and tilt, and it will show power produced per day for each month. Some sites show changes in spectrum as the light comes through the air - longer path in winter and early/late in the day.

If 7:00 to 10:00 AM looks good, what happens from 10:00 to 1:00 PM? 6 hours is 90 degrees rotation. If you aimed at 10:00 AM sun, then at 7:00 AM and 1:00 PM sun will hit panel at 45 degree angle (0.7 times as much area presented to sun.) In Winter, 7:00 AM (standard time) is dark. Maybe aimed 11:00 AM would work better, trying for 8:00 AM to 2:00 PM sun, unless there is shade.

 

[cisumma]

There are areas of my yard with South and West exposure. There is a hill to the East, so sun comes up a bit later.
Some tall trees to the South, and one big bush on the West side.

I originally placed all my panels aimed at 2:00 PM SW, tilted for Spring/Summer/Fall (due to time of use rates.) 3:00 PM would have been centered in Noon-6:00 PM, but less sun late in the day, especially during winter.
Now (17 years later) a small bush blocks two arrays, one even at 2:00 PM. I plan to orient it more SE and less tilted, so it catches more morning and summer overhead sun.

I'm also paralleling strings of multiple orientations onto the same MPPT input. There is a small (2%) expected reduction due to not quite maximum power voltage for the arrays, but it lets me put 50% more panel wattage on the controller (or inverter in my case.)

Look at Insolation websites which consider your latitude (some your actual location, for weather). You can enter orientation and tilt, and it will show power produced per day for each month. Some sites show changes in spectrum as the light comes through the air - longer path in winter and early/late in the day.

If 7:00 to 10:00 AM looks good, what happens from 10:00 to 1:00 PM? 6 hours is 90 degrees rotation. If you aimed at 10:00 AM sun, then at 7:00 AM and 1:00 PM sun will hit panel at 45 degree angle (0.7 times as much area presented to sun.) In Winter, 7:00 AM (standard time) is dark. Maybe aimed 11:00 AM would work better, trying for 8:00 AM to 2:00 PM sun, unless there is shade.

Right on, I will approach the due east and due West witho the next 1kw.
Likewise, I have a old metal fence just as you do and I will accomplish 20° OR 30° ( OR THE SINE of .0.259) I guess that radians or something. I can line them all up along the ground along the old 22' 'metal fence. Line facing due south.
Anywho, I have the gas pipe vice I think in need to get me a 1/2" threader too.
Question, due think my 2kw ov array would like an aluminum service drop?
Does DC like solid aluminum?
Additionally, if the service drop outside is cool; then, since the high voltage and the low amps in the run to the controller (MPPT) is safe; ( disclaimer) due you know some other electrician that would condone the aluminum service drop to extend an additional 50' to the MPPT.
Then, I understand that the MPpT steps on it for the 12v battery bank. Which I think will need to be on a 6' 4 awt with a 50 amp fuse.

 

[cisumma]

Due south:

 

[Hedges]

1/2" pipe - what for?

The larger span arrays I have (4 panels across in landscape orientation) use 2" conduit.
For the fence, I put 1" conduit along the top, also 1" conduit near the top of the concrete retaining wall. That I mounted on U-channel that has anchor bolts into the wall. Fence slopes up and wall doesn't, so longer pieces of channel hold conduit parallel to top of fence. A couple cross members form triangles so uprights don't see as much torsion.

AC or DC doesn't care if wire is stranded or solid. 60 Hz AC barely starts to notice skin depth in the 2/0 to 4/0 range.
All that matters is good electrical contact and insulation resistance to sun & water.
When PG&E replaced an underground transformer, I found a crimp connection they lost. It works with aluminum wire.

If you have some leftover aluminum service drop wire, you'll just need a suitable way to get through the oxide and make good connection. There are some Cu/Al terminals and splices available. But unless you have your 2kW array in parallel, it is going to be low current and you don't need the large gauge of service entrance wire. I use 12 awg copper for my series strings that are 2500W to 3000W, up to 7A. I have use conduit with THHN/THWN wire, junction box connects MC pigtails and panels plug into them.

 

[cisumma]

"1/2" pipe - what for?"
I could thread metal pile together to pin the base down.
Also I can order the 80' of weather resistant wire with a good connector. I was just curious about why aluminum is used in the first place. Cost I guess.
I haven't mentioned anything to the city so i am not sure if they scrutinize over DC circuits.
Thanks,

 

[cisumma]

I have 6 panels on the way and an 100 foot home run of 10 gage wire to an inverter that I will shop for.
Also, I have 13 mc4 connectors.
What does the wiring for one of your arrays look like ?
Will I be able to daisy chain all 6 and 355 watt (48 v , 9 amp output ) and run a homerun to the controller?

