According with the Victron blog, they are using, according with the article in the link below, 3 x 3.6kWh UFLEX supercapacitor storage system
Why would one use supercapacitors instead of LiFePo4 batteries for such system?
From what I know, at a similar capacity, LiFePO4 is much more cost effective.
Maybe because the system is used only during the day or as an UPS?
But still…
Thanks for your thoughts… 
Very likely the fast charge and discharge ability.
The c rating for a lithium for that system size for size capacity would hurt it.
Possibly also environment conditions.
I know some of the storage choices on projects we have been involved in consider theft as a factor. Rack mount batteries are very sought after in the ‘second hand’ market.
Often replacement or loss is a greater cost than initial.
I also know that not all super capacitor batteries are that- sometimes they are lithium titanate… Marketing nonsense
Or maybe they were just the guys prepared to help in a project like that?
Good evening,
I think it is due to the high temperatures that they choose these batteries.
A second advantage is that these batteries can handle about 3 times more cycling than a LiPo, so they should last half a century.
Regards, Jeroen.
Good morning,
Maybe this will help.
A test we did last year, see below our results and findings.
| Lifetime in years of Supercaps and Lithium cells with 1 charge and 1 discharge a day. | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| These were tested by charging and discharging 1 time per minute to simulate years of use. | |||||||||
| After 3 months of switching several cells on different DOD’s this is the outcome: |
| Supercap | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| temp | 100% | 90% | 80% | 25% | 20% | 15% | 10% | 0% | charge |
| 15 | 80 | 120 | 180 | 50 | 40 | 20 | 8 | 0 | |
| 20 | 50 | 80 | 120 | 30 | 25 | 13 | 5 | 0 | |
| 25 | 31 | 53 | 80 | 18 | 15 | 8 | 3 | 0 | |
| 30 | 20 | 35 | 52 | 12 | 10 | 5 | 2 | 0 | |
| 35 | 13 | 22 | 35 | 8 | 7 | 3 | 1,5 | 0 | |
| 40 | 9 | 15 | 22 | 5 | 4 | 2 | 1 | 0 | |
| 50 | 3 | 6 | 9 | 2 | 1,5 | 1 | 0 | 0 | years |
| Lithium | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| temp | 100% | 90% | 80% | 25% | 20% | 15% | 10% | 0% | charge |
| 15 | 25 | 40 | 60 | 15 | 13 | 7 | 3 | 0 | |
| 20 | 17 | 25 | 40 | 10 | 8 | 4 | 2 | 0 | |
| 25 | 10 | 18 | 25 | 6 | 5 | 3 | 1 | 0 | |
| 30 | 7 | 12 | 17 | 4 | 3 | 2 | 0 | 0 | |
| 35 | 4 | 7 | 12 | 2,5 | 2 | 1 | 0 | 0 | |
| 40 | 3 | 5 | 7 | 2 | 1 | 0 | 0 | 0 | |
| 50 | 1 | 2 | 3 | 0 | 0 | 0 | 0 | 0 | years |
| With the same tests the supercap cells have a general extended lifetime of about 3 times over that from a Lithium cell. | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Supercap cells can handle better under hot and cold conditions, Lithium should not be used below zero degrees and above 35 degrees. | |||||||||
| When both cells get below the 20% charge then this reduces drastically their lifetime. | |||||||||
| At cooler temperatures it is however possible to fully charge and to discharge to 15%. | |||||||||
| Cycling of Lithium is very difficult to count as the formula for 1 cycle is; see 1 example. | |||||||||
| Is charged to 100% and then discharged to 20%, then charged to 80%, then discharged to 50%, then charged to 100%. | |||||||||
| Discharges do not count, so only charges, (80-20+100-50=110%), this means it made 1 cycle by passing above 100% and 10% will be used for the next cycle. | |||||||||
| Cycling of the Supercaps is basically endless and will outdo the Lithium with that. | |||||||||
| The maximum lifetime against 1 charge and 1 discharge per day to temperature is calculated as follows; see 2 examples. | |||||||||
| 100% charge and then discharged to 20% charge at 20 degrees, is both years together and then divided by 2. | |||||||||
| Lithium is (17+8)/2=12,5 years of lifetime and Supercap is (50+25)/2=37,5 years of lifetime. | |||||||||
| 90% charge and then discharged to 25% charge at 25 degrees, is both years together and then divided by 2. | |||||||||
| Lithium is (18+6)/2=12 years of lifetime and supercap is (53+18)/2=35,5 years of lifetime. |
Regards, Jeroen.
