A discussion about my new battery backup system

[Dom]

I've replaced the two batteries on my tank which are responsible for keeping the system running during power outages.

The batteries are (2) Duralast deep cycle marine batteries, each rated at 65 amp hours.

I have them connected in parallel for a total of 130 amp hours and have cross connected the charger so that it functions as one battery.

For the purposes of this thread, I will call the total power consumption of devices on the tank 1000watts (1kW). In actuality, its 991watts.

I am surprised to see that the backup barely provides 1 hour of support.

The lights are Hydra 32s and according to the website, have a power consumption of 90watts. I have 3 for a total of 270watts. If I move them to the grid side, I save a lot of power but sacrifice light during a power outage. I could also move only (2) to the grid side and have one, on backup.

Additionally, I have (2) 300watt titanium heaters in the sump for a total of 600watts. If I place these on the grid side, along with all 3 lights, my support hours go up to 4.5 hours. But moving one heater to the grid side will be a good amount of work as it will require 2 temperature controllers, one for each heater.

So, I am interested in hearing other perspectives and how you would deploy this resource on your tank.

Thank you,
Dom

 

[Jekyl]

Portable generator. Have a 9500w that powers my house, not just the tank.

 

[Dom]

Portable generator. Have a 9500w that powers my house, not just the tank.

I have one of those too. But since it is portable, I need something to bridge the gap until I set it up. Also, I wouldn't leave the generator running all night, so battery backup is important to me.

 

[dangles]

@telegraham is a great batt backup resource. I'm not sure how much he hangs around here anymore (too many Aperture groupies running around for his taste ) but his IG and YT have lots of great stuff on the subject.

 

[Jekyl]

I have one of those too. But since it is portable, I need something to bridge the gap until I set it up. Also, I wouldn't leave the generator running all night, so battery backup is important to me.

I leave mine on overnight all the time during outages. The time to set it up won't cause any issues with the tank either. Generators are designed to be ran a long time.

 

[BeanAnimal]

I've replaced the two batteries on my tank which are responsible for keeping the system running during power outages.

The batteries are (2) Duralast deep cycle marine batteries, each rated at 65 amp hours.

I have them connected in parallel for a total of 130 amp hours and have cross connected the charger so that it functions as one battery.

For the purposes of this thread, I will call the total power consumption of devices on the tank 1000watts (1kW). In actuality, its 991watts.

I am surprised to see that the backup barely provides 1 hour of support.

The lights are Hydra 32s and according to the website, have a power consumption of 90watts. I have 3 for a total of 270watts. If I move them to the grid side, I save a lot of power but sacrifice light during a power outage. I could also move only (2) to the grid side and have one, on backup.

Additionally, I have (2) 300watt titanium heaters in the sump for a total of 600watts. If I place these on the grid side, along with all 3 lights, my support hours go up to 4.5 hours. But moving one heater to the grid side will be a good amount of work as it will require 2 temperature controllers, one for each heater.

So, I am interested in hearing other perspectives and how you would deploy this resource on your tank.

Thank you,
Dom

You want the real world answer? You shouldn't run loads like this off of a DIY battery array. It is not cost effective or safe. 130amp of DC current is no joke and a shorted cell is no joke. Each batter should have its own inline fuse or fusible links, as should the array. Your inverter losses at 12v to 120v are substantial as well. You better bet is to use a battery for a single flow device and a generator for anything that requires longer than a few minutes of run time.

Opinions on generators will vary... but you can't (absolutely can't) go wrong with a HONDA Inverter. They are super quite, a 10 year old kid can start them on the first pull and they are extremely powerful for their weight and footprint. They have fuel pumps and can use external fuel cells and if you buy two, they can be paralled. Because they are inverter based, they don't have frequency regulation or governor issues.

If you can't afford a whole house standby generator, then get a Honda.

Whatever you do - ditch the idea of running the whole tank on a battery, the expense, safety and size of the array become prohibitive extremely quickly.

 

[areefer01]

@telegraham is a great batt backup resource. I'm not sure how much he hangs around here anymore (too many Aperture groupies running around for his taste ) but his IG and YT have lots of great stuff on the subject.

IG and YT is just as bad if not worse but we can leave it at that. Good source of DIY solar and battery information search on Will Prowse on YT. Should keep one busy for a bit.

