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Discussion Starter · #1 ·
I've promised this for a while, but I finally got around to documenting and wanted to share the battery backup system I made for my Simplicity DC return pumps.

Before you read below, please note that I'm not an electrician and I make no warranties whatsoever about whether the below is safe or will work in your situation or prevent your fishes from suffering a grim-power-failure-induced-fate, or whether I know how to annotate wiring diagrams correctly or generally what the heck I'm talking about. However - this functions as intended.

Premise - the pump in question works on 24 volt, Direct Current power, 24v dc. Batteries make DC current. Two 12v batteries together will make 24v dc power sufficient to run my DSC3200 simplicity pump.

battery wiring.jpg


Here's the problem - how do you hook this up so the battery works when the main pump power supply shuts off (Power goes out)? I used a power relay switch and some 2.1mm x 5.5mm DC Terminal Jack Socket wires I got off the interwebs.
A relay is a device that uses an electromagnetic coil to switch from one power source to another. When the coil is charged because the power is on, the pump is pulling power from the power supply that came with the pump. The 2.1 5.5mm jacks are the correct ones to plug directly into the pump controller and power supply. When the coil is not charged, like for example, the power goes out, the relay is providing power to the pump from the batteries. Here's a pic of the relay all wired up.
Relay big picture.jpg


I got a relay that goes on socket base for easy wiring. This then goes on a standard bus rail and screws to the wall of the stand. The relay has a wiring diagram that corresponds to numbers 1-8 where wires attach. Here is how I've wired mine up. Check inside the red box.
Relay Wiring.jpg


Total investment for the relay, some 18AWG wire, and a 10 pack of the plug ends was about $25. This is simply to build the switch. You will also need batteries and something to charge them up.
 

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Discussion Starter · #2 ·
Batteries are where the real expense in a system like this is. Just ask any fisherman who got a really neat trolling motor and then had to get batteries for it. How big? How long will they last?

In my case, I was a little size constrained behind my ATO res in my stand. So, I had to shop by shape and size. I'm guessing a LOT of folks will be in the same bucket in trying to fit something like this under the stand, so size vs. capacity became the trade off. I found that two mobility scooter batteries (these may be more common in the states... :D :lol: ... would work well for me. They need to be deep cycle batteries made to charge and discharge more fully. I wanted AGM batteries because they are not spillable and don't require maintenance.

These bad boys weigh in at 55AH. What the heck does that mean? AH means Amp Hour - think of it the way I, a true dummy, do. The battery could put out 1 amp for 55 hours (theoretically, but what else I got to go on? Nothing. That's right... keep walking). Or, it could put out 2 amps for 27.5 hours. Or, it could run 2.3 amps for about 24 hours.

The funny thing about batteries when you put two together is that you get either double volts (wired in series) or double amps (wired in parallel). So - 2 55AH batteries will run at 24v, but they will still only run for 55AH.

So how long is that? I borrowed a DC bench power unit from a friend when I was playing around with this, and determined that my simplicity 3200 is drawing about 2.3 amps set at about 85%. Therefore I know that this will keep my pump going for about 24 hours. Just a pump? Why just a pump? Long story short, my system is huge and it will not cool down quickly. So in a power outage, what kills the fish first? Suffocation. If you're running a heavily stocked tank and relying on water movement and surface agitation to provide gas exchange, your fish can all suffocate in as little as an hour if that movement goes away. I elected to keep one pump going through the sump and discharging at the surface to agitate.

In my case though, only keeping one pump going instead of 2 has some interesting side effects that will help to keep the water oxygenated. First, if the flow drops in half, the Bean Animal no longer works the way it's supposed to, and the secondary durso stops working all together. The water level in the overflow tower drops to the level of the main drain. This drain is no longer a siphon, so it's sucking air and introducing it into the sump compartment. It gets loud.
Since the water level in the overflow tower drops, it's now 6 inches below my weir, and the water falling also is loud and introduces gas exchange. Finally, and probably most important, the water level in the main display drops about an inch and puts the discharge that much closer to the surface also introducing extra gas exchange.

Do I think I have enough fish in my tank to die in an hour? Nope.
Am I going to prepare for this eventuality anyway? Yep.

So, the battery buys me a day. A day to get somebody over here to get the thing on a generator, or figure out a longer term solution. Also, for the record, I've lived here for over 10 years and have never had the power go out for more than 12 hours. I think that this is about to change though. Wars in the future will be fought with infrastructure attacks. Be a good steward and prepare for that.

At the very least, when the power went out this winter, I saw somebody posting on social media how they had lost 400 fish. Tragic.
 

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Discussion Starter · #3 ·
WAIT RIGHT THERE!

