Wikipedia says : F = A s / V

3600F = Ah/V

Ah = 3600F . V 

F.V = Ah/3600

Correct?

Also, that sort of explains why capacitance comes down when you series. An ampere is one Coulomb per second. Placing "batteries" in series ups the voltage