Can I build a battery bank in a metal equipment rack?

This rack has all of my electronics for a large salt water aquarium. If I ground the entire rack, can I use it for this purpose?

I plan on building something out of wood, because a metal rack for this purpose just doesn't feel right. Unless I get feedback from the more experienced users saying otherwise.

Thank you.

You can buy batteries that have metal cases or plastic cases.

Design it well and it won’t matter…
Design it poorly and it won’t matter either…
(But because you are asking the questions- I would bet on a good design from you).

Just make sure the cells are well insulated.

Good Luck!

DXHum said:

This rack has all of my electronics for a large salt water aquarium. If I ground the entire rack, can I use it for this purpose?

I plan on building something out of wood, because a metal rack for this purpose just doesn't feel right. Unless I get feedback from the more experienced users saying otherwise.

Thank you.

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I used a big metal box. https://diysolarforum.com/threads/the-big-blue-box.55099/ I just purchased another big metal box and will be building another like that one for my shop.

The whole metal box has an EGC to it. Do not tie to the battery negative.

Anything metal that can carry current and is tied to your AC power system must be grounded in case of a ground fault.

Zwy said:

I used a big metal box. https://diysolarforum.com/threads/the-big-blue-box.55099/ I just purchased another big metal box and will be building another like that one for my shop.

The whole metal box has an EGC to it. Do not tie to the battery negative.

Anything metal that can carry current and is tied to your AC power system must be grounded in case of a ground fault.

Click to expand...

Just checked out your build; I am impressed.

The (2) lead acid batteries I will use, I plan on placing inside a plastic milk crate which will rest on a pair of 2x4s on the metal base of the rack.

I've already run 10 gauge, solid core from the water main to the rack location. My plan is to ground the rack to the water main, and then ground the equipment to the rack.

But can I/should I ground the negative terminal of the battery to the rack?

DXHum said:

Just checked out your build; I am impressed.

The (2) lead acid batteries I will use, I plan on placing inside a plastic milk crate which will rest on a pair of 2x4s on the metal base of the rack.

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I would use a wooden structure with lead acid. If given a choice, instead of lead acid find some cheap LFP.

If the lead acid are free, sell them and apply the profit towards LFP. The only time I would use lead acid would be if I needed to charge in below 32°F (0°C) temps.

Long term, LFP is cheaper per watt than any lead acid. Any metal structure around lead acid will corrode from any fumes vented by the lead acid. Useable capacity of lead acid is 50% of rating, while LFP can be used to 90% of capacity. If lead acid is commonly used over 50% capacity, sulfation will set in quickly and kill the battery quickly. LFP requires an absorption charge regularly, daily basically, and this takes time. Time is limited using solar for charging.

There is a place for lead acid, don't get me wrong. Examples would be extremely cold climate in winter and no way to keep batteries warm. Lead acid will suffer reduced capacity in cold as will any battery, so keep that in mind. A cabin used just on weekends where heat is not supplied during the week and batteries could be recharged to 100% SOC with absorption is a good application. There are others, but that gives you an idea of when to use lead acid and when not to use it.

DXHum said:

I've already run 10 gauge, solid core from the water main to the rack location. My plan is to ground the rack to the water main, and then ground the equipment to the rack.

Click to expand...

Is this tied to any current grid AC system?

Any exposed ground wire under NEC is required to be minimum 6AWG.

DXHum said:

But can I/should I ground the negative terminal of the battery to the rack?

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No.

More details on what plans you have for your system would probably be a good idea. Members here can help you but without more details it may not be good advice. The revelation of possible lead acid batteries changes things considerably.

Zwy said:

I would use a wooden structure with lead acid. If given a choice, instead of lead acid find some cheap LFP.

If the lead acid are free, sell them and apply the profit towards LFP. The only time I would use lead acid would be if I needed to charge in below 32°F (0°C) temps.

Long term, LFP is cheaper per watt than any lead acid. Any metal structure around lead acid will corrode from any fumes vented by the lead acid. Useable capacity of lead acid is 50% of rating, while LFP can be used to 90% of capacity. If lead acid is commonly used over 50% capacity, sulfation will set in quickly and kill the battery quickly. LFP requires an absorption charge regularly, daily basically, and this takes time. Time is limited using solar for charging.

