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by jonescg
Yesterday, 18:54
Forum: Technical and conversion discussion
Topic: Prelude conversion project - some questions
Replies: 74
Views: 5281

Re: Prelude conversion project - some questions

Starting to put the battery modules together now. I reckon i can make two modules a week working only evenings and weekends...
Module assembly.jpg
Module assembly.jpg (122.43 KiB) Viewed 14 times
I picked up some thermostats too - might be worth using these to only turn the fan on, since the pumps should be fairly quiet by comparison.
by jonescg
Yesterday, 18:23
Forum: General EV Discussion
Topic: Bring on the BERM please
Replies: 3
Views: 43

Re: Bring on the BERM please

Oh but making your own would be a hoot!
I know Husqvarna make a very solid electric ride on mower.
by jonescg
Fri, 16 Nov 2018, 18:26
Forum: Technical and conversion discussion
Topic: Prelude conversion project - some questions
Replies: 74
Views: 5281

Re: Prelude conversion project - some questions

Yeah I think I might leave the aircon set to 100% PWM and leave it as an on-off switch. Those NO thermostats - you stick them to the base or side of the charger? I figure if you drive up a steep hill and park on a warm afternoon, the motor and inverter will still be rather warm, and the coolant in t...
by jonescg
Fri, 16 Nov 2018, 16:16
Forum: Technical and conversion discussion
Topic: Prelude conversion project - some questions
Replies: 74
Views: 5281

Re: Prelude conversion project - some questions

As I put the battery together I started to map out the plumbing. Apologies in advance for the potato-camera. As the battery modules will be in parallel for inlet and outlet I want to ensure they all get the same flow, so that means making sure the flow path for all 8 modules is the same length. Frus...
by jonescg
Thu, 15 Nov 2018, 06:42
Forum: General EV Discussion
Topic: DO HYDROGEN FUEL CELL PHEVS QUALIFY?
Replies: 3
Views: 60

Re: DO HYDROGEN FUEL CELL PHEVS QUALIFY?

I'd argue they are more like a conventional series hybrid. It's not an EV unless you can plug it in and charge it from renewable electricity. Can the HFCV be charged at home? If they increased the size of the buffer battery and treated it like a PHEV then maybe.
by jonescg
Thu, 15 Nov 2018, 06:38
Forum: Batteries, charging, management and monitoring
Topic: Cell compression?
Replies: 7
Views: 99

Re: Cell compression?

I have pouch cell stacks which aren't compressed still working well with a few lines of Kapton tape. I think your efforts will be fine.
by jonescg
Wed, 14 Nov 2018, 20:06
Forum: Batteries, charging, management and monitoring
Topic: Cell compression?
Replies: 7
Views: 99

Re: Cell compression?

Yes the equivalent of 14 kg per square centimetre, or about 1 ton per pouch cell :o
by jonescg
Wed, 14 Nov 2018, 14:36
Forum: Batteries, charging, management and monitoring
Topic: Cell compression?
Replies: 7
Views: 99

Cell compression?

Some recently published research on the impact of cell compression on charge retention and internal resistance.
226 Effect of compression on Li Ion cells.pdf
(1.24 MiB) Downloaded 13 times
Conclusion: Some compression is good, but it's possible to overdo it. 1.4 MPa was ideal in this instance.
by jonescg
Tue, 13 Nov 2018, 10:43
Forum: Members Machines
Topic: Francisco's Electric Pajero
Replies: 56
Views: 1532

Re: Francisco's Electric Pajero

I have some data on Tesla packs somewhere I can share, and I also have the mass flow calculations for heat flux out of the battery. I will see if I can get them into an easily shared format first.
Chris
by jonescg
Thu, 08 Nov 2018, 10:34
Forum: General EV Discussion
Topic: All about the money :)
Replies: 13
Views: 230

Re: All about the money :)

Jon wrote:
Thu, 08 Nov 2018, 09:17
For sure if I buy it :) ... I get the feeling though that the battery assembly isn't standard practice?
Most of us don't have the patience to put thousands of cells together like this, so I'm keen to see how it was done.
by jonescg
Thu, 08 Nov 2018, 08:41
Forum: General EV Discussion
Topic: All about the money :)
Replies: 13
Views: 230

Re: All about the money :)

Jon wrote:
Thu, 08 Nov 2018, 07:21
Hey thanks! The batteries are units composed of Samsung 25R cells. 3000 of them.
I gotta see a picture of this...
by jonescg
Wed, 07 Nov 2018, 09:48
Forum: The Lounge
Topic: which power specification is correct?
Replies: 13
Views: 152

Re: which power specification is correct?