 

[Hedges]

All of my inverters are rated for 600V absolute max PV input. They vary in terms of what minimum voltage the MPPT will work at.
My arrays are 24, "12V" panels in series, 12, "24V" panels in series, and 8, "36V" panels in series.
I mix & match multiple strings connected in parallel to any given inverter.
They will never exceed 600Voc at record cold temperature for San Jose. I measure about 480 Voc on a typical day and 380 Vmp with inverters operating.

6 x 48V in series would be 288V. Is 48V Voc, or Vmp?
What is the max PV voltage rating of your controller, and what is the MPPT range?
If the voltages are within range, that daisy chain (series string) will be fine, and wiring can be 12 awg for as long as a 500' run (to stay within 5% loss out of 288V)

10 awg and 100'?
That's only 1 milliohm per foot, so 0.2 ohms round trip, 1.8V drop or 0.6%
You could parallel 3 strings of panels, 6s3p and have 5% drop.

 

[cisumma]

I have some more studying to do. I don't realize if I want parrell and series.or both.
Also, I will have the panels here in a week or so. And I will connect the mc4 connectors to them and connect the mc4 connector to the 80 ' homerun to the battery bank.
Then, I would have to calculate how many 355 watt panels can run 80' on a 10 awt wire And how to physically make the connections.
I would have to start with finding the waterproof way to connect all the panels to one 80' run ; but, the salesman tried to explain that only 3 of the 6 panels could be physically connected together. I dont understand that yet.
I might have to run 2 80' homeruns to the battery bank.
Will 6 panels on one 80' ,10 awt wire be dangerous?

I do not have a Mppt or inverter yet. I imagine I will start with a controller and remain all DC for a minute. ($$$).
Thanks again.

 

[Hedges]

How you connect them depends on the voltage and current your MPPT charge controller wants.

If you're going with these panels: https://diysolarforum.com/threads/battery-bank-lead-acid.20708/page-4

"Open circuit voltage (VOC): 47.8 V" "Max power current: 9.06"

If you connect 6 panels in series, it is almost 300VDC, which would be dangerous if you touched the wires.
If you connect 6 in parallel, it would be 54A. A 10 awg wire is good for 30A. Carrying 54A it would get too hot, well over 100 degrees C.

Consider if you were going to use this charge controller: https://store.santansolar.com/product/epever-8415-80a-mppt-solar-charge-controller/

It says "Rated charge Power: 2000W/24V", which fits your 6 x 355W panels (it is OK for PV wattage to be slightly higher)
"Max. PV open:200V" so you can connect 3 panels in series for about 150Voc
"Rated charge current:80A" which indicates how thick a wire you'll need connected to battery.

If you connect your panels 3s2p, that will be 145Voc, 19A Isc.
To connect two strings in parallel you can use MC4 "Y" adapters: https://store.santansolar.com/product/pigtailadapter/
With just two strings, no need for fuses (if 3 strings in parallel you would need 3 fuses.)

Here are MC cables, available 100' long with cut ends to put in charge controller: https://store.santansolar.com/product/pair-of-pv-cables-with-standard-solar-connectors/

If you use a 24V battery, then one of these charge controllers is sufficient. (for 12V battery, twice the current so need two charge controllers.)
If a 48V battery, then a smaller charge controller will work or you could add more panels to the 80A charge controller.

 

[cisumma]

Great information, thanks

"If you connect your panels 3s2p, that will be 145Voc, 19A Isc. "

Have to figure exactly what( Voc, isc) refer to and how calculate that,


"If you connect your panels 3s2p, that will be 145Voc, 19A Isc.
To connect two strings in parallel you can use MC4 "Y" adapters: " will these need fuses before the controllers?

This seems the way to go.i will run 2 home runs 10awt to a couple of MPPT's and I can calculate the output wire and fuse.

this info should get me started.
Thanks again

 

[Hedges]

"If you connect your panels 3s2p, that will be 145Voc, 19A Isc. "

Have to figure exactly what( Voc, isc) refer to and how calculate that,

If this PV panel: https://store.santansolar.com/product/hansol-355w/ is says:

"
Specifications:

• Rated Power: 355W
• Open circuit voltage (VOC): 47.8 V
• Max power voltage (VMP): 39.2 V
• Short circuit current (ISC): 9.65 A
• Max power current: 9.06

"

(That last one is "IMP")

These are at nominal 25 degrees C. Data sheet should say how much Voc increases as temperature decreases and you take in to consideration your location's record cold temperature. Or just add 20% to the voltage as a decent estimate.

