Nodge68
Well-Known Member
Maybe not, but I did spot her (her parents probably) has radiators, so presumably burns something to heat them!
Alibro
Well-Known Member
I've been struggling to decide the best way to link the battery modules inside the battery box and I figured it was important to sort this out before going any further with the box fab.
The screw terminals are close to the sides of the box and I wasn't completely happy bending ring terminals at 90 deg. The original solid copper cables are really hard to bend and many of them are not suitable for the position I have the modules now. At first I thought I wouldn't be able to reuse them but a mate suggested just cutting and joining them so after a bit of fettling this is the current idea.
I just need to trim back the insulation, drill holes in them and bolt them together. I might twist them 90 deg so it's easier to isolate the bolts from the battery case but I'll decide that when I have the case finished.
The screw terminals are close to the sides of the box and I wasn't completely happy bending ring terminals at 90 deg. The original solid copper cables are really hard to bend and many of them are not suitable for the position I have the modules now. At first I thought I wouldn't be able to reuse them but a mate suggested just cutting and joining them so after a bit of fettling this is the current idea.
I just need to trim back the insulation, drill holes in them and bolt them together. I might twist them 90 deg so it's easier to isolate the bolts from the battery case but I'll decide that when I have the case finished.
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I'm assuming you'll have a way of insulating the wire joints? If you do, you woild be best served to have the "wires", which appear to be more like solid copper flat bar, AC tig welded together....
Orange original insulator
Blue new insulation
Yellow copper conductors
Green welds
Alibro
Well-Known Member
You're right, they are solid copper bars 35mm2 It looks like they're soldered to the connectors so at first I was thinking of soldering the bars together but there is one good reason why I can't do that nor weld them. I need to be able to screw the connections to the battery modules BEFORE I set them in the box.
If you look at the position of the terminals on the modules many of them will be impossible to access after they are set in the box. I only realised this when I went to tighten the connections nearest the two uprights.
I will probably have to change the center links for this reason too as I will not be able to set all four modules into the box bolted together.
Insulating them shouldn't be a major issue and is why I'm thinking of putting a twist in the bars so the bolts will be horizontal.
If you look at the position of the terminals on the modules many of them will be impossible to access after they are set in the box. I only realised this when I went to tighten the connections nearest the two uprights.
I will probably have to change the center links for this reason too as I will not be able to set all four modules into the box bolted together.
Insulating them shouldn't be a major issue and is why I'm thinking of putting a twist in the bars so the bolts will be horizontal.
Nodge68
Well-Known Member
Soldering would be my preferred joining method.
Thinking slightly outside the box (no pun intended), couldn't you simply assemble the battery pack outside the box, and lower the packs in as one unit, if you put a shaped board underneath them for support, and use a couple of loops of webbing as a lifting aids?
Alibro
Well-Known Member
Four large + 2 small modules will weigh around 60kg, space is very tight and If anything went wrong the chances of damaging one of them would be high, and they are VERY expensive.Soldering would be my preferred joining method.
Thinking slightly outside the box (no pun intended), couldn't you simply assemble the battery pack outside the box, and lower the packs in as one unit, if you put a shaped board underneath them for support, and use a couple of loops of webbing as a lifting aids?
It may not be optimal but I think I will be bolting them together.
Nodge68
Well-Known Member
Ah yes, that's heavy and potentially expensive, so maybe not such a good plan.
The only thing to remember, is drilling hole for bolts will reduce the current carrying capacity of the bus bars.
I know the battery packs are expensive, so obviously you don't want to damage them, but is it possible to solder the bus bars in situ with a very large soldering iron? I've soldered pipes many times in tight places, with combustible materials all around the blow torch. Its possible to protect delicate or combustible materials with fire proof matting, metal sheets, or some other material like fire board.
I know it's a faff compared to bolting, but soldering is a secure and reliable electric connection, which bolting in my experience isn't.
