Solar powered reef tank?

Discussion in 'DIY' started by HiFidelity, Feb 19, 2016.

  1. HiFidelity

    HiFidelity Guest

    Hi folks, me again with my DIY ideas :p

    Last night I picked up a couple of AGM (Absorbed Glass Mat) marine batteries for 2 of my cars, these cars are a hobby and don't get driven like normal cars, therefore they spend extended periods of time untouched, well this is a problem when it comes to Lead Acid batteries because they're not very good at retaining a charge for prolonged periods, also they tend to go bad if discharged all the way which happens if you let it sit plugged into the car's electrical system.

    Enough background, when I got home my brain started ticking lol. I already had plans to use similar batteries as backup for my reef tank, I was going to put them on a "battery tender" which is basically a trickle charger built to maintain stored batteries and wire it all up so that if main power cuts out I have 10+ hours worth of battery powered power heads, heater, etc.

    I wonder now, what if I powered this whole concept with a solar panel? but I have no experience whatsoever with solar panels and haven't a clue if a couple of these batteries can run a tank's low power items (Reef Angel, pumps, power heads, LED lighting) around the clock? what are your thoughts?

    note: I know I know before you say it, I need a kill-a-watt to measure my tank's current consumption. Kw in vs Kw out is where I need the advice of an expert as I am not familiar w/ efficiency loss in the conversions, etc.


  2. aqua-nut

    aqua-nut Supporting Member

    First a disclaimer! I am in NO WAY an expert!

    Label says 120 minutes of reserve at 25A. If you try to run all of your stuff, how many amps do you estimate? Big users are heaters, return pump and lights. I consider the lights the least critical of those three and would eliminate them from the back up.

    Can the RA tell it's not powered by the usual AC source? If it can, have it shut off lights and perhaps heaters while on backup. After that, it's mostly figuring out a budget for the amps used vs. time you expect to need the backup.
  3. HiFidelity

    HiFidelity Guest

    no worries John lol I'm no expert which is why I am here with this post :)

    So in my list of items I want to run off this thing you'll notice I excluded heaters, I have 2 relay boxes for my Reef Angel, one will plug in the wall and one will plug into solar (in theory) so if power is lost one box shuts down (heaters and all unecessary stuff) while the other box and Reef Angel control module stay on.

    You read the spec wrong, it's okay I had to go back & read to remember how the formula works, so here goes;

    The standard of output measure on this type of battery is (XX A.H. @ XX Hr) in my case 55 Amp Hours @ 20 hours (2nd photo) now to derive how long the battery will go before running out of juice you have to divide the AH by the Hours so 55 รท 20 = 2.75 Amps
    From that formula we can conclude that at a max draw of 2.75 Amps this battery will run for 20 hours straight before running out. 5.5 amps = 10 hours and so on. In my case I would run 3 of these, 2 on solar panels & 1 on back up, there will also be a device that senses when solar system is out of juice it will switch to A/C power (wall outlet) adding another one of these devices in the mix, the 2nd can sense if A/C power was lost and it'll switch to battery back up. It's a bit complicated I know, I haven't fully understood it yet and need to do more precise math as well as measure my current draw.

    The nice thing is having 2 of these :D


    Now I can draw 5.5 amps over a 20 hour period or 2.75 over a 40 hour period (I will laugh in the face of a generator hehehe)

    Keep in mind I didn't buy these little guys for this design concept, these are specifically for my cars. If you notice the front label says "Group 34" that's a size standard which means they are exact fitment as my OEM battery. Why do we care? well this type of AGM battery comes in much much larger size than these and as you might imagine also much higher rating than 55 A.H. I personally would go for 100 A.H @ 20 Hr. multiply that by 2 batteries, now we're talking 20 amps for 20 hours :eek: which is insane, I could run my entire tank, heaters & all for over 20 hours with that kind of system, probably all the lighting in my house as well.

    My concern right now is not the storage capacity as I have detailed there is more than enough of that, if 2 batteries don't cut it, add a 3rd & a 4th... my concern is how large of a solar panel would I need to meet discharge demand in the night hours, this is where my knowledge is much more limited.
    Last edited: Feb 19, 2016
  4. rygh

    rygh Supporting Member

    Ahh, a great topic. Something I have spent a fair bit of time thinking about.

