48v saftey considerations

[Nsmith0723]

Are there any saftey considerations you would include that you wouldn't include with a 12v system. Im very familiar with 12v automotive systems. I'm told you dont need touch protection with 48v? Someone else told me to use one hand? I'm planning on having saftey glasses because batteries. I'm going to insulate my tools as well as I can to prevent a short. Attention to detail maybe? It seems really easy to make a mistake with my type of batteries. There is conflicting information out there and some real world experience would be helpful. From what I gather as long as I dont make myself especially conductive I should be fine? Thanks again!

 

[OffGridInTheCity]

The general idea is that a 48v 'system' will have a battery than can range up in the 55+ volt range - and so 48v and above is high enough to induce electrical shock - similar to 120v at your home. This is why electrical codes were written for 48v (and above) systems but for 12v you don't have a shock issue.

I would just treat things (safety wise) as if it were 120v/240v - even if you don't think you'll feel a shock it could still hurt you.

 

[Nsmith0723]

The general idea is that a 48v 'system' will have a battery than can range up in the 55+ volt range - and so 48v and above is high enough to induce electrical shock - similar to 120v at your home. This is why electrical codes were written for 48v (and above) systems but for 12v you don't have a shock issue.

I would just treat things (safety wise) as if it were 120v/240v - even if you don't think you'll feel a shock it could still hurt you.

Exactly the information I needed, Thanks.

 

[Nsmith0723]

The general idea is that a 48v 'system' will have a battery than can range up in the 55+ volt range - and so 48v and above is high enough to induce electrical shock - similar to 120v at your home. This is why electrical codes were written for 48v (and above) systems but for 12v you don't have a shock issue.

I would just treat things (safety wise) as if it were 120v/240v - even if you don't think you'll feel a shock it could still hurt you.

Typically you would de energize the circuit with 110v, which I cant do with the batteries, I mean I could drain them below what would be 48v all together, but I'm guessing most people just use insulated tools? Thank you!

 

[JoeHam]

If you drain them below 48v it wouldn’t be much safer and could ruin your battery.

So yes, use insulated tools to assemble the battery but then place a proper DC rated breaker at the battery and you CAN de energize your system to work on it.

 

[OffGridInTheCity]

Typically you would de energize the circuit with 110v, which I cant do with the batteries, I mean I could drain them below what would be 48v all together, but I'm guessing most people just use insulated tools? Thank you!

No need to drain the battery - I have a master on/off circuit breaker between the battery and the load. I just turn that off before working on the circuits T

 

[Nsmith0723]

No need to drain the battery - I have a master on/off circuit breaker that I just turn off before working on the circuits

Is there a circuit breaker that you would recommend? I bought the fuses on www.mobile-solarpower.com/fuses.html. still though the circuit breaker wont help with building the battery itself and installing the bms. I will just use caution and not contact the terminals I'm thinking. I know they are not rated, but I'm thinking 5mil nitrile gloves as a secondary precaution. Going to shrink wrap the shank of my screw driver, pretty sure I can get plenty of torque on the bolts still. Pretty sure there is more than enough rubber on it to keep me safe. It wont be hard to disconnect the fuse. Is it considered safe with just one terminal disconnected? Thanks again, I'm trying to use extreme caution!

 

[jimbob420]

Personally I'm not too concerned about the modest voltage of a "48v" pack, I don't wear gloves or anything to put in terminal screws, for example. I do use a spanner that I've put several wraps of insulating tape around, mostly to avoid it shorting against anything like another terminal, racking metalwork, etc. Proper insulated tools are ideal if you can afford them, but 6 or more layers of insulating tape is sufficient. To disconnect a pack for working on, to make sure it is under no load, I use battery plugs - nothing like a physical break to guarantee disconnection!

 

[OffGridInTheCity]

Agree with @jimbob420 above

Is there a circuit breaker that you would recommend? I bought the fuses on www.mobile-solarpower.com/fuses.html. still though the circuit breaker wont help with

This link didn't go anywhere.

building the battery itself and installing the bms. I will just use caution and not contact the terminals I'm thinking. I know they are not rated, but I'm thinking 5mil nitrile gloves as a secondary precaution. Going to shrink wrap the shank of my screw driver, pretty sure I can get plenty of torque on the bolts still. Pretty sure there is more than enough rubber on it to keep me safe. It wont be hard to disconnect the fuse. Is it considered safe with just one terminal disconnected? Thanks again, I'm trying to use extreme caution!

