Jonathan Hunt's posts

Posted by Jonathan Hunt on Apr 4, 2008 10:59 am

#1 -  Renewable Energy > Technical Discussion: Other > Re: Small PV Data Logging
Hi John,

I saw your post the other day on the automatic switching for your PV system and thought it was really cool.

How much did the voltage controlled switch, relay and Automatic AC Transfer Switch cost?  Also, did you need to special inverter that can be controlled by the relay or is the relay just in the line from the battery to the inverter?

Two of the Lascar USB data loggers, one for straigh voltage and one with a shunt for current should be able to get me almost everything I want.  Thanks for the suggestion.  Do you know of an easy way to synchronize two of these data loggers?  Is there a button on them to reset the logging that I could press simultaneously?


Posted by Jonathan Hunt on Apr 3, 2008 04:11 pm

#2 -  Renewable Energy > Technical Discussion: Other > Re: Small PV Data Logging
The PentaMetric is definitely more the price I'm looking for and at first glance here:


appears to do everything I want.  What is the power source for the input unit?  Does it run off the batteries, have its own batteries or run off an external power supply?

Does the TriMetric

enable me to offload the data to a computer, or is that why I'd need the PentaMetric?

Posted by Jonathan Hunt on Apr 3, 2008 01:27 pm

#3 -  Renewable Energy > Technical Discussion: Other > Small PV Data Logging
I have a small 47W off-grid PV setup.  I'm using a Doc Wattson DC meter to manually log data about the power generated, peak Voltage & Current, and minimum Voltage.

I'd like to find an inexpensive system that could log this information automatically, ideally shipping it off to a computer so I could monitor it from the web.  I've seen systems designed for larger arrays from Fat Spaniel or others that cost over $1,000.  The cheapest I've found that might meet the needs is from Hobo start at $299 plus sensors.

Has anyone built such a system or know where I could buy one?  I've got a spare laptop around that I could use to host the data once logged.

The things I'm really interested in are:
V & I at various times throughout the day.

Thanks for any suggestions

Posted by Jonathan Hunt on Mar 14, 2008 01:09 pm

#4 -  Renewable Energy > RE General Discussion > Re: Renewable City Generation
Robert, to answer your question from my personal perspective, I would love to have a grid-tied system because for every kWh I would put back into the grid, that's 1-3 kWh worth of fossil fuel not being burned at the power plant.  As it stands, I have a tiny off-grid system that I am playing with, but can't power much with it.

Also, being tied to the grid, enables you to install a smaller system that only supports part of your load.  That system can be expanded over time to meet all of your needs, but many places don't have enough usable solar area to meet their needs.  Grid-tie systems (at least those without battery backup) require less maintenance than a system with batteries that need to be replaced every 5 or so years.  They are also easier to design because you do not have to meet your load precisely or provide backup generators when the sun isn't enough.

Loosing power once in a while is not a big deal for most people.  My electric company shut down power for about an hour for maintenance this past week and even though I was aware, I forgot to do anything about it.  All I had to do to recover from the outage was power on one computer (DVR) and reset the clocks on the microwave and oven.

And finally, I would consider it helping out the local community by providing them with clean power when my production exceeds my load.

I hope this helps you see the bigger picture and you can sleep better.

Posted by Jonathan Hunt on Mar 10, 2008 11:24 am

#5 -  Renewable Energy > RE General Discussion > Re: Smallest PV size for Grid Tie
Thanks, the micro grid tie systems are what I was looking for in general.  Would it be possible to substitute Evergreen panels, like the ES180 ES190?  I like the low embodied energy, physical size of the panels and the price seems the cheapest per watt through the Alternative Energy Store.

I'm hoping to do the physical installation myself as I'm likely to do a non-standard setup and use the panels as structural elements for the walk-way cover.  I find it unlikely I could find someone that would install the panels the way I am thinking.  I hope to build in a small hinged flap next to the building to be able to adjust the angle from +15 to -15 degrees of the Boston Latitude.

Any idea what an electrician might charge to wire the panels and the system together or how long that would take someone?

