Run a Solar Outback/Radian on 48v Super Caps?

[Systems Planet]

Shenzhen Toomen claims they are coming out with new Carbon Capacitor cells in 3Q-2020 that have:
20.0Ah 25000F 4.0VDC 120mm x 200mm form factor. Full spec attached.

I emailed Shenzhen Toomen to obtain 20 of their new cells for a 6 month evaluation.
The goal is to create a drop in replacement for deep marine batteries.

I'm looking for someone smart to point me to an engineer, equipment, and docs I need to figure this out.
- how to charge these guys
- how to discharge them
- how to wire them for 48volts for a Outback Radian storage.
- how to program the mate3 to support the capacitor: float, discharge, etc.

BACKGROUND
I am building a 15 KW Outback Radian FLEXmax 80 grid-tied ground mount solar system
for our new home by end of this year. I designed and built a 5kW Outback Radian system about 10yrs ago for my house.
It uses 100% maintenance-free AGM batteries.
I have a computer degree from GA Tech and 30yrs experience hacking stuff.

I'm pretty handy, but do need help if there's anyone out there with experience charging/discharging super capacitors.
I'd prefer to fail fast, if this won't work, so I can switch to something more traditional.

thanks.

 

[svetz]

Short Answer: Look for a traditional approach

Long Answer:
The first issue you'll run into is one of the ways batteries and capacitors differ:

Capacitors ​

So, while a battery is discharging it's power the voltage is relatively stable. A capacitor's voltage doesn't hold steady as it discharges.

A device like the FLEXmax 80 can only work above a certain voltage, so you need some sort of voltage regulation to get all the power out of the capacitor when the voltage is low. It can be done, but it's not a simple drop in replacement.

 

[Craig]

Shenzhen Toomen claims they are coming out with new Carbon Capacitor cells in 3Q-2020 that have:
20.0Ah 25000F 4.0VDC 120mm x 200mm form factor. Full spec attached.

I emailed Shenzhen Toomen to obtain 20 of their new cells for a 6 month evaluation.
The goal is to create a drop in replacement for deep marine batteries.

I'm looking for someone smart to point me to an engineer, equipment, and docs I need to figure this out.
- how to charge these guys
- how to discharge them
- how to wire them for 48volts for a Outback Radian storage.
- how to program the mate3 to support the capacitor: float, discharge, etc.

BACKGROUND
I am building a 15 KW Outback Radian FLEXmax 80 grid-tied ground mount solar system
for our new home by end of this year. I designed and built a 5kW Outback Radian system about 10yrs ago for my house.
It uses 100% maintenance-free AGM batteries.
I have a computer degree from GA Tech and 30yrs experience hacking stuff.

I'm pretty handy, but do need help if there's anyone out there with experience charging/discharging super capacitors.
I'd prefer to fail fast, if this won't work, so I can switch to something more traditional.

thanks.

I don't have any experience with super caps but plenty of experience with yinlong lto cells that have a similar 10c charge/discharge rate.
They still charge the same as most other batteries

 

[Craig]

I am curious though as to why you want super caps and what they cost? There is no wrong answer it could be just because you think they are cool.

 

[Ampster]

I am curious though as to why you want super caps and what they cost?

I have the same question especially for a stationary storage application. I can inderstand it for a 1/4 mile EV dragster.

 

[RCinFLA]

Supercap is an electrolytic capacitor. The 'paste' used between plates creates a very large effective surface area, like the inner pores in a sponge. A capacitor of Farads in value can be made.

As usual you do not get something for nothing. Super caps have a typical voltage breakdown of 2.5 to 3 vdc. You can make a higher voltage cap by series stacking but you get the series cap reducing in capacitance at the higher voltage. There is also a problem in keeping the voltage distributed across the series stack just like series stacked batteries so you don't let any of the caps exceed their individual voltage rating.

By themselves, Supercaps probably do not make a good battery replacement, but they have some benefits if you mate them up with a normal battery pack. Supercaps have a very low series resistance meaning they can recharge and discharge a high amount of current for a short time.

Tesla bought Maxwell company last year. Maxwell makes high quality super caps.

