What Thickness Of Steel For Battery Boxes?

[The Mighty Volt]

Hi there. I am going to knock up some boxes for some 16ah 36v batteries, LiFePo4, so you can imagine they would need to be able to absorb and hold quite a bit of weight. I have a TIG/MMA welder which I am going to use {most likely the MMA option} to weld them up. I am going to cut the boxes out of sheet steel with a dremel tool or circular saw.

Any idea what thickness of steel I should use? I don't want to use something too light but I don't want to turn the bike into an armoured car either by adding too much steel. It is already a bit heavy with the frame, suspension, big X5 and batteries.

I MIGHT be tempted to use aluminium to save on weight IF somebody here can tell me how to weld the damned stuff with a stick welder. Thanks.

All and any suggestions would be welcomed. Thanks.

 

[Punx0r]

I used some 1mm stuff I had knocking about. Thick enough to be dent resistant IMO (I've dropped the bike a few time at speed).

A dremel will be a waste of time unless it's paper thin. A circular saw won't touch steel unless it's a special, steel cutting blade (and saw to match). A jig saw or air shear are decent tools for sheet steel.

 

[The Mighty Volt]

I used some 1mm stuff I had knocking about. Thick enough to be dent resistant IMO (I've dropped the bike a few time at speed).

A dremel will be a waste of time unless it's paper thin. A circular saw won't touch steel unless it's a special, steel cutting blade (and saw to match). A jig saw or air shear are decent tools for sheet steel.

Thanks for the advice. 1mm might be a bit warp-prone when welding, that's another concern I should have mentioned. Thanks.

 

[dogman dan]

In steel, 1/8 inch thick would be overkill. Too heavy to go that thick. No more than 1mm or so sounds good to me. Same thickness you'd get if you cut up an old fridge or something.

 

[LSBW]

My box is welded from 1 mm sheet metal.
Plus it's lined inside with 0.8 mm plastic.
No problems so far.

 

[atom1025]

I bend steel boxes for a living.

.030" is to thin in my opinion.

.047" seems perfect in my mind. We use this on the majority of computer casings and chassis.

.060" is tough stough if you aren't as concerned with weight.

 

[Kingfish]

I used two Sears Craftsman Toolboxes to hold 15 batteries each for my custom trailer.

With that much weight in them the boxes tended to flex. However, I had them mounted to the floorboard which eliminated the problem.

If I had to guess, they are made from 0.047 inch/1.2mm thick sheet.
Dang: The battery in my digital micrometer just died - so I can't tell you for sure. Maybe after tomorrow when I fetch a new watch battery :wink:

Good hunting, KF

 

[miro13car]

Why use steel in first place
What about rust
All my battery boxes are made of ABS

 

[fizzit]

My battery box is made of .040 aluminum sheet that is riveted together. You might consider using aluminum instead of steel if you want to save a little weight.

 

[dogman dan]

My best homemade battery boxes are made from old aluminum road signs. I didn't steal them, honest to god. But the previous owner of my house might have.

I make the boxes with wood ends and bottom, and the alloy sheet sides. Man, can they take a beating in crashes.

I don't know the guage, it's about 1/8" . Thick enough to be able to countersink a screw in it which is nice. Good stuff, and I'm sure similar thickness can be found somewhere. Cuts easy with a skillsaw,table saw or jig saw.

In steel, it can be much thinner and be just as tough. Toolboxes have been great, I've got some of those with good dings in em. So that thickness should be good enough.

 

[edventure]

You may want to consider other materials like plastic. I am working on my first e-bike and I am attempting to make 3 battery enclosures out of a plastic called Delrin. One enclosure will go inside the triangle and the other two will hang to either side of the rear rack. I can't say from experience whether this will work or not but, I hope to have the triangular enclosure complete by the end of next week. I posted some photos of the material so you can see what it looks like. This will make the main body of my enclosure and the sides will be a textured black ABS that is 3/16" thick. The Delrin body parts are 1/4" thick but extremely light. In addition I am lining the inside of the enclosure with a high temperature silicone mat that is capable of handling temps above 500 degree F to at minimum slow down any potential fire hazard. This is the same material used in modern oven mitts. I wanted to use aero-gel, but it was kind-of cost prohibitive.

One downfall of using these materials are, they can be more expensive, but many of these materials including the silicone insulation can be had from Mcmaster-Carr at a decent cost. I attached some photos of my current progress. ALso I pasted a paragraph here from a company describing the benefits of the Delrin plastic. Also, this plastic can be easily polished to a very high shine, "if that's what you like" when it becomes scratched or nicked.

