Capacitor storage

[jflorey2]

So...back on topic here...LOL

I just ordered 4 of these: http://teslamaker.com/product/boostp...balance-board/
and 24 of these: http://www.mouser.com/Search/Product...V3560-2R7407-R

I have a 48V off-grid system with an Outback FP1-1 (FX3048T) powered by 8 Trojan L16 batteries (more here: https://www.solarpaneltalk.com/forum...entral-america)

Whenever my pressure pump turns on, all of the lights in my house dim momentarily, and it bugs the crap out of me....one of these brownouts destroyed my high end Zojirushi rice cooker and my wife was devastated.

When I first looked into the idea last year on the Outback forums....the idea was poo-poo'd like some of what I have read here....but nevertheless, I want to test out a capacitor bank connected in parallel with my battery bank to see if I can get more robust power delivery...I am not concerned with energy storage in the least.

Before you do that, measure your battery voltage with a good (fast) meter or better yet a scope. If it's not dropping below about 44 volts, then nothing you will do on the DC side will help.

[miahallen]

So...back on topic here...LOL

I just ordered 4 of these: http://teslamaker.com/product/boostp...balance-board/
and 24 of these: http://www.mouser.com/Search/Product...V3560-2R7407-R

I have a 48V off-grid system with an Outback FP1-1 (FX3048T) powered by 8 Trojan L16 batteries (more here: https://www.solarpaneltalk.com/forum...entral-america)

Whenever my pressure pump turns on, all of the lights in my house dim momentarily, and it bugs the crap out of me....one of these brownouts destroyed my high end Zojirushi rice cooker and my wife was devastated.

When I first looked into the idea last year on the Outback forums....the idea was poo-poo'd like some of what I have read here....but nevertheless, I want to test out a capacitor bank connected in parallel with my battery bank to see if I can get more robust power delivery...I am not concerned with energy storage in the least.

I also looked at the Eaton super-cap here: http://www.mouser.com/ProductDetail/...wk7qMmlUePQ%3d
Which looks very cool, but I would not want to invest so much.

In my youth, I was deep into car audio and I remember explaining the difference between capacitors (admittedly in ignorance) and batteries as a large pitcher of water with a small spout (battery) and a small cup of water which could be dumped out instantly (capacitor). Now with more technical knowledge of the subject, I believe this analogy was actually quite elegant.

The formula's SK linked above were helpful, so I believe since I will be using 24pcs 400F each, my overall capacitance will be about 16.7f effective, is that correct?

So, I will post back in a few weeks after I receive the parts and am able to do some testing.

[DanKegel]

Dan: Get it straight. I do not believe you will find a post where I claimed any particular skills in electrical engineering. I claim no particular skills beyond the basics in EE

I think energy in a capacitor counts as the basics.

I'm sorry you took things the wrong way. I was extending an olive branch to both of you.

[Sunking]

JPM sorry you got dragged into this. However I will make it worth your time by putting a huge smile on your and everyone's face except Dan. Should make you spew that cup of coffee all over your keyboard and monitor. Wait for it. Dans new nick name he worked so hard for.













<redacted>

[J.P.M.]

I was really asking without any spite - was just hoping you could straighten out SK's math for him, since SK seems to trust you, and since you've emphasized that you're good at math and EE things.

Sometimes a cigar is just a cigar!

Dan: Get it straight. I do not believe you will find a post where I claimed any particular skills in electrical engineering. I claim no particular skills beyond the basics in EE, which is why I almost always stay out of threads or topics in that area, as you will see if you choose to look.

I've also never clamed any particular knowledge in mathematics on this forum, although I'll say it's been a lifelong hobby since childhood as well as a very useful tool in my practice of mechanical engineering. Do not try to twist what I write to fit what may be a convenient inference for what I see as your ego centric outlook on the world.

Not speaking for SK, and unlike you apparently, not doing his thinking for him, any trust SK may place in my engineering opinions is probably the result of observation and his experience as a professional engineer. Some others may think I have some correct information as well, or not. All the same to me.

I'm done with this thread. Leave me out of it.