    Step 1: Convert all pumps to 24V DC.
    Very battery friendly that way. And easy nowadays.

    Step 2: Wrong kind of solar for heating.
    You want a solar hot water heater type.
    Tubes full of water in the sun, heat a large insulated tank of water.
    You pump that hot water through a plastic tube in your sump as needed.

    Step 3: Augmented natural sunlight
    Add solar tubes, like directed skylights, to bring in the real sunshine.
    Add blue for enhanced PAR and better look.

    Doing that, you only need small batteries. Perhaps 3. (run at 36V?)
    But you do need to have an AC charger and backup lights and heaters
    for the cloudy weeks we get here in the winter.
    HiFidelity likes this.
  5. HiFidelity

    HiFidelity Guest

    Mark, I damn near expect you to respond when it comes to these topics as our brains seem to run in parallel when talking electronics, etc. :p

    I'd have to disagree with steps 2 & 3 haha, my tank is a tiny 57G and it's going to be in the heart of my house meaning ambient temps will never be bellow 60 and never above 80 so minimal demand from heaters, in addition the tank is being flushed against a load bearing wall so no way to channel solar photons from the roof which is a full level and attic away from the tank. What does this leave me with? only one obvious choice;
    crystalline Silicon Solar Cells (to the unfamiliar that's what's on top of people's homes and takes light then converts it into electric current)

    Not going to worry about cloudy days as the system will be smart enough to automatically switch to grid power if solar system runs out. If grid power is gone it'll have a 3rd stage where it switches to a separate backup.

    Now spill some knowledge my way pleeeease because I don't know much beyond the correct terminology for said product haha

    DC pumps & LED power is going to be standard, already have all the DC pumps & powerheads in hand. Building new LED system that's going to be powered by LDD Drivers so full DC throughput.
  6. HiFidelity

    HiFidelity Guest

    I should have explained that I'm not being crazy with these ideas, my most recent PG&E bill was $450 and I don't currently have the means to go full solar on my house...
    I am running a dedicated power line from the tank to the main breaker box in my garage which is adjacent to a useless area in the backyard where I foresee it being perfectly utilized by a single highly efficient solar panel so essentially I can run 2 dedicated power lines, one to grid & one to solar.
  7. ddrueckh

    ddrueckh Supporting Member

    I am no expert either, but here is what I know from my travel trailer that I installed a solar system on:

    -I think you would be better off with two 6 volt golf cart batteries (only issue is they need to be vented - kept outside). Tied in series, they would give you 220AH @12 volt total, but only 120AH useable. You should not run batteries all the way down. Lead acid only 50%. I know you can run AGM batteries down a little more, but not too those 55AH batteries will not give you the full 55AH without damaging the batteries. I also recommend the golf cat batteries because you can get them at Costco for like $90 each. Much less expensive.

    -Now on to solar. A decent solar system is not cheap. I have two 160 watt panels on my trailer. They put out about 6AH each in good sun. Sometimes a little more. If you use 48AH of power, it takes 4+ hours to recharge. Charging becomes slower when the batteries near full charge. You need a charge controller and I highly recommend a battery monitor. The monitor tells you exactly how many AH you have used and what percentage charged the batteries are. It is invaluable when using a system like this so you don't run your batteries too low. You also need heavy gauge wires to connect everything. I don't know All the science, but 110V can travel through small wires but 12V does not travel as well. I get my equipment through AM Solar. Look them up at Check out their signature system cores. A system like mine will cost about $1,500. The final thing you might want is a converter. A converter changes the power from 12V to 110V. If you get one, get a pure sine wave inverter. They cost more. Some sensitive electronics will not run without a pure sine wave of could be damaged. You can find a lot of info on RV and trailer sites as many RVers use solar. Let me know if you have any questions and good luck.
  8. rygh

    rygh Supporting Member

    So given the normal sized tank and good ambient temperature, I have to ask:
    Are you sure that your tank is the power hog??