Regenerative electric/hybrid auto braking is presently limited by the charge rate the batteries can take without damage. By supplementing with supercaps, the auto can recover more regenerative braking energy and then transfer that energy to battery charging over a spread out time acceptable to battery maximum recharge rate. This is the primary reason Tesla bought Maxwell supercap technology.

Short period high current discharge is also a good use of supercaps. You could make a relatively small six supercaps pack and parallel with some small capacity rechargeable batteries and use it for your car battery. As long as your car does not draw too much current when not running it will work pretty well and you will be able to run the car starter from the supercap charge. There are some Youtube videos of people that have put together six packs of Maxwell supercaps and replaced battery in their car. One guy parked his car Friday afternoon and it started up fine Monday morning with just supercaps in place of battery.

Another application is for high power car stereos, replacing heavy auxiliary battery in trunk.

 

[Systems Planet]

I am curious though as to why you want super caps and what they cost? There is no wrong answer it could be just because you think they are cool.

I don't have a quote yet.

Them reason I want them is lifespan.
10,000 cycles is probably a understatement

This is a once in a life-time change.

 

[gnubie]

You definitely want to look into the voltage vs charge thing before you leap. If they don't provide a datasheet for them that says otherwise, assume they behave like any other capacitor in this regard. In effect you won't be able to touch a lot of the energy stored in them with anything designed for use with a battery.

 

[Systems Planet]

Short Answer: Look for a traditional approach

Long Answer:
The first issue you'll run into is one of the ways batteries and capacitors differ:

Capacitors View attachment 16153​

View attachment 16150

So, while a battery is discharging it's power the voltage is relatively stable. A capacitor's voltage doesn't hold steady as it discharges.

A device like the FLEXmax 80 can only work above a certain voltage, so you need some sort of voltage regulation to get all the power out of the capacitor when the voltage is low. It can be done, but it's not a simple drop in replacement.

Thank for an explanation of what I'm up against.

Super Caps aren't new. I'm surprised there is not already a circuit out there to accomplish this.

 

[Craig]

Thank for an explanation of what I'm up against.

Super Caps aren't new. I'm surprised there is not already a circuit out there to accomplish this.

Yes but 20 ah supercaps are I think. Check out yinlong cells they will do what supercaps do with 30,000 cycles and probably cheaper. These are what I use.

 

[gnubie]

Thank for an explanation of what I'm up against.

Super Caps aren't new. I'm surprised there is not already a circuit out there to accomplish this.

As the voltage falls the current must rise to keep the load satisfied. At 50% voltage, you still have 50% capacity stored in the device but you now have to double the current to get it out at rate that will satisfy the load. 25%, you now have to quadruple the current, yet you still have plenty of capacity to go. You'll be dealing with extremely high currents to get to most of the energy stored, and that isn't cheap.

 

[svetz]

You might also find this thread of interest: Graphene Ultracapacitor now the same $/lifecycle as LiFePO4?

 

[Systems Planet]

Just got this reply:

Thanks for your request.

As such, we don’t deliver cells but only customer specific battery packs based on our hybrid powercapacitors.

For the moment we can use:
- 18500 and 18650 cells (cylindrical)
- 23680 (in pre-order)

The pouch cells you are referring to are not yet available. They use the same technology as the 23680 cells.

 

[svetz]

Interesting, perhaps they've done something to stabilize voltage during discharge? That they're "pouch" and "hybrid" makes me think they're combined with some form of Lithium battery as per the other thread and explains the lower life-cycle count. If so, probably more suited to EVs than solar.

Ask for a graph of charge and discharge voltage characteristics at various C-rates.

 

[RCinFLA]

Super caps do not have a charge/recharge cycle limitation, per say.

As with most electrolytic caps they are vunerable to being exposed to excessive temperature drying out their paste.

Like the classic problem with LCD monitor power supply filter caps, excessive rapid repetative charge/recharge currents (ripple current) through internal series resistance can cause internal heat build up, which is on top of any environmental elevated temperature.


You have to use a super cap more like a current source then a voltage source. Either mate it up with a conventional battery and/or a switching power supply to make a voltage source. I = C * delta V / delta T is the rule.