Thanks for the info.
What’s the definition of “lifetime”?
How is the health state of the cells after lifetime period expired?
Good morning Alex,
These cells were all tested till “death”.
Below is another test we did, and installed as we promised.
| Volt | surge Volt | WH usable | discharge RMS | discharge peak | Cycles | Watts rms | Combined Lifetime | Lithium Lifetime | Lithium Lifetime | |
|---|---|---|---|---|---|---|---|---|---|---|
| 3x Pylontech US2000C | 48 | 53,5max | 6840 | 75A | 270A 15 seconds | 6000+ | 3600W | 16 years 1 charge cycle/day | 8 years 2 cycles/day | 5,5 years 3 cycles/day |
| 3x Licap SM0062-018-P | 54 | 55,8 | 6,3 | 19A | 200A 1-2 seconds | 1 million | 912W | 16 years 170 cycles/day | no capacitor | no capacitor |
| 1 Solar charge only | solar + genset/grid | Solar + genset/grid | ||||||||
The voltage drop when something heavy is switched on is a lot for Lithium (48V to 45V normally) but not for a capacitor (48V to 47,8V normally) and so the capacitor will take all the start currents from the load.
The Licap with 3 in series to create a higher voltage is suitable in combination with Lithium, the Lithium battery can be fully charged without overcharging the capacitor.
The advantage is that the little capacitor can give very high peaks, but as can be seen the 9600W peak is 3 times enough for a normal household, start peak is 1.5xnominal power, so 2000W will be started with 3000W in 1-2 seconds.
As can be seen is that the small capacitor will take the start loads 170 times more than the Lithium and so saving the lifetime of the Lithium battery, and nobody starts so many times such loads at home.
So, the capacitor will outlive the Lithium battery when all goes well with just one charge cycle a day to the Lithium battery, every cycle counts and will shorten the Lithium lifetime.
So, conclusion, if you start something frequently then it is very interesting to use a super capacitor with the battery in combination to reduce it’s cycle lifespan.
Another is that when you have to start the grid or genset to charge your Lithium, that will drastically reduce the Lithium even more, buy more Lithium modules to reduce genset or grid costs.
In the summer you might have enough power, longer days less electricity used, the winter shorter days more electricity used, what to do.
Buy just enough Lithium and panels to pass 2 summer days 48 hours with only 1 full charge, this should be enough to get you through the winter in 1 day.
Now you see that during summer you only have to charge one time in 2 days, saving 25-35% on cycling of the lithium per year.
| Seconds | Amps | ohm | Watt | |
|---|---|---|---|---|
| 1 | 727 | 0,066 | 34883 | shortcut |
| 2 | 363 | 0,13 | 17130 | |
| 3 | 242 | 0,2 | 11713 | |
| 3,6 | 200 | 0,24 | 9600 | maximum |
| 4 | 182 | 0,26 | 8612 | |
| 5 | 145 | 0,33 | 6938 | |
| 6 | 121 | 0,4 | 5856 | |
| 7 | 104 | 0,46 | 4975 | |
| 8 | 91 | 0,53 | 4389 | |
| 9 | 81 | 0,59 | 3871 | washing machine |
| 10 | 73 | 0,66 | 3517 | water pump |
| 15 | 48 | 1 | 2304 | |
| 25 | 29 | 1,66 | 1396 | |
| 38 | 19 | 2,53 | 913 | RMS |
| 50 | 15 | 3,2 | 720 | |
| 60 | 12 | 4 | 576 | fridge on old one |
| 120 | 6 | 8 | 288 | fridge on class 5 star |
| 240 | 3 | 16 | 144 | |
| 360 | 2 | 24 | 96 | lights on |
| 720 | 1 | 48 | 48 | lights on |
| 1440 | 0,5 | 96 | 24 | lights on |
| 2880 | 0,25 | 192 | 12 | lights on |
The above list is very positive and the time can be cut by 4 due to cable losses, voltage drops, capacitor voltage drop, etc, etc.
So the washing machine has 2,25 seconds to start, and it will in that time, and the capacitor takes all that load instead the Lithium.
The waterpump has 2.5 seconds to start, the fridge can run 15 to 30 seconds on the capacitors alone.