Alibro
Well-Known Member
I was thinking the same but ultimately it's no different to putting on a ring terminal. Maybe I can flatten them a bit to make them wider and lose less material, also should be able to use two bolts per connection and could use M5 bolts to minimise the hole size.Ah yes, that's heavy and potentially expensive, so maybe not such a good plan.
The only thing to remember, is drilling hole for bolts will reduce the current carrying capacity of the bus bars.
I know the battery packs are expensive, so obviously you don't want to damage them, but is it possible to solder the bus bars in situ with a very large soldering iron? I've soldered pipes many times in tight places, with combustible materials all around the blow torch. Its possible to protect delicate or combustible materials with fire proof matting, metal sheets, or some other material like fire board.
I know it's a faff compared to bolting, but soldering is a secure and reliable electric connection, which bolting in my experience isn't.
Soldering after installing had crossed my mind too but I think bolting is the answer. My 80W iron wouldn't look at soldering two 35mm2 copper bar and I don't fancy putting a welding torch any where near it.
Bolts will be fine.
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I have started doing something involving RC helicopters, the aircraft at the heart of the project has a 180amp ESC on it, albeit only running 12s so circa 50v, for that I've went with 5.5mm solid brass bullets, and a soldering iron was wholly ineffective against them, what did work a treat was the duchesses mini blow torch that she initially bought for carmelising icing sugar on deserts. For I don't think such a torch would work for your wires, and I certainly would never recommend soldering in situ ontop of lipo batteries, especially such big ones, but plumbers soldering gear would probably be man enough to heat the copper enough to melt the solder onto it. Although I'd reiterate to solder them off the bateries.
Were I doing this, I'd do it with solder or weld, as the cables are quite maleable, and will hold their shape once they've been gorillad into position, it should be relatively simple to offer them up, mark them, remove them, solder them insulate them and refit them. In my minds eye I envisage myself doing it something like:
https://www.autoelectricsupplies.co.uk/product/1373/category/285
...but I haven't looked to see how much support they have for terminals / junctions etc they have, but there has to be someone selling this stuff, hello google my old friend?
As for the battery box, I'm thinking this is moving along the lines of being a metal frame built around the batteries, with rivnuts embedded in it, ontowhich you will bolt on fibreglass panels with neoprene foam taled along the edges, and rubber then penny washers on the outside to keep it as sealed as we can. However, you'd need to make the top of the box flanged so it goes on before you jack the box uptowards the vehicle, then the sides can be bolted onto that. Main computer is still in a million bits as the warranty replacement waterpump arrived DOA - so you'll have to make do with that lengthy wordy description of the box construction rather than my signature diagrams etc. But I should be in a position to put this box design into CAD for you before you've finished interconnecting the battery modules.
Were I doing this, I'd do it with solder or weld, as the cables are quite maleable, and will hold their shape once they've been gorillad into position, it should be relatively simple to offer them up, mark them, remove them, solder them insulate them and refit them. In my minds eye I envisage myself doing it something like:
- Lay cable end from battery terminal 1
- Lay cable from terminal 2 towards terminal 1
- Cut both ends ~1cm short of them meeting
- Make a bridging peace that overlaps the joints and mark the insulation where the ends of the ibridging piece goes on the cables
- Make secondary makrs 20mm or 30mm further back from the fist marks
- Remove the cables, cut insulation back to first marks
- Scratch (scribe) those lines on the cable's copper flatbar core
- Remove the additional 20/30mm of insulation to the second marks
- Improvise a jig for clamping the cables in such a position as the bridging piece is at both of the scribed first marks
- Now the hotwork, here there are two alternative paths
- I'd suggest you get someone to TIG braize thecable ends to the bridging pieces as this will become one contiguous piece of copper
- Alternatively its now a case of heavy soldering with plumbers torch to solder the bridging pieces to the exposed cable cores
- After the topside has been joined to the bridging pieces, the top side should be secure enough to remove the clamps and flip the cables over to TIG/Solder the underside
- Do your insulation
- Refit cable, move onto next one, rinse repeat
https://www.autoelectricsupplies.co.uk/product/1373/category/285
...but I haven't looked to see how much support they have for terminals / junctions etc they have, but there has to be someone selling this stuff, hello google my old friend?