I use Midnite Solar circuit breakers (UL/ETL) such as this - https://www.amazon.com/gp/product/B004EQK8SA/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1. They have a wide range of amps and snap to DIN rail, but a control box is needed.

These type are not so good https://www.amazon.com/gp/product/B07CXYGBGH/ref=ppx_yo_dt_b_search_asin_title as they fail (in my experience) with just a few on/offs.

There are many options. Fuses are OK also - you just can't do on/off, so maybe a switch + fuses. These types of switches are popular - https://www.amazon.com/gp/product/B005DUUL9W/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[jwelter99]

The general idea is that a 48v 'system' will have a battery than can range up in the 55+ volt range - and so 48v and above is high enough to induce electrical shock - similar to 120v at your home. This is why electrical codes were written for 48v (and above) systems but for 12v you don't have a shock issue.

I would just treat things (safety wise) as if it were 120v/240v - even if you don't think you'll feel a shock it could still hurt you.

IEC 62368-1:2014 defines "safe" as 60VDC. For AC the limits are 30VAC. These are considered safe for an ordinary person but you still cannot leave exposed connectors/wires lying around as there's the whole chapter of "electrical fires" to consider.

Please stop with the constant FUD over 48V systems being a shock danger.

For some fun:

 

[Nsmith0723]

Personally I'm not too concerned about the modest voltage of a "48v" pack, I don't wear gloves or anything to put in terminal screws, for example. I do use a spanner that I've put several wraps of insulating tape around, mostly to avoid it shorting against anything like another terminal, racking metalwork, etc. Proper insulated tools are ideal if you can afford them, but 6 or more layers of insulating tape is sufficient. To disconnect a pack for working on, to make sure it is under no load, I use battery plugs - nothing like a physical break to guarantee disconnection!

See this is where I get fuzzy. I have one person telling me to treat it like 110v ac, which means to me like you treat it like any touch will kill you and other couple people telling me I can bare hand terminal screws. Now I've come into contact with live 110v ac more than I care to admit, and I understand there are no absolutes with electricity. I'm not trying to be rude or anything, but this all seems like highly conflicting information. I appreciate the help!

 

[OffGridInTheCity]

See this is where I get fuzzy. I have one person telling me to treat it like 110v ac, which means to me like you treat it like any touch will kill you and other couple people telling me I can bare hand terminal screws. Now I've come into contact with live 110v ac more than I care to admit, and I understand there are no absolutes with electricity. I'm not trying to be rude or anything, but this all seems like highly conflicting information. I appreciate the help!

I agree there are differing opinions - but remember that in the beginning I explained that a '48v battery' could go up significantly higher than 48v. Mine goes to 58.8v full charged. My scooter goes to 67.2v fully charged. At these levels - its in the relm of possibility to get enough current flowing thru you to cause risk.

Also - I'm not talking about the battery itself, but about the wiring system / loads down stream. Part of treating this like 120v beside shocks is I don't want to cause shorts! I've done this and its not good.

The US NEC codes specifically address 48v+ systems with a set of regulations - because they believe there is risk of injury. But maybe they are just govt entities that want to expand their reach.

I agree that I (personally) am not an electrician or have I ever been shocked - but I am passing on the best knowledge I've gathered over several years of doing this and reading many posts.

The point of this discussion is not for me to be right OR to tell you what to do. This is DIY. The point of this discussion is just to assist you in making your own decision. You might decide to consult an electrician, you might just not worry about it, but as DIY, its your decision and I don't think any of us here should judge you

Maybe let us know at some point in the future what you decide / come to believe

 

[upnorthandpersonal]

Your 48V pack might sting a bit, but it's nowhere near touching 120V AC (or 240V AC where I am). One thing you do have to be very careful with is not shorting the battery (especially when you're working on it and you're 'before' the fuse. A short (especially with LiFePO4 cells) will dump a huge amount of current that will melt metal. You don't want that flying molten metal - wear safety glasses and gloves just to be sure, and no shorts and flip-flops. I know some people don't, but really, it's a minimal set of safety features.
You won't feel touching a single pole by the way because there is no closed circuit. That's why you can easily work on the terminal screws or bus bars without getting stung - as long as you only are in contact with one of the terminals.

Edit: yes, I have been shocked multiple times with anything up to and including 20kV.