You can keep 100Watt of lights on for 1.5 minutes when you switch the batteries off, or 12 minutes at 12Watt lights.
Regards, Jeroen.
Do I understand it correct?
Is the investment off the condensator financial effective?
Good afternoon Stefan,
On all your questions, it is a yes.
However, the capacity of the capacitor and/or supercapacitor must be calculated, pending on battery size, lithium or lead acid, voltage, inverter size, single phase or 3 phase, start load, cable losses, ripple, etc.
This as overdimensioned capacity can create also a slight negative effect and unnecessary costs.
Maybe you know the car audiophiles, who place very large capacitors over their bass amplifier terminals, exactly the same effect, better bass handling, but too much capacity creates extra use of power.
Cost effective, absolutely, a basic rule is for each KWh you can take from a battery, about 40 euro must be spend for such system with capacitors to make it work properly.
Meaning a 2000 euro lithium battery with 5KWh you must spend about 200 euro on capacitors to make it right, 10 to 1.
Regards, Jeroen.
Ok thanks for quick feedback.
How can the size off the capacitor be calculated ? Where do I find all these parameters & formula ?
Isn’t it a drawback that a supercap draws a lot of power when recharging ?
Hello Jeroen,
that sounds good.
how much farad (F) do you install for 1 KWH ?
Thanks
Thomas
Good morning,
@ Jo, no, it isn’t the way you think, check this topic first, VDC ripple improvements
@ Stefan and Thomas, for that we need first all above mentioned information.
Better is, to make a graph in VRM to see the voltage drop, amperes and ripple when you start your heavy load, then things can be calculated accordingly with the real data instead trying to calculate this theoretically in advance.
Normally we test first bog standard and improve the system only when needed as it is an add-on and easy to install.
3 fast shortcuts can be made in general;
1 for the ripple improvement, first place the same amount (or slightly more, +20%) of F in electrolytic capacitors (which are already in the inverter) over the inverter to battery terminals individually, this should reduce the ripple with at least 35-45%, place several smaller ones to handle the total ripple current instead of 1 big capacitor.
2 for the start load improvement, place a minimum of 2/3 of the battery capacity in KWh in F in supercapacitors (more is pending on voltage drop, etc) over the terminals of the battery, 30KWh is about 20F, be sure there is only a small ripple, as these do not handle ripple very well.
3 for further ripple and load improvements (if needed, very very rare), a CLC circuit must be made in the busbar line, see above mentioned topic for that, pending many variables.
But there it can be 1/20 KWh/F with electrolytic capacitors and the L must be chosen to handle the maximum current of the inverters and in between 0.68-3.3micro-H and between 0.13-0.42milli-Ohm.
Various L-s or complete CLC-s can be placed on the busbar in parallel to handle the total current.
This is a bit costly but we place those only in case of long cables from the inverters to the batteries, so at home that’s not the case normally and not needed.
Regards, Jeroen.
Because super caps can be charged and discharged at greater rates, can be charged and discharge cycles many more times than lithium no toxic materials no risk of fire and last for years just a few benefits but like you say the cost is the down side
For me they take up too much space, to be efficient they also need extremely short and fat wires to the Multiplus.
I’ll wait for the sodium batteries and see how they do 
You are welcome. We use also sodium batteries from fzsonick. Thomas
but you will have the same issue with the sodium batteries.
on load changes they will stop the charging stream …
Thomas
Good afternoon,
See how we mount a capacitor on a Multi or Quattro and a supercapacitor, examples.
The mounting holes in the bottom of the inverter we use together with a plastic clamp, instead the steel one.
This, as the plastic one does not damage the isolation sleeve of the capacitor.
The white thingy is the safety valve, keep it upside as it is mounted here.
The wiring is 6mm2 silver speaker cable, as the maximum current is only 40A and the wires very short.
The supercaps are also very compact, these are on a 24V system with a rating of 36V and 31F.
These have 10mm2 silver speaker cables, as these are 1 meter long and mounted against the wall close to the battery terminals.
See the fuse mounted in between, that saves a fuse holder and 2 connecting points less resistance.
Regards, Jeroen.
Hi Jeroen,
thank you very much !
Which Brand is the Supercap with 36V and 31F ?
The other one seems like eaton.
Thanks ! Thomas
He was talking about two caps of 62F/18V connected in series…