What happens when your batteries are dead?
Did you drain them more than halfway? Did you run them til they stopped? They you might have killed them. Batteries hate that. Sorry. But your fishes are alive! And that's priceless. Get you some new batteries and set up for next time.

If you didn't do that, you'll need a charger. Your system is 24 volt though, so you can't just get a regular old battery charger and throw it on there all wired up. You can take the batteries out and charge them up one at a time on just about any battery charger made for car batteries or 12v deep cycles.

I did not want to have to do that. Or move a charger, or unwire anything. I'm super lazy. It's a thing, you'll learn to love it about me. I want something like a battery tender I can just put on there and leave it and not think about it, but the 24v system becomes a little more challenging. You have to either get a 24 volt charger to charge both batteries at the same time, or get one with 2 "banks," or get two chargers... I guess... you got that kinda room on your power strip? Under your stand? Nope. Nobody does.

Power matters too. How many amps? The more amps the faster the charger will be able to charge the battery. This is a very good thing for battery longevity. Remember that for your next trolling motor, but does it matter here? I don't expect to use this system very often, so what's more likely to happen is that I'll wind up replacing the batteries every two years preventatively, and the discharge won't be a big deal. Also, more power means more expensiver chargers. Is it worth it? I decided that it was. What often happens in a storm is that the power goes out and comes back on a few times. I'm hoping for overall more use through a sustained power outage. Or, if I need to run a generator in a sustained outage, the larger charger will fill the batteries up longer for the generator break.

I went with a 2 bank charger with 4 amps per bank. It is designed and intended to be mounted as an onboard charger for a trolling motor bank so it's waterproof and fully sealed. It's intended to be plugged in all the time to maintain and desulfate the batteries and keep it all going longer. It cost about $95, but the one designed for the purpose was worth it to me. Plus the cool green lights on it telling me that everything is OK makes me feel happy.
 

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I'm glad you started a thread for this. I'm not an electrical engineer but I am a mechanical engineer and took some basic electrical courses in college so it's all very interesting stuff to me.

The funny thing about batteries when you put two together is that you get either double volts (wired in series) or double amps (wired in parallel). So - 2 55AH batteries will run at 24v, but they will still only run for 55AH.
Maybe you know this already but the above isn't totally accurate. Well the series part is, but not the parallel part technically. Only if you had a contant power load (wattage) and it didn't care about the voltage. Then this is correct. But I'm sure you know a DC motor DOES care about voltage. Votage = Speed and Current = Torque. If you cut your voltage in half it can't just draw twice the current to compensate. (Maybe. At least that's the simple DC motors I remember about. I don't know if they're fancier nowadays.) And if it's running half the speed the torque (current) required should be about 1/4 the current for full speed since torque of a centrifugal pump is proportional to the square of speed. (I actually help design/analyze centrifugal fuel pumps for my career, coincidentally)

HEY, that gives me a thought. When you tested your current draw at 85% speed did you also measure voltage? Did you measure on the line going into the pump (out of the controller) or did you measure on the line going into the controller?

2 thoughts actually.

1) if all the controller is doing to control speed is turn down the voltage to the motor like I suspect, you would NOT need to supply 24V and you wouldn't even need a controller either. You could run your batteries in parallel and just bypass the controller (maybe the controller does always need 24V?). Your pump should run off the controller at half speed, require 35% of the total current (0.8A) required to run at 85% speed, and being split between 2 55AH batteries in parallel (0.4A each) means your same battery would then last about 137.5 hrs rather than the 24hrs you planned for - over 5 and a half days.

2) if you did measure your current on the line going into the pump (out of the controller) it (probably) won't be the same as the current coming out of the batteries so you might get a few more hours than you think. It feels right to me that power would be conserved (wattage in = wattage out (plus losses, heat which I'll ignore), wattage = voltage times current). You're supplying the controller with 24V always, but if you're running at 85%, (probably) only 20.4V is going to the pump. If you measured 2.3A going into the pump at 20.4V, that's 46.9W. To have the same wattage in at 24V would only be about 1.95A. And that's what would actually be coming out of the batteries. So you'd get a little over 28hrs rather than the 24hrs you thought running the batteries in series into the controller. If you measured the 2.3A current on the line into the controller, disregard this.

I think thought (1) might be worth looking into for you. If you can live with a single pump at 50% speed rather than 85% speed you might get a lot more emergency buffer out of your current equipment. I'd want to get a multimeter and measure current through the pump and voltage across at each one of those set points the controller has before trying that though. It's possible the voltage across the pump motor itself isn't even really tied to the voltage being supplied to the controller. That 24V might just be the bank the controller needs to function. Theoretically (I think) the voltage could be either increased or decreased in the controller
(wiki article for reference) so 100% speed might be even greater than 24V depending on what the controller is actually doing.

