What kind of safety measures do you take when building battery at home?

[Cyclomania]

Hi

So I am probably going to try to build my first battery in the next few months. I have nickel strip, case, cells, spacing and bms. I am now going to try to build and weld the actual battery. So I can use it, for a bike most likely.

The battery is going to be a 52volt 14s-battery. Most likely 14s6p.

What kind of safety precautions do you take before you build a lithium battery at home?

Do you guys use some special type of clothing? For example, a welding helmet and some protective clothing or something like that?

Where do you put the battery when you are building it? Maybe an oven tray or something like that? So if a fire starts it is easy to carry it outside on the asfalt ?

 

[Hwy89]

A metal oven tray isn’t a good idea. You need a nonconductive work surface and as much as possible nonconductive tools. A bucket half full of sand on the floor next to you might be a good idea. I found that ordinary bamboo shish ke bab skewers are the handiest items to have around. I use them to help position the strips, hold things down, build a frame with rubber bands to keep loose cells in a row and dab flux were needed.
Stay focused and think about every move before you make. The times that I’ve made sparks happen we’re always when someone or something distracted me.
If you aren’t making arcs and sparks you won’t need that welders helmet.

 

[amberwolf]

The first and best safety precaution is information.

If you know enough about what you should and shouldn't do, by reading and following the many battery-building threads here on ES and elsewhere, you will probably not need to worry about accidents, fires, sparks, etc.

It will probably take a lot of hours of reading, but you will learn things from that that you won't get from just asking questions of your own, because there will be things discussed that you didn't even think of.

This might not sound like helpful information, but it's the best safest first thing you can do before you even start buying parts for a battery build.

 

[lnanek]

Build outside and keep a couple fire extinguishers ready. I use these:

https://www.amazon.com/dp/B09H33LX31

They barely have enough in them to put out a burning p-group, but I like how they are small enough to fit in my cycling fanny pack the rest of the time. I also have a metal ammo can half full of dirt I dump thermal runaway packs in. For thermal runaway cells, I put them in a fiberglass lipo safe charging bag and dump them in a bucket of water overnight to fully short them out.

I have a portable table I put outside the garage in the driveway. My spot welder runs on battery and any other tool that needs power can use an extension cord from inside.

I used to build in the garage, but I use high quality brand name cells that vent when damaged into a short and the black gunk got all over my garage walls, a table, and some equipment when I blasted a burning cell with an extinguisher. It's really tough to clean. Like easier to repaint your walls tough.

 

[Cyclomania]

The first and best safety precaution is information.

If you know enough about what you should and shouldn't do, by reading and following the many battery-building threads here on ES and elsewhere, you will probably not need to worry about accidents, fires, sparks, etc.

Yeah I have read a lot. But I would like to read more. I am trying to go through everything that could go wrong. So I have good safety measures at hand. I am going to try to build a 14s18ah battery.

If you Amberwolf could point me to some threads you think are the best in here, for noobs building and for safety, I would much appreciate the information. Then I know I am reading good information.

 

[Cyclomania]

Build outside and keep a couple fire extinguishers ready. I use these:

https://www.amazon.com/dp/B09H33LX31

They barely have enough in them to put out a burning p-group, but I like how they are small enough to fit in my cycling fanny pack the rest of the time. I also have a metal ammo can half full of dirt I dump thermal runaway packs in. For thermal runaway cells, I put them in a fiberglass lipo safe charging bag and dump them in a bucket of water overnight to fully short them out.

I have a portable table I put outside the garage in the driveway. My spot welder runs on battery and any other tool that needs power can use an extension cord from inside.

I used to build in the garage, but I use high quality brand name cells that vent when damaged into a short and the black gunk got all over my garage walls, a table, and some equipment when I blasted a burning cell with an extinguisher. It's really tough to clean. Like easier to repaint your walls tough.

Haha a lot of good information here. Do they become runaways pretty often then? What did you do wrong when they became rogue? I hope to avoid this since I am renting the underfloor/basement here .

I do have the ability to step outsie and do it outside soon when it gets a bit warmer. If it is a fine sunny day. Although perhaps that should be after a rainy day since the lawn is close to the stone-floor just outside my basement.

The ammo pack sounds like a good idea. Just throw them in there if they become shorty? What model do you use for the ammo pack? Something like this? Amazon.com

And what portable table? Just a regular wooden table or more like a non conductive-table of some sort?

 

[Cyclomania]

A metal oven tray isn’t a good idea. You need a nonconductive work surface and as much as possible nonconductive tools. A bucket half full of sand on the floor next to you might be a good idea. I found that ordinary bamboo shish ke bab skewers are the handiest items to have around. I use them to help position the strips, hold things down, build a frame with rubber bands to keep loose cells in a row and dab flux were needed.
Stay focused and think about every move before you make. The times that I’ve made sparks happen we’re always when someone or something distracted me.
If you aren’t making arcs and sparks you won’t need that welders helmet.

