Uninterrupted Power Supply - hybrid

[Subsea]

I am experimenting with 12VDC to use as an uninterrupted power supply for life support functions. I have two seperate 12VDC systems, one uses a RV battery tender rated for 1500 watts and a 500W inverter that runs two 70W Mag 7 return pumps on 75G & 120G displays and will run for 72 hours. There are no switching devices on this system.

While researching UPS system, I decided to get a 12VDC air pump and in doing so, I found some 12VDC 8W light strips as well as a 4” pancake fan. For this UPS system, I have a 20A battery charger and inexpensive automobile battery.

So, this picture is 16W of 7000 Kelvin color spectrum in 75G tank. It makes red sponge look a little orange.

 

[Besieged]

Interested to see how this works out for you, as well as what you learn along the way.

I don't care for the idea of spending $200 on a consumer-grade UPS that won't actually run the tank (particularly heaters) very long. Nor do I want to pay for EcoTech's solution, either, especially as I'm not using VorTech pumps.

I'd love to do something purpose-/custom-built using COTS components, if it can be made safe and cost-effective. I have a rather solid tech background, along with some electronics, but I don't mess with electricity much, so am unsure about the voltage regulators, etc.,

Why no switching?

 

[Subsea]

Interested to see how this works out for you, as well as what you learn along the way.

I don't care for the idea of spending $200 on a consumer-grade UPS that won't actually run the tank (particularly heaters) very long. Nor do I want to pay for EcoTech's solution, either, especially as I'm not using VorTech pumps.

I'd love to do something purpose-/custom-built using COTS components, if it can be made safe and cost-effective. I have a rather solid tech background, along with some electronics, but I don't mess with electricity much, so am unsure about the voltage regulators, etc.,

Why no switching?

“Why no switching?”

More devices, more failure points. What I have is dependable for life support. It works and I don’t need to learn anything.

Don’t know what COTS is. Educate me.

If you want heaters & lights, get an automatic generator. Before moving to Austin, the rural coop that supplied my electricity would fail too often and always at the worst time.

I installed a 14KW AUTOMATIC STARTUP GENERATOR. Generator cost $4000 and labor cost was a barbaque with friends.

 

[Subsea]

@Besieged
I googled COTS backup electricity.

I challenge you to put together a dependable system for less money. I got everything off the self from Amazon.

 

[VintageReefer]

I do not believe a inexpensive car battery will power 140 watts of pumps for 72 hours

Watt hours = watts x hours
Watt hours = 140 x 72
Watt hours = 10,080


Amp hours = watt hours / volts
Amp hours = 10,080 / 12
Amp hours = 840

Typical car battery is around 60 - 100 amp hours

Something isn’t adding up and:

A) If you’ve tested this and got 72 hours of run time, in curious to learn more about the setup and watts being pulled

Or

B) if you have not tested this, I suggest you do because I fear a false sense of security and that the runtime is greatly overestimated and in an emergency it won’t last as long as you expect

 

[CHSUB]

72 minutes?

 

[Subsea]

@VintageReefer
The inexpensive car battery runs four 8W pankake fans, four 8W led light and one 10W air pump. All are 12VDC. This is not my primary life support, but the air pumps could be.

Primary life support batteries are two 120 AH

Using those numbers comes out to less than 17.4 hours.

I ran several operational checks. Not sure now which wattage I used to check. I knew I wanted more batteries for at least 24 hours backup. I did this in the house next to tanks so that it was easy to monitor during initial startup. Now that it is proven, I will move everything to back porch where I have more room for batteries.

 

[VintageReefer]

Watt hour = amp hour x volts
Watt hour = 240 AH x 12
Watt hours = 2,880

runtime for dc watt hours converted through inverter to ac power
(Watt hours x .85 efficiency) / watt load = runtime hours

(2,880 x .85) / 140 w = those two 70w pumps will run a total of approx 17.4 hours

 

[VintageReefer]

This is not even factoring for the fact that lead acid batteries shouldn’t be discharged below 50% or you risk damaging or drastically reducing the life and health of the battery

Something isn’t adding up. Either the watt draw is not correct or the 72 hour runtime is not correct

 

[vlangel]

I have 1000 W inverter about 10 years ago in case of an emergency, which we had never had from 1986 when we moved to our current house. However about 6 years ago a wind storm knocked over a tree on our road that knocked out electricity and created a leak in a gas line. So although nearby neighborhoods were restored of power, ours was delayed about 6 days until the gas company could fix the gas leak. That power inverter hooked up to our running car powered my tank, fridge and computer. I lost nothing in my reef system and all I needed was the inverter and an extension cord. I have considered getting a deep cell marine battery to give the car a break but just never did.
I did not run the heaters as my tank is close to our livingroom fireplace (within 12 ft) so although the temperature dropped it was not dangerous, around 69-70°F. Also I only ran the lights for a shortened duration and no powerheads, only the DC return pump.