As for the battery box, I'm thinking this is moving along the lines of being a metal frame built around the batteries, with rivnuts embedded in it, ontowhich you will bolt on fibreglass panels with neoprene foam taled along the edges, and rubber then penny washers on the outside to keep it as sealed as we can. However, you'd need to make the top of the box flanged so it goes on before you jack the box uptowards the vehicle, then the sides can be bolted onto that. Main computer is still in a million bits as the warranty replacement waterpump arrived DOA
- so you'll have to make do with that lengthy wordy description of the box construction rather than my signature diagrams etc. But I should be in a position to put this box design into CAD for you before you've finished interconnecting the battery modules.
Alibro
Well-Known Member
The plan is to build a frame using angle and weld a steel skin to it then fit a lid before raising the box into place. I really appreciate your welding/soldering ideas but as I mentioned earlier it won't work as once the box is built there won't be room to access the bolts on the modules. They need to be secured before the modules are fitted so I need to be able to connect the leads after.I have started doing something involving RC helicopters, the aircraft at the heart of the project has a 180amp ESC on it, albeit only running 12s so circa 50v, for that I've went with 5.5mm solid brass bullets, and a soldering iron was wholly ineffective against them, what did work a treat was the duchesses mini blow torch that she initially bought for carmelising icing sugar on deserts. For I don't think such a torch would work for your wires, and I certainly would never recommend soldering in situ ontop of lipo batteries, especially such big ones, but plumbers soldering gear would probably be man enough to heat the copper enough to melt the solder onto it. Although I'd reiterate to solder them off the bateries.
Were I doing this, I'd do it with solder or weld, as the cables are quite maleable, and will hold their shape once they've been gorillad into position, it should be relatively simple to offer them up, mark them, remove them, solder them insulate them and refit them. In my minds eye I envisage myself doing it something like:
An alternative to welding or soldering up the connections would be to have a look at the various electrical factors and see what they do for EV terminals. I know I've seen the roange heavy high voltage EV cables for sale...
- Lay cable end from battery terminal 1
- Lay cable from terminal 2 towards terminal 1
- Cut both ends ~1cm short of them meeting
- Make a bridging peace that overlaps the joints and mark the insulation where the ends of the ibridging piece goes on the cables
- Make secondary makrs 20mm or 30mm further back from the fist marks
- Remove the cables, cut insulation back to first marks
- Scratch (scribe) those lines on the cable's copper flatbar core
- Remove the additional 20/30mm of insulation to the second marks
- Improvise a jig for clamping the cables in such a position as the bridging piece is at both of the scribed first marks
- Now the hotwork, here there are two alternative paths
- I'd suggest you get someone to TIG braize thecable ends to the bridging pieces as this will become one contiguous piece of copper
- Alternatively its now a case of heavy soldering with plumbers torch to solder the bridging pieces to the exposed cable cores
- After the topside has been joined to the bridging pieces, the top side should be secure enough to remove the clamps and flip the cables over to TIG/Solder the underside
- Do your insulation
- Refit cable, move onto next one, rinse repeat
https://www.autoelectricsupplies.co.uk/product/1373/category/285
...but I haven't looked to see how much support they have for terminals / junctions etc they have, but there has to be someone selling this stuff, hello google my old friend?
As for the battery box, I'm thinking this is moving along the lines of being a metal frame built around the batteries, with rivnuts embedded in it, ontowhich you will bolt on fibreglass panels with neoprene foam taled along the edges, and rubber then penny washers on the outside to keep it as sealed as we can. However, you'd need to make the top of the box flanged so it goes on before you jack the box uptowards the vehicle, then the sides can be bolted onto that. Main computer is still in a million bits as the warranty replacement waterpump arrived DOA
Steel frame + a skin is a yes, but I'd suggest you make the skin removable so you can indeed access the batteries.