[SunEagle]

I am still leaning toward giant springs and hamster wheels for stored energy options. Although those rats do eat a lot.

[inetdog]

OK, finish gloating everyone, and get this back on topic.
Caps do store power. Batteries do too. Each have their uses.

That sounds like a very moderate opinion.

[Mike90250]

OK, finish gloating everyone, and get this back on topic.
Caps do store power. Batteries do too. Each have their uses.

[DanKegel]

he incorrectly refers to my criticism of his behavior and comments as an ad hominemm attack.

Well, let's see: ad hominem is defined (see e.g. en.wikipedia.org/wiki/Ad_hominem ) as
when "an argument is rebutted by attacking the character, motive, or other attribute of the person making the argument, or persons associated with the argument, rather than attacking the substance of the argument itself". And I'm afraid many of your posts have attacked me personally rather than addressing the topic at hand (e.g. energy in a capacitor).

All inetdog was saying is, it's better to attack the idea expressed in a post, rather than the person who made it, since even a left-coaster like me can sometimes do math

[DanKegel]

I do stand corrected and you know I admit when I was wrong.

I was wondering for a while there.

It really is true, supercaps are quite limited, their energy density is crap compared to batteries, and it requires interesting electronics to get the most out of them.

And yet, when power rather than energy density is what you're after, they can be a good choice.
GM is using them in a "voltage support system" in some start-stop light hybrid systems this year
(see for instance autonews.com/article/20151019/OEM10/310199977/new-energy-for-stop-start-tech
and search for Ultra Capacitor in my.cadillac.com/content/dam/gmownercenter/gmna/dynamic/manuals/2016/Buick/Multi-Model%20PDFs/2k16buicklimwm2ndPrint.pdf )

So lighten up! You can win the argument -- supercaps suck in general! -- and yet admit that they might have a real application or two somewhere.

[Sunking]

And, BTW, SK, were you trying to troll DK with a false fact or were you just thinking AH and saying WH?

No sir, I was using a parable comparison making a distinct difference between a Cap and battery. In a series battery circuit a AH does not divide. I do stand corrected and you know I admit when I was wrong. Just been to many years behind me.

Back to the subject at hand. I can give 1101 reasons why Super Caps will not ever become mainstream energy storage. Jeff is correct but conveniently left out crucial information and Dan does not want anyone to know about.

1. Discharge curves make them impractical use. Unlike say a 12 volt battery discharge curve runs roughly from 14 volts to 10.5 volts. A Cap discharge curve is from charge voltage of say 14 volts down to 0 volts. So if you are using a 12 device like a Inverter, you rdone at 10.5 volts. You cannot the last 50 to 60% of the energy in Cap. There is a work around of course. For a 12 volt system you can run the cap voltage up to 100 to 600 volts so you have access just about all the energy. But that comes with great cost and complexity.

2. Round trip efficiency is horrible. Charge efficiency is 50 %, and discharge efficiency is 50%. That adds up to 25% round trip efficiency. That is something Dan likes. Take 4 units of energy and throw 3 of the 4 energy units away. It would make energy so expensive not many could afford it. Not to mention rob future generations. Dan does not give a crap about the lower income folks or bankrupting biz. Either that or he is clueless. Take you pick.

OK Neil here is the meat on the bone. You have more Inverter than you have battery. Common mistake. Now there is a product, several actually that are Supe Caps. In fact one is perfect for your application, but you will soon realize it is plain stupid, and only fools would buy it. It is a Drop In replacement for a BCI 31 size battery., one of the most common size passenger vehicles and light truck batteries made and used. But there are two catches. I am only going give you the least significant reason it is a fools plan. You had better hope your vehicle starts in 2 seconds or less. If longer you will need a tow truck because your new Super Cap is completely discharged. I wil let you and all others figure out the biggest down side.

I am sorry, I forgot the last 1097 reasons why Caps will not work, and why Dan is clueless. The list is to long so I will just post a link to the other 1097 reasons for time sake. So if you clicked the link, you see why Jeff did not bring it up, and what Dan does not want you to know.

