Micro-Solar Setup : My First Experience w/Off-Grid Electricity

[bruss01]

Ok, I am just delving into my first experience (other than generator) with off-grid power.

Please - before commenting - can I ask that you see what my goals for this system are before commenting, as I think that the objectives inform the method. Thanks.

My goals for this system are very modest, I think. I do NOT want to power the house. I DON'T want to run the furnace, washer, fridge, power tools, welding rig or any such power-hungry device. If I did, I would have chosen an altogether different strategy.

The goal is to provide a very small amount of power for a set of very small devices.

The devices I want to power are things like LED flashlights, cell phones, Kindle reader, a netbook computer, portable DVD player, shortwave radio (receiver only, not HAM), etc. Things that have replaceable/rechargeable batteries which don't draw a lot of current.

My goal in doing this is to always have some power available for these devices, even if there is a reason why the generators cannot or should not be run (noise signature, fuel shortage, etc). After the initial cost of getting set up, the energy should be basically "free" and infinitely renewable.

In pursuit of this modest ambition, I have acquired two 6 volt batteries (Trojan T-105 RE which are basically golf cart batteries that have been beefed up for use with renewable energy applications) which are hooked up in series, and a Harbor Freight 45 watt 3-pannel kit. I've heard some folks are not thrilled with the HF kit, but like I said, I'm not planning to power the house, just "float" a couple of batteries for emergency use. I installed everything last night. Because of the modest ambitions for this kit, I am not concerned about optimal placement of the pannels. Right now I have them propped up in the windowsil, facing due south. I want to see how they perform in this position before taking the experiment further. If needed, they can be mounted outside in a more favorable position. We have a large tree in the west that shades the house after about 3-4 in the afternoon. I am hoping that the pannels will still generate a trickle charge even if they are not receiving direct sunlight.

I like that the regulator unit of the HF kit has several kinds of power outlet - 12v Auto, 5v USB, etc... I have heard people say it is a crappy unit, but never heard anyone say what specifically they didn't like about it. For all I know it could be the color or that they wanted some option that it doesn't offer. I'd consider upgrading the regulator if there was a significant reason to do so. I'm hoping that for what I want to do, it will be sufficient. I actually like the form-factor and it sits on a bookshelf, out of the way yet easily accessible - it doesn't require mounting.

Last night when I got everything connected (after the sun went down) I had a chance to test the system a little bit. The batteries read right at 12.3 v and the two (included) 15 w CFL's worked fine, as expected. When I got up this morning (before sunup) it was still reading 12.3 v and by the time I left for work (8 am) there was a bit of good daylight and I noticed the battery reading was up to 12.4 so it looks like it's taking a charge even with sub-optimal placement of the pannels.

Hopefully this evening I can put up some photos and report on charging performance in this configuration. Total cost of the whole system so far is about $700 which is just under $200 for the HF kit and around $500 for the batteries, cables, battery boxes etc. Yes, I could have gone cheaper with a simple deep-cycle marine battery but I thought it was worth the money to go for a little more capacity and the reliability of the Trojan product. I expect this system to spend much time charging and little time being drained, so hopefully this setup will meet that need.

[wolfracer]

For what you are trying to do this should work fine. The real test would be after you run it for a while and see how well your batteries recharge. Let us know because this looks like something worth doing.

[Daelith]

People tend to not like the HF system because it's cheaply built and not very efficient. That said, if all you want is a trickle-charger setup and you won't be pulling much power then it's not a bad deal. One thing to remember is if your batteries do end up getting drained (extended cloud cover, etc) 45W will take a LONG time to recharge 225AH batteries. Two weeks would not be unexpected to charge from a 50% drain, but as long as you're not running the devices for longer than there is sunlight you should be okay.

[bruss01]

People tend to not like the HF system because it's cheaply built and not very efficient. That said, if all you want is a trickle-charger setup and you won't be pulling much power then it's not a bad deal. One thing to remember is if your batteries do end up getting drained (extended cloud cover, etc) 45W will take a LONG time to recharge 225AH batteries. Two weeks would not be unexpected to charge from a 50% drain, but as long as you're not running the devices for longer than there is sunlight you should be okay.

Understood. I have two pieces of equipment left to acquire to complete this system. One is a wall-outlet battery charger for use when the grid is up or when the generators are being run for another purpose (such as running the washing machine) so I can capture some volts even if, like you say, there is a shortage of watts via sunlight. The other piece is a pure sine wave inverter. From what I've read a 1500 watt unit ought to be sized about right for this sort of setup. That will give me the ability to tap into some of that deep capacity if needed for something that does require 125v AC power, even if it is only for brief usage. A few other additions would be minor things like a car-charger unit for my Ryobi Plus-One cordless power tools. It will probably be a few months before I can make those additions but they are on the list.

My wife will be thrilled if I can keep her computer, cell phone and Kindle charged up. That gal does love her modern technology!

[bruss01]

I just got word it is now up to 12.7.... up from 12.3 this morning!

It is charging. Probably won't win any quick-charge awards.... but it IS charging. I expect it will take a while to build up the charge in these large capacity golf cart batteries.

[Gothmolly]

The pure sine wave inverter is key. Otherwise you run the risk of cooking your electronics.

