24 Volt Battery Box Vent Fan Control Circuit

Battery vent fan control switch

Schematic for 24VDC Battery box vent fan controller

One of my backup systems uses a Magnum MS-PAE 4024 inverter, which doesn’t have any built-in fan controller. Since batteries give off hydrogen during both normal and equalization charging, it’s important to vent the batteries to the outside with a brushless fan. This little circuit does the job nicely for a 24 volt battery bank. Here’s how the circuit works: Battery voltage comes in and goes directly to the LM358 op-amp and P1-R1. P1 sets the trip point where the fan will turn on. VR1 and R2-R3 provide a stable reference voltage for the op-amp. R4 adds some hysteresis so the fan doesn’t cycle on/off when near the trip point. the 4 volt zener assures that Q1 turns fully off, since the output doesn’t swing to the rails. R5-R6 assure that Q1 turns on/off completely. Q1 is good for fans that use up to 100 milliamps of current. If you have a bigger fan, use Q1 to turn on a relay… This won’t work for 12 volt or 48 volt systems, but I might design those if there’s any interest here…. Enjoy!

Lightning Arrestors. Use them!

I’ve never discussed this, but these devices are cheap insurance (not really, but you get the idea…) against all kinds of problems that can come about as a result of electrical storms. I’ve used the powered type in the past, and have one installed currently, but I came across a totally passive version that uses no power, is self resetting, and if it does fail, it fails OPEN, so it won’t cause problems. Best of all, you can get them for 30 bucks on ebay, brand new, including shipping. Just search for “LA302R”.  It has 3 wires, and you simply install it in your electric box to a breaker connected to L1, L2 and Neutral. If you’re not an electrician, hire one to do this. It takes about 2 minutes. It takes longer to get the cover off your breaker box than it does to install one!!

Serious grid-tied/grid-backup system!

DIY Solar grid backup system

Ground mounts are an attractive alternative if you don’t have much roof space and want a system that allows you to live comfortably WITHOUT the grid!!

Nestled in the middle of a 26 acre plot is this cozy updated farmhouse with almost 6KW of solar power. The home is well insulated, and fitted with all the high efficiency goodies. Propane fired DEMAND water heater, wood stove for heating, LED lighting and more! At first I assumed he wanted a ground mount to keep it away from the house, but when I arrived on site I knew right away the real reason – no room on the roof! But seriously, this setup goes way beyond just a large array. The owner wanted plenty of AUTONOMY – that’s lots of days of off grid operation without worry of running the battery bank down. And plenty of power, so that if he wants to do laundry while off grid, it won’t be a problem. So we got together and discussed the options and the owner decided to DO IT RIGHT the first time. I explained that batteries would be a large part of the project cost, and he would have to understand and CARE for the battery bank if he expected it to last 10 years or more.  He was more than willing to listen, read, study and understand the care and feeding of his battery bank, and as a result is VERY pleased with his installation.

 

DIY Solar ground mount everything in place and ready to add panels

Trench backfilled, horizontal pipe (3 inch galvenized) added front and back, and vertical rails to carry the solar panels installed. Ready for panels and wiring. Owner and a few helpers accomplished this in 2 days of hard work. Not much daylight in December, but DIY folks are not afraid to work sunup to sundown!!

