Hello im off grid in no. NEVADA

[Rob775]

Hello Everyone,

I am relatively new to solar. I currently have a simple 12v solar system. 22, 6 volt GC3 batterys, 8 Hanwha 36.8v 235 watt 8.44 amp panels with 2ea. tied together. Outback Flexmax 80 charge controller. Pushing a 2000 watt inverter.

Using some of this same equipment ( and more ) it is time to step up to a 48v system.

I have a Outback FP2 7200w (prewired by Outback) with dual inverters and charge controlers.

30 (2 strings of 15. 3 tied together ( + to - ) of the Hanwha panels, 2 midnight solar combiner boxes

I am in the final phases of wiring and almost ready to finish and go online.

I also have a Air40 48v wind generator.

I have ran the 12 v system for 2 years while assembling everything to convert to 48 volts. I think I have this 12v stiff figured out. However 48v is not so clear.

I have all the questions and no confidence to finish and turn on the system on my own.

So Here I am and What the H €《《 have i done. LOL
I spent a crapton of $$$$ I dont want to fry myself or the equipment cant afford to screw up and I have no solar educated help near by.

Im hoping there are some kind people that will put up with my lack of knowledge and help me thru the next few steps successfully.

Thank you in advance.

Rob the newbie

[Rob775]

Panels

[Rob775]

Outback FP2 7200

[Rob775]

Interstate GC 3 batteries.

[SunEagle]

Well to start you will need more batteries to wire up a 48V system using 6V batteries. Even then you will have 3 sets of 8 x 6V in parallel which is not a good thing but better then 11 pairs of 2 x 6V in parallel.

With 7000 watts of panels you will need both of those 80amp CC's. Your battery system should be sized about 10 times the 150amps the panels can generate or 1500Ah. So Those batteries will need to be rated about 300Ah each to get that 1500Ah system (5 x 300Ah = 1500Ah) They can be as low as 240Ah each which creates a 1200Ah system but if they are less then that you should removed some of your panels to get that C/10 charge rate.

I am not exactly sure what the max DC input voltage is for those CC but that value will determine how you wire your panels to them.

[Rob775]

SunEagle,
Thank you for thw reply. When i switch over to the 48 v system i will get 2 more batterys so i have 3, 48v. Strings. I get these batterys $65 each plus a core so i will most likly have 4 strings.

Also looking at some Excide 48v 580 ah batteries that are 3 years old. If i can get for a good price.

I understand storage is key to off grid solar. Just cant afford all the good stuff at one time.

[Rob775]

48v 510 ah

[Rob775]

The mathematics of the batteries is my weakest area of understanding how they add up and work

[Ampster]

The mathematics of the batteries is my weakest area of understanding how they add up and work

One of the things you may want to have in your toolkit is an understanding of Ohm's law and how to calculate Wattage. You can find the answers using a simple Internet search. Then look up Watthour to understand your system in terms of Watthours of consumption and Watthours of battery storage.

[Mike90250]

> have a simple 12v solar system. 22, 6 volt GC3 batterys,

22ea 6v batteries, is not simple. The days of massive parallel 12v battery banks, ended in the mid 80's

here's a write up on battery wiring

http://www.smartgauge.co.uk/batt_con.html

[Rob775]

Mike90250
Thank you. That was a good read. Im going to have a another look at how mine are connected.
the load and charger wires are connected same place.

[SunEagle]

The mathematics of the batteries is my weakest area of understanding how they add up and work

Well I made a mistake by telling you how many 6V batteries you need for a 48V system. When I said 20 x 6V batteries wired as 5 parallel strings of 4 would get you a 48V system. it would really only be a 24V system. You have determined the correct number of 6V as being 24 which wired in 3 parallel strings of 8 will get you a 48V system.

For future reference, when you wire batteries in series you add up the voltage but the Ah is the same as one, when you wire batteries in parallel you add up the Ah rating but the voltage is the same.

As for a 3 year old 48V battery, I would be cautious about getting even half their rated life cycles but if they are cheap then they might be worth it.

[Rob775]

Ok so these are the specs.on the batteries I have now

[Rob775]

225 ah 6v x 8 = 48 v 225 ah bank

x 4 banks = 900 ah

900 ah x 48v = 43,200 watt hours

43,200 wh = 1000 wh load 43.hours

Did i learn this correctly ?

[SunEagle]

225 ah 6v x 8 = 48 v 225 ah bank

x 4 banks = 900 ah

900 ah x 48v = 43,200 watt hours

43,200 wh = 1000 wh load 43.hours

Did i learn this correctly ?

Yep. The only thing you may have wrong is the number of wh load for 43 hours. Most Pb battery systems can be safely discharged 20% to 25% each day or you end up shortening their life and reduce the number of allowed cycles.

To be safe I would say your bank can deliver 43,200 wh x 25% or 10800wh which comes to a load of 450 watt for 24 hours. Of course less time allows for a bigger load.