>> make a system with 2 and or 3 turbines and still have only 24v in the
>> battery bank and inverter. If each Roof Turbine is 24v, How can 2 be
>> 24v together? Also, why aren't we using 12V, seems more common?
Hi James,
It's called PARALLEL wiring, Parallel wiring increases capacity but NOT voltage. So, we wire the turbines to be used in Parallel. This is a very common practice in wind/solar systems and battery banks. Parallel wiring increases capacity but NOT voltage. So, I'm really glad you asked because it's instructive for others to post here on the wind power forum.
In the battery bank, we can use 6v batteries. We wire them in groups of 4. This, or each group of 4 is wired in SERIES. Series wiring increases voltage but NOT amp/hour capacity. So, 4 6v batteries wired in SERIES is making 24V. Series wiring increases voltage but NOT amp/hour capacity.
So, 4, 6v 200Ah batteries wired together in SERIES, = 24v 200Ah...
Series wiring increases voltage but NOT amp/hour capacity.
NOW, ANOTHER CURVE..
You can put sets of 4, 6v batteries on the system, up to 12. So, can be 4,8, or 12 battery bank. To do an 8 or 12 battery bank, we need BOTH Series AND Parallel. Groups of 4 wired in SERIES to get to 24v, each group connected together by wiring in in Parallel to stay at 24v.
So, 4 6v 200Ah batteries wired together in SERIES, = 24v 200Ah...
Series wiring increases voltage but NOT amp/hour capacity.
2 Groups of 4 like that, wired in Parallel increases capacity but NOT voltage. So, 8 battery bank of 6v 200Ah ea. = 24v 400Ah
3 Groups of 4 like that, wired in Parallel increases capacity but NOT voltage. So, 12 battery bank of 6v 200Ah ea. = 24v 600Ah
So, adding more batteries in the bank helps you sustsin more time between charging, windy or sunny periods. Gives you additional run-time and makes a system more reliable. But, you can always start out with 4 or 8, then upgrade to 12 later. Many people doing that. I recommend getting 12 if you can afford it, or planning to upgrade to 12 as soon as you can afford it. People with great wind/solar resources need the batteries less than those with weak resources. The poorer your wind/solar resources and or the larger your system the more battery bank you want to employ.
>> Also, why aren't we using 12V, seems more common?
Well, the biggest advantage of 24 volt systems vs. 12 volts is that wire size can be cut in half throughout the system as compared to 12v. Besides affecting battery bank wires, this includes solar panels, wind turbine generator and micro hydro turbine wiring. If you have hundreds of feet of wire, this cost can add up quickly. Additionally the 24V at this wattage has a power generation efficiency that is better than other voltages for efficiency.