While all this activity was going on outside,  I was busy in the basement, hanging the TWO Sunny Island inverters on the wall, mounting the small EMERGENCY POWER breaker box and running conduit between the inverters, the main breaker box and the new Emergency power box. I’d come up for air once in a while to check on the ground mount work, just to make sure it was square and plumb, but these guys knew what they were doing and got it all right on the very first pass!  Looking at the pics below, we chose to use TWO Sunny Islands for several reasons. 1st and most important was that the Sunny Island is without question the best BATTERY TENDER around. It can use the grid or the array charge the batteries, and it has sophisticated software to monitor the battery health and adjust things as needed to optimize the battery care. It LEARNS over the 1st 8 weeks how the battery supplies power and how it accepts charge and then adjusts itself for the best possible care. We used TWO Sunny Island inverters so that we could SLAVE them together and create 240VAC “split” phase. The Sunny Island is a 120VAC unit and would otherwise need a lossy transformer to boost the output to 240VAC.   We doubled the available continuous output power to 13,000 WATTS by doing this. That is a LOT of backup power, and will allow completely normal living in an off grid situation. The owner wanted lots of autonomy (days of power off grid) so we went with the largest batteries withing the budget – Rolls FLA 6 volt 820AH.  EIGHT of them to reach the 48VDC the Sunny Islands need.  That’s almost 40KWH of backup power. And remember, when off grid, the sun on the array will recharge them, as well as power the house!  I didn’t have time to hang around while a battery BOX was built, so we put up a poly tent and connected the vent fan. This was only a temporary fix and has since been replaced by an appropriate battery box. The exhaust fan is programmed to come on while the batteries are charging – since this is when they give off Hydrogen gasses which are explosive in small amounts.  The owner has since also installed RECOMBINATION CAPS which reduce the outgassing by 99% and reduce fluid losses considerably – making it only necessary to check acid levels in the battery every two months or so, rather than every 2 weeks. A wise investment – since it minimizes outgassing of Hydrogen if the vent fan were to ever fail! Batteries are a VERY serious bit of hardware and you MUST care for them if you expect to get 10+ years of service!  Always wear safety glasses, a rubber apron and rubber gloves when checking/filling the cells!

DIY Solar grid-tied backup system connected and ready for power!

Some of the AC lines have been moved to the emergency breaker box, all covers are on, and temporary poly cover over battery box has been connected to the power vent fan. When the battery bank charges (at 38 amps DC) the batteries bubble up hydrogen gas and without the fan and cover, the room would reach explosive hydrogen levels in less than 1 minute. NEVER power up a battery system without a vent system!! A 4% concentration level of Hydrogen gas is highly explosive.

Battery bank, inverters and emergency breaker panel on DIY Solar installation

Two Sunny Island battery/inverters on the wall, eight 6 volt 820AH batteries below elevated off floor to make watering easier. DC cables connected and AC interconnections in Plastic conduit for safety. Ready to move some wiring from the main box to the emergency breaker box. Only items in the emergency box will be powered when running off grid. System cuts over instantly when grid drops out. Barely a flicker of the lights, it happens so fast! Same thing happens when power is restored. Back on grid in an instant.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

When a lead-acid battery is discharged, the electrolyte (sulfuric acid) and the active material on the plates of the battery (lead) are consumed to produce water and lead sulfate and current flow. The chemical equation for a lead-acid battery during discharge is: PbO2 Pb 2H2SO4 –>PbSO4 2H2O Ideally it’s just hydrogen gas, but when doing Equalization charging, you’re going to get some hydrogen sulfide as well – you’ll know it by it’s Sulfur smell and the stinging sensation to your eyes! Make sure the battery box power exhaust fan works BEFORE you turn on your system. In this setup, I programmed the fan to run whenever the batteries are charging. As long as the fan is running, there is negative pressure in the box (or temporary tent in this case) so even any holes or leaks will take fresh air IN to the box/tent and then OUTside the house through the white PVC vent at the left. Happy to say that the 1st charge cycle was free from problems and there wasn’t even the tiniest hint of any gas in the room. The use of RECOMBINATION caps is HIGHLY recommended. They will eliminate almost all of the outgassing and make the battery liquid levels go down MUCH slower.

Backup System finished at Little House

Magna Sine inverter and Rolls batteries. Whole house transfer switch also.

Off-grid installation complete at the Bunker!

