Chris Olson
26th January 2011, 10:06
Due to need to use 24 volt power with 12 volt equipment, and not willing to give up the 12 volt stuff I have in place in my house, I built this new bus. The photo was taken when the bus was temporarily hard-wired in parallel before I hooked up the controllers. The bus bars are labeled P1, N1, P2 and N2 from left to right. Battery bank # 1 (2,000 amp-hours) is hooked to P1 and N1 and supplies power to two 12 volt inverters - a 3 kW AIMS that powers half my house and a 2 kW Schumacher that runs the freezer.
Bank #2 (1,000 amp-hours) is hooked to P2 and N2 and supplies power to a 3 kW AIMS inverter that powers the other half of my house, as well as the 12 volt circuits in the house (for powering laptops, cell phone chargers, 12V florescent lighting in the kitchen, 12 volt sump pump). The normal loads are higher on Bank #1 than they are on Bank #2.
In the second photo below is the series/parallel bus controller. What the bus controller does is monitor the voltage of Battery Bank #2 and if the voltage on that bank gets to 14.85 volts it switches off the series connection in the bus and hooks the two banks in parallel. In this photo you can see the bus controller is activated (red light lit), which also clamps the turbine down to 12 volt and slows it down so it puts out less power while the banks equalize.
I don't have the black leads of the Doc Wattson (the ones with the shunt) hooked up because the system runs over 100 amps on a regular basis - I'm just using the meter to monitor the bus voltage. When the controller switches the bus out of series the amp inrush is over 250 amps from the turbine when it brakes the turbine and slows it down. The Doc Wattson doesn't have enough smoke in it to handle that without replacing the shunt in it with a bigger one.
The bus controller holds the bus in 12 volt mode for five minutes, or until the voltage of the bank drops to 12.6 volts. When either of those two criteria are met it switches the bus back to series 24 volt and lets the turbine take off again. Switching the bus out of series also "clamps" the solar down to 12 volts, but the panels don't seem to care - they put out about the same watts whether "clamped" to 12 volt or running on 24.
The load controller (third photo) operates an Allen-Bradley 3 pole, 30 amp contactor with power supplied to the contactor coil by the inverter on Bank #1, the neutrals from both AIMS inverters passed thru, and the "hots" from both inverters switched by the contactor. The contactor tuns on power from the inverters to two 1,200 watt 120 volt water heater elements in my water heater. If the voltage of Bank #1 gets to 14.85 volts it closes the three-pole contactor and heats water off both banks, using both AIMS inverters, for five minutes, or until the voltage of Bank #1 drops to 12.6 volts.
If during water heating when the bank is in parallel, the voltage of the bank drops to 12.6, or the five minute time has elapsed, the bus controller switches the bus back to series to start charging at 24 volt again.
In the photo you can see the green light is glowing steady and it's about ready to start heating water. The 440 amp series/parallel relay is mounted in the bottom of this box and is operated by the bus controller. Basically, all the series/parallel switch does is break the connection in the bus from N1 to P2 and connect N1 to N2 and P1 to P2.
Both controllers are Coleman Air DLC boards with EDM.
It keeps the two banks pretty well balanced - under normal operating loads sometimes the voltage of the two banks can vary by up to 1.4-1.5 volts, especially with the heavier loads on Bank #1. But if I shut everything down to check the at-rest voltage of the banks I've yet to find them more than .08 volts difference, with Bank #1 usually being the slightly lower of the two.
I also have a switch (last two photos) that I can switch the bus controller from 12/24V Auto to 12V. In the next to last photo you see it's in auto mode and the bus voltage is 25.87.
In the last photo you can see I switched it to 12 volt manual and the bus voltage is now 12.94 volts.
