DIY Oversized Battery Backup

[bumpyj38]

This thread is to show others how and why I built a battery back up that will run my return pump for 26 hours. It includes an automatic transfer switch, 100Ah battery, and a battery monitor so I could check battery status. No, it doesn’t provide answers to every situation. But these are some things that came up when I was building mine. Here are a few points to consider about his post:

1. I wanted to run my return pump on back up. If I’m going to build my own I thought might as well make it for a return pump. It keeps my whole system running and the nozzles should provide for some flow in the tank. Also, what better way to provide gas exchange then just running the whole system?

2. I am a Firefighter so I am gone for 24 hour shifts with no one to be able to hook up a generator for long periods of time. I wanted it to run for at least the entire time I’m gone until I can get back home.

3. It must operate, change over to battery, switch back over to grid power, and recharge battery all on its own.

4. It’s bulky and ugly right now but will be cleaned up. The case is an extra one I had lying around. It will get moved into my reef cabinet and look organized when I get around to it.

 

[CoralB]

Good job !!! Probably saved some money making yours !!!

 

[bumpyj38]

First up is the battery. This is obviously the main point of of the back up system. I chose LiFePO4 (also called Lithium Iron Phosphate) and here is why.
- Without getting too much into it, other batteries, like car batteries for example, can be more dangerous (such as let out dangerous gases, catch fire, etc.). Overal LiFePO4 is considered safer.
- The two main battery backups (vortech and icecap) use sealed lead acid. These batteries are not supposed to be fully discharged and if they are it damages the battery. When charged again, it is no longer able to charge to the same capacity. This equals shorter and shorter battery life. LiFePO4 batteries have a battery management system built in (if you buy it with one) and can be discharged all the way down until the BMS prevents it from being over discharged (also prevents over charging).
- The expected life out of a LiFePO4 battery is 8–10 years. I can easily spend a little more for the reliability and duration.
- Scour the internet and YouTube for battery reviews to pick one out. I recommend Will Prowse on YouTube. He disassembles, tests, and reviews lots of batteries.

 

[bumpyj38]

ATS (Automatic Transfer Switch)

For a battery backup to be effective it has to switch on when you are not home. This is accomplished by an ATS. Think of a device with three plugs. In one end you plug the load (whatever you are powering). Another end gets plugged into the wall (grid/utility power). The last end get connected to a battery. In my case I plugged it into an inverter (more on the inverter later). Keep in mind that an inverter converts DC power to AC power. There is a lot of energy lost here to do it this way so you would need to oversize the battery some to make up for this. Long story short, try to power a dc pump with a dc battery. It’s much more efficient. If your return pump is AC (like mine) then you may have to do it this way.

 

[bumpyj38]

Inverter

For this backup I am using an inverter. My pump is AC and cannot be connected any other way. There are a couple things to know when selecting an inverter. When an inverter converts power from DC to AC, some power is lost in the process. Some (usually more expensive) Inverters are better at this then others. You should be able to look up the max efficiency rating when researching which inverter you want. The one I selected is 87% efficient. Which means it loses 13% when converting power over to AC. The other thing to note is that you don’t want to oversize the inverter by too much. Typically the larger the capability of an inverter the more inefficient it is at lower loads. I happen to know, through power monitoring, that my return pump uses 47 watts on its current setting. If I get an inverter rated for 2000 watts, it is most likely very inefficient operating at 47 watts and there may be way too much battery power lost in the process. For this reason I got a 12v inverter capable of just 250 watts.
The other very important thing to consider when selecting an inverter is making sure it is a “pure sine wave” inverter. I would not recommend a “modified sine wave” inverter. Pure sine wave inverters put out “cleaner” energy and are generally safer for sensitive electronics. I dont know the science behind which electronics in our reef tank are considered sensitive but it was worth it to me for a small price increase to get pure sine wave.
Lastly, due to advice I received from someone smarter then me, I recommend not being cheap when it comes to selecting the battery cables that connect the battery to the inverter. Get pure copper.

 

[bumpyj38]

Battery Monitor

The next piece is a battery monitor. This isn’t necessary but worth it to me to know what capacity my battery is at. This one displays remaining battery life (as amp hours or battery percentage), amp hours used, currently charging, or currently discharging, and a few other metrics. If I came home from work to a tank with no power, I wanted the ability to be able to look at how much battery life was remaining. The process of installing this was actually pretty easy. It comes with a shunt (small piece of metal that is wired in between the battery and the inverter) and a display. This has to be wired a certain way so that it measure the flow of energy in both directions (discharging and charging). YouTube had plenty of instructions on this.

 

[mandarin417]

Great write up. Is there another component that charges the battery or is that included in the configuration here?

 

[bumpyj38]

Great write up. Is there another component that charges the battery or is that included in the configuration here?

Yes there is. When the power comes back on, any amount of battery that is used will need to be topped off. I must’ve forgot to add it. I’ll add it right now to the write up.