Wow, it’s taken a while to get this posted, but I’ve got the grid-backup system completed at our little house (we fondly refer to it as THE BUNKER…). I was recently out there during a freak snow storm that dumped 5 inches of wet snow in about 2 hours, and when the power went out, there was just a slight flicker of the lighting as I was sitting at the computer checking my email. The UPS on the computer didn’t even get a chance to kick in! I excitedly went downstairs to the basement to check out the inverter, and sure enough, it was on line, quietly humming away, providing full power to the main electric breaker box for everything that was presently on in the house. The Magnum MS-PAE 4024 inverter can provide about 4,000 watts of continuous power until the batteries discharge 80% of their capacity. Since the house normally consumes only about 500 watts (average) power, this represents about 20 hours of run time. Fortunately, when the backup system is in operation, the solar PV system can “back feed” through the breaker box and provide the power the house needs as well as re-charge the batteries, so this setup can run pretty much indefinitely, as long as there is a few hours of sun each day. Even on a cloudy day, the 2.4KW (Twelve 220 watt panels) solar array provides about 500 watts, so that extends the capacity of the system pretty well.

 

Home Brewed Genset simulator for transfer switch activation

In order to make the TRANSFER SWITCH operate, I had to build my own little GENSET SIMULATOR. It connects to the output of the backup inverter and provides the necessary voltage and control signal to the transfer switch to make it kick over when the power goes out. These TRANFER SWITCHES are designed to normally work with a gas or diesel GENERATOR SET, as they are called.

It took a little studying and research, but I figured out how to SIMULATE the voltage and signals that normally come from a GENERATOR SET that would connect to a WHOLE HOUSE TRANSFER SWTICH on the V+, GROUND, and PIN 23. These are the 3 wires that are standard on any gas or diesel generator. Since I’m using an electronic inverter (Magnum MS-PAE 4024), such signals were not available, so I came up with a little box that has 2 relays in it. One is standard and the other is a 5 second delay unit so the system won’t “chatter” if power drops in/out rapidly. If you’d like the details on how to build one, I’ll be glad to send you a schematic. Just drop me a line at: Joe@cincihomesolar.com

back up system Battery Bank

ROLLS 520 AH 6 volt batteries.

 

 

 

 

 

 

 

These are the batteries I chose. Since I’m on a tight budget, I chose the best bang-for-the-buck, and it ended up being the Rolls 6 volt 520AH model. I splurged on the funky looking RECOMBINATION CAPS, rather than the normal vented caps that come with the batteries. By installing the RECOMBINATION CAPS, the hydrogen gas generated during charging is sealed inside the battery 99%, and the battery loses MUCH LESS liquid over time than a VENTED battery would. A box and vent fan are still required for safety though, and I will add this to complete the project very soon. Without these special caps, in just 30 seconds of charging at 90 amps, the hydrogen gas coming from the batteries would reach 4% concentration and become highly explosive, so this is nothing to fool around with! VENT YOUR BATTERY BANK TO THE OUTDOORS!

EERE Residential PV Inspector training

Just finished (and passed) the new EERE Residential PV Solar inspector training program. It’s FREE, for now, at http://www1.eere.energy.gov/solar/sunshot/index.html and it’s very educational. It covers every aspect of a residential solar install and not only instructs on the backing materials, but offers a chapter by chapter self assessment (test) to see if you learned what they were trying to teach! All but ONE chapter was a breeze for me, and the tough chapter was on equipment. I think the questions/answers could be a little more clear in this chapter, but HEY, this is a BRAND NEW TRAINING AID, and I recommend that ALL installers take it and PASS it, just for the sheer value of knowledge!!

Back up system going in soon!

I’m stoked! My solar buddy, Brock, is going to help me pull new wires in from the meter outside the house down through, and to, the whole house smart switch, breaker box and Magnum backup inverter & battery bank this coming week! Will take a bunch of pictures when it’s done. Working with 3 other clients now on similar systems. One will even have a generator tie in! I can’t tell you where it is, but maybe I’ll be able to post some equipment pictures of the gear when we get that far. Right now it’s all in the planning stages. He’s going ALL the way off the grid! Me, I just want to get through a couple days of zombie armageddon… (just kidding!)

