Search found 3281 matches

by jonescg
Jan 21 2019 10:51pm
Forum: Battery Technology
Topic: E-powered Kayak battery charger....
Replies: 2
Views: 19

Re: E-powered Kayak battery charger....

As long as the voltage of each cell doesn't exceed 4.2 V, you can charge it with anything you like. 12.6 V is spot on.
For the 10s pack, most E-bike chargers will deliver 42 V max, so you're safe there too. BMS sounds like it should take care of any excursions.
by jonescg
Jan 21 2019 9:20pm
Forum: Battery Technology
Topic: Clarification on the 20% Rule
Replies: 11
Views: 133

Re: Clarification on the 20% Rule

Charge it to the voltage you need - if that's 95% then so be it. Just make sure you only charge it to that voltage immediately before you use it. If you only need 1/3rd of your pack's total capacity to get somewhere, you might as well charge from 33% to 66% as needed. But for a long trip you can't a...
by jonescg
Jan 21 2019 7:45pm
Forum: Battery Technology
Topic: Clarification on the 20% Rule
Replies: 11
Views: 133

Re: Clarification on the 20% Rule

Yeah generally running a cell in the lower 2/3rds of it's voltage range is better long term than running it in the upper 2/3rds.
by jonescg
Jan 18 2019 9:59pm
Forum: Battery Technology
Topic: The "thermal management of LiPo" thread!
Replies: 91
Views: 7198

Re: The "thermal management of LiPo" thread!

Using distilled water, the voltage differential between tabs won't be an issue. If the clamps were brass or copper, you could just solder a piece of small copper tubing to each one. ... I have some big lasers at work that use direct water cooling around the high voltage parts. Like up to 20kV. Pure...
by jonescg
Jan 17 2019 10:15pm
Forum: Battery Technology
Topic: The "thermal management of LiPo" thread!
Replies: 91
Views: 7198

Re: The "thermal management of LiPo" thread!

So this is the current thinking - L=shaped cooling plates which link the flat surface of each cell to the baseplate.
Cooling fins.jpg
I'm doubtful it will be that much better than the current system with potting compound, but I'll have to come up with a prototype and test it.
by jonescg
Jan 16 2019 8:36pm
Forum: Battery Technology
Topic: The "thermal management of LiPo" thread!
Replies: 91
Views: 7198

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: 38
Views: 619

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: 38
Views: 619

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: 91
Views: 7198

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: 91
Views: 7198

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: 5
Views: 220

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: 91525

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: 25536

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: 628

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: 91525

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: 8071

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: 331

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: 1573
Views: 162594

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: 352

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: 352

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: 352

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: 91525

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: 91525

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: 91525

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...