small off-grid: solar charge controller + inverter compatibility for LVD purpos?

20 Posts
Jan 13, 2014 03:12 pm
small off-grid: solar charge controller + inverter compatibility for LVD purpos?

Hi,
Our non-profit helps train about, and install, renewable energy systems in remote villages in developing countries.
Some years ago, I started a topic on this forum, lamenting the fact that small (100-400W) inverters were not compatible with solar charge controllers (e.g. Morningstar or Phocos 12V -10A).  As a result, if an inverter was connected to the DC load side of a controller, it could fry it.  However, LVD protection on such small inverters is often at a very low voltage (e.g. 10.5V) instead of the controller LVD of 11.7V.  So if the inverter is connected directly to the battery, chances are that it will run the battery dead.  Some solutions were offered at the time, involving a relay connected to the DC load output to switch off the inverter.  A simpler approach, but requiring user education and discipline, would be to connect a 1W LED to the DC load, and instruct the user to swithc off the inverter when the LED is off.
However, I noticed that newer solar controllers seem to include new features, e.g. "improved lightning protection", programmable lighting functions, etc.    Does anybody know if  there are either controller-inverter combos, or controllers that would be compatible with inverters, in the 50Wp to 200Wp 12V system range and at reasonable price?
Thanks.
 
462 Posts
Jan 19, 2014 01:25 pm
Re: small off-grid: solar charge controller + inverter compatibility for LVD purpos?

Michael, one thing you didn't metion was the size of your solar PV panel. eg. How many Watts?. This will determine how much power you are receiving daily and therefore how much power you can use daily irregardless of the controller or inverter.
  Your inverter should be hooked up to your battery, not your controlller. A small load such as a light can be hooked up directly to the controller as long as it is within the output power of the controller in combination with the panel.
 You must do the math with regards to how much power you are using each time you use it in order not to drain the system's battery.
There are calculators here at AltE to help you understand this.
 
20 Posts
Jan 21, 2014 03:28 pm
Re: small off-grid: solar charge controller + inverter compatibility for LVD purpos?

Hi Tom,
I did mention the siez range: 50-200Wp.  This is not for me, this is for remote systems in developing countries.  We do provide user training & guidelines on not draining the battery too much, but the users are usually illiterate and I'm looking for something more bulletproof than instructions.
Thanks, I do know how to do the calculation, as I have been giving workshops on this for years.  I'm just enquiring about possible improvements in the controller and/or inverter hardware.
 
462 Posts
Jan 22, 2014 02:26 pm
Re: small off-grid: solar charge controller + inverter compatibility for LVD purpos?

Mike, I get where your coming from. I have also dealt with instalations in rural areas where systems were not properly used.
 The best way is to use numbers. If you can afford to put a small digital readout for battery voltage then they may be able to visually see that they need to turn off the inverter or whatever lighting or appliance they are using..... Or an inliine low voltage disconnect that leads to the loads for automatic operation.
 
20 Posts
Jan 22, 2014 03:50 pm
Re: small off-grid: solar charge controller + inverter compatibility for LVD purpos?

Thanks Tom.  So, do you mean that in this power range there are "online LVD's ", i.e. standalone devices that can be connected inline with an inverter or a load?   The only LVD's I'm aware of so far are built into charge controllers (but only disconnect a directly connected DC load), or built into inverters (but only disconnect when the battery voltage is about 10.7V)
If I could find a standalone (programmable?) device, that would be great.
Thanks
 
462 Posts
Jan 22, 2014 04:57 pm
Re: small off-grid: solar charge controller + inverter compatibility for LVD purpos?

Mike, here is a couple of links for a cheap lvd...

http://www.nemosolar.com/dcsubmersiblepumps/id45.html

http://www.powerplanted.com/12vss.html

Just do an internet search for DC low voltage disconnects and you should be able to find one that fits your needs at a decent price...
« Last Edit: Jan 22, 2014 05:05 pm by Tom Mayrand »
 

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

Share

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

Feedback

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!!