    I would hate to see you spend all the expense and time, and save $50 of $450.
    Time to measure everything!!!!

    I saved a ton of power with LED lighting in the kitchen plus a new dryer.


    Do you really want batteries at all??
    Another thought is to just run solar during the day.
    It powers your lights and pumps as possible.
    During the night, use normal house power.
    That eliminates a LOT of complexity.
    In fact, you need little more than a DC-DC converter and a big diode.
    But it means doing the electronics yourself.


    Agree with above that running 110 can have a lot of benefits.
    The science is that for the same power, higher voltage = lower current, and low current means less power loss in wires.
    Key formulas:
    Voltage = Current * Resistance.
    Power (watts) = Current * Voltage

    BUT: Using that means converting it back and forth, plus it means dealing
    with safety issues and possibly code issues and inspectors.

    Side note: I hate the term "Amp-Hours" that is used on batteries. It is wrong.
    Without voltage, it is basically meaningless.
    And on batteries and such, voltage changes pretty significantly.
    Watt-hours is what the power company uses, for good reason.
  9. HiFidelity

    HiFidelity Guest

    grrrrrr you're the second person who said savings won't offset cost, I guess I was just enamored by the idea of powering my tank by the sun haha.

    Remember the current tank is in the garage while I build the setup inside, therefore right now it is being a power hog, past bill covered the coldest part of this season where I suspect the heaters were running nearly non-stop and I had put a 3rd one on for a month or so.
    Once tank is in the house it'll be more efficient by heaps & bounds, already bought a brand new He washer & dryer, whole house is cfl but recently started switching to LED starting with the most powerful bulb :)

    I now wonder about Lithium Ion for power storage haha that would definitely make the cost go sky high
  10. HiFidelity

    HiFidelity Guest

    ddrueckh somehow I missed your comment earlier... my best bet on this is just use a couple of the batteries you mentioned as a backup (noticed how much cheaper they are) and only put powerheads on it, I've managed to run powerheads for hours before on a common car battery so it'll be nice to at least automate that feature.
    I really appreciate the info you provided, if I don't do this on my tank I might still end up having to build a solar setup of some sort for a larger project (not reef related) so definitely info I'll be using in the future.
  11. rygh

    rygh Supporting Member

    Most AGM batteries are "Deep Cycle" as are most golf cart batteries.
    So either should be fine.
    Key is not using a standard starter battery.
  12. HiFidelity

    HiFidelity Guest

    from what I've seen online golf cart batteries are AGM.
    I'm all to familiar with the shortcomings of regular car batteries, in 5 years I've gone through 4 batteries in 2 cars due to the fact that they don't get used, I'm probably never buying another Lead Acid battery again :mad:
  13. sfsuphysics

    sfsuphysics Supporting Member

    If you want to power your tank via solar my advice is don't, power your house with solar and then let the house power the tank. Now I know you said you don't have the means to go full solar but hear me out.

    After reading a few things I see certain items that pop out at me.
    1) $450 bill, tank in garage. Now IMO, this is a seasonal cost, hell my power usage was 1000kWh for 2 months straight and that's with 3.26kW of solar panels on my roof. Now just like you my tank is in my garage/basement area (cooler than normal area, so yeah more heat when it's colder). Now I get you want to get away from this level of power, but you also said you're building a tank inside, presumably the garage ones go away then? If so hold off, your power bill most certainly will drop once you bring the tank out of a cold basement. Also is your house heated via natural gas or electric heat? If it's electric heat I'd look a little to that being a culprit as well.

    2) Solar can help, in general solar has a very poor RoI, however in the lovely bay area where PG&E likes to stick it to us in the keister for "using too much power" by jacking rates up to fairly high levels. In fact compared to the rest of the country we have some of the highest rates there are (Hawaii and maybe a couple other states are higher), so solar actually has a much better RoI here simply because what it does is it knocks power off those highest charged energy tiers which end up costing you like 35+cents per kWh (and it will keep going up) where as most RoI calculations go out the window, because they assume you're going to be paying 10-15 cents per kWh and use that number to calculate your RoI. Now the problem is that it knocks off those highest tiers FIRST, so if this in fact a seasonal power spike then you're going to not use as much power in the summer so might not make good financial sense (also note you will make less power in the winter months too), now if you have a house that uses AC and that brings you back up to those high prices then it's totally worth it.

