oatnet
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I am building a 48v80ah pack (16s8p) capable of 400a continuous at 5c, for my 1980 Comuta-Car Modernization project: http://www.endless-sphere.com/forums/viewtopic.php?f=7&t=7880 This is also going to be a testbed for developing a much larger pack on my 2nd EV project, the VW Bus conversion: http://www.endless-sphere.com/forums/viewtopic.php?f=7&t=8012
Last Wednesday I initiated a wire transfer to Headway for (120) 38120s 10ah 5c LiFePO4. Earlier today I emailed Victoria to see if it cleared, she responded promptly and said they had shipped in were in the US already. Much to my amazement they arrived today, in a mere 3 business days! That is service!
View attachment new cells 800x_5493.JPG
It cost me $480 to ship, which is more than by boat but the premium is worth it to avoid the angst .I’ve cleared customs myself before (yech), and had DHL do it for me (2*yech + $$$), and it is so worth it to have it just show up at your door. Plus it arrives fast.
Anyhow, I have a pack design in mind, I’d like to throw it out there for critique from more experienced folk to help me flesh it out.
I planning on mounting the individual batteries between a pair of 1.5†Polypropylene sheets. To make an 8p 80ah “battery,†I’ll drill a row of (8) holes on one side of each sheet, each hole big enough for a cell's body to slide into (with slop for heat expansion.) The cell will only go in an inch, just enough to be supported by the body while leaving as much as possible exposed to cooling air. I’ll neck the hole down to the contour of the cell cap, and the hole will stop 1/2" short of the other side.
On the other side of the sheet I will route a ½â€ channel, just deep enough to expose the tops of 8 cells. I’ll put 1†copper strap in that channel with matching screw holes drilled into it. 8 parallel cells between two sheets like this makes an 80ah cell. 16 rows of these cells will make a 48v pack, joined with more channels and strap. Current will flow into the “cell†via the strap at one end, and out the opposing strap at the other end, so all cells are nominally the same electrical distance.
I’ll space the cells 1/8â€Â-1/4†apart to allow cooling airflow, and put posts between the sheets to keep the cells from being compressed/tensioned at the ends. I’ll cover the copper-strap channels to make them save.
Road bumps are experienced as a vertical vector, so I’ll mount the cells horizontally, standing the Polypropylene Sheets on their edges, so that the cells are supported by the end of the cylinder. I figure the second strongest vector is forward/back, so I plan on mounting the sheets parallel to the doors, with the length of the cell facing forward. A blower will force air into the pack at the bottom on one end, and let it out the other end at the top.
A whole pack built like this would only be @ 1 foor * 2 feet * 7â€Â, tiny but so is the Commuta-Car this is destined for. I’ll probably have to make several small 8p packs that fit the space.
I am going to charge them with tiny Vicor 48v-3.7v DC-DC converters. I will mount one to each cell so they can be charged via a common dedicated charging bus, with a third signal wire to switch them on/off – a safety interlock should be doable. Then I can slap on any 48v source for charging, such as the portable 48v25a Vicor charger I purchased on Doc Bass’s recommendation.
-JD
Last Wednesday I initiated a wire transfer to Headway for (120) 38120s 10ah 5c LiFePO4. Earlier today I emailed Victoria to see if it cleared, she responded promptly and said they had shipped in were in the US already. Much to my amazement they arrived today, in a mere 3 business days! That is service!
View attachment new cells 800x_5493.JPG
It cost me $480 to ship, which is more than by boat but the premium is worth it to avoid the angst .I’ve cleared customs myself before (yech), and had DHL do it for me (2*yech + $$$), and it is so worth it to have it just show up at your door. Plus it arrives fast.
Anyhow, I have a pack design in mind, I’d like to throw it out there for critique from more experienced folk to help me flesh it out.
I planning on mounting the individual batteries between a pair of 1.5†Polypropylene sheets. To make an 8p 80ah “battery,†I’ll drill a row of (8) holes on one side of each sheet, each hole big enough for a cell's body to slide into (with slop for heat expansion.) The cell will only go in an inch, just enough to be supported by the body while leaving as much as possible exposed to cooling air. I’ll neck the hole down to the contour of the cell cap, and the hole will stop 1/2" short of the other side.
On the other side of the sheet I will route a ½â€ channel, just deep enough to expose the tops of 8 cells. I’ll put 1†copper strap in that channel with matching screw holes drilled into it. 8 parallel cells between two sheets like this makes an 80ah cell. 16 rows of these cells will make a 48v pack, joined with more channels and strap. Current will flow into the “cell†via the strap at one end, and out the opposing strap at the other end, so all cells are nominally the same electrical distance.
I’ll space the cells 1/8â€Â-1/4†apart to allow cooling airflow, and put posts between the sheets to keep the cells from being compressed/tensioned at the ends. I’ll cover the copper-strap channels to make them save.
Road bumps are experienced as a vertical vector, so I’ll mount the cells horizontally, standing the Polypropylene Sheets on their edges, so that the cells are supported by the end of the cylinder. I figure the second strongest vector is forward/back, so I plan on mounting the sheets parallel to the doors, with the length of the cell facing forward. A blower will force air into the pack at the bottom on one end, and let it out the other end at the top.
A whole pack built like this would only be @ 1 foor * 2 feet * 7â€Â, tiny but so is the Commuta-Car this is destined for. I’ll probably have to make several small 8p packs that fit the space.
I am going to charge them with tiny Vicor 48v-3.7v DC-DC converters. I will mount one to each cell so they can be charged via a common dedicated charging bus, with a third signal wire to switch them on/off – a safety interlock should be doable. Then I can slap on any 48v source for charging, such as the portable 48v25a Vicor charger I purchased on Doc Bass’s recommendation.
-JD
