DIY Universal Battery Backup For Your Reef

[RamsReef]

1. You should fuse both the point of sale and neg lines of your cells, or each battery (Bank of cells)

2. You can parallel relays to get your desired current rating no problem.

3. Those APC UPS operate on 24volt batteries. You can easily wire in 2 x deepcycle batteries and use them as the UPS battery. I have done so and the APC functions as normal and will actually behave normally (You can even log in if you have the software and see run time remaining etc.) The system is also scale-able. I have 4 batteries, 2 x 2 hooked up in my UPS.

4. Lithium batteries are better, HOWEVER, they are extremely energy dense and I would not have them in my house unless they are in a metal enclosure that can contain a complete battery failure and vent the hot gas. I am into RC helicopters and cars and have seen many a "whoa that looks cool" I also keep my batteries in the garage in ammo crates.

 

[chipmunkofdoom2]

Thanks @Ramasule for the input.

Out of curiosity, what do you mean by "parallel" the relays? Do you mean using two separate relays to get double the current capacity? I was under the impression that this was not a good idea because relays may not open/close at the same time (I must admit, I'm not an electrician, that info has come mostly from Google). Or does paralleling mean using the separate poles on the same relay to carry the same current, which thereby doubles the effective capacity? It would make sense that if you had a 15A DPDT relay, for example, and you wired both poles with the positive from your 12V battery, that you could effectively switch double the current (15A x two poles = 30A). For switching power from a battery to an inverter, 30A is still pretty low (12VDC x 30A = 360W). While most people will not likely run more than 360W of equipment in an outage, that still seems rather low.

 

[RamsReef]

Yes, the difference in the open / close time is negligible and the relays can handle current spikes.

IF IT WERE ME
I would get
https://www.digikey.ca/product-detail/en/american-electrical-inc/CC18-110/288-1505-ND/6220382

A contactor and wire each of the poles parallel. The relay I linked would grant you 40A / Pole * 3 Poles = 120 Amps total.

Bring your heavy gauge wire from your battery bank into a bar of alluminum (if your cheap) or a automotive battery splitter (slightly fancier). From that bar tap off 3 leads to go into the contactor. On the other side of the contactor do the opposite.

 

[RamsReef]

50 AMP option
https://www.digikey.ca/product-deta...umfield-relays/3100-15T1999/PB1643-ND/1427173

 

[chipmunkofdoom2]

@Ramasule that's true with the 40A option. For the configuration I was recommending, however, we'd need a double throw relay so that we could connect the battery to the NC terminals. That way, the battery would only connect to the inverter when the relay loses power. Something like this would work, but if I were to go this route, I'd probably spend a few more bucks and make sure I'm getting a quality relay from a reputable manufacturer.

 

[RamsReef]

Use a small SPDT relay to switch the contactor.

I think you are making it way to complicated, I would neglect the "ghost" load of the inverter, the battery charger should more than make up for that.

I would just stick to switching the AC side like you have done, lower current = cheaper relays + more lifetime of contacts.

 

[chipmunkofdoom2]

I would neglect the "ghost" load of the inverter, the battery charger should more than make up for that.

Definitely agreed. This is what I do with my system. I just leave the inverter on and let the charger pick up the slack. It has no trouble keeping up. The only reason I had brought it up was because a user had mentioned in a previous post that they charge their battery with solar panels and would prefer that the inverter not be a parasitic load.

 

[Sea MunnKey]

Honestly we have a lot of (Thank You's) genius DIY'ers on here .... what can I say but Hallelujah!!!

 

[RamsReef]

OIC.

R Relay
https://www.digikey.ca/product-deta...umfield-relays/KUMP-14A18-120/PB619-ND/678252

1 pole switch hots
1 pole switch neutral
1 pole NC contact used for invert power

C Relay
https://www.digikey.ca/product-deta...umfield-relays/2272229-1/2272229-1-ND/5423175
Limit Inverter to 1500W
or
https://www.digikey.ca/product-detail/en/american-electrical-inc/CDC18-12/288-1519-ND/6220396
Parellelelel all three poles.
Limit Inverter to 1400W

 

[RamsReef]

OIC.

R Relay
https://www.digikey.ca/product-deta...umfield-relays/KUMP-14A18-120/PB619-ND/678252

1 pole switch hots
1 pole switch neutral
1 pole NC contact used for invert power

C Relay
https://www.digikey.ca/product-deta...umfield-relays/2272229-1/2272229-1-ND/5423175
Limit Inverter to 1500W
or
https://www.digikey.ca/product-detail/en/american-electrical-inc/CDC18-12/288-1519-ND/6220396
Parellelelel all three poles.
Limit Inverter to 1400W

I take payments in frags.