[homer]

I have the same HF setup (45 watt) and the single 15 watt panel with a separate smaller HF charge controller. I use both setups to charge car type batteries (yes I know car batteries aren't optimal) in my out building. The 3 45w panels are in an upstairs south facing window, this significantly reduces output. My 15w panel is outside, laying face up in a pick up truck bed and puts out 2 to 3 times the power as it did when it was in the same window the 3 45w panels are in now. I measured output with a DVOM, same day, 2nd story vs truck bed, and a distance of maybe 10ft between the 2 spots. As soon as I figure out where to put the 45w panels that are in window now, they will be outside too. Outside really seems to make a difference, especially if the window has a screen.

I have no complaints, and am very happy with the both HF setups. I think some of the HF negative comments are like the Hi-Point firearms negative comments, by people who have never owned or even touched the said product. I would buy either of the HF setups again.

These are my real world experiences for the last year or so.

homer

[bruss01]

Thanks Homer.

BTW I have checked again now that the sun is down and the battery is back to reading 12.4v by the regulator readout. It has had no load at all. Just wondering if others with solar setups notice a rise during the day, and a fall at night, with no power consumption...

[Tdale]

Bruss01:

First, congratulations on your solar setup. I'm sure it will deliver the power you need for your stated purpose

However (not trying to nit-pick) If it were me I would have gone with a 100 watt panel for $135 http://www.solarblvd.com/p1394/Solar...887cc2ba5c4dcf and a Morningstar charge controller like the $44 Sunsaver SS-10 10A http://www.solarblvd.com/Charge-Cont...duct_info.html.

Same cost as the HF kit but over 2X the wattage, a better charge controller, and a 5 year warranty vs the HF 90 day warranty.

As far as the HF regulator, from what I have read, it is less efficient then a morningstar and prone to breaking (for lack of a better term) don't be surprised if you have to replace it with-in the 1st year.....but again I have never owned a HF solar setup, so take that for what it's worth.

That said you made a wise choice on the batteries 2 T-105's will probably give you 8 years of service life with your low usage requirements.

But they should have only been about $150 each.....http://www.altestore.com/store/Deep-...FSHatgodOgMn0w

Also Interstate makes a T-105 battery for about $120 ea http://www.atbatt.com/product/24026....m_term=GC2-XHD ($150 shipped) the reviews I have read on it say that it is the same quality level as the Trojan T-105. The Golf Course I play at uses the Interstate Batteries in their golf carts and they last for years under harsh abuse. I'm sure for a small solar setup they would last just as long as the Trojan T-105's, but you cant go qrong with Trojan, thats waht I used when I had a smaller system at my BOL, now I use Rolls, both are great batteries.

All that said it sounds like your system is working just fine for your intended application, my comments are really just how I would have tweaked the items to get a little more wattage and saved a little on the system cost.

If I can make a suggestion for your batteries, take a look at the Water Miser battery caps http://www.altestore.com/store/Deep-...Watering/p535/ they will lessen your battery maintenance and greatly reduce water and acid loss. I use then on my Rolls batteries, they are really amazing.

For your inverter a Pure Sine Wave will be better, but a modified sine wave will probably work just fine in your application (because the items you listed like the laptop, convert the AC to DC anyway) so using a modified sine wave inverter will work just fine and cost much less. An $80 1100 watt unit like this http://www.amazon.com/Power-Bright-P...3161826&sr=8-3 would work just fine for running the items you listed. If you think you need a 1500 watt a $140 watt unit like this http://www.amazon.com/Power-Bright-P...3164809&sr=8-6 would work just fine.

I run this 2300 watt inverter http://www.amazon.com/Power-Bright-P...3165080&sr=1-2 at my off grid BOL, it has served me well for many years, so I can personally recommend the Power Bright inverters and I have never had an issue running anything off Modified Sine Wave.

Just make sure to use THICK wire 2/0 AWG or thicker for the battery to inverter connection if you go with a 1500 watt inverter.

[Tdale]

Thanks Homer.

BTW I have checked again now that the sun is down and the battery is back to reading 12.4v by the regulator readout. It has had no load at all. Just wondering if others with solar setups notice a rise during the day, and a fall at night, with no power consumption...

Your battery voltage will always meter higher when they are actively being charged because your charge controller inputs a higher voltage then the battery to overcome the internal resistance in the battery......so battery voltage while charging is not an indication of your actual battery charge.

Once the panels stop charging then your battery bank voltage will come down to the actual battery voltage and you can guestimate your battery's charge level by reading the voltage after several hours has passed since you had a charge on the batteries..... However using a voltage reading is a rough guess

State of Charge 12 Volt battery Volts per Cell
100% 12.7 2.12
90% 12.5 2.08
80% 12.42 2.07
70% 12.32 2.05
60% 12.20 2.03
50% 12.06 2.01
40% 11.9 1.98
30% 11.75 1.96
20% 11.58 1.93
10% 11.31 1.89
0 10.5 1.75

If you went from 12.3 volts to 12.4 volts, that's about a 10% increase in your batteries capacity (12.32 volts is about 70% full and 12.42 volts is about 80% full) so you put about 20 amps into your batteries, that's not too shabby for a 45 watt panel.

however a much better way to measure your batteries charge level is to use a hydrometer to measure the specific gravity of your electrolyte solution.

here is a good battery read http://www.windsun.com/Batteries/Battery_FAQ.htm