videovic
New member
- Joined
- Jun 7, 2018
- Messages
- 3
I have been following all about the 18650 since I discovered Jehu garcia and his VW van. Thanks so much Jehu, now i am hooked!!. It is very exciting to be on the cutting forward edge of the inevitable general acceptance and use of lithium ion cells.
I am SUPER excited to be able to buy cells from a reliable source in the states. Hopefully I will be driving down and pick some up some day.
My first battery was a foolish 50 volt battery created inside a U shaped 1/2" copper pipe. I guess in retrospect, it was a potential bomb actually. My theory was that the copper would act as a super efficient heat sink. For a laugh, I include some photos of it.
Most of the focus to date in the DIY space has been on large format battery packs for cars and e-bikes and e-scooters, as well as home power walls and solar combos.
I have seen some amazing non weld or solder construction designs and schemes ranging from friction fit, to magnet connection, and see them as a great way to allow for repair down the road, especially when using less reliable used cells.
However they do suffer from a lack of fusing, which I believe is very important factor in assuring the
safety of a battery pack.
For instance, not only are e-bike cells not fused in any way individually, AND are glued directly touching each
other, on the surface this seems a not so safe way to combine the cells.On the other hand, i don't remember hearing of any of them blow up or burn up or injure anyone. ( Am I right on this?)
It is fascinating watching all of us DIY'ers sharing info and slowly the use of 18650s is getting more efficient and safer and cheaper.
To my mind, surplus cells are the best way to reduce the cost factors in the way of the adoption of lithium ion technology and getting them into the hands of mr and mrs everyperson.
I have been watching the evolution of the huge 80+ cell power wall packs and agree that fused cells are the way
to fully protect us from ourselves. ( i mean protect us from the fire hazards the cells "could" have)
Currently, the twisted busbars are not generally properly secured, (one design is secured with zip ties) but the fine fuse wires are exposed to mechanical damage. That to me is a MINOR flaw of using the twisted solid copper wire method.
On to my new buss bar idea. i want to share and get feedback on.
I am testing out the new idea on smaller batteries containing up to maybe a max of 36 cells or so. my first one is a 24 cell block which I will initially wire up as a 24 P block, and do some high drain current/resistance/temperature tests on.
My design can be called a PCB bussbar scheme. The design
uses a double-sided PCB as a bussbar to which each cellis individually fused. The PCB can be easily affixed to
the cell holders and provides unlimited variety of interconnection methods . The 2 surfaces of each PCB are connected together to double the current capability using solid copper wire vias (12 Gage) soldered in place, or perhaps only solder created vias. ( maybe 6 on all)
The bottom negative collector plate ( bussbar assy) in a single parallel block can be composed of aluminum plate and use aluminum rivets to create the bump that is needed to contact the cellsfirmly. I will try this in my second block, but this time i want to fuse both ends of the cells mainly to time out the fusing and find any weaknesses in the operation.
The entire thing can use a 16/32 bolt in the middle to tie the assembly together and even provide a negative terminal on the top of the battery is needed.
I have the feeling that it will be more reliable, faster to assemble ( or the same speed), and easily repeatable.
These PCB bussbars can also be used, with some strategic trace removal to create a multicell battery for 11.1v,
16.8v all the way up to 18 volts.
this busbar also lends itself to mass production of the pcb boards. Such boards could also be plated thru the
holes and on all the edges and remove the need for vias to connect the 2 layers. Theoretically, a board could
have more layers if more current capability is needed.
other multi Series blocks, (using 2 PCB bussbars), would use fuses on both ends of the cell to create 2s,3s,4s,or 5s configurations as having multi piece aluminum plates on the neg end would be difficult, although strictly possible.
My idea for using slightly smaller blocks comes from my desire to make repair and replacement of batteries easy
to maintain. I also want all the batteries i build to be as safe as humanly possible.
Once the buss plate is ready, by drilling all the holes and cleaning and pre-tinning for the fuse wires, the cells need to be cleaned and pre-tinned so attachment of the fuse wire will be quick and simple.
the fuse wire will be laid across all the cell holes and soldered. then each cell will be attached and the remainder trimmed.
A plastic "plate" will be placed on top and fixed in place to protect the fuse wires and insulate the bussbar surface.
of course the connector will be added to connect the output.
for testing i will use a relay board designed to shut off the load when the cells reach 3 volts.
the initial current draw will be 10 amps for the duration of the drain test, while temp is monitored as this is the max of my electronic load.
the second test will be 24 amps, 1 amp per cell.
I doubt that this scheme would be practical for an 80 cell block such as those used for power wall schemes,
all the holes can be drilled in under 10 minutes and 2 minutes to grind the edges. so i would say the 2 PCB buss bars would take about 15 minutes to create including cutting to size and drilling, as the 2 plates are drilled at the same time. That almost matches the prep time for a twisted bus bar scheme.
I agree the cost might be a little higher than twisted bussbars but it's pretty isn't it?
anyway, comment if you like, and ill post as i do some more work done on it.
thanks!!
*************************************************
Prepping the PCB busbars
*************************************************
The images below show the steps that i took next.
The first image is the PCB polished and ready for drilling out for the VIAS to join the 2 layers. I will use 12 GA solid hose wiring (romex) This will be plenty of connection to handle any current i can ask of it. As you can see, I then soldered the wire and clipped it and ground it as flat as i could.
