Search found 3276 matches

by jonescg
Jan 16 2019 8:36pm
Forum: Battery Technology
Topic: The "thermal management of LiPo" thread!
Replies: 85
Views: 7018

Re: The "thermal management of LiPo" thread!

Stuff looks amazing, but there's $17,000 worth of graphite for a $24,000 battery.
I reckon aluminium might be a winner hey...
by jonescg
Jan 16 2019 8:31pm
Forum: Battery Technology
Topic: LFP mobile House bank - xSyP serial vs parallel design thoughts
Replies: 33
Views: 493

Re: LFP mobile House bank - xSyP serial vs parallel design thoughts

If you parallel all 16 cells and have a many-hundred amphour, 3.2 V cell, it will need to be charged up to 3.55 V in order to drive any balancing. If left to sit, the currents flowing into the lower cells will be in the microamps, and take years to eventuate. At least by charging up to Vmax it will ...
by jonescg
Jan 16 2019 1:43am
Forum: Battery Technology
Topic: LFP mobile House bank - xSyP serial vs parallel design thoughts
Replies: 33
Views: 493

Re: LFP mobile House bank - xSyP serial vs parallel design thoughts

Almost always the preferred layout is parallel at the cell level first to build capacity, then put these guys in series to achieve your desired voltage (4s for 12 V nominal). Sure, if one cell is a dud, it will drag all cells in parallel down with it, but that's a fairly uncommon thing. If you inste...
by jonescg
Jan 16 2019 12:17am
Forum: Battery Technology
Topic: The "thermal management of LiPo" thread!
Replies: 85
Views: 7018

Re: The "thermal management of LiPo" thread!

How about L shaped sheets of pyrolytic graphite? They could be thinner than aluminum and much more effective (but spendy). https://www.digikey.com/en/product-highlight/p/panasonic/pyrolytic-graphite-sheets I wonder if it's only good through the facial plane, as opposed to the X-Y plane which is the...
by jonescg
Jan 15 2019 11:24pm
Forum: Battery Technology
Topic: The "thermal management of LiPo" thread!
Replies: 85
Views: 7018

Re: The "thermal management of LiPo" thread!

So I did a discharge test and measured the efficacy of the cooling loop with one of these modules. It's not great; better than nothing, but I'd prefer more heat transfer. temp plot.JPG This was a massively artificial discharge test though - 4.4 C for 8 minutes from a cell rated to 2 C continuous. St...
by jonescg
Jan 13 2019 9:09pm
Forum: General Discussion
Topic: I'm starting a DIY EV group on a new and upcoming social media site - MeWe
Replies: 4
Views: 154

Re: I'm starting a DIY EV group on a new and upcoming social media site - MeWe

I may well quit facebook soon, but I'll never leave this place. I find forums to be the best tool for the job - mostly great for technical discussion and chronological documentation of builds, and a little bit of social banter in there as well. I mean, I use this forum to share progress on my bikes,...
by jonescg
Jan 11 2019 7:56pm
Forum: Items for Sale - New
Topic: Assembled Hi-Power LiPo battery packs - any interest?
Replies: 545
Views: 91347

Re: Assembled Hi-Power LiPo battery packs - any interest?

Tab cooling is the most effective way to cool a pack but other than air convection you're limited to low thermal conductivity polymers stuck to the battery terminals. Not only that you cant seal a battery completely from the elements when you aircool. This is the perpetual dillemma. Base cooling is ...
by jonescg
Jan 11 2019 7:43am
Forum: Large EV General Discussion
Topic: Aussie EV Autocross Special
Replies: 314
Views: 25401

Re: Aussie EV Autocross Special

The weight distribution being a little rear-biased would probably explain part of the understeer, and the lead weight should give some indication if that's the source of the problem. But as for four-wheel dynamics, I'm not the guy :) Awesome that you've got a reliable rig though. Shame we didn't see...
by jonescg
Jan 11 2019 2:19am
Forum: Battery Technology
Topic: Building a high Amp output battery question
Replies: 37
Views: 592

Re: Building a high Amp output battery question

LiPo pouches might be the best compromise for you then - 30C continuous and still ~158 Wh/kg.
by jonescg
Jan 10 2019 9:04pm
Forum: Items for Sale - New
Topic: Assembled Hi-Power LiPo battery packs - any interest?
Replies: 545
Views: 91347

Re: Assembled Hi-Power LiPo battery packs - any interest?

I finally got around to testing the cooling system on this battery module. To be honest I'm disappointed, but it's not all bad. Let me explain. First up, this is a 4.4 C discharge on a cell which is nominally 1-2 C and 5 C burst - so I'm fairly hammering it. At 330 amps, the busbar linking the two h...
by jonescg
Jan 09 2019 9:48pm
Forum: Items for Sale - New
Topic: li-ion 18650 Adjustable size BATTERY HOLDER - Honeycomb Layout
Replies: 39
Views: 7997

Re: li-ion 18650 Adjustable size BATTERY HOLDER - Honeycomb Layout

Those nickel tapes look amazing! How, may I ask, were they made? Stamped out? I have tried water jet cutting but it was quite rough.
by jonescg
Jan 09 2019 9:37pm
Forum: Battery Technology
Topic: Balancing a 20s battery back
Replies: 16
Views: 310

Re: Balancing a 20s battery back

BC168 (or clones thereof) is almost mandatory for DIY battery builders. I highly recommend one.
by jonescg
Jan 07 2019 9:33pm
Forum: Battery Technology
Topic: Thread for new battery breakthrough PR releases
Replies: 1571
Views: 162178

Re: Thread for new battery breakthrough PR releases

^ Hehe, battery companies telling FIBs :wink: Anyway, seems aluminium carbon battery cells have attracted some attention. An older article: https://www.chemistryworld.com/news/super-fast-charging-aluminium-batteries-ready-to-take-on-lithium/8427.article And some recent developments: https://www.desi...
by jonescg
Jan 07 2019 1:45am
Forum: Battery Technology
Topic: Cap cooling of 18650, thermal output graphs?
Replies: 8
Views: 318

Re: Cap cooling of 18650, thermal output graphs?

