Supercapacitor Battery Replacement

[Nautilus]

Possible solutions:

1 x 44Ah sealed-lead-acid ---------------------- ~10kgs / 22lbs
2 x 12Ah AGM + supercaps ------------------- 8.7kgs / 19.2lbs
no wooden box or hardware
1 x 20Ah AGM + supercaps ------------------- 8.0kgs / 17.7lbs
2 x 14Ah AGM + supercaps ------------------- 9.7kgs / 21.4lbs

Ideally it should be

2 x 16Ah lithium + supercaps ---------------- 7.4kgs / 16.35lbs

But this last one is out of the acceptable price range for just an experiment...

[gumby79]

One of the pitfalls of AGM, the jell which is electrolyte has no ability to pass gas this is why AGM Chargers are specific.
over rate charge / discharge and it will generate hydrogen bubbles witch get traped and insolate the core reducing capacity. Batteries have a C rating . A C rating is the number of times above its capacity it is Happy charging or discharging lithium ion for example typically 1C charge 5c discharge Lithium Polymer 1C charge up to 90 C discharge with the advances in technology these numbers have been bumped up to 5c charge and 180 C discharge. RC cars batteries are getting closer to being capacitors but they're still batteries

[redpoint5]

FYI- Found a new company called skeletontech making supercaps with the same specs as BCAP3200. 2.85v and 3200 farads.

They sell a box of 10 for 480.00 € which is $542 USD. That's $54 each! Much better price than Maxwell, which I don't even think is selling the 3200s anymore.

Maybe Tesla bought the wrong company?

https://www.skeletontech.com/ultraca...836/category=0

EDIT: Just realized they want 300.00 € for shipping. Those Germans must have the least efficient shipping process in the world.

[Ecky]

You can get the Maxwell 3000's from China for around $20-25 per though. Same caps. I wonder if they might be B grade?

Anyhow, in other news Maxwell recently released 3.0v supercaps up to 3000F, which means we could get away with one fewer cap in the series and end up with more capacitance to boot, since you have to divide total capacitance by the number of caps.

[redpoint5]

Oooh, I like 3v. That makes running 5x (15v max) in series less risky for exceeding any single caps voltage rating. My 5x 3400 farad caps with a 2.85v rating is getting a bit close for comfort with a 14.25v max voltage.

I just wish they would invent a cap with a 15v rating to boot, even if it needs thicker insulators and has less power density. A single 500 farad cap with a 15v rating would be sweet. No balance issues to contend with, and no loss of capacity from adding multiple caps in series.

[redpoint5]

Just browsed Digikey today to see what exciting new developments have occurred in the Ultracapacitor space. Looks like nearly all the Maxwell parts have been removed and nothing really exists in the very high capacity market anymore.

Then I Google it and learn that Tesla sold Maxwell's Ultracapacitor business back to the original owners that started UCAP to produce ultracaps.

https://electrek.co/2021/07/21/tesla...er-executives/

Disappointing that years later, this tech has not only not advanced, but has gotten worse as far as available products and pricing.

[serialk11r]

Just speaking from experience, I don't think the 3kF caps really make sense for any kind of passenger car. You don't need much energy storage to start an engine, and if you switch to lithium ion batteries you will never have a problem with cranking (40Ah will crank V12s no problem). Maybe a 83F bank to help bolster a dying lead acid battery.

I bought a 16F ultracapacitor pack (6 100F units) and put it in parallel because the BMS was causing some issues with the car's electronics. It supplies all the power the car needs for those fractions of a second the BMS is behaving funny and the lights have stopped flickering, but I haven't noticed any change in engine cranking (this is my V8 Vantage, which really really struggled when it had its original 90Ah lead acid battery).

[redpoint5]

Agreed that above 1,500 probably doesn't make sense in most passenger vehicle applications. That said, 5x 3400 in series was insufficient to reliably start my diesel truck due to grid heater and massive draw from low pressure + high pressure fuel pumps, plus starter.

I speculated that it might be sufficient to start an Allis-Chalmers one-ninety, which would be extremely useful since the enormous lead-acid batteries are enormously expensive. Haven't tested this theory yet since that tractor only gets used once every few years.

Was hoping to at least see BCAP1500 listed since that might be the sweet spot for eliminating the battery in the motorcycle. I can get by with 400 farad in series barely, but would be nice to have some reserve for the unexpected, and to give a few more days of sitting before the bike is no longer able to start.

I'd have been happy just to see a price reduction, but the opposite has happened. Harder to justify experimenting with these when prices go up as the technology ages.

[serialk11r]

Maybe try a few of these in parallel + battery to get the heater going?
https://www.aliexpress.com/item/3256802444317854.html

I still think these days it's better to just cough up money for lithium ion batteries.

[Nathan jones]

https://www.allbatteries.co.uk/lead-...f-amc9001.html

This battery works ok in a Prius although it does not get cranked at all and is not light as you require. They are used in tanks that go to -40. That may be a compromise in the coldest of winter time

It may not help at all...