With regards to tele I can't speak to his content but seems like a straight shooter.

 

[dangles]

IG and YT is just as bad if not worse but we can leave it at that. Good source of DIY solar and battery information search on Will Prowse on YT. Should keep one busy for a bit.

With regards to tele I can't speak to his content but seems like a straight shooter.

I meant Telegraham's YT and IG specifically. Not generally. You're right in that sense!

He has made a lot of enemies with some of the stances he's taken against the big players in the industry. But yes, definitely a straight shooter and not afraid to call things as he sees them. He's very pro-little-guy and tries to push back against the "reefing has to be expensive" mindset that's so prevalent among the influencers. Looking out for the poors among us!

 

[BeanAnimal]

He can read all of the posts in the world. A watt is a watt is a watt....

130ah of battery is a fixed amount of energy.
- inverter loss
- heat
= available runtime.
_____________________________
period.

Some batteries are better than others with regard to output voltage dip under load, but in general we can model them all the same.

So 120V load (that too varies, but lets use it) and 1000 Watts of load.
Best case - just over an hour of run time. Real world, real inverter, real batteries, real wires and real power factor? 45 minutes at best.

So he wants 4 hours? That is 8 batteries. But 8 parallel batteries is pretty dang dangerous with regard to current and shorts. Also, because the input is 12v and the output is 120v, we have an inverter that is going to not be very efficient.

So he chooses a series setup... That is 96V and a 96V inverter. Great, but now were dealing with dangerous voltages and more internal resistance and therefore lower battery efficiency... Fusing at high voltage DC starts to also become a problem, as there is no sinewave, an arc is not self extinguishing and if an arc jumps a blown fuse, there may as well be no fuse...

Etc...

Battery backups are just not cost effective or safe for large loads, unless you really have a grasp of what you are getting into. This is ignoring off gassing, problems with maintenance vs maintenance free or AGM cells, etc.

 

[dadnjesse]

Marine batteries are not true deep cycle. The same thing they put in campers. The problem is once they get discharged beyond on certain volts they won't charge back.

 

[areefer01]

Battery backups are just not cost effective or safe for large loads, unless you really have a grasp of what you are getting into. This is ignoring off gassing, problems with maintenance vs maintenance free or AGM cells, etc.

This is true with this hobby or any other. Safe, reliable, battery back up be it small scale or larger whole home needs someone mechanically inclined, a good budget, willing to pay someone licensed to do what you can't, possible permits, and more. It isn't for the feint of heart. But it can be done.

I think your note earlier about a generator is sound. Every hobbyist should have one. Ideally every home owner who doesn't have solar and battery storage should have one to include a transfer box. Every year a reef tank matures, colonies grow, fish get collected or aged the cost to replace is 10 fold.

In any case just ranting I guess.

 

[Dom]

You want the real world answer? You shouldn't run loads like this off of a DIY battery array. It is not cost effective or safe. 130amp of DC current is no joke and a shorted cell is no joke. Each batter should have its own inline fuse or fusible links, as should the array. Your inverter losses at 12v to 120v are substantial as well. You better bet is to use a battery for a single flow device and a generator for anything that requires longer than a few minutes of run time.

Opinions on generators will vary... but you can't (absolutely can't) go wrong with a HONDA Inverter. They are super quite, a 10 year old kid can start them on the first pull and they are extremely powerful for their weight and footprint. They have fuel pumps and can use external fuel cells and if you buy two, they can be paralled. Because they are inverter based, they don't have frequency regulation or governor issues.

If you can't afford a whole house standby generator, then get a Honda.

Whatever you do - ditch the idea of running the whole tank on a battery, the expense, safety and size of the array become prohibitive extremely quickly.

So I do have a Honda 3000is. It is a portable gas generator, that is very economical on gas.

My hope was that I could use battery power as a bridge to the generator.

The equipment is purchased, so there is no turning back.

You sound like you know your stuff. I wouldn't mind hearing how I could make this a safer setup.

 

[telegraham]

IG and YT is just as bad if not worse but we can leave it at that. Good source of DIY solar and battery information search on Will Prowse on YT. Should keep one busy for a bit.

With regards to tele I can't speak to his content but seems like a straight shooter.

