Going off grid

oil pan 4 · April 2017

If you want a 24v automotive type alternator just buy one. Or see if the 12v alternator you have has a 24v regulator.
Or connect the v-sense wire to one 12v battery to trick the alternator into producing 24v.

wellbuilt · April 2017

I would like to use the alt that I have , it is rated for continuous use charging large marine battery banks.
I will take the alt to the rebuild shop and see what they can do.
Thanks for the reply

wellbuilt · May 2017

Could some one tell me how I would run this panel in a 48 volt battery system into a outback flex max 80 charge controler. Please .

littleharbor2 · May 2017

Into an outback MPPT controller you would need 3 panels series wired for a 48 volt system

wellbuilt · May 2017

So we would be looking at vmpp 36.81 x3 =110 . 43 volts in to a 150 volt max charge controler .
It get cold here may be - 20/-30 would I still be ok with these panels ?

littleharbor2 · May 2017

Actually the maximum voltage rating is taken from the open circuit voltage which is 137.25 at 25 degrees Celsius , Standard test conditions (STC). You need the temp. coefficient numbers for those panels (should be on the data label) to calculate the numbers for your lowest expected temps in your area. Sounds like it will be too high. though. If you had a Midnite solar Classic 150 you have Hyper VOC protection which gives you an additional 48 volts headroom on a 48 volt system. Or a classic 200 would give you plenty of headroom although at a lower maximum charging amperage rating. This Hyper VOC is only there to protect the controller. You will get no charging if your array is producing over 150 volts. I'm not sure but ,at some point I believe you will transition to a charging state which would naturally have lower voltage than open circuit voltage.

mcgivor · May 2017

wellbuilt said:

So we would be looking at vmpp 36.81 x3 =110 . 43 volts in to a 150 volt max charge controler .
It get cold here may be - 20/-30 would I still be ok with these panels ?

Have you considered using the Outback string calculator for their recommendations?
http://www.outbackpower.com/outback-support/string-sizing-tool

wellbuilt · May 2017

No haven't figured out how to work the string calculator yet sorry

wellbuilt · May 2017

2 panels in series at 91.50 volts won't charge a 48 volt bank ?

mcgivor · May 2017

2 in series would probably be the better choice, close to double battery voltage which many claim to be optimum.

littleharbor2 · May 2017

91.5 would be the Voc. Once you put a load on them the voltage will drop to 73.62. Problem that number is at standard test conditions. In the real world you will only see that number when it's cold outside. When it gets hot, or even warm the surface temps of the panels will get considerably warmer than the air temp and the voltage drops. that's where the temp. coefficient comes into play again. keep in mind that equalizing voltage will run up over 60 volts on a 48 volt bank, regular charging voltage will be upwards of 58 volts. This is the reason the 60 cell panels some people think are 24 volt panels wont work for 24 volt battery charging as a single panel. MPPT controllers want to see 150 to 200 % of the battery voltage to work effectively. Feeding an MPPT controller a 48 volt nominal voltage, which is what two panels in series is, will gain you little advantage over a PWM controller, at least when it's warm out. When it's cold you will see some amperage boost. Anyway that's better than cooking your controller by wiring 3 in series.

Raj174 · May 2017

72 cell 36 volt panels 2 in series are not adequate for charging flooded lead acid batteries. Best to use 60 cell 250 to 275 watt panels 3 in series. That's 90 to 95 volts VMP and VOC is not too high. Just last week a friend was using several strings of 4 100 watt panels, string voltage was 75 volts and during 64 volt EQ ( 225AH T-105's) the charge controller was cycling from full wattage to rest every couple of minutes.
The panels could not produce VMP high enough for the MPPT charge controller to maintain the EQ charge voltage.

Rick

wellbuilt · May 2017

Thanks guys , I just found the panels at 100 bucks each new in the box
20 min from my house .
I'll keep looking .
I'm looking for a panel that has a voc of 38-+ to series 3 together to get around 115 volts+- .

littleharbor2 · May 2017

Most 60 cell panels are 30.x VMP and 36.x VOC. Some of the latest 285-300 watt 60 cell panels will be higher.

jonr · May 2017

> MPPT controllers want to see 150 to 200 % of the battery voltage to work effectively.

Specs I've seen are highly variable and depend on the absolute voltage values. Ie check your specific charge controller. Or consider PWM.

littleharbor2 · May 2017

Of course you can push the max voltage envelope and still charge a 12 volt battery bank but you will give up some efficiency in the voltage step down process while creating more heat and likely shortening the life of the controller.

wellbuilt · May 2017

Hi all ,
I'm getting ready to run some wires at my place , and I need to add a grounding rod .
Can I just use 1/2 rebar or dose it need to be a brass rod ?
I've seen it both ways .
I'm on ledge with 6" to 12" of dirt over a granite ledge .
Could I dig a trench say 10' from the back of the garage and lay the rod in the ground?
How about if I drilled a series of holes 30" deep and zigzaged the ground rod between them .
I could of grounded to my footing when we poured the concrete but I did not have the lugs or wire at the time.