Sometimes they refer to the 'cooling power' or the rate of heat removal. That would be closer to 1.8 kW I'd think.
by jonescg
Wed, 07 Nov 2018, 08:43
Forum: Technical and conversion discussion
Topic: Prelude conversion project - some questions
Replies: 74
Views: 5281

Re: Prelude conversion project - some questions

The cells are standing on top of the flat cooling plate, and the thermal epoxy fills the air gaps between the base of the cells and the plate. Since the electrodes inside the pouch cells stand upright, most of the plates will have a short thermal path to the cooling plate. Sure, it goes via the poly...
by jonescg
Tue, 06 Nov 2018, 21:37
Forum: Members Machines
Topic: Francisco's Electric Pajero
Replies: 56
Views: 1532

Re: Francisco's Electric Pajero

I'm working with 44 volt modules of 72 Ah, so they too would need some hefty testing equipment. Although I would never expect to see more than 2C peaks (140 amps).
by jonescg
Tue, 06 Nov 2018, 14:44
Forum: Members Machines
Topic: Francisco's Electric Pajero
Replies: 56
Views: 1532

Re: Francisco's Electric Pajero

You will only need to produce a 315 amp current. A coil of MIG wire around a ceramic support, submerged in water will work.
by jonescg
Tue, 06 Nov 2018, 13:15
Forum: Technical and conversion discussion
Topic: Prelude conversion project - some questions
Replies: 74
Views: 5281

Re: Prelude conversion project - some questions

No - I'm filling that gap with a thermally conductive (electrically insulating) filled epoxy. There are silicon encapsulants out there too, but they are all in the 1.0 to 2.0 W/m.K range. Generous application is the key though, as you're aiming for a uniform temperature gradient from cell to sink.
by jonescg
Tue, 06 Nov 2018, 13:13
Forum: Nissan Leaf
Topic: Non OEM Leaf battery upgrade?
Replies: 22
Views: 1196

Re: Non OEM Leaf battery upgrade?

If I was to replace a Leaf battery with a home-brew battery, I'd aim to increased the capacity by as much as feasible.
by jonescg
Tue, 06 Nov 2018, 13:02
Forum: Members Machines
Topic: Francisco's Electric Pajero
Replies: 56
Views: 1532

Re: Francisco's Electric Pajero

Richo if the cells have a very low DCIR it's probably OK without a cooling system, or at least a fairly simple one will work. But the high energy density pouch cells are typically in the 20 mOhm range, so a 25 kWh battery is likely to dish out ~4 kW of waste heat at 2C. A sealed battery would warm ...
by jonescg
Tue, 06 Nov 2018, 12:55
Forum: Members Machines
Topic: Francisco's Electric Pajero
Replies: 56
Views: 1532

Re: Francisco's Electric Pajero

Good effort on the cooling channels. I'd advise you cover the cells in some kind of contact plastic so the foil can't rub against the cooling surface. Kapton would be expensive but polyethylene is possibly OK.
by jonescg
Tue, 06 Nov 2018, 11:52
Forum: Technical and conversion discussion
Topic: Prelude conversion project - some questions
Replies: 74
Views: 5281

Re: Prelude conversion project - some questions

Yes, some pressure to ensure they can't swell further than their originally manufactured thickness. The internal resistance will increase if the cell is allowed to expand considerably. Over time they will soften up as the electrolyte is able to off-gas (generating CO2) but this is normally accelerat...
by jonescg
Tue, 06 Nov 2018, 08:22
Forum: Technical and conversion discussion
Topic: Prelude conversion project - some questions
Replies: 74
Views: 5281

Re: Prelude conversion project - some questions

The pouches only need to be snug - enough to prevent them from swelling should they ever be pushed to that point. But the cells will only swell if they've been treated mean, and I hope to not do that.
by jonescg
Mon, 05 Nov 2018, 08:25
Forum: Members Machines
Topic: Weber and Coulomb's MX-5
Replies: 1691
Views: 289590

Re: Weber and Coulomb's MX-5

I use my insulated tools regularly :)
96s2p nearing completion.jpg
96s2p nearing completion.jpg (200.04 KiB) Viewed 245 times
by jonescg
Sun, 04 Nov 2018, 21:29
Forum: Technical and conversion discussion
Topic: Prelude conversion project - some questions
Replies: 74
Views: 5281

Re: Prelude conversion project - some questions

Well the Prelude project is ticking along - I have given myself till the end of the year to finish it, or at least have the car rolling on electric power. The plan is to build these 12s10p battery modules in the meantime, before the hoist is installed in the shed and I can start taking the fuel tank...
by jonescg
Sun, 04 Nov 2018, 20:47
Forum: Members Machines
Topic: Weber and Coulomb's MX-5
Replies: 1691
Views: 289590

Re: Weber and Coulomb's MX-5

Yes stray capacitance can be a hazard. Not because it will shock you (although that can be unpleasant) but because you might flinch and drop a tool somewhere you shouldn't... How long until you pull all of Mexy's cells out and put some NMC cells in? You can probably get some impressive range out of ...
by jonescg
Sat, 03 Nov 2018, 11:17
Forum: Batteries, charging, management and monitoring
Topic: My latest battery build
Replies: 0
Views: 96

My latest battery build

This is a nominal 355 volt, 10 Ah battery built using 5 Ah pouch cells (96s2p). It's for the UWA formula student team's race car. The intention was always to use this battery as the dyno-testing and bench-tuning battery given it's capacity, but if push comes to shove, then can drop it into the car a...