Hmm perhaps a glass oven tray if I make it inside? One of those big ones. If I do it inside my thought was to have all the windows open with a table outside the windows. So if something starts to burn/short on that glass tray I could just lift it outside. And then perhaps throw sand and dirt over it outside. Water might not be the best idea when doing this right? Sand is better?

What gloves do you guys use when building batteries? Should be both light over the hand and non-conductive right.

 

[Hwy89]

I have always assembled the parallel cell groups first and set them aside until all of them are ready for the final assembly in series. These individual groups are less than 4.2 volts and can handled without gloves. It isn’t until you start connecting then in series that there starts to be a risk of shock. Normal skin resistance of dry fingers will protect you up to around 50 volts but I’ve never tried testing that theory. I’ve been working live electrical equipment bare handed for a long time and know where not to put my fingers. The only time that you might need gloves is if you screw up and things start getting hot and at that point you might not have time to put them on.
Remove all jewelry, piercings, dog tags etc before working on even the low voltage stuff.

 

[honya96]

Fully charged 21s hurts just a little, not enough to get scared and throw the battery

 

[jonyjoe303]

For me the dangerous part is taking cells apart, thats when there is risk of shorting out cells. The only fire I had was when I was taking a battery pack apart and the cell shorted out causing a hole in the cell. This set off a fire.
Pouring water was enough to to keep the fire from spreading to the other cells by keeping everything cool. Water won't put the fire out because as soon as you stop pouring water it reflashes but eventually the fire goes out. The fire is like a blow torch in intensity. If you can keep the fire to 1 cell cell its manageable.
The high discharge cells are the most dangerous as far as shorting out.
It don't matter what chemistry the cells are, they all will catch on fire. The fire I had was with A123 26650 lifepo4 cells (everyone says lifepo4 is suppose to be safer) ,I never had any problems with 18650 li-ion laptop cells and I built many packs with those.
It would be good idea to work on cells that are very low voltage, so they won't be so volatile. Usually when I built packs they are usually almost fully charge, now I try and make sure they arent at max voltage.
And take your time when taking packs apart. I was rushing when I shorted the cell that caught on fire. Now I use hard plastic as a buffer between the pliers and the battery so no metal to metal contact occurs. Since that incident (about 3 years ago) havent had anymore fires or shorts, and I built/tore down several packs since then.

 

[lnanek]

I'd recommend watching some videos of thermal runaway packs online, and setting some cells off yourself. Carrying a burning pack up stairs to go outside on an oven tray seems insane to me. Even if you had a welding mask to protect your face from the flames and a respirator to protect yourself from the fumes, they still sometimes shoot cells off the pack ballistically.

If you won't work outside, and don't have a table with wheels in a room you can roll it outside, best bet is one you can tilt to let the pack slide into a large metal trash can half filled with sand and a bucket to dump more sand on top, I suppose. I just wouldn't build a pack in those circumstances, though.

 

[docw009]

New cells and battery packs have to be at 30% SOC to meet shipping regulations, and it's been my experience that they'll hold that voltage for months. When I build with new cells, they're usually at 3.42 volts. When I have gone with second hand cells, I'll test them first for capacity, and take the time to bring them under 30% too. Probably should short one intionally to see what happens at 3.3V.

For safety, I only use name brand cells which have thermal vents and also CID's. I accidentally shorted a cell, put it in a cell holder backwards, and by the time I pried it out, it had vented.

For construction, I like to use cell holders with fish paper o-rings on the positive ends. If it's a glued pack, fish paper around each p-group for extra insulation. I bought some inexpensive glued packs, and eventually took them apart and put them into cell holders. I saw that the balance wires were laid atop the nickel on one pack, and the insulation had melted in spots, so now I route those wires away from the nickel.

 

[hemo]

1. Read up on build techiniques .
2. Read up on arduino mini welders and the type of buss tecniques used for welding.
3. Make sure no jewellery is worn, so no rings, bracelets, watches or chains.
4. Use cell holders and insulators.
5. Don't use metal tools , plastic or wooden implements only. The only metal tools will be the welder probes.
6. Make sure you know how to use/read a multimeter correctly.
7. If not sure ask first.
8. Cover any exposed part of the battery not being worked on, stiff card is handy and a bit of tape.