    3) Batteries, ditch the batteries, the only reason you want to use batteries with solar is if you a) want off the grid completely, or b) have a remote area where running wire is not feasible. Instead go with a microinverter for your panels. These are nifty little devices where you attach one per panel instead of the big inverter box, and the transfer the DC right to AC at the source. You tie into your house electrical, let PG&E be your battery and then at night you don't have to worry about the total capacity of your battery, and best of all if you make more power than you would use on what you plug into the panel you don't waste that power. They allow you to build at your rate so you can put one panel in, then 2 panels in 3 months, or whatever your budget allows, you basically daisy chain them together as you add more (up to the capacity of the line that's carrying electrical into your house) plus they have the added effect of not caring if your panels are all aligned with each other, or if one is getting shadowed, etc. They will add $100-160 per 250w worth of panel, but compared to the price of a deep cycle marine battery, it's not too bad. Also the downside is if you get tiny 100W panels, they don't make much financial sense, you really want to maximize the wattage so that you can get the most out of each inverter (which you need to add to each panel)

    Now the 64 dollar question is, how much money were you looking to spend? A good quality panel will cost you in the neighborhood of $200 for ~250 watts (yeah you an get them for less than a buck a watt), the inverter again $100-160. How are you going to mount them? That cost money too. Are you going to run the wires? Get permits? basically how much of this is paying someone to do it vs. DIY on a weekend when inspectors don't work. Also do you live in a HOA which might ban them? Solar panels themselves are really not that expensive if you can do the work yourself, or know someone who can help in certain aspects and it costs you a case of beer and a pizza or something. It's when you need to get a company to install them, where the cost literally explodes to 3+ times the cost of the materials.

    However if you're going to do a single 250watt panel, then at 4.5hrs of full sunlight on average per day throughout the year, then that's .250 kW * 4.5 hours = 1.125 kWh per day, or over a month that will knock off almost 34kWh off your PG&E bill, and this is calculated with 100% efficiency so the real amount will be lower, so even at the highest tiers that translates to about $11/month. Solar really is a long term thing, so do you want to spend $300 + a whatever extra to save $11/month? Over a year that's $130, over 10 years that's $1300 and that's big time pay day... but like I said, is this a seasonal cost and one that that will be remedied in a few months when you get your tank out of the garage and you'll never hit those high prices again?
    rygh likes this.
  14. HiFidelity

    HiFidelity Guest

    you hit the nail on the head Mike :)
    My summer bills can be as low as $150 but right now I'm burning $150 in natural gas alone, heater & stove are both gas powered and everything else is electrical so this is certainly a seasonal spike. I have a stone tile roof and frankly I don't love the idea of panels up there so I was going to stick to the side/back yard but then I can only run a couple of panels so ROI is near nothing. Also I might not be in this house 5 years from now and the refi, etc. etc. so way too many variables keeping me from going full solar.

    That being said I am sure the savings will come once the tank is nestled within the house, if anything I'll end up having to worry about cooling the tank in the summer since we run no Air Conditioner and the sump, equipment & everything is going to be housed in a utility room which will be ventilated, furthermore the tank is going to be encased on 3 sides inside an insulated wall. Should be really efficient in winters haha.

    Again I really appreciate the knowledge you guys are sharing, this will be very handy because at some point in the future I do foresee an "off the grid" project in a remote area where solar could be the primary source of power in a place where space is no object.
  15. Flagg37

    Flagg37 Officer at large

    I think the biggest reason to use the batteries is for when there's a black out but you don't need solar for that.
  16. aqua-nut

    aqua-nut Supporting Member

    I misread the first post. That's what I thought the OP was trying to do. :oops:
  17. HiFidelity

    HiFidelity Guest

  18. iani

    iani Guest

    BTW, anyone thinking about going solar in the future needs to switch the rate schedule to the e6 schedule ASAP. PGE is getting rid of the rate schedule to new applicants starting March 1st.

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