 

[VintageReefer]

I have 1000 W inverter about 10 years ago in case of an emergency, which we had never had from 1986 when we moved to our current house. However about 6 years ago a wind storm knocked over a tree on our road that knocked out electricity and created a leak in a gas line. So although nearby neighborhoods were restored of power, ours was delayed about 6 days until the gas company could fix the gas leak. That power inverter hooked up to our running car powered my tank, fridge and computer. I lost nothing in my reef system and all I needed was the inverter and an extension cord. I have considered getting a deep cell marine battery to give the car a break but just never did.
I did not run the heaters as my tank is close to our livingroom fireplace (within 12 ft) so although the temperature dropped it was not dangerous, around 69-70°F. Also I only ran the lights for a shortened duration and no powerheads, only the DC return pump.

a good solution but you are essentially making a generator. You are using gasoline to power an engine to power an alternator to keep the battery charged

 

[CHSUB]

This is not even factoring for the fact that lead acid batteries shouldn’t be discharged below 50% or you risk damaging or drastically reducing the life and health of the battery

Something isn’t adding up. Either the watt draw is not correct or the 72 hour runtime is not correct

My inverter drains battery to 10% and has efficiency of 95%. Does that seem correct?

 

[Reefering1]

Watt hour = amp hour x volts
Watt hour = 240 AH x 12
Watt hours = 2,880

runtime for dc watt hours converted through inverter to ac power
(Watt hours x .85 efficiency) / watt load = runtime hours

(2,880 x .85) / 140 w = those two 70w pumps will run a total of approx 17.4 hours

Something to consider is that many of these agm batteries are rated ah/hr. Example 100ah/20 hrs means it will provide 100 amps per hour for 20hrs. Your math is correct for discharge rate, as in how fast can it safely discharge all its current.( this is where lithium batteries shine- getting the power out fast). Agm/deep cycle batteries, not so much.
Remember my system...
(4) 100ah/20hr batteries carrying about 700w for 18hrs+...
So this setup is a bit more than 1/2 my battery, but 1/5 the load- for 4x runtime sounds realistic compared to what my system does...

 

[vlangel]

a good solution but you are essentially making a generator. You are using gasoline to power an engine to power an alternator to keep the battery charged

That is exactly right. I was set to buy a $400 gasoline generator (this was 10 years ago). However when I learned that the generator should be pushed out of the garage 3-4 Xs a year and fired up to keep oil circulating through the engine of the generator, I decided against it. I knew my hubby and I might do that for the first year or so but eventually we would get lackadaisical and a good chance the generator might not fire up when we needed it. Another factor for us is a lot of our appliances are natural gas powered so electricity was not as crucial. Mainly the tank, fridge and freezer were the high risk items. The inverter was only $75, it is small and easily stored and it needs no maintenance when not in use. I have never considered anything else since it worked so well for us.

 

[VintageReefer]

Something to consider is that many of these agm batteries are rated ah/hr. Example 100ah/20 hrs means it will provide 100 amps per hour for 20hrs. Your math is correct for discharge rate, as in how fast can it safely discharge all its current.( this is where lithium batteries shine- getting the power out fast). Agm/deep cycle batteries, not so much.
Remember my system...
(4) 100ah/20hr batteries carrying about 700w for 18hrs+...
So this setup is a bit more than 1/2 my battery, but 1/5 the load- for 4x runtime sounds realistic compared to what my system does...

That is not how the rating system works

A 100ah / 20h battery will discharge 5 amps per hour for 20 hours
You will not get 100 amps per hour for 20 hours

https://www.payperwatt.com/post/what-is-mean-by-a-100ah-battery

 

[Subsea]

Something to consider is that many of these agm batteries are rated ah/hr. Example 100ah/20 hrs means it will provide 100 amps per hour for 20hrs. Your math is correct for discharge rate, as in how fast can it safely discharge all its current.( this is where lithium batteries shine- getting the power out fast). Agm/deep cycle batteries, not so much.
Remember my system...
(4) 100ah/20hr batteries carrying about 700w for 18hrs+...
So this setup is a bit more than 1/2 my battery, but 1/5 the load- for 4x runtime sounds realistic compared to what my system does...