So Neil if you clicked the link, you now understand why you would not touch a Super Cap with a 10 foot pole. Nor would any normal person with common since. As you can see, Super Caps have very limited applications like high energy weapons. So unless you are building a Death Ray or Rail Gun, I do not think you or very many folks have any use for Super Caps. They have been around for 4 decades. Your best option is to correct your error, and redesign the system to work as expected.

[DanKegel]

I WAS taking issue with what seem to be attempts by Dan to haul me into a thread for no other reason than, in light of our ongoing animosities, seem at about the level of adolescent spite, particularly where I have had no prior input or much of anything to say and even less desire to do so.

I'm a big boy and all that stuff, but I believe I'm the aggrieved party in this one, and that's what I was responding to.

I was really asking without any spite - was just hoping you could straighten out SK's math for him, since SK seems to trust you, and since you've emphasized that you're good at math and EE things.

Sometimes a cigar is just a cigar!

[J.P.M.]

JPM: whatever problems there may or may not be with Dan's overall argument about the value of supercaps, his math on energy storage is right and SK is dead wrong.
Even a stopped watch is right twice a day (once for 24 hour face), so you have to look at each argument rather than dismiss the author out of hand.

And for those who take note of the fact that a supercap cannot deliver the full energy into a conventional power converter because of the limited voltage drop allowed, please also take note of the fact that if the same percentage drop in V is allowed, you still get N times as much energy from a series string of N caps.

Did you read my post, or only Dan's response to it ? I was not dismissing (or endorsing) anyone's logic, math or arguments in the thread, out of hand or any other way. You may note my post made no comment about anyone's math, or science or engineering, or anything else about the subject of the thread. I don't know what the particular contents of the thread are, and don't particularly care - not my area of interest. I saw my handle being taken in vein, read the post, and responded to the contents and the sense of that post in what I believe to be an appropriate way.

I'd respectfully suggest and ask that you please pay particular attention to the second paragraph of my post. I WAS taking issue with what seem to be attempts by Dan to haul me into a thread for no other reason than, in light of our ongoing animosities, seem at about the level of adolescent spite, particularly where I have had no prior input or much of anything to say and even less desire to do so.

I'm a big boy and all that stuff, but I believe I'm the aggrieved party in this one, and that's what I was responding to. I also seem to remember Dan doing the same when he gets raked over the coals by SK, or when he incorrectly refers to my criticism of his behavior and comments as an ad hominemm attack.

Before you jump to conclusions, you might ask me what I meant.

[inetdog]

J.P.M., are you saying my math is wrong? Or are you just saying you'd rather die than admit that I'm right about something?

JPM: whatever problems there may or may not be with Dan's overall argument about the value of supercaps, his math on energy storage is right and SK is dead wrong.
Even a stopped watch is right twice a day (once for 24 hour face), so you have to look at each argument rather than dismiss the author out of hand.

And for those who take note of the fact that a supercap cannot deliver the full energy into a conventional power converter because of the limited voltage drop allowed, please also take note of the fact that if the same percentage drop in V is allowed, you still get N times as much energy from a series string of N caps.

[inetdog]

SK: Your math is leaving out the fact that the stored energy in a string of capacitors is (1/2)CV². The square is important.

One cap, C, one volt gives .5Joules.
Two caps, C/2, two volts, gives 1.0 Joules, twice that of a single cap even though the capacitance has been cut in half.

And, BTW, SK, were you trying to troll DK with a false fact or were you just thinking AH and saying WH?

Substitute Farads for AH so a 5^th grader can understand. Say a 2.5 volt 1 AH battery has 2.5 Watt Hours of capacity. By your misplaced logic if you put two in series you should have 5 watt hours. Wrong answer. You would have 5 volts @ .5 AH with two in series.The exact same 2.5 watt hours.

I am pretty sure that two 2.5W-h batteries in series do store 5.0W-h of energy.
The problem with substituting Farad for AH is that for a battery Energy = V x AH (no square there). And AH is unchanged by putting two identical batteries in series.