Basic Battery backup with solar

[Fred]

I have a single 120V .23Amp pump on a 55 gallon system.

On occasion we have power outages so I setup a 45amp hour battery with a 400watt inverter.  I've connected a 2amp battery maintainer and I'm now running the pump from the battery via inverter.

Does anyone have any suggestions for adding solar to this setup?  I have two 20 watt panels I could connect but I'm not sure how they'd fit into the system.  Where would I put a solar charge controller while keeping the battery maintainer running?

[George]

You might want to rig the panels to be ready to go in case of long term power outage.  If that happens and once your battery drains down, you could probably attach those panels directly to battery without a controller (if 12-volt panels).  I doubt that overcharging will be a problem.  You could check the battery from time to time with a meter but too little power will likely be more of a problem than overcharging.  You might want to get a volt meter if you don't have one, just to see how well your battery minder is doing.  I had one that was suppose to begin charging upon low battery but it didn't work as advertised - that was a "Smart" charger.  

Otherwise, you have a nice backup system as is and many could benefit by doing the same.  It's relatively cheap insurance.   

[Fred]

Thanks George.  I purchased a 2 amp 'smart' batter minder and connected this to the battery with the 400W inverted.  I checked the voltage before and after it ran a few hours.  Initially the voltage was dropping very slowly but I noticed the charger was getting pretty hot (it's a sealed plastic unit).  I decided to mount it to the outside of my tank since it's usually 60-80F.  This worked and once the temp of the charger was a cooled, it kept up and started charging the batter.  It's at 13.3V now and climbing slowly.  

[George]

A tank heater to boot.  Nice charge.  I'm not getting more than 12.8 on a good day from my panels/charge controller. 

[Matt T.]

Harbor Freight has some controllers there, that are fairly cheap. I would think that you would not need the maintainer, if you used the solar panels to charge. Otherwise I think you would just hook them both up at the same point. Its not like you will be doubling the voltage, you will be increasing the wattage though. But so long as they are automatically cycled on, and off, it should be fine. How are you going to rig up a switch to turn the twelve volt system on, after a power failure on the household electric? Been thinking of making a backup system myself, but the switch over system is still to be worked out. All I can think of for now is a photocell that would send a signal when the lights go out?

   They sell some nice onboard chargers for deep cycle batteries used on fishermens trolling motors. They are automatic, have cooling fins, and available in several amperage designs. A minimum would be 10 amps for a deep cycle or AGM battery. Bass Pro Shops, and Cabelas sell them, as do a lot of farm stores like Tractor Supply, Fleet Farm to name a few.

[Michael Clegg]

Matt,     Harbour Freights controllers are waste of good money. Try Steca, they make an excellent reg and they are quite affordable. Always look for a reg with MPPT, Maximum Power point Tracking. Start with a solar module that has a high dc voltage, 21-23 VDC. The reg "takes" this voltage and lowers it to the needed 17VDC and with that conversion you will realize a higher amp output, up to 30% higher.

We use 24 VDC, but for clarity in the following example we will use 12 VDC. Our 3000 watt output divided by 17 will give the amp output of 176.4 amps. But with MPPT we realize a higher number, in this case, 229.4 amps/hour. That means we appreciate 53.0 additional amp output. Which for us it is important, while we have a backup generator we never use it.

Here at Synergy Aquaponics we use both sun and wind to provide for our electrical needs. We have 3000 watts of solar modules, 18 Rols/Surrette- 450 amp batteries, 3 - 3000 watt Outback inverters w/100 chargers, 1 Outback reg, 2 Blue Sky regs and 1 SouthWest 1000 watt Wind turbine on 30' tower. 

We also have 140' of swimming pool heaters. which keep the tanks and troughs heated, after all, Tilapia do not "like" water below 75 F - 23.9 C

Some folks said that it was near impossible to run such an operation using solar and wind, but then again, that is what so many said to Thomas Edison.  Cheers

[Matt T.]

Thanks Micheal. That is a mighty impressive setup you have out there. Not sure I'm ready to go that large, but I do appreciate the info you've given me on the controllers. Harbour Freight does have some shoddy merchandise, but some of it works fairly. You do have to dig through it to find some of the deals. I've seen identical items sold at some catalog houses for twice the price, but still, its all just as poorly made....