 

[beemac]

Whilst I built my first battery (14s4p) I kept next to me a pair of leather welding gloves, a fire extinguisher and a metal container big enough to carry the battery outside in. Definitely a bit nerve wracking the first build - lots of concentration. Tbh I won't build another inside

I also made these notes from that build - not all safety related - and I'm sure mostly covered in many other battery threads

Weld series first - and use thickest material
Using sunkko 709a and 0.2mm nickel - after struggling to get the welds strong reckon I need to either upgrade 709a or split strips - preferably both...
Upgraded my sunkko with 25mm2 cable and 1.5mm copper electrodes, then use '10x60' setting for 0.2mm nickel (single 10x0.2mm series strip - slotted) and '1x40' for 0.1mm nickel plated steel (double 4x0.1mm parallel strips)
Either cut slots in strips where they lay over batteries - or buy preslotted strips/half width strips and lay side-side
If using a honeycomb cell holder and it's tight - lightly grease cells and holder when inserting to prevent damage to insulation
Put connectors on any cables before you wire them to the battery
Mask off adjacent parallel groups with insulating tape when welding
Presolder any wires to strips before welding
Rub strips with sandpaper where you want to solder to help the solder 'stick'

 

[Cyclomania]

I'd recommend watching some videos of thermal runaway packs online, and setting some cells off yourself. Carrying a burning pack up stairs to go outside on an oven tray seems insane to me. Even if you had a welding mask to protect your face from the flames and a respirator to protect yourself from the fumes, they still sometimes shoot cells off the pack ballistically.

If you won't work outside, and don't have a table with wheels in a room you can roll it outside, best bet is one you can tilt to let the pack slide into a large metal trash can half filled with sand and a bucket to dump more sand on top, I suppose. I just wouldn't build a pack in those circumstances, though.

How do I put one off safely on my own?

I was not thinking about carrying the stuff upstairs. It is not far to go outside. Window is at the lowest floor in a house so I can just lift it outside if I have a table or metal trash can or something like that out there. But rather have it close to a window and lift it outside to a table or for example a metal trash can that people have also been mentioning.

Or.. maybe do it outside with an extension cable to sit outside the windows when I put it together. There are stoned paved floor kind of outside my windows. Where I could sit. A little bit furter out is the lawn. This one I dont want to set on fire. What do you think?

Yeah the ballistic missile throw away from the pack seems the most scary to me I dont like that idea.
That is why I was thinking perhaps welding mask or something like that. But lot of people seem to think this migt be unnessecary if doing it proprely, right?

Chances of that happening might be lowered when having lower voltae in the cells, right? Then they havent as much stored up energy?

What type of metal trash can do people use? Amazon might have a good one? We have Amazon here.

 

[Cyclomania]

I used to build in the garage, but I use high quality brand name cells that vent when damaged into a short and the black gunk got all over my garage walls, a table, and some equipment when I blasted a burning cell with an extinguisher. It's really tough to clean. Like easier to repaint your walls tough.

Do you use some kind of face protection or something when you build? I reckon those dust blasts could have gotten to your face maybe if it made the walls black?

 

[tomjasz]

Build outside and keep a couple fire extinguishers ready. I use these:
https://www.amazon.com/dp/B09H33LX31

About as effective as peeing on the pack. Not to be rude but have you ever tried to extinguish a lithium battery fire? I'd hate to have someone think those little purse-sized extinguishers would be of any real suppression.

 

[AnthonyC]

I'd recommend watching some videos of thermal runaway packs online, and setting some cells off yourself. Carrying a burning pack up stairs to go outside on an oven tray seems insane to me. Even if you had a welding mask to protect your face from the flames and a respirator to protect yourself from the fumes, they still sometimes shoot cells off the pack ballistically.

If you won't work outside, and don't have a table with wheels in a room you can roll it outside, best bet is one you can tilt to let the pack slide into a large metal trash can half filled with sand and a bucket to dump more sand on top, I suppose. I just wouldn't build a pack in those circumstances, though.

Bear in mind that the chemical energy in a cell is very roughly ten times the capacity and doesn't need air to burn. While you're assembling the groups a 14s6p pack will have about 750Wh x 10 to burn off in a few minutes, that's a 75kW untamable blaze if you're unlucky. Now count the posts above that mention mishaps and check you're happy to "just lift it outside" to a trash can.
If it were me I'd try to find someone to build a pack with my parts who's willing to show me how it was done. I wouldn't try setting off cells myself, if they only vent that doesn't mean it's all they'll ever do. There are some great questions (and answers) on this thread but sometimes that's not enough.

 

[Cyclomania]

I found that ordinary bamboo shish ke bab skewers are the handiest items to have around. I use them to help position the strips, hold things down, build a frame with rubber bands to keep loose cells in a row and dab flux were needed.
Stay focused and think about every move before you make. The times that I’ve made sparks happen we’re always when someone or something distracted me.
If you aren’t making arcs and sparks you won’t need that welders helmet.

https://www.aliexpress.com/item/1005003456210394.html?spm=a2g0o.productlist.main.1.70ddw1zIw1zIGw&algo_pvid=111a8529-dafb-429c-a100-0052c642bb9b&algo_exp_id=111a8529-dafb-429c-a100-0052c642bb9b-0&pdp_npi=4%40dis%21NOK%2125.18%2118.83%21%21%212.30%21%21%40211b613916972887412111846eb757%2112000025870799990%21sea%21NO%21167266123%21&curPageLogUid=solVqcvUTHn1

Kind of like these?