What happens when your batteries are dead?
Did you drain them more than halfway? Did you run them til they stopped? They you might have killed them. Batteries hate that. Sorry. But your fishes are alive! And that's priceless. Get you some new batteries and set up for next time.
Another thing you might want to consider is what do your batteries do as they start to drain. Do they lose voltage or do they mostly keep the same voltage. If they're scooter batteries they probably don't start to lose voltage until they're nearly drained. But if you fry your controller or pump because they don't like running very long on less than 24V you might not care about the cost, as you say, fish alive is priceless, but inconvenient to say the least if the pump doesn't start back up when the power comes back on.

you got that kinda room on your power strip? Under your stand? Nope. Nobody does.
weeeellllll... I wired up my stand with 3 outlets/6 plugs. And a switch for under-stand lights. For me- heater, pump, canopy lights (on plug in timer), and 2 aquaclear 110's with 1 plug left over is how I ran before. I could always plug in a wire strip or wire in more outlets :D. 'Course, they all go in/out the same pipeline and plug. I was even dumber back then than I am now, I hacked up an extension cord to do all my wiring. I didn't even know what gauge/amperage it's rated for. Well the breaker should trip at 20A but the wire may only be 10A or 15A rated. Well it didn't melt when I was running before. Rewiring my stand is on my list of things to-do but that's a story for another thread. Don't tell the electricians!
 

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Discussion Starter · #5 ·
Rhinox said:
Maybe you know this already
LOL, Nope. You give me a lot of credit I don't deserve. I had to learn all this from the interwebs and some friends who told me I was dumb a few times.
The whole system I made up was to eliminate all the clever things you talk about. How do I get power directly into the controller to not have to worry about any setting changes or weirdness when the power shuts off. So, I built the batteries to emulate the power supply supplied. 24v 5.25A. I sized the relay to be about double this "Maximum" power so it would be able to handle the current. All my knowledge of DC motors comes from trolling motors and the research I did for these return pumps.

I measured current into the controller. I got a bench power unit from a friend, who I am sure thinks I am a crazy moron, set it to 26.4v to emulate power coming out of a 2 battery bank and then watched what kind of current was flowing. 2.3 Amps. Just about 4 at full speed, so this seems to match the curve you were mentioning there.

Oh, that brings me to another reason for going with 2 batteries, and I think that all the math you put above is what you're saying, but 24 volts is more efficient on energy use than 12. I'm also guessing that I'm not likely to fry the controller, but if I do, another pump is still there. I say this because of the apparently not exhaustive research I did while I had that bench power unit.

And here, I have to tell on myself. I have 30 plugs in my reef. 1x10 plug strip in the canopy for lights and two in the stand. The two in the stand run off two separate circuits I put in while I was waiting for the tank to be built. Redundancy everywhere.
 

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How do I get power directly into the controller to not have to worry about any setting changes or weirdness when the power shuts off. So, I built the batteries to emulate the power supply supplied. 24v 5.25A.
Certainly a very reasonable and safe approach

then watched what kind of current was flowing. 2.3 Amps. Just about 4 at full speed, so this seems to match the curve you were mentioning there.
My career breathes a sigh of relief :D

but 24 volts is more efficient on energy use than 12. I'm also guessing that I'm not likely to fry the controller, but if I do, another pump is still there. I say this because of the apparently not exhaustive research I did while I had that bench power unit.
Only thing I can think that makes 24V more efficient than 12V would probably be that for any particular wattage, higher voltage would use less current. Less current means all the little components aren't going to heat up as much and heat is a big way to lose efficiency. That was also the basis of my concern about burning up a controller. If the voltage drops it might draw more current because it needs to maintain a certain amount of input power in order to supply the set voltage and current to the pump. The current might create too much heat and kill the controller, or maybe the controller will limit itself and shut down if the voltage is too low. In that case you wouldn't have to worry about destroying your batteries either. If you hooked the batteries directly up to the motor without the controller, they almost certainly would just keep draining down to nothing unless the motor itself has some kind of fancy circuit board to prevent that.

I almost want to go plug my laptop power supply into my 2100DC controller (probably the same as yours) and see if it still works and if it spins the pump about the same speed, or if it just doesn't do anything. It says it's 19.5V output. Sorry but I don't think I want to put my pump on the line :D

Any RC hobbyists out there could probably tell me how wrong I'm being right now but just saying be careful with that controller if the voltage varies to much either way from it's designed input voltage.

And here, I have to tell on myself. I have 30 plugs in my reef. 1x10 plug strip in the canopy for lights and two in the stand. The two in the stand run off two separate circuits I put in while I was waiting for the tank to be built. Redundancy everywhere.
Why do I feel like I already knew this would be the case :D
 
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