I didn’t think that I had lead acid because they are sealed batteries, However, they are lead acid and
100ah/10hr. I did operate them without power for half a day: 10-12 hours. When I move system to back porch I will add batteries to get 24 hours of operation.

Note: In considering battery backup systems, I only run life support. And in my case, I could drop out a 70W water pump and replace with 8W air pump for life support.

 

[Reefering1]

That is not how the rating system works

A 100ah / 20h battery will discharge 5 amps per hour for 20 hours
You will not get 100 amps per hour for 20 hours

https://www.payperwatt.com/post/what-is-mean-by-a-100ah-battery

Hmmm, guess it's possible I'm confusing the math. But my response is based of repeated experiences. 700w for 18 hrs out of (4) 100ah batteries ran at 24v.

 

[Besieged]

“Why no switching?”

More devices, more failure points. What I have is dependable for life support. It works and I don’t need to learn anything.

Don’t know what COTS is. Educate me.

If you want heaters & lights, get an automatic generator. Before moving to Austin, the rural coop that supplied my electricity would fail too often and always at the worst time.

I installed a 14KW AUTOMATIC STARTUP GENERATOR. Generator cost $4000 and labor cost was a barbaque with friends.

@Besieged
I googled COTS backup electricity.

I challenge you to put together a dependable system for less money. I got everything off the self from Amazon.

FWIW, it was a genuine question.

What I meant was that I would like to do something like you're doing here, with Common Off The Shelf bits like the RV battery tender and inverter, as opposed to trying to buy something purpose built for reefing, which by sheer dint of having "marine" or "reef" in the description, is going to be 3x more expensive than it probably has to be, like just about everything else in this hobby.

Not saying there aren't occasionally good reasons for that last, especially when things are built well for the purpose and the environment.

Still, no, when it makes sense and is cost effective, something like what you've done is what I'd like to do - that's why I was asking for more info.

A generator is down the road yet. My power here is reasonably dependable, but falling branches in storms still take it down once in a while. It's usually back pretty quick, but... I've got UPS' for everything that matters, I'd just like to be able to run at least a single powerhead and my Apex unit for up to 24 hours or so.

I'd definitely turn my lights off or WAAAAAY down - tank can tolerate a "cloudy" day or two if need be - but I'd love to be able to run just one of my two heaters or something. But, I see now reading further you weren't intending to run heaters with this setup, which I guess would take a much more robust set of batteries instead of just the one you're using.

Presuming then also, you're kicking this on manually during an outage, not having it trigger automatically somehow?

 

[VintageReefer]

Hmmm, guess it's possible I'm confusing the math. But my response is based of repeated experiences. 700w for 18 hrs out of (4) 100ah batteries ran at 24v.

I don’t question your experience! I fully believe you and think you are one of the few with a good agm setup

Your math though…

 

[Subsea]

FWIW, it was a genuine question.

What I meant was that I would like to do something like you're doing here, with Common Off The Shelf bits like the RV battery tender and inverter, as opposed to trying to buy something purpose built for reefing, which by sheer dint of having "marine" or "reef" in the description, is going to be 3x more expensive than it probably has to be, like just about everything else in this hobby.

Not saying there aren't occasionally good reasons for that last, especially when things are built well for the purpose and the environment.

Still, no, when it makes sense and is cost effective, something like what you've done is what I'd like to do - that's why I was asking for more info.

A generator is down the road yet. My power here is reasonably dependable, but falling branches in storms still take it down once in a while. It's usually back pretty quick, but... I've got UPS' for everything that matters, I'd just like to be able to run at least a single powerhead and my Apex unit for up to 24 hours or so.

I'd definitely turn my lights off or WAAAAAY down - tank can tolerate a "cloudy" day or two if need be - but I'd love to be able to run just one of my two heaters or something. But, I see now reading further you weren't intending to run heaters with this setup, which I guess would take a much more robust set of batteries instead of just the one you're using.

Presuming then also, you're kicking this on manually during an outage, not having it trigger automatically somehow?

Nothing is manual.

I will get off the shelf list and post. RV battery tender is $150 charges battery bank. Then 12VDC goes to an inverter that runs 24/7 supplying 120VAC that is filtered and clean as a modified syne wave.

So charger & inverter at $200. The batteries will always be the cost factor. That’s why I limit what’s on life support.
Even when I installed 14KW generator, designated circuits were chosen and some things were not backed up. Bigger generators cost more. There are always trade offs.

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