Endless Sphere

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.

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...

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.

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...

So this is the current thinking - L=shaped cooling plates which link the flat surface of each cell to the baseplate.
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.

Stuff looks amazing, but there's $17,000 worth of graphite for a $24,000 battery.
I reckon aluminium might be a winner hey...

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 ...

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...

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...

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...

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,...

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 ...

How I make them.



Enjoy!

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...

LiPo pouches might be the best compromise for you then - 30C continuous and still ~158 Wh/kg.

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...

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.

BC168 (or clones thereof) is almost mandatory for DIY battery builders. I highly recommend one.

^ 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...

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...

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 ...

I have some data you are chasing. Will look for it today.

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.

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 ...

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...