Sodium Ion Batteries from evpromax.com

A selection of sodium ion cells. 18650, 26700 and 33140 cells offer 1300mAh, 3300mAh and 10,000mAh respectively.

[gxfif]

Surely 390 is 39 ohms? That means your current calculations are off by an order of magnitude (77mA not 7.7mA). I suggest you measure the resistor before you go too much further.

[lint]

Very interesting and I love the exposure to different battery types and exploring their implementation.

[paulladdie]

Julian, get yourself a 3D printer, and you can make your own battery holders 🙂

[davidwillmore]

Could you run two cable ties through the center going opposite directions?

[Sopheris]

Wow those 33140 cells seem to be perfect for safe and cold resistant ebike build. I might try that for my winter commuter im going to build soon.

[jameshancock]

Lifepo4 are now cheaper /wh and have way longer life spans while being higher density /kg and m3. And are basically as safe.

They really need to get the price down.

And even then the really wide voltage range makes them a pita with extra cost to use them in lots of cases.

[michaelkaliski]

Having a power supply that provides a steady output voltage is the most important factor in ensuring the reliability of connected equipment. Using a buck boost converter is a prerequisite when using these types of batteries as a power supply. The additional cost and complexity is trivial in the overall cost of the project.

[CornishMiner]

Looking forward to seeing your experiments with these cells.

[benbaselet]

Isn't 390 39 ohms not 390? Damn these markings sometimes.

[himselfe]

Personally I'd always opt for some regulation between the circuit and the source. Might be OCD but I just like the idea of having a consistent voltage supply regardless of the source. I also lean towards efficiency though so that entails a pure buck setup which I guess would require 6S with this chemistry to achieve 12v across the range. If you want to be really fancy you could always have a buck boost setup to charge some supercaps and then a buck from the caps to the supply circuit. That way you can swap battery banks in and out and mix & mach packs as you please without the load even noticing.

[crappyatlife]

I like cheerios especially the honey nut ones

[GodmanchesterGoblin]

For the lights, I have found that many (but perhaps not all) MR16 LED bulbs will work well between 8 and 16 volts. Due to their internal electronics (bridge rectifier, buck regulator) they are not polarity sensitive and give an almost constant light output across the voltage range. I use these in my garden lighting setup where long cable runs mean lower voltage, and fully charged batteries push the voltage on the nearest lamps towards the upper limit.

[EsotericArctos]

Sodium Ion is an interesting technology.
How are you finding them compared to Lithium Ion batteries?

[gregw]

I'd be interested in seeing weight comparisons between the various battery technologies you have. One can lookup energy density, but data from specific products on the market is more interesting

[andytipping]

did you meter the 390 resistor? - to me -using the usual convention, firs digit is a multiplyer so 3 9 and no zeros - = 39 ohms, not 390ohms?

[RBCHOKE]

Will a lithium battery charger and lithium BMS work with the sodium ion batteries?

[Kirmo]

I had no idea they were already comercially available!

[chrisw]

3v across 39 ohms is 77 mA, just under 1/4 watt. And 7v yields 179 mA, = 1.25 watts! Pretty sure those little resistors won't like that at all! But those LEDs are more likely to be 3.2 or 3.4 volts, so it'll be a little less - sadly not enough less to save those surface mount resistors.

[deslomeslager]

You had the LED strip at your workbench, you could have tried them out on 16 down to Volts. But I'd rather go for buck/boost. Or buck only, since I would not mind seeing the lights dim at 9 Volt-ish. That would tell me to recharge the batteries!

[rasimbot]

But you didn't open them. What if these are lithium cells