Mother Earth News Fair 2012 Solar Presentation

These are the slides that backed up my solar presentation at this year’s MEN Fair in 7 Springs, PA last weekend. There’s some text in the basic solar section, but they’re mostly slides. Primarily examples of things you’ll need to do/file/apply for if you are contemplating a DIY solar project. All the things I help out with if you sign up as a DIY solar client!! Also includes some great pictures of a variety of ground mount systems that I researched 2 weeks ago while attending the Solar Power International trade show in Orlando Florida. Please feel free to download and pass this around. No problems with that at all…
Mother Earth News Fair 2012 presentation

What it takes to keep your power UP when the grid is DOWN!

It’s been a long time coming, and I’ve been hesitant to make the investment, but recent power outages caused by the weather, combined with the state of affairs around the globe, have given me the motivation to finally make it happen. Please come back here at least twice a month to check my progress on this project! I’m doing this at my “bunker” in the mountains of Ohio. I’ve already got a 2400 watt system running using the older Enphase M190 micro-inverters along with 12 assorted PV Panels, and it’s covering 90 to 100% of the electric bill. But, I lost a refrigerator full of food when the power was down for too many days… so, I’m adding all the parts to keep the power flowing when the grid is down! Here’s a list of the parts I’ve got on the way:

  • Magnum Distribution panel 250/30A-2P
  • Magnum MS-PAE 4024AE 4kW 240VAC Pure Sine Inverter
  • Magnum LCD Remote Panel (for programming and monitoring inverter status)
  • Magnum BP-MMP Metal Mount for MMP enclosure and inverter
  • ROLLS 6V 530AH Wet 40000S EKG Battery (X4=24 Vdc)
  • Battery Box fan 24volt, 6 CFM
  • ROLLS R+ Recombination Caps (X12) keeps battery watering to a minimum
  • Outback Spill Control Tray for the batteries – in case of a case crack or acid spill
  • #4/0 gauge flex wire with lugs for battery interconnections and inverter hookup

There’s also a whole house SMART SWITCH and some other parts to modify the incoming service wiring…

That pile of parts is worth about $4500 if you’re considering doing this. Well worth the price if the grid goes down for ANY reason! I’ll take pictures as I go and do updates to describe my trials and tribulations!
DIY Solar is affordable and reliable ( and a great way to prepare for Zombie Armageddon ) just kidding… and have a SUNNY day!

Cinci Home Solar DIY Assistance job chosen as Array of the week by Enphase!

I was honored to hear from ENPHASE that one of my recent solar consulting installations was chosen as ARRAY OF THE WEEK! Check out the link and photos at:Enphase Array of the Week Truly an honor – and good demonstration that with my SOLAR DIY assistance you can end up with an array that is professionally designed, installed, commissioned and functional! If you’re suffering from commercial installer sticker shock when getting your special project quoted, just give me a call at Cinci Home Solar! I cover the Ohio, Indiana, Kentucky and Western Pennsylvania area, and will go farther if the job warrants!!

2012 Ohio SREC Pricing Average

Average Weighted Price for 2012 Solar SRECs in Ohio

Average Weighted Price for Ohio SRECs

If you’ve got your solar system up and running and are getting close to your first 1,000 KwHour mark – otherwise known as an SREC, here’s the latest average pricing from the GATS website. This is where you TRACK and RECORD your energy production on a month by month basis, and when you hit 1MW HOURs, you generate an SREC which you can then transfer to the BULLETIN BOARD where the folks who BUY SRECs look. You can set the price low or high – it’s up to you. Lower sells faster. Higher may never sell… kind of like playing poker…

Bottom line is that there is more SOLAR in Ohio now than ever before and the availability of SRECs is greater than the need, so you’ll have to think hard about how your price them – but thanks to tools on the EIS-GATS website, you can pull up the average for any period and make an INTELLIGENT decision about where to set your selling price!!