BB. · May 2017

You can also use ground plates buried in your shallow soil... These are copper and, I am sure, not cheap:

http://www.tlpinc.com/products/grounding/ground-plates.html

If this is not inspected... I would think about using buried lengths of "L" Blue or "K" Orange lettered copper pipe (red is thinnest, Orange is thick wall copper pipe. "M" is read letter and the lightest grade for interior of home copper piping). Bury a few 10 foot lengths of copper pipe in a star pattern. And make all of your connections at the center of the star (or 1/4 circle of star pattern--the point of the star closest to the wall/building/where your ground wire comes to earth).

Running 6 awg for 10 feet is note great for lightning grounds... It has higher "impedance" and the lightning will try to find another path rather than follow 10-20+ feet of 6 awg cable. (lightning has "higher frequencies" and behaves differently than 60 Hz or DC current--Higher frequencies tend to want to leave the conductor (magnetic field forces electron flow to the skin of the wire). If you have to make a run, 3/4" copper pipe should be better (or get true lightning rated braided grounding cable).

If you have dry soil, they even go as far as back-filling with bentonite clay and a dry well to add water to reduce resistance. This is a nice catalog with lots of lightning attachments and fittings. Note that they are using something like 2 AWG minimum copper cabling (building less than 75 feet tall--I think) for their grounding.

https://www.erico.com/catalog/literature/E1147C-WWEN.pdf

I am in no way a lightning expert--Just some ideas.

-Bill

wellbuilt · May 2017

I do have some 20 g copper flashing 12"x 15' left from a job.
If I rolled over one edge of copper flashing and clamped it to a 7' piece of ground rod then bent the rod at 90o to stand up out of the ground with the proper lug connection to attach my ground wire , would that be OK .
Some of the plates are 30"x48" 20gadge copper .
I also have a bunch of 3" wast line that could be pounded flat and run out away from the house in a fan shape ( half a star ) starting at the wall with the ground rod bent in a l shape standing up for ground lug .
Maybe braze the ground rod to one lenth of pipe and bolt thru all three pipe ends

BB. · May 2017

20 gauge sheet metal is about 0.0375 inch thick. Those were 0.250 inch [1/4"] thick copper plates I linked to.

K wall 3/4 pipe is 0.065" thick (just one wall).

I would not be a fan of 20 gauge copper buried for long life.

3" pipe would not be bad (copper or iron?).

- Bill

Estragon · May 2017

I have similar conditions and used a couple of grounding plates, one for array and one for cabin. They're about a foot square by 1/4" thick and have a connection lug bolt. About $20 from the orange box store IIRC.

I buried them in small depressions where the ground is less likely to dry out.

wellbuilt · May 2017

The pipe is copper 3" wast line from the 60s cut out of a building last year it has a thick wall.
bill some of the links were 1/4" but some were 20 gage but I would just buy ground plates if that is better ,
i just need to find them .
Estragon , I know the orange store like the back of my hand and have never seen grounding plates here, but I will look in the am .
I am trying to figure out my utility room now , lots of stuff to go in that room

Lumisol · May 2017

Looks like fun. I am building with adobe, not wood.

wellbuilt · May 2017

Adobe , I would like to try that I've been a mason for 35 years.
I built with a lot of stone and concrete but never mud.

BB. · May 2017

I lived next to the ocean for a few decades... Just saw so much corrosion, I always planned for the worst.

If they have 20g grounding plates, I cannot say they are wrong.

I am no expert.

- Bill

wellbuilt · May 2017

I'm going to see what I can get from the ELEC supply house thanks bill

wellbuilt · May 2017

Hi all , I am making some progress , we have been crunching a lot of #.
In the end I have decide to go with a out back flex power one system 3600/48 volt .
It was really a no brainer .
Want to start with 8 gc 215 for now , but upgrade to good RE battery in a few years 400 450 ah .
How much panel do I need for reliable charging in Albany ny for the larger battery .
The panel will be on the roof at 37o pointed south . Thanks in advance

wellbuilt · May 2017

The panels are just 265 watt from AWS .

westbranch · May 2017

Give us your best guestimate of the number of Whrs/ Ahrs you you will use in a day and days of autonomy you desire...

wellbuilt · May 2017

I was hoping for around 3200 but looks more like 4000 4200 .
With 2 days storage .
My outback CC will hold 4000 watts and I have room for a array 8 panels wide by 2 panels high soooo I was thinking to run 3 series 5 strings , my quot came in with 265 watts 12 panels .
I don't want to have to add later .

Going off grid

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