[MechanicalBird]

Hi all,
I am just beginning the install process for our off grid solar system. Looking for any tips or suggestions. At the moment I have:

925w total PV panels
These will be up to 200ft from the battery bank. All wired In series to produce max. 216v @ 5.76 amps. All will be wired through combiner box.

I will use Direct buried #8 cable to the midnite solar 250 charge controller.

I think I will use 24v battery bank of
400ah-800ah. I'm a little confused as to how many batteries my panels can actually charge and maintain.

Also, I am still trying to figure out what to use for protection in between charge controller and batteries and between batteries and inverter.

I want to hook my honda 3000 into the system to charge batteries but am unsure how to wire it in.

Any help will be appreciated. Thanks!

 

[wy_white_wolf]

Ideally batteries should be charged between C/8 and C/12. C = AH capacity. So for a 24V bank they could support between:

975/24*8= 325AH and 975/24*12 = 487AH Bank.

Try to get batteries in the size that will allow wiring in 1 string only.

Have you ran any calculations on how much power you are going to use?

WWW

 

[MechanicalBird]

Thanks for the reply. So it looks like I could have a 400ah bank no problem.

Do you know what kind of fused disconnects I should use between CC and Battery and between Battery and Inverter?

 

[TnAndy]

Do you know what kind of fused disconnects I should use between CC and Battery and between Battery and Inverter?

Kind, or size ?

You ought to have one on the incoming side of the CC...it can be small, as you noted, there is only >6amps to deal with. A pull out, fused, AC disconnect works fine...put a 10-15amp fuse in it.

Between the CC and battery, same thing, maybe a 20amp fuse on that side.

Between the battery and the inverter is going to depend on the size of the inverter.....2500w @24vDC, you'll need in the 150amp range.

Something like this:

http://www.wholesalesolar.com/products.folder/disconnect-folder/MidniteSolar/MNE125-250LT.html

Have you considered a pre-wired power panel, such as the Outback Flex Power 1 ? Everything is packaged in a nice, neat package....all you do is plug in your wire from the combiner box, then attach the wires from the FP1 to the battery bank, and run your AC wires out to whatever AC load center you'll use. Plug and play.

To connect your generator, assuming you're using an inverter/charger, you'd connect the AC output of the generator to the AC side of the inverter, and it will take care of the battery charging.

 

[Jim-mi]

Consider going with a larger battery bank right from the get go.
All too many folks badly underestimate their electrical "needs" . .and end up abusing the battery from over discharging the battery bank.
It is very easy to add PV a year from now, where as adding to the battery bank "a year from now" is NOT a good idea.

SquareD QO breakers are DC rated . . an easy way to go for a disconnect......beware other makers of equipment . . . they are not DC rated.....

 

[MechanicalBird]

What about a Blue Sea DC breaker between the batt bank and inverter?

Looks like they come in different amp ratings.

Also, I have a DC fridge and a couple DC ceiling fans I really want to get sorted out and working first. I can add the inverter later.

What's the easiest way to power DC appliances from my battery bank?

Thanks so much for the help.

 

[Jim-mi]

As said above the size of the inverter dictates the size of breaker you will need.

A DC Converter Battery Equalizer is needed when you want to tap say 12vdc off from a 24vdc battery bank.
Backwoods Solar has a good one for $200 . . it is rated 40 amps.....
A good one like that will last a long time . . . and your battery bank will be much better off.

I have for years been using a Vanner 100 amp converter to power a water pressure pump (25 amps) and a 12vdc fridge (6amps)

 

[MechanicalBird]

Thanks Jim.

I have yet to purchase an inverter but I'm looking at around 2000w with built in charging capability so I can hook my generator to it.

My DC fridge and fans can use 24v so no need to convert right?

I am just confused on how to wire these appliances from the battery bank. Would I need to have a separate DC breaker box?

 

[TnAndy]

I am just confused on how to wire these appliances from the battery bank. Would I need to have a separate DC breaker box?

You should.

As Jim said above, go buy a SQUARE D "QO" series panel ( you can get small ones...12 circuits) at any home improvement store or electrical supply place. They are normally used for AC loads, but are UL approved for DC up to 48v.

You can see mine in the first photo below, the gray panel to the far right that says "24v DC only". My charge controllers run into that panel, on to a breaker that then back feed the bus bars. The bus bars are connected straight to the battery. That way, I have a disconnecting means between the battery and the charge controller....AND....have a 24v panel that I can use for anything 24v.

While on this photo...you can see the disconnect for my CC's...marked "DC feed in from PV panels". I used a double pole disconnect, using one pole (fuse) for my East array, and one for the West array. The negative wires simply on thru that box to the CC's.

In the second photo, you can see the white Xantrex 175amp disconnect that feeds my twin Outback inverters.