DIY Battery backup

[Skullring]

This is my attempt at making a diy battery backup for my 10 gallon mixed reef tank. I have a small generator for prolonged outages but wanted a short term solution for when I was away at work or the power went out for a few hours I would not need to pull the generator out of the shed.

I have a tiny Jebao DC-500 return pump. It is a tiny pump that is 24 volts dc and draws about 1 amp. I started with 2 Mighty Max 12 volt sealed lead acid batteries that are rated at 12 amp hours each. They were about $30 each on Amazon. I decided this was a good compromise between price and capacity since a one amp pump should last 12 hours with 12 amp hour batteries.

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Since these are 12 volt batteries I would wire them in series to give me 24 volts that I needed for my pump. That is hooking the positive to the negative which will give you 24 volts on the terminals. If you hook them together in parallel you can increase your capacity. Check Youtube if you need an explanation between series and parallel. So these two batteries hooked together in series gives me 24 volts dc with 12 amp hour capacity.

Next I found a switching power supply rated for 120-240 volts ac input and 24 volts dc output. The model number of the one I used was SC-120-24. Some of the key words are switching power supply with ups. I bought this one off of Alibaba for about $25 but you can find them on Amazon and all over the web. I am not
sure if the return pump I have has any shutoff protection if you try to power it with less than 24 volts but I know some of them do so I decided to stick with 24 volts.

The hookup is straight forward from left to right. Line AC input Positive Neutral Ground. DC output to pump Negative and Positive. Output to battery this is
the red and black wires that go to charge the batteries. A circuit breaker and a voltage adjustment screw so you can adjust your output voltage.

I have my charging voltage set at 26 volts dc.

My output to my pump connector is 24 volts dc.

This gives me the benefits of

1. Charging my 24 volt battery bank
2. The pump runs from the power supply when the main ac power is on.
3. The power supply switches over automatically from power supply to battery power when the main ac power is disconnected.

I hope this helps someone. This is a small setup due to it being a nano tank and having a small return pump but could be scaled up if necessary with
batteries with larger capacity. I have been running this for the past 6 months and it gives me 12 hours of runtime on battery backup when the main ac power goes out. If anyone has any comments or improvements please let me know.

I appreciate all of the help that is on Reef2Reef.

 

[P-Dub]

NICE!!!

 

[Kjames]

This is a nice and straightforward DIY project! I'm wondering is it feasible to extend the capacity of the batteries by limiting the power draw of the pumps when on battery?

 

[Skullring]

Sure, If you have a controllable dc pump you can turn down the volume to extend the run time.

My pump has a control box where I can dial the pump volume up and down.

You can also use higher capacity batteries to extend your run time. You just have to balance your amp hours vs what you are willing to spend.

I decided on 12 amp hours because they were inexpensive and usually I would not be away from the tank for more than 12 hours. This gives me time to get home and connect to my portable generator if necessary.

 

[Ratherbeflyen]

Nice DIY project.

I think you might be undercharging the batteries a little bit at 26v. If I'm seeing it correctly, the printing on the battery says 13.6 - 13.8v for standby use. Of course in series that would be 27.2 - 27.6v. If you can turn up the voltage a little bit, your batteries should last a little longer.

 

[Skullring]

Thanks for the tip. I will turn up my charging voltage.