 

[Rcko]

Good to know

 

[chipmunkofdoom2]

@Ramasule that's probably the best way to do it. A 3PDT switches the inverter, mains, and lead from the the battery. The lead from the battery is on NC and current flows when the mains is off. That 12V lead from the 3PDT goes to the high-current relay between the battery and the inverter.

While we're on the subject of relays, do you have any thoughts on redundancy for the primary relay, the one that switches between inverter and mains? Another commenter suggested using two relays, but if one of the relays fails, it will inevitably lead to one relay connecting the inverter to the output, another connecting the mains to the output. The result is effectively the mains and inverter being connected, which I think is undesirable for many reasons.

 

[RamsReef]

@Ramasule that's probably the best way to do it. A 3PDT switches the inverter, mains, and lead from the the battery. The lead from the battery is on NC and current flows when the mains is off. That 12V lead from the 3PDT goes to the high-current relay between the battery and the inverter.

While we're on the subject of relays, do you have any thoughts on redundancy for the primary relay, the one that switches between inverter and mains? Another commenter suggested using two relays, but if one of the relays fails, it will inevitably lead to one relay connecting the inverter to the output, another connecting the mains to the output. The result is effectively the mains and inverter being connected, which I think is undesirable for many reasons.

Wouldn't worry about it.

You would have to have the NO fuse closed, in which case it wont move over to the NC contact anyways.

EVEN IF IT MAGICALLY DID, Your inverter is fused and your mains has a breaker.

 

[siggy]

Cool Beans guys, Ever thought about these...Of course the runtime needs to be upgraded, the large metal can will hold several smaller batteries in parallel. It is a one and done and basically what you get with a Ice cap or ecotech .
https://www.homedepot.com/p/Lithonia-Lighting-36-Watt-Steel-Emergency-Lighting-Unit-ELT36/205910322

 

[siggy]

For the wiring impaired,
https://www.amazon.com/Xantrex-8080...d=1521405963&sr=8-10&keywords=transfer+switch

 

[James Kanouff]

Very well done sir. Thank you for putting that all together. This may very well save someones tank in the near future. I have two APC computer battery back up boxes connected only to a critical intank flow device in each tank. I also have an old ECOTEC battery back up box I intent to cut apart and utilize a larger battery to back up my ecotec pumps because they can utilize 12 volt circuits very simply. You have resparked my interest in this project.
Folks should also consider the usable life of there battery is 4-6 years and should put it on a replacement schedule and possiblly keep it inside a small plastic vented tub. I have seen a hand full of old batteries on trickle chargers go a bit haywire when they fully melt down. Usually only over working the trickle charger. But its not to hard to set in into something to stop any splits if a battery case splits then the plates fail inside eventually.

 

[Cool Fish]

Thanks for a very informative article, chipmonkofdoo m2! This has always been a huge concern of mine. Frankly, I'm surprised someone or some company hasn't come out with a product for us reefers. I'm sure folks would scoop it up! I would actually like to see something that would kick on when I'm not home. When I'm on vacation, for instance. Something other than an expensive backup generator. Good job!

 

[mitch91175]

This is awesome. Will be looking into doing this in lieu of a generator for the time being.

 

[DSmithZ28]

So I'm pretty comfortable with this setup and know the math and method needed to hook up but what I'm stuck on is how do you convert over to battery backup when you are not home and there is a power outage? So I run a Jebao DCT8000 (68w) and have it setup through my reefkeeper. When there is a power outage how can the battery backup take over automatically?

 

[chipmunkofdoom2]

So I'm pretty comfortable with this setup and know the math and method needed to hook up but what I'm stuck on is how do you convert over to battery backup when you are not home and there is a power outage? So I run a Jebao DCT8000 (68w) and have it setup through my reefkeeper. When there is a power outage how can the battery backup take over automatically?

Is your question about the mechanism that does the transfer? If so, check out this transfer switch. It requires a bit of wiring, but basically there are two inputs, one from your inverter (which draws power from your battery) and the other from the wall. When the utility power is on, the transfer switch sends power from the utility to the output. When the utility power fails, it switches over to the inverter automatically. When the power comes back on, it switches back over again.

Or was your question about how to run your return pump, and only your return pump, if your Jebao is plugged into your Reef Keeper?