Charge Ultracapacitor Array?

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bksutherland asked Feb 5, '19

Charge Ultracapacitor Array?

I have a 6 ultracapacitor array with dynamic balancing, which I use to run LED lighting and as a UPS for computers.

Ultracaps unlike batteries can recharge 100,000 - 1,000,000 times, and they avoid the harsh chemicals and metals batteries use.

However, these guys make a lot of current, and they often charge differently from batteries -- for example they typically charge to the open circuit voltage due to the near zero resistance.

The Victron SmartSolar MPPT 100/20 Solar Charge Controller 100V 20A with Bluetooth seems designed for managing and maintaining batteries.

Can it also charge this array safely, from a Canadian Solar 300W panel, 44V open voltage?

battery charging ups

ultracap-dc-lighting.jpg (1.6 MiB)

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boekel ♦ commented · Feb 05, 2019 at 09:23 PM

You might want some insulation on those exposed terminals / busbars

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bksutherland boekel ♦ commented · Feb 06, 2019 at 06:04 PM

They are actually a metre off the ground, on a raised non-conductive platform. Point well taken, though!

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markus ♦♦ bksutherland commented · Feb 06, 2019 at 06:35 PM

would be interesting what happens, if you short those innocent looking cells...

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bksutherland markus ♦♦ commented · Feb 07, 2019 at 06:27 PM

I think the balancing circuitry also has a cut-off for short circuits. Yes, 10,000A of 12V is a lot.

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wkirby answered · Feb 05, 2019 at 04:26 PM

It should be fine. In a 6S configuration the maximum "absorb" Voltage would be 17.1V.
I haven't had much dealings with Ultracapacitors, but I'd guess you'd want to have your "cell" Voltage a tiny bit below maximum.

With a MPPT 100/20, you'd select a 12V battery, then choose a custom "User Defined" charge profile. Set absorb and float to the same Voltage since capacitors only need one target Voltage (I suspect). The maximum Voltage the MPPT can reach in a 12V battery mode is 17.3V, so this should cover the Voltage of your array.

Why not "try-before-you-buy" and download the VictronConnect App today and choose the MPPT 100/20 from the list of demo models and play with the settings yourself.

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Modifications Space

Node Red Space

Answer 1 · 2019-02-05T17:00:37Z

bksutherland answered · Feb 05, 2019 at 05:00 PM

Thanks, W. Kirby!

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Answer 2 · 2020-02-28T17:14:00Z

marijuss answered · Feb 28, 2020 at 05:14 PM

hello,

sorry for necroposting, but may I ask was it working normally after straight connection?

I'm planing scheme like this:

solar---victron mppt charger 75/50 ---ultracaps bank(30v)---victron dc-dc 18-30v-24v---load 24v

I have worries for autosensing 12/24v and other for starting with empty ultracaps bank - would charger shut down or not?

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Answer 3 · 2020-02-28T18:45:47Z

bksutherland answered · Feb 28, 2020 at 06:45 PM

Hi, Marijuss:

I ended up with a different autosensing charger (not Victron although I still like Victron for my future domestic installation) and it does shut down with an autosensing fault when there is zero load (not connected), so I see your point.

I haven't tried it with the ultracaps on it yet, will have to do that when the snow clears off my test panel on the roof (pretty deep right now). However, I would guess putting a battery in parallel with the caps might solve that problem, as it's a common configuration for cold weather heavy engine starting -- you'd get more conventional resistance appearing to the MPPT, extra storage, as well as the peak shaving and materially benign benefit of the ultracaps.

DC-DC converters can act a little strange around ultracap arrays since they usually rely on oscillation circuits to buck/boost the voltage and capacitor arrays oscillate a bit as they accumulate and bleed power -- you can get some effects happening from the significant current levels the converter wasn't designed to handle if not careful.

~ BkSutherland

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Answer 4 · 2020-03-01T12:38:16Z

marijuss answered · Mar 01, 2020 at 12:38 PM

thanks, bksutherland.

it seems it will be experiments time.

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