The battery builders club

What sort of consideration? Sort of that new style of welding the negative you have everyone doing these days? :sweat_smile:

Have you guys heard of Graphite sheets? A friend sent me this earlier today and i thought it would be an interesting material for extra safety on our packs.

https://sg.rs-online.com/web/p/thermal-pads/7123992/?cm_mmc=SG-PLA-DS3A--google--PLA_SG_EN_Fallback--All+products--7123992&matchtype=&pla-293946777986&gclid=CjwKCAjw0qOIBhBhEiwAyvVcf8GTXooQDrxQaCTZk-TITNAF4T4-W27NPcpkIVs7mVkP2Sih9nI8YxoC95sQAvD_BwE&gclsrc=aw.ds

Pricing however, itā€™s about $18 USD for a 90mm x 115mm sheet.

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Set the value to 0. it will be always on.
If the bluetooth is off you can activate it by connecting a cell between the 2 small red and black cables that come from the BMS.

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Itā€™s so thin, how would you interface this with a battery pack? Unless you have a single pouch, I personally donā€™t see a use in this application.

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For removing heat?
A sheet could indeed move some heat along its length but then you need a way to take the heat out of the sheet. You would also need several sheets, contacting every cell in the pack. It would probably cost several hundred dollars and we still need a way to remove the heat from the sheets. :pensive:

A graphite sheet along the top or bottom of the cells wouldnā€™t do much as the nickel strip is already a good heat conductor. But even then we still have the same problemā€¦the heat is trapped in the nickel strip.

In the end itā€™s probably easier to just add another cell to each p-group (to spread out the load) or to design the pack to allow air flow or contact with aluminum sheets between cells.

Having said all that I would love to see a no-holds-barred ultra-high performance pack made as small as possible and using graphite sheets or cell holders to get the heat to the outside of the pack and then some great way to interface each sheet/holder to a heat spreader or heat sink. LOLā€¦it would be a $1000 pack but it would be very cool to see.

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Orrrrrā€¦ just build a watercooled pack. :smiley: For Efoils f.e. this would be much less of a hassle, as they mostly use watercooled ESCs already.

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Thatā€™s an idea I hadnā€™t consideredā€¦a sheet between each pouch cell in a pack. Outrageously expensive but the heat would be moved along each sheet very efficiently. Getting it out of the sheets would be the challenge IMO.

Not sure how much more efficient (overall, once all the elements in the cooling system are considered) it would be compared to copper or even aluminum though. Certainly lighter, thatā€™s for sure.

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I think Iā€™ll actually do that. I was going to do otherwise in case power consumption too high but my pack is massive and itā€™s very little difference between standby and full power.
Screenshot_20210804-114954_Gallery

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Did you find this setting? I have the same BMS and I need to plug a charger in to turn the lights on and off its a huge pain in the ass. I rather it have a 12 hour auto shutoff.

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Same answer, put 0 in standby time and activate it with a cell on the 2 small black and red cables.

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According to NASA test the best thing for heat and thermal runaway is a small airspace between cells. If that is done then it would be easy to use active cooling with a small fanā€¦no heatsink needed

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Yup! Itā€™s the automatic standby time. Now it connects with bluetooth all the time and the bluetooth led on the bms is always on, not just the sleeping led.

Thank you all for your help

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All you did was hook the switch up to the first p group?

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On an LLT bms (or any bms in general maybe?) could I just have the B- and balance wires connected to the BMS and leave the C- disconnected? Meaning the charge wires would go to the battery, and I wouldnā€™t have any issues?

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Thatā€™s totally possible, but you would only be able to use the static balance mode, and there would be no over voltage protection when charging. Knowing that it would really make the bms more of a cell monitoring device but truthfully with these, itā€™s not that much different from using it as charge only.

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kinda like Fuse+loopkey+external BMS

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I have decided to go down this road. Iā€™ve opened the tiller pack on my build from 2018. Since Iā€™m refurbing the rest of the board (which now my wife rides) there was no way to avoid it.

To be fair, the pack charges to 100% and hasnā€™t given me really any problems, besides the massive sag- weā€™ll get to that.

The refurbed board


the guts

The battery


why

This was supposed to be a quick repaint, now Iā€™m building a new damn pack! Fantastic!

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i fucked up xD

When trying to get you the Vbms app the plan was to buy it on the playstore, make a backup, send the apk and then refund it.

Well i bought it, sent the apk file (which didnā€™t work) and then i fell asleep, missing the refund period. Now i have bought a 6ā‚¬ app that i donā€™t even need. Fuck. Karma lol

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Well, maybe someday youā€™ll build something with an ANT BMS in it, and youā€™ll have saved yourself 6ā‚¬.

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True. I doubt iā€™ll use a smart bms anytime soon though.

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