To connect two strings in parallel you can use MC4 "Y" adapters: " will these need fuses before the controllers?

If single string 3s, or two strings in parallel 3s2p, no need for fuses. (only needed if 3 or more strings in parallel)

This seems the way to go.i will run 2 home runs 10awt to a couple of MPPT's and I can calculate the output wire and fuse.

What battery voltage are you going with? The 80A controller I linked, one would be enough for all 6 panels if 24V battery.
Then just one pair of 10 awg (apparently 10 "awt", if it exists, is a different size) would be sufficient.

If 12V battery then you need two charge controllers and each needs a pair of wires for PV. Gets expensive to do low battery voltage.

By the way "Epever" is an economy brand, and some of the models have been causing people headaches. I'm not clear exactly which. There are other brands like Victron and Midnight which are more highly regarded.

 

[cisumma]

Thanks for the info. I was able to catch the order before it shipped. I added 2@ y connectors 3 to one y connections and another 80' of 10awg wire to accomplish a 3s2p.
I like 2 @ mppt's but I have to wait and do some math I can get one mppt for now and get started and then I'll negotiate the next mppt and then get a bad mamerjammer inverter with that 3000 surge voltage hehe ; but , the inverter is not for another 2 months.
Anyway, I have to learn this math and then figure the fuses for the controller.
I have a lot of work to do.
I don't know, right now I have a complete emergency lighting system and the 300 watts of harbor freight are running that and charging ( phone etc) and the battery bank is holding at 11.9v everynight. I think I will keep a 12v system for now and fuse everything for higher amperage. It definitely needs that 1kw a.s.a.p. that should maintain 13 v .and then add the other 1kw to run a 12amp deep freeze and mission accomplished.
Untill the next 2mw goes on the roof.
.personally, bolting 22 ' of panels to the roof just seems like a engineering marvel.
I have look at the hardware for that. I'm afraid it would tare the roof off. But I have enough to work on for now.
Again, the inverter is a couple months away; but, I was liking a couple of the " AIMS. What do you think about that one?

3000 Watt Pure Sine Inverter Charger - ETL Listed Conforms to UL458 / CSA 22.2 Standards

3000 Watt Pure Sine Inverter Charger - ETL Certified Conforms to UL458 Standards

www.aimscorp.net

Thanks again for the help.
Take care.

 

[cisumma]

Pay close attention to the units (V, A, Ah, W, Wh) in my description below.

It isn't volts to worry about, it is Wh. (Watt Hours) Volts alone will not tell anything about how much available power is in the battery.
A watt is volts x amps. A watt hour is watts x hours. A 300 watt panel delivers 300W. If it delivers 300 watts for 2 hours, that is 600Wh. Note that the unit (Wh) follows the math used to derive it. (watts x hours) Batteries are usually rated in Amp hours. Since a watt is volts x amps, to convert Ah to Wh you need to multiply Ah by the volts. So, a 12V battery that is 80Ah is 960Wh. From that, you can estimate how long it will take a 300W panel to charge it, over 3 hours, if there is full sun and the panel is producing 300 watts.

Then you can work the other way for how long the battery will last. If your refrigerator uses 5 amps at 12 V, then you can divide 80Ah by 5A, and get 16 hours.

There are other considerations concerning efficiency and how much capacity in a battery is really usable, but that should cover the math and help you understand the terminology at least.

When calculating wh of battery banks do you use total amp hours or available ah?

 

[cisumma]

How you connect them depends on the voltage and current your MPPT charge controller wants.

If you're going with these panels: https://diysolarforum.com/threads/battery-bank-lead-acid.20708/page-4

"Open circuit voltage (VOC): 47.8 V" "Max power current: 9.06"

If you connect 6 panels in series, it is almost 300VDC, which would be dangerous if you touched the wires.
If you connect 6 in parallel, it would be 54A. A 10 awg wire is good for 30A. Carrying 54A it would get too hot, well over 100 degrees C.

Consider if you were going to use this charge controller: https://store.santansolar.com/product/epever-8415-80a-mppt-solar-charge-controller/

It says "Rated charge Power: 2000W/24V", which fits your 6 x 355W panels (it is OK for PV wattage to be slightly higher)
"Max. PV open:200V" so you can connect 3 panels in series for about 150Voc
"Rated charge current:80A" which indicates how thick a wire you'll need connected to battery.