 

[bumpyj38]

Battery Charger

Obviously when a battery is discharged it will need to be recharged. This is done with a battery charger. But not just any battery charger. It must be compatible with the battery you have in your battery back up. In my case it actually required a few different characteristics. I missed this in my first purchase and ended up wasting a little money. You need to purchase a battery charger that is compatible with LiFePO4 batteries as well as compatible with the size of battery that you bought. My first purchase was correct in that it could charge LiFePO4 batteries but I didn’t realize it was for batteries 5-85Ah. The charger may have worked but I didn’t want to risk it and I also figured it would be better to get a charger that could charge the battery a little faster just in case power came back on momentarily. For the one I have pictured below, it can charge 7-160 Ah batteries and, although cheap, had good reviews. It also came with a few safe guards such as over-temperature protection. One extra thing to consider about a charger rated for this big of a battery is that it will draw 5 amps. It’s not a ton but since we already have a lot of reef equipment on these circuits, you will want to consider possibly placing it on a separate circuit breaker in your house. The battery charger is hooked to the battery posts. But don’t forget that if you are using the battery monitor you will need to hook it to the shunt so that it can also detect when the battery is recharged as well.

 

[Sherman]

Good sharing. Very detail.

 

[mandarin417]

Thank you for this great information.

I would like to put battery backup on my Sicce SDC 9 return pump and the Sicce. It is a DC pump but has no direct DC interface. Am I right in stating that the transformer on this pump converts AC to DC to run the pump?

The pump specs are 95W when running at full power and 24VDC. If amps = watts/volts, does that mean this pump is 3.9 amps? So with your configuration, does that mean I could run the pump for 50AH/3.9amp = 12.8 hour and half of that since your battery is 12V and the pump runs 24V so 6.4 hours?

Ideally I would like to run this return pump for circulation and my skimmer for aeration but I did not through in the specs of the skimmer pump.

Thanks,

Bob

 

[ninja120]

Im new to this, but do you have a diagram how everything is wired up?

 

[BamaCoastPyrat]

Thanks for the write up. I am a firefighter that works 48s and I'm in hurricane land, so if we get hit, I could be on shift for a long time. I haven't finished reading everything yet. But amount how much does it cost to buy a good inverter? I would think a decent DC return pump would be cheaper than a good AC/DC converter.

 

[ninja120]

The inverter he bought is about $102

 

[BamaCoastPyrat]

The inverter he bought is about $102

That's cheaper than I thought it would be.

 

[bumpyj38]

That's cheaper than I thought it would be.

It would certainly be better to use a DC pump. You do not have to buy an inverter that way. Not only do you save that money, you will have no wasted battery power when converting from DC to AC since your pump would be straight DC. You would probably need a bigger battery for 48 hours though. But depending on how much power your DC uses, it may not have to be much bigger.

 

[ninja120]

Anyone have an idea how set this up? Just curious if it is LifePo4 Battery -> Autotransfer switch -> Inverter -> Powerhead/Pump?

 

[ninja120]

That's cheaper than I thought it would be.

Anyone have an idea how set this up? Just curious if it is LifePo4 Battery -> Autotransfer switch -> Inverter -> Powerhead/Pump?

 

[bumpyj38]

Anyone have an idea how set this up? Just curious if it is LifePo4 Battery -> Autotransfer switch -> Inverter -> Powerhead/Pump?

Sorry missed your earlier question. What components will you be using? I see you said inverter. Are you also using a battery status monitor?

 

[bumpyj38]

First let me start by saying I am not an electrician. If you are considering wiring electrical, you should consult an electrician. This is just how I wired it so do so at your own risk.

Start with the battery. Attached to the battery is the inverter and a battery charger (by way of battery cables attached to the posts). The battery charger gets plugged into the wall.

Your ATS should have 3 wires on it. One is plugged into the inverter (this should be your backup wire). Another end of the ATS is plugged into your home outlet (this one should say “primary” or something along the lines). The last end is what you plug your load into. This is the tricky part.
You have a few options here. If you just want one pump backed up you can plug it in here and be done. However it won’t be able to be controlled by an apex or aquarium controller if you have one. If you want it to be controlled you can plug in your EB832 and it will be powered and controllable. However, all the other things you have plugged into that EB832 will also be draining the battery.
Another option is to buy an old EB8 or EB4, plug it in, and only have your one pump on this power strip. That would add to your cost a little though.

There is one more option that I used but is fairly complicated but solved all the issues in one. There is a YouTube video online (and a reef2reef thread) of a guy who wires a standard house plug to his EB832 using a power relay and a 24v cable. This cable hooks in to your EB832 24v connection and gives you 2 plugs that are separate from your EB832 outlets but still controllable. I made one of these and plugged mine into the ATS. Then plugged my return pump into this outlet.

Just to be clear, this isn’t my video. I just did what this guy did

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