The last image shows how i tapered the PCB to make sure the through bolt cannot create a short between the 2 layers, as long as an insulator is used at either end of the bolt.
I am SUPER excited to be able to buy cells from a reliable source in the states. Hopefully I will be driving down and pick some up some day.
My first battery was a foolish 50 volt battery created inside a U shaped 1/2" copper pipe. I guess in retrospect, it was a potential bomb actually. My theory was that the copper would act as a super efficient heat sink. For a laugh, I include some photos of it.
Most of the focus to date in the DIY space has been on large format battery packs for cars and e-bikes and e-scooters, as well as home power walls and solar combos.
I have seen some amazing non weld or solder construction designs and schemes ranging from friction fit, to magnet connection, and see them as a great way to allow for repair down the road, especially when using less reliable used cells.
However they do suffer from a lack of fusing, which I believe is very important factor in assuring the
safety of a battery pack.
For instance, not only are e-bike cells not fused in any way individually, AND are glued directly touching each
other, on the surface this seems a not so safe way to combine the cells.On the other hand, i don't remember hearing of any of them blow up or burn up or injure anyone. ( Am I right on this?)
It is fascinating watching all of us DIY'ers sharing info and slowly the use of 18650s is getting more efficient and safer and cheaper.
To my mind, surplus cells are the best way to reduce the cost factors in the way of the adoption of lithium ion technology and getting them into the hands of mr and mrs everyperson.
I have been watching the evolution of the huge 80+ cell power wall packs and agree that fused cells are the way
to fully protect us from ourselves. ( i mean protect us from the fire hazards the cells "could" have)
Currently, the twisted busbars are not generally properly secured, (one design is secured with zip ties) but the fine fuse wires are exposed to mechanical damage. That to me is a MINOR flaw of using the twisted solid copper wire method.
On to my new buss bar idea. i want to share and get feedback on.
I am testing out the new idea on smaller batteries containing up to maybe a max of 36 cells or so. my first one is a 24 cell block which I will initially wire up as a 24 P block, and do some high drain current/resistance/temperature tests on.
My design can be called a PCB bussbar scheme. The design
uses a double-sided PCB as a bussbar to which each cellis individually fused. The PCB can be easily affixed to
the cell holders and provides unlimited variety of interconnection methods . The 2 surfaces of each PCB are connected together to double the current capability using solid copper wire vias (12 Gage) soldered in place, or perhaps only solder created vias. ( maybe 6 on all)
The bottom negative collector plate ( bussbar assy) in a single parallel block can be composed of aluminum plate and use aluminum rivets to create the bump that is needed to contact the cellsfirmly. I will try this in my second block, but this time i want to fuse both ends of the cells mainly to time out the fusing and find any weaknesses in the operation.
The entire thing can use a 16/32 bolt in the middle to tie the assembly together and even provide a negative terminal on the top of the battery is needed.
I have the feeling that it will be more reliable, faster to assemble ( or the same speed), and easily repeatable.
These PCB bussbars can also be used, with some strategic trace removal to create a multicell battery for 11.1v,
16.8v all the way up to 18 volts.
this busbar also lends itself to mass production of the pcb boards. Such boards could also be plated thru the
holes and on all the edges and remove the need for vias to connect the 2 layers. Theoretically, a board could
have more layers if more current capability is needed.
other multi Series blocks, (using 2 PCB bussbars), would use fuses on both ends of the cell to create 2s,3s,4s,or 5s configurations as having multi piece aluminum plates on the neg end would be difficult, although strictly possible.
My idea for using slightly smaller blocks comes from my desire to make repair and replacement of batteries easy
to maintain. I also want all the batteries i build to be as safe as humanly possible.
Once the buss plate is ready, by drilling all the holes and cleaning and pre-tinning for the fuse wires, the cells need to be cleaned and pre-tinned so attachment of the fuse wire will be quick and simple.
the fuse wire will be laid across all the cell holes and soldered. then each cell will be attached and the remainder trimmed.
A plastic "plate" will be placed on top and fixed in place to protect the fuse wires and insulate the bussbar surface.
of course the connector will be added to connect the output.
for testing i will use a relay board designed to shut off the load when the cells reach 3 volts.
the initial current draw will be 10 amps for the duration of the drain test, while temp is monitored as this is the max of my electronic load.
the second test will be 24 amps, 1 amp per cell.
I doubt that this scheme would be practical for an 80 cell block such as those used for power wall schemes,
all the holes can be drilled in under 10 minutes and 2 minutes to grind the edges. so i would say the 2 PCB buss bars would take about 15 minutes to create including cutting to size and drilling, as the 2 plates are drilled at the same time. That almost matches the prep time for a twisted bus bar scheme.
I agree the cost might be a little higher than twisted bussbars but it's pretty isn't it?
anyway, comment if you like, and ill post as i do some more work done on it.
thanks!!
*************************************************
Prepping the PCB busbars
*************************************************
The images below show the steps that i took next.
The first image is the PCB polished and ready for drilling out for the VIAS to join the 2 layers. I will use 12 GA solid hose wiring (romex) This will be plenty of connection to handle any current i can ask of it. As you can see, I then soldered the wire and clipped it and ground it as flat as i could.
The last image shows how i tapered the PCB to make sure the through bolt cannot create a short between the 2 layers, as long as an insulator is used at either end of the bolt.
