Using Renewable Energy: The Move to 24v Part2

The move to 24v part 2.

In the first part I listed some reasons to go to 24v and the plan.  The plan included an additional solar panel and a decent inverter.  I picked up both and went to work.

The first thing I did was to configure the battery bank to 24v.  I started with two batteries and wired them in series.  Then did the same for the other two pair.  This gave me, essentially, three 24v batteries.  I then connected the three 24v batteries in parallel.  This gave me one large bank of 24v.  Here is essentially how the 6 batteries are configured:

I did some testing with my multimeter for voltage.  Everything looked good!  I connected the charge controller to the right most parallel positive post and the left most parallel negative post.  The charge controller read the pack at 24v.  This was good!

Next step was to hook up the two panels in series.  The first thing I did was disconnect the positive lead going from the existing panel to the charge controller.  I left the negative of the panel connected to the charge controller.  I put the two panels side by side and connected the positive lead from the existing panel to the negative lead from the new panel.  Then I connected the positive lead from the new panel to the charge controller.  I brought the panels outside and they began charging the battery pack!  While the panels were outside, I connected them with a couple hinges.  This made moving them around much easier.

 Now that the battery pack and panels are configured for 24v the next step is to work on the inverter.  The inverter is an Exeltech 24v 600watt.  It was originally used as a transfer switch.  It was hooked up to AC power, an AC Load and to the battery bank.  If the AC Power was lost, it would switch to battery and provide the AC in less than 50ms.  My guess is that this was used in the medical equipment field.  While the transfer switch is a great feature, I don't really need it.  The inverter does not come with an on/off power switch (that's automatic when used as a transfer switch) but it does have a RMT lead. The RMT lead, when grounded to the negative Battery, will turn the inverter on.  I installed a rocker switch in between the battery negative and the RMT.  Now when the rocker is 'on' the RMT is grounded to negative and the inverter turns on.  It works perfectly.  I now had a way to turn the inverter on without using it as a transfer switch! 

Here is the inverter before I configured it with the on / off switch.  Notice the two gray wire clusters for AC Utility and AC Load.  That small red wire is the RMT.  

Spring can be a tricky season.  The amount of clouds we are getting doesn't really help the output of the panes.  It does charge the battery pack though.  My wife and I are still charging our smartphones and tablets via the pack.  One day when it was really nice / sunny out, I put the panels in direct sunlight.  I was charging two devices off the USB on the charge controller, and running the stereo in the garage using the inverter.  The battery pack never fluctuated, which tells me that the panels provided more than enough power to keep the battery pack topped off, charge the two devices and run the inverter / stereo. 

Plans!
The next step is going to be an entry panel to get the wire into the house without having to have a door open (or garage door closed on the wire).  I ordered an 'entry panel' for exactly this purpose.  It will be time to punch a hole in the wall of the garage somewhere to get a wire to come though.  More on this once the entry panel arrives!

I would also like to upgrade the charge controller to something better, like an MPPT 30A controller.  That will leave room to expand, I could feed that controller with up to 90v and it will recognize 12 or 24v battery pack.  It's just a 'smarter' controller.  And the increased voltage will allow me to use a longer run of 10 AWG wire.

I also ordered a 'kill-a-watt' meter.  This way I can plug the power strip in my office into it (or anything with an electrical plug) and measure how much power the office is pulling.  If it stays under 600watt, I may try and run the office off of the panels / pack during the day. 

Stay tuned for the next update!