Good to know about the MA rebate needing 1kW.  How much is the rebate at that point?

Posted by Jonathan Hunt on Mar 9, 2008 05:49 pm

#6 -  Renewable Energy > Technical Discussion: Other > Re: 24 volt panels to charge 12 volt battries
26V is definitely too high to safely charge a 12V battery bank.  I think you should reconfigure the bank to be 24V which should be pretty easy unless you have an odd number of batteries in your battery bank.  I'm thinking that you could just put half of the batteries in series with the other half and be done with that part of it.

As for running a large 12V load from the mid point of the batteries, I'm not sure.  You could also look at a DC-DC converter to go from 24V to 12V.  I'm not sure what is practical in that arena.  If most of your loads are 12V in nature, then you could alternatively leave the bank at 12V and use the DC-DC converter (I seem to recall some charge controllers able to do this for you) between the panels and the battery bank. Hopefully someone else will chime in with more details about running a load in the middle.  I've wondered about that in the past myself.

Posted by Jonathan Hunt on Mar 9, 2008 04:23 pm

#7 -  Renewable Energy > RE General Discussion > Smallest PV size for Grid Tie
I'm toying with the idea of a small, i.e. about half a kW, solar array on my house and am wondering what is out there for small grid tie systems.  I'm also curious about what I should expect to pay to have the wiring done by an electrician in Massachusetts as I want this to be done with a permit.

I've got a fixed fiberglass overhang of the south side of my house that will need to be replaced in the next few years and I'd love to replace it with PV (or PV & Thermal) panels.


Posted by Jonathan Hunt on Feb 27, 2008 11:58 am

#8 -  Renewable Energy > Technical Discussion: Other > Wattage for a Wind Turbine - what does it mean?
I was looking at the Air Breeze information as compared to the Air X and noticed that the Air Breeze is rated at 200W while the Air X is rated at 400W.  However the descriptions indicate that they both should generate about 20-30 kWh/month in the same wind conditions.  The descriptions also indicate that the Air Breeze is more efficient at lower speeds and is in general a better choice.

Can someone help me understand why two very similar models have a factor of 2 difference in their specifications?

Air Breeze

Air X


Posted by Jonathan Hunt on Feb 26, 2008 01:05 pm

#9 -  Renewable Energy > Technical Discussion: Other > Voltage tolerance for various network switches, cable modems, etc.
I have a small off grid solar setup.  Evergreen 47W panel, through a 4.5A SunGuard charge controller connected to a 12V deep cell marine battery.

I currently power one network hub in my house by going through a 75W inverter, then to the power brick to 7.5V DC into the device.  I know this is not efficient.

What I would like to do is to power the 4 (or as many as I can) network devices (hub, cable modem, wifi router, and switch) with DC-DC step down converters.  While looking into that route, I noticed that 3 of the devices are actually 12V DC inputs.  What I'm wondering is can I power those devices directly from the battery (through a DC fuse of course) when I know my battery voltage varies from about 10V to 14.1V without harming the devices or hampering their performance?

Anyone have experience with this or know what the tolerance on Netgear home networking components are?


Disclaimer and Disclosure

The Alternative Energy Store, Inc reserves the right, within its sole discretion, to refuse or delete any posting or portion thereof, or terminate or block the access to this forum.

The opinions and statements posted on this forum are the opinions and statements of the person posting same, and do not constitute the opinion or act of the Alternative Energy Store, Inc (AltE). The Alternative Energy Store, Inc does not endorse or subscribe to any particular posting. No posting shall be construed as the act or opinion of the Alternative Energy Store, Inc.

Click here for BBB Business Review

McAfee SECURE sites help keep you safe from identity theft, credit card fraud, spyware, spam, viruses and online scams
Desktop Website | Mobile Website


Click on an icon to share! If you don't see the method you want, hover over the orange "+".


What can we do to help you?

Please enter a summary
Sorry, the copyright must be in the template.
Please notify this forum's administrator that this site is using an ILLEGAL copy of SMF!
Copyright removed!!