If you connect your panels 3s2p, that will be 145Voc, 19A Isc.
To connect two strings in parallel you can use MC4 "Y" adapters: https://store.santansolar.com/product/pigtailadapter/
With just two strings, no need for fuses (if 3 strings in parallel you would need 3 fuses.)

Here are MC cables, available 100' long with cut ends to put in charge controller: https://store.santansolar.com/product/pair-of-pv-cables-with-standard-solar-connectors/

If you use a 24V battery, then one of these charge controllers is sufficient. (for 12V battery, twice the current so need two charge controllers.)
If a 48V battery, then a smaller charge controller will work or you could add more panels to the 80A charge controller.

145Voc, 19A Isc. ?
Is there a formula for this 19A calculation?


Further;
"Max. PV open:200V" so you can connect 3 panels in series for about 150Voc
"Rated charge current:80A" which indicates how thick a wire you'll need connected to battery.


If you connect your panels 3s2p, that will be 145Voc, 19A Isc.


When the MPPT Steps 150 VOC down to 12 Voc how do you find the new aperage?
Thanks.


I'll give the specs I was working with:


Specifications: for Hansol 355 watt panels : 6 panels total.



Rated Power: 355W


Open circuit voltage (VOC): 47.8 V


Max power voltage (VMP): 39.2 V


Short circuit current (ISC): 9.65 A


Max power current: 9.06


Maximum system voltage: 1000V UL


Fuse Rating: 15 A


IP68 Junction Box with bypass diodes and industry standard solar connectors


Weight: 49.6 lbs


Dimensions: 78.5×39.37×1.58 inch
-_-_-_-_-_-<--_-_-_--_-_-_-_-_--_-_-_-_-_-_-_-_

expand...

VMAXTANKS AGM high performance batteries. Wide selection of top of the line deep cycle maintenance free batteries.


Vmaxtank lead acid battery bank configuration.
( I am using 3@ marine deep cycle 12v batteries in parallel with the vmax tanks until the battery bank upgrade)


Battery bank consist of deep cycle SEALED lead acid batteries.


12 v battery bank consist of 8 @ 6v
Vmaxtanks 225ah


And an additional 3@ marine deep cycle batteries in parallel. (Temporarily)


Vmax ah
2s4p = 900ah
Marine :135ah, 130ah, 130ah = 395ah


Total: 1295ah. Available: 1295/2= 647.5ah


-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_--_-_-_


I do not have the PV setup yet.
I will have configuration of panels,
Components I have already and I will have to calculate in for 2@ mppt controllers, fuses inverter.
I am totally DC at the moment.


I plan on 2@ 80' homeruns on 10awg wire. Y adapters


I plan on 3s2p for the 355watt panels.

 

[mike95490]

Panels are priced / sold in watts
you take the panel watts and divide by your battery charging voltage, and that yields the amps under lab test conditions. Expect 20-30% less wattage from panels in the field

355w / 14V = 25.3A from a MPPT charge controller
355w / 56V = 6.3A from a MPPT charge controller - lots of room for expansion

 

[Hedges]

"145Voc, 19A Isc. ?
Is there a formula for this 19A calculation?"

Short circuit current (ISC): 9.65 A
2 PV strings in parallel
9.65 x 2 = ~ 19A

"When the MPPT Steps 150 VOC down to 12 Voc how do you find the new aperage?
Thanks."

"Specifications: for Hansol 355 watt panels : 6 panels total."

355W x 6 = 2130W
2130W / 12V = 177.5A (more or less depending on exact battery voltage and exact wattage produce. But limited to whatever charge controller firmware controls its output to.

These show why it is more convenient to use long cheaper smaller gauge wires for PV panels, and short large gauge wires from charge controller to battery, also battery to inverter. Also, charge controller is trying to regulate battery voltage, but the voltage it sees is different from exact battery voltage due to current draw X wire resistance. Voltage drop in wires from PV panels doesn't affect regulation.

With current like 177A, you would use about 2/0 awg cable. Better to have 24V or 48V battery, cutting current in half or quarter.

 

[cisumma]

Right now my concern is to have 2 10awg wires running 50' thru the house .
Personally, I want to build a safe 12v system and spend the money etc. So that everything is fised correctly to always be able to fall back on just plain old 12v DC current.
As I learn and understand the math and the science and real world applications I will then be able to make the jump to 24v and possibly when I gain more knowledge and respect for DC i could find that 48v is the way to go. ( 48 v is lethal)
I am drawing up a schematic of what i have as i go. I want to be certain that 10awg wire is going to handle 3 of those panels.
Anyway, asap i will incorporate the formula you showed me .
Thanks again.