DELRIN® possesses high tensile strength, creep resistance and toughness. It also exhibits low moisture absorption. It is chemically resistant to hydrocarbons, solvents and neutral chemicals. These properties along with its fatigue endurance make DELRIN® ideal for many industrial applications. In addition it has excellent UV-resistance. DELRIN® (Acetal Homopolymer) is a crystalline plastic which offers an excellent balance of properties that bridge the gap between metals and plastics.

Good Luck in whatever route you go. I will post more pictures as my project comes along.

 

[The Mighty Volt]

Why use steel in first place
What about rust
All my battery boxes are made of ABS

What about paint?

Steel is easier for me to weld than aluminium!!! Aluminium is so damn hard to weld, unless you got a good TIG set up and I don't have those facilities right now.

 

[The Mighty Volt]

You may want to consider other materials like plastic. I am working on my first e-bike and I am attempting to make 3 battery enclosures out of a plastic called Delrin. One enclosure will go inside the triangle and the other two will hang to either side of the rear rack. I can't say from experience whether this will work or not but, I hope to have the triangular enclosure complete by the end of next week. I posted some photos of the material so you can see what it looks like. This will make the main body of my enclosure and the sides will be a textured black ABS that is 3/16" thick. The Delrin body parts are 1/4" thick but extremely light. In addition I am lining the inside of the enclosure with a high temperature silicone mat that is capable of handling temps above 500 degree F to at minimum slow down any potential fire hazard. This is the same material used in modern oven mitts. I wanted to use aero-gel, but it was kind-of cost prohibitive.

One downfall of using these materials are, they can be more expensive, but many of these materials including the silicone insulation can be had from Mcmaster-Carr at a decent cost. I attached some photos of my current progress. ALso I pasted a paragraph here from a company describing the benefits of the Delrin plastic. Also, this plastic can be easily polished to a very high shine, "if that's what you like" when it becomes scratched or nicked.

DELRIN® possesses high tensile strength, creep resistance and toughness. It also exhibits low moisture absorption. It is chemically resistant to hydrocarbons, solvents and neutral chemicals. These properties along with its fatigue endurance make DELRIN® ideal for many industrial applications. In addition it has excellent UV-resistance. DELRIN® (Acetal Homopolymer) is a crystalline plastic which offers an excellent balance of properties that bridge the gap between metals and plastics.

Good Luck in whatever route you go. I will post more pictures as my project comes along.

Thanks for your wishes and for the time and effort to write the above post.

One Idea I did have was to use plywood and aluminium, this would keep things light, strong and eliminate the need for welding on the boxes at all.

This then creates the problem of how thick/thin the aluminium should be, personally, I am feeling 1.5mm right now.

Unfortunatley, I cannot put in the time or money into looking at new materials right now,. Part of what kills my projects is chopping and changing. One thing I had heard people were using was plastic chopping boards, like they use in restaurants.

 

[zoom2136]

If you want't some fire protection use FIBERFLAX. Its an aircraft firewall coating. Light and effective.

http://www.aircraftspruce.ca/catalog/appages/fiberfrax.php?clickkey=161217

 

[The Mighty Volt]

My best homemade battery boxes are made from old aluminum road signs. I didn't steal them, honest to god. But the previous owner of my house might have.

I make the boxes with wood ends and bottom, and the alloy sheet sides. Man, can they take a beating in crashes.

I don't know the guage, it's about 1/8" . Thick enough to be able to countersink a screw in it which is nice. Good stuff, and I'm sure similar thickness can be found somewhere. Cuts easy with a skillsaw,table saw or jig saw.

In steel, it can be much thinner and be just as tough. Toolboxes have been great, I've got some of those with good dings in em. So that thickness should be good enough.

That's what I will be doing now. Except I don't plan on crashing lol....but then again, who does?

3/4" ply, 1.5mm aluminium, and some choice bolts. I've found that a tiny pilot hole is best, then just ratchet the appropriate bolt on in there. I cannot see the need for threaded inserts here, surely?

Now....I am going to try and connect the boxes to the side of the BMX frame using.......slide-rails.

 

[The Mighty Volt]

If you want't some fire protection use FIBERFLAX. Its an aircraft firewall coating. Light and effective.

http://www.aircraftspruce.ca/catalog/appages/fiberfrax.php?clickkey=161217

LiFePo4 bro No fires here!! Thanks anyways, cheers.