 

[Supervstech]

See this is where I get fuzzy. I have one person telling me to treat it like 110v ac, which means to me like you treat it like any touch will kill you and other couple people telling me I can bare hand terminal screws. Now I've come into contact with live 110v ac more than I care to admit, and I understand there are no absolutes with electricity. I'm not trying to be rude or anything, but this all seems like highly conflicting information. I appreciate the help!

It is all about conditions and tolerances. I bare hand deal with 110 and 240V all the time… I don’t put myself in the circuit, so I am isolated, even though in direct contact…
Same with 48V… mild safety, and no danger. However, I have been knocked on my butt by 24V, and even 12V on hot sweaty days… salty wet skin and a mistake in procedure… and yeah… it hurts.

 

[A.Justice]

Your 48V pack might sting a bit, but it's nowhere near touching 120V AC (or 240V AC where I am). One thing you do have to be very careful with is not shorting the battery (especially when you're working on it and you're 'before' the fuse. A short (especially with LiFePO4 cells) will dump a huge amount of current that will melt metal. You don't want that flying molten metal - wear safety glasses and gloves just to be sure, and no shorts and flip-flops. I know some people don't, but really, it's a minimal set of safety features.
You won't feel touching a single pole by the way because there is no closed circuit. That's why you can easily work on the terminal screws or bus bars without getting stung - as long as you only are in contact with one of the terminals.

Edit: yes, I have been shocked multiple times with anything up to and including 20kV.

Seconded on everything said here.

To OP;
The biggest danger is arcing that voltage from positive to negative and blowing molten metal in your face (that's still just as true with 12 volt systems as well).

Remember that AC can go from hot to ground, through you. DC goes from positive to negative, so unless you make contact with both, it won't shock you.

Try and keep one hand behind your back while working, don't touch live stuff if you are sweaty, and WEAR GLASSES.

 

[400bird]

See this is where I get fuzzy. I have one person telling me to treat it like 110v ac, which means to me like you treat it like any touch will kill you and other couple people telling me I can bare hand terminal screws. Now I've come into contact with live 110v ac more than I care to admit, and I understand there are no absolutes with electricity. I'm not trying to be rude or anything, but this all seems like highly conflicting information. I appreciate the help!

With DC voltage there is a large range for different people.

I have a small adjustable DC power supply that goes up to 120vdc.

With one hand, thumb on + and pinky on negative, I slowly cranked the voltage up. I could feel the voltage tingle at roughly 90. I wet my fingers and it was 60.

My coworker was roughly 20 volts lower for both (70 dry and 50 wet)

Very small sample size, but NEC says 60v is safe.
Just don't be dumb, work with dry hands or gloves or both. And insulated tools are important if there is any chance the tool can hit two different points in the circuit. But, this the same at any voltage, even 6 volts.


I'm sure some of you will think we were taking our life in our hands (literally, lol) but, we started the test at 12v and slowly increased the voltage and stopped when we could 'feel' it and didn't go any further.

 

[upnorthandpersonal]

 

[Nsmith0723]

Seconded on everything said here.

To OP;
The biggest danger is arcing that voltage from positive to negative and blowing molten metal in your face (that's still just as true with 12 volt systems as well).

Remember that AC can go from hot to ground, through you. DC goes from positive to negative, so unless you make contact with both, it won't shock you.

Try and keep one hand behind your back while working, don't touch live stuff if you are sweaty, and WEAR GLASSES.

This is a specific nugget of info I needed. It may seem obvious, but I'm used to ac where you have to worry about the potential to ground. I can certainly handle one terminal at a time easy. Yeah it would seem shorts are bad with any voltage honestly. Thanks again

 

[chrisski]

It becomes slightly harder to parts rated at 48 VDC, and even harder more expensive for above that.

I have noticed that a lot of items are rated for 48 VDC, but charge voltage can reach 56 VDC and equalization voltage could be closer to 65 VDC. I briefly considered a 48 VDC upgrade instead of a 24 VDC upgrade but some of the stuff I had was rated to 48 VDC, not 49 VDC.

I don’t know what happens if you put 56 VDC through the typical Blue Sea 300 amp / 350 amp on/off switch that is rated for 48 VDC.

THere’s a hole slew of little thing like that. Other common parts are way to low rated voltage wise to use like ATC and Maxi fuses to name a few.

I had also not considered a 48 volt upgrade earlier, so my SCCs can only charge up to 24 VDC battery packs.

 

[Nsmith0723]

Needs a thicker nail ?