Hence the removable skin on the box
Serviceability will come from making the sides of the box removable.
Alibro
Well-Known Member
I don't think I could make the sides removable and water proof at the same time. In any case the box will be above the rear subframe in the fuel tank space so pretty much inaccessible anyway.Steel frame + a skin is a yes, but I'd suggest you make the skin removable so you can indeed access the batteries.
Hence the removable skin on the box
Serviceability will come from making the sides of the box removable.
I've pretty much come to the conclusion it will need to be built sealed and installed so serviceability will not really be an option.
Just to add onto the solder or bolt discussion which is already over. In high voltage high current scenarios I don't think soldering is all too popular. Solder imperfections can potentially add in some extra resistance through the join, then in the event of a very high current draw the solder can get hot enough to melt and then cause all sorts of fun if it touches something else in the battery while still connected to the HV connection. Or just melt off and cause a break.
Bolts and crimps are generally prefered as they are less bothered by heat and vibrations from normal driving.
Bolts and crimps are generally prefered as they are less bothered by heat and vibrations from normal driving.
Alibro
Well-Known Member
Thanks Wonk, it was a concern for me that I would have no way to confirm whether a solder joint was a good one or not. Sometimes you think your joint is good but it breaks off very easily and without tested repeatable procedures I could easily end up with a bad connection. Especially in the situation of trying to make the connections in an awkward tight location where heat being applied to the cells is VERY undesirable.
My mate seemed to think think the original connections were soldered but I'm not so sure so bolted they will be.
That was why I was saying to get the cables tig welded; but that opened up a chicken and egg conversation... If you made a frame with angle at all the edges, and rivnuts in place, got sheet material (metal/perspez/fibreglass) and taped the edges with sticky back neoprene foam, then offered it up with bolts and washers, the sides would be removable, the neoprene foam would compress to form a gasket/seal, and the box will still be 95% waer tight, probably as good as you're going to get welding the sides to the box if we're being honest. For belt and braces there would be nothing stopping you buttering all the mating faces with a sealant like tiger seal or silicone mastic etc.
Also doing the box frame with bolt on panels means you can put fire blanket on the batteries to protect them from sparks / conductive grinding dust / spatter, and easily remove the fire blanket before fitting cables and side panels.
Also doing the box frame with bolt on panels means you can put fire blanket on the batteries to protect them from sparks / conductive grinding dust / spatter, and easily remove the fire blanket before fitting cables and side panels.
Nodge68
Well-Known Member
I'd prefer the rivnut and bolt solution, mostly because my welding although strong enough for vehicle repairs, isn't pretty enough for something that is on show.
Also production EV battery boxes are all bolted together (clamshell) style, and sealed with sealant, which presumably is for ease of assembly, if not for subsequent repair.
Alibro
Well-Known Member
There are many ways to cook an egg and 10 different experts will come up with ten different solutions.
I've decided I will be bolting the solid copper bars together as I don't believe it will cause any issues yet is simple, safe and strong. KISS is my favourite saying.
As for using stick on panels with rivnuts this may be the way to go. I was going to weld them all in place (and still might weld some of the smaller ones in) but like you say welding will not be watertight anyway.
Gobs of sealant will be liberally applied as suggested.
Yip as said I'm now leaning this way.
Alibro
Well-Known Member
My order of M5 10.9 grade bolts, spring washers, penny washers and lock nuts arrived today so I'll be working on this again tonight and report back later. I figured M5 would be strong enough, especially if I doubled them and would result in smaller holes in the copper than M6.
I also received M8 nuts and bolts so I can weld in the securing nuts for the smaller modules.
I also received M8 nuts and bolts so I can weld in the securing nuts for the smaller modules.