 

[Cyclomania]

Build outside and keep a couple fire extinguishers ready. I use these:

https://www.amazon.com/dp/B09H33LX31

They barely have enough in them to put out a burning p-group, but I like how they are small enough to fit in my cycling fanny pack the rest of the time. I also have a metal ammo can half full of dirt I dump thermal runaway packs in. For thermal runaway cells, I put them in a fiberglass lipo safe charging bag and dump them in a bucket of water overnight to fully short them out.

I have a portable table I put outside the garage in the driveway. My spot welder runs on battery and any other tool that needs power can use an extension cord from inside.

I used to build in the garage, but I use high quality brand name cells that vent when damaged into a short and the black gunk got all over my garage walls, a table, and some equipment when I blasted a burning cell with an extinguisher. It's really tough to clean. Like easier to repaint your walls tough.

What about sitting close to the outer door?

Having a metal bucket with sand in it right? Would be good? Would the sand in the metal bucket + plus som extra sand at the side be enough to extinguish a rogue battery that is thrown inside there?

So my thinking is to have this bucket half filled with sand. And when I am making the battery, if something starts to short out, burn etc.. Then I would throw the battery-pack into that bucket. And then throw the rest of the sand from this bag into that bucket. What do you guys think about that? Would it be enough to make the fire go out? Perhaps then hose some water on top of the sand after or something.

 

[Hwy89]

Funny, I never thought about having to purchase packaged sand but I’m a desert dweller and it isn’t hard to find here in Arizona. It doesn’t need to be pure, any loose dry dirt will smother a fire.
Yes those are the bamboo sticks I use. very handy to have when soldering or spot welding small things.

 

[Cyclomania]

Funny, I never thought about having to purchase packaged sand but I’m a desert dweller and it isn’t hard to find here in Arizona. It doesn’t need to be pure, any loose dry dirt will smother a fire.
Yes those are the bamboo sticks I use. very handy to have when soldering or spot welding small things.

Great.

I am going to go with those. What kind of voltages do you keep the cells at when you start the actual build?

And what kind of machine do you use for discharging cells to the voltages you want them at?

What do you guys think about explosions? I have a welding mask so then at least if it explodes it would not go right into my face. But then again it is not as easy to see details inside that mask.

But is it not right, that the explosion risk is more probable if they are very highly charged? So for example below 3,7 volts they are more likely to cause a fire and at least not an explosion?

 

[Cyclomania]

By the way, what is the most dangerous part of the battery build? Is it when I connect the BMS and it starts to equalize the cells?

I describe my battery pack, with 84 cells, in this other thread below. It is 91 slots in that sheet for the cells. But I have picked the 52volt version which will be 84 cells. 6 in parallell. Right now, I am doing the research about the nickel sheet, since it is a little bit confusing when everything is diagonal and so on .

Feel free to give me advice on how you would have gone about doing it in this thread as well if any of you guys have input:

BMS for 52volt 14s?

Looks like 14s6p = 84 cells. 14s7p would have been 98 cells, so doesn't fit in that case. The reason you have two rows of 6 next to each other most of those plates is because you are suppose to put six cells' positive ends down on one half of the plate, then 6 cells negative ends down on the...

endless-sphere.com

Since I am going with 84 cells it will leave seven slots empty. That is quite neat because right now I cannot fit the BMS into the pack. But since there will be three slots empty there my thinking is I am going to cut/saw of three empty slots from the battery sheet. And in that way I think I will make room for the bms inside the battery pack, below the pack.

My cells looks like in the below image.

As you can see they came with cells insulations paper only on one side. So do you guys think I should put that on the other side as well perhaps?

 

[docw009]

I like to build batteries with the cells at 3.3-3.4 volts. Wear safety glasses, but a welding helmet will cause you to miss welds. It's too dark. You only want paper washers on the positive end. It keeps the nickel from contacting the negative edge of the can.

If your welder is set too high, sparks will fly up from the nickel. This may include molten metal. That's why you wear safety glasses. Also, if the welder settings are too strong, you can blow holes thru the nickel. Sometimes you could blow a hole in the metal can. The cell will squeal as hot gas escapes. Then it will leak electrolyte and the cell has to be replaced. This usually happens when you miss the nickel and contact the cell case with the welder probe.

 

[Bandit1961]

Practice practice practice... Get some dead cells & try building a smaller pack with them first.
Your bound to make mistakes no matter how much good/bad advise your given... So get yourself some practical experience 1st & build up your confidence.