There is a place for lead acid, don't get me wrong. Examples would be extremely cold climate in winter and no way to keep batteries warm. Lead acid will suffer reduced capacity in cold as will any battery, so keep that in mind. A cabin used just on weekends where heat is not supplied during the week and batteries could be recharged to 100% SOC with absorption is a good application. There are others, but that gives you an idea of when to use lead acid and when not to use it.



Is this tied to any current grid AC system?

Any exposed ground wire under NEC is required to be minimum 6AWG.



No.

More details on what plans you have for your system would probably be a good idea. Members here can help you but without more details it may not be good advice. The revelation of possible lead acid batteries changes things considerably.

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Thank you for the detailed reply and guidance.

When I discovered that the two lead-acid batteries were dead, I went out and purchased two more, as they performed well for my application. Unfortunately, I can not return them. So I will have to work with these, and upgrade the batteries when these lead acid are at the end of their life.

Yes, this system uses a 120v AC inverter which is plugged into the grid. When power fails, it switches over to the batteries and inverter. I recall reading earlier that any system tied to an AC grid should be grounded, so I did.

I don't know what "NEC" is.

Electrical code varies from state to state and often varies within states. As an example, electric code in NYC is much more strict than code in outside areas beyond the city.

As far as my "plan" is concerned, I intended to just reinstall new batteries and keep it as configured. But conversations I've had here has illuminated the fact that I need to come up with a better plan. It is through conversations here that I hope to develop my plan.

NEC is the National Electric Code

The NEC is adopted by all states, some use newer versions and adopt the most recent as soon as it is released but it is the standard for electrical installations.

If you are using this as a backup system like a UPS, then you will be fine with using lead acid as you can use a grid charger to maintain charge. If you are cycling these daily, then lead acid is not suited for the purpose well.

If you are running this as a standalone power supply with only a battery charger tied to grid power, then you are basically not bound by NEC although following NEC will provide a system that is safe.

DXHum said:

But can I/should I ground the negative terminal of the battery to the rack?

Click to expand...

Most of us don't ground the battery negative.

Zwy said:

NEC is the National Electric Code

The NEC is adopted by all states, some use newer versions and adopt the most recent as soon as it is released but it is the standard for electrical installations.

If you are using this as a backup system like a UPS, then you will be fine with using lead acid as you can use a grid charger to maintain charge. If you are cycling these daily, then lead acid is not suited for the purpose well.

If you are running this as a standalone power supply with only a battery charger tied to grid power, then you are basically not bound by NEC although following NEC will provide a system that is safe.

Click to expand...

NEC: National Electric Code. I thought that might be it.

Yes! That is exactly how I'm using it; stand alone power supply charged by the grid. It is a backup that supports the tank until I can roll out the Honda.

I have an alarm on the system which notifies my phone if the grid drops. But the grid here is very reliable and we are on the same grid as the military base. Hospitals and government installations are the priority when it comes to getting the grid back on line, so, when the base is up, so am I.

I will run the batteries quarterly as a test when we have uninterrupted power by the grid during that same amount of time. So if the grid is up and running for a full year, that is still 4 battery tests over the course of the year.

Ultimately, making this a SAFE, working system is the priority. I haven't any objections to following the NEC protocols if it means a safe system.

hwy17 said:

Most of us don't ground the battery negative.

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I wondered why grounding the battery negative is practiced. Isn't an in line fuse off of the negative terminal all you need?

DXHum said:

I wondered why grounding the battery negative is practiced. Isn't an in line fuse off of the negative terminal all you need?

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I don't really know why. Maybe the logic was the same as for AC systems, to clear faults. If you don't have the negative grounded then you could have a positive fault to the equipment rack, making the whole rack live with 12v DC. In a negative grounded system, this fault would clear by blowing the fuse when it happens. In an ungrounded system, the rack could remain live with 12v unnoticed until someone then makes a rack to negative fault.

Basically grounded systems clear faults on the first fault, ungrounded systems clear faults after two faults.