Submitted for people to see, as a setup like this is probably not all that common. It evolved from starting with an off-grid 12 volt power system with several turbines, to one larger turbine and solar array that puts out too many amps on 12 volt, and hence the need to jump charging voltage to 24 volt to lower incoming amps. But at the same time, using existing 12 volt equipment. All I had to do to change incoming voltage is swap out the stator in the turbine and rewire the solar array series/parallel 24 volt. Total cost in the auto-switching bus, with the controller, is about $200.
--
Chris
Bank #2 (1,000 amp-hours) is hooked to P2 and N2 and supplies power to a 3 kW AIMS inverter that powers the other half of my house, as well as the 12 volt circuits in the house (for powering laptops, cell phone chargers, 12V florescent lighting in the kitchen, 12 volt sump pump). The normal loads are higher on Bank #1 than they are on Bank #2.
In the second photo below is the series/parallel bus controller. What the bus controller does is monitor the voltage of Battery Bank #2 and if the voltage on that bank gets to 14.85 volts it switches off the series connection in the bus and hooks the two banks in parallel. In this photo you can see the bus controller is activated (red light lit), which also clamps the turbine down to 12 volt and slows it down so it puts out less power while the banks equalize.
I don't have the black leads of the Doc Wattson (the ones with the shunt) hooked up because the system runs over 100 amps on a regular basis - I'm just using the meter to monitor the bus voltage. When the controller switches the bus out of series the amp inrush is over 250 amps from the turbine when it brakes the turbine and slows it down. The Doc Wattson doesn't have enough smoke in it to handle that without replacing the shunt in it with a bigger one.
The bus controller holds the bus in 12 volt mode for five minutes, or until the voltage of the bank drops to 12.6 volts. When either of those two criteria are met it switches the bus back to series 24 volt and lets the turbine take off again. Switching the bus out of series also "clamps" the solar down to 12 volts, but the panels don't seem to care - they put out about the same watts whether "clamped" to 12 volt or running on 24.
The load controller (third photo) operates an Allen-Bradley 3 pole, 30 amp contactor with power supplied to the contactor coil by the inverter on Bank #1, the neutrals from both AIMS inverters passed thru, and the "hots" from both inverters switched by the contactor. The contactor tuns on power from the inverters to two 1,200 watt 120 volt water heater elements in my water heater. If the voltage of Bank #1 gets to 14.85 volts it closes the three-pole contactor and heats water off both banks, using both AIMS inverters, for five minutes, or until the voltage of Bank #1 drops to 12.6 volts.
If during water heating when the bank is in parallel, the voltage of the bank drops to 12.6, or the five minute time has elapsed, the bus controller switches the bus back to series to start charging at 24 volt again.
In the photo you can see the green light is glowing steady and it's about ready to start heating water. The 440 amp series/parallel relay is mounted in the bottom of this box and is operated by the bus controller. Basically, all the series/parallel switch does is break the connection in the bus from N1 to P2 and connect N1 to N2 and P1 to P2.
Both controllers are Coleman Air DLC boards with EDM.
It keeps the two banks pretty well balanced - under normal operating loads sometimes the voltage of the two banks can vary by up to 1.4-1.5 volts, especially with the heavier loads on Bank #1. But if I shut everything down to check the at-rest voltage of the banks I've yet to find them more than .08 volts difference, with Bank #1 usually being the slightly lower of the two.
I also have a switch (last two photos) that I can switch the bus controller from 12/24V Auto to 12V. In the next to last photo you see it's in auto mode and the bus voltage is 25.87.
In the last photo you can see I switched it to 12 volt manual and the bus voltage is now 12.94 volts.
Submitted for people to see, as a setup like this is probably not all that common. It evolved from starting with an off-grid 12 volt power system with several turbines, to one larger turbine and solar array that puts out too many amps on 12 volt, and hence the need to jump charging voltage to 24 volt to lower incoming amps. But at the same time, using existing 12 volt equipment. All I had to do to change incoming voltage is swap out the stator in the turbine and rewire the solar array series/parallel 24 volt. Total cost in the auto-switching bus, with the controller, is about $200.
--
Chris