+1 for Will. He's a great resource.

 

[EricR]

If the goal is short term backup for life support (like a few hours), personally, I wouldn't run the heaters or lights on the backup battery setup.
*I say that without any knowledge of expected room temperature so there's that to consider

For longer term, I agree with previous posts that 12VDC batteries aren't the best option.

 

[telegraham]

So I do have a Honda 3000is. It is a portable gas generator, that is very economical on gas.

My hope was that I could use battery power as a bridge to the generator.

The equipment is purchased, so there is no turning back.

You sound like you know your stuff. I wouldn't mind hearing how I could make this a safer setup.

I just presented this topic at the local club this past weekend.

I see no reason to power anything beyond critical equipment. Critical to me = a return pump and power heads. No lights, no heaters, no skimmer, and no controller stuff beyond that which you need to maintain awareness. If you want to get fancy, and you have a gas furnace, I'd power that to keep your tank warm (and your family happy).

As for your batteries, every time you discharge them below 50%, that negatively impacts future capacity. Consider LiFePO4 (LFP) batteries. They're around $200 for 100Ah, they'll sag less under load, and they'll generally have 80% of their capacity at 10 years.

Remember...only what you need. Nothing more.

 

[telegraham]

Regarding 12V, I like it. It certainly isn't as efficient as 24 or 48V, but it's easy to get if needed and when your day goes very sideways, you can use your car to power your inverter.

 

[BeanAnimal]

I just presented this topic at the local club this past weekend.

I see no reason to power anything beyond critical equipment. Critical to me = a return pump and power heads. No lights, no heaters, no skimmer, and no controller stuff beyond that which you need to maintain awareness. If you want to get fancy, and you have a gas furnace, I'd power that to keep your tank warm (and your family happy).

As for your batteries, every time you discharge them below 50%, that negatively impacts future capacity. Consider LiFePO4 (LFP) batteries. They're around $200 for 100Ah, they'll sag less under load, and they'll generally have 80% of their capacity at 10 years.

Remember...only what you need. Nothing more.

Welp you type that faster than I could....

 

[ReeferLou]

Here is my solution:
2500/7500 Watt Inverter
20KWhr of LiFePo4 battery
600W solar panels

This also helps me arbitrage my time of day electiricity use and powers up my furnace and a few fridges and washer dryer if needed. It can run my tank only for a few days.

 

[BeanAnimal]

Regarding 12V, I like it. It certainly isn't as efficient as 24 or 48V, but it's easy to get if needed and when your day goes very sideways, you can use your car to power your inverter.

Exactly - and 12V means limiting the number of parallel cells to a reasonable amperage that is not a serious danger... More cells means more chances of a bad cell shorting causing a very serious high current short and more imbalance between cells creating heat and resistance.

 

[BeanAnimal]

You sound like you know your stuff. I wouldn't mind hearing how I could make this a safer setup.

I have worked with high current and high voltage DC for many years (mining industry). 650V trolley wire, equipment that runs series parallel battery packs etc. Photo below is a "scoop". Everything to the left of the visible wheels is a series parall array of 12V deep cycle batteries that total 1240ah (~300kWh). The tram motors alone are are ~60kW and a large scoop has TWO (75 horsepower each) and the hydraulic pump motors are 26kW (35hp). Battery maintenance is electrifying

I also worked with UPS systems for server and data centers. Some as large as a typical room in your house, with a rack or racks of batteries that may span several aisles.

I am also pretty into building tube amplifiers and high voltage tube electronics.

Anyway - I know enough to get shocked, maybe not much more.

You will want a slow blow fuse on each battery at the bare minimum. The fuse should be smaller than the maximum continuous current rating of the battery (in this application) to be on the safe side... but if you look at the maximum inverter current, you can size the fuses to that spec (that will likely be far less than the battery mcc).

If these are AGM or sealed then ventilation is not an issue. If they are good old-school wet cell marine batteries, then you MUST have positive ventilation of some kind, as the byproduct of charging is hydrogen gas. It can (and will) collect in pockets and is explosive. I wouldn't have wet cells indoors!

I don't aim to be your resource, the topic is broad and I am not comfortable giving specific build advice. There are other well built and vetted resources for you to find what you need.