I am researching 18650 cell cooling, one source said that tab cooling prolongs cell life by reaching into all the layers of the battery, is it the same for cylindrical batteries? These tests were done on a high energy storage cell (probably a Panasonic GA cell) and the results of cooling axially ve...
by jonescg
Jan 01 2019 7:58pm
Forum: Battery Technology
Topic: Cap cooling of 18650, thermal output graphs?
Replies: 8
Views: 318

Re: Cap cooling of 18650, thermal output graphs?

OK I know where the plotted data are but I won't be able to get them for a few days. But in any case, I suggest you read a paper by Drake et al. (2014) http://www.uta.edu/faculty/jaina/MTL/pubs/Drake-JPS2014.pdf The thermal conductivity of a cylindrical cell is two orders of magnitude higher in the ...
by jonescg
Jan 01 2019 6:44pm
Forum: Battery Technology
Topic: Cap cooling of 18650, thermal output graphs?
Replies: 8
Views: 318

Re: Cap cooling of 18650, thermal output graphs?

I have some data you are chasing. Will look for it today.
by jonescg
Dec 31 2018 6:23am
Forum: Items for Sale - New
Topic: Assembled Hi-Power LiPo battery packs - any interest?
Replies: 545
Views: 91347

Re: Assembled Hi-Power LiPo battery packs - any interest?



Hehe, so it turns out it's a 330 amp discharge, which is almost 5C. Considering how they don't sag a huge amount, I reckon that's pretty good. At worst this pack will see 2C continuous, for about 2 minutes or so.
by jonescg
Dec 31 2018 3:50am
Forum: Items for Sale - New
Topic: Assembled Hi-Power LiPo battery packs - any interest?
Replies: 545
Views: 91347

Re: Assembled Hi-Power LiPo battery packs - any interest?

So I decided to set up the test rig for measuring heat removal with the liquid cooling plate. I borrowed a few parts from work, including the PC cooling pump and radiator. However, the thermocouples are not giving satisfactory readings through the multimeters, so unfortunately I will have to borrow ...
by jonescg
Dec 30 2018 7:59pm
Forum: Items for Sale - New
Topic: Assembled Hi-Power LiPo battery packs - any interest?
Replies: 545
Views: 91347

Re: Assembled Hi-Power LiPo battery packs - any interest?

Hey Arlin, I didn't cycle each one, but I do check voltage and DCIR. If a cell was below 3.80 volts I left it out, and likewise if the DCIR was above 15 mOhm I put it aside. Most of them fell a few milliohms either side of 8 mOhm. I hope to finally get around to thermal testing it this week, but the...
by jonescg
Dec 30 2018 7:24am
Forum: Items for Sale - New
Topic: Assembled Hi-Power LiPo battery packs - any interest?
Replies: 545
Views: 91347

Re: Assembled Hi-Power LiPo battery packs - any interest?

These things are works of art dude good job, my only thing is why the hell would you do all that work only to run lipos with a 5c rating when there are single cells out there with 50c rating? Specific energy. These 5C cells are over 208 Wh/kg at 1C, so using 18650 testing regimes they are well over...
by jonescg
Dec 23 2018 2:04am
Forum: Battery Technology
Topic: spiralling environmental cost, lithium batteries
Replies: 18
Views: 595

Re: spiralling environmental cost, lithium batteries

Once lithium, nickel and cobalt get scarce enough they will go looking for more. And formulate ways of using less of it. And eventually we'll have a decent battery recycling system in place, so I wouldn't be too concerned.
by jonescg
Dec 21 2018 8:50am
Forum: Large EV General Discussion
Topic: RIPPY KART
Replies: 28
Views: 1760

Re: RIPPY KART

Pic showing LiPo cell swelling. This cell was low voltage. Not sure what causes the swelling. Usually swelling is because the layer of lithium salts which precipitate on the anode start to decompose into carbon dioxide, causing the cells to puff. Hitting them with high discharge rates, letting them...
by jonescg
Dec 16 2018 7:11am
Forum: Battery Technology
Topic: 30Ah 28s LiPo from 7s bricks
Replies: 3
Views: 256

Re: 30Ah 28s LiPo from 7s bricks

Happy to help if you want some screw terminations and busbars etc :)
Too many XT90s makes me shudder.
by jonescg
Dec 13 2018 6:49am
Forum: Large EV General Discussion
Topic: jonescg's eCRX pre-build thread!
Replies: 84
Views: 14606

Re: jonescg's eCRX pre-build thread!

Oh man this is so good. CRX on Hoist.jpg So it turns out the space available isn't as good as I thought. I'll still have to pull the tank out to know for sure, but it looks like some important structural spars are in the way of where I'd like my pack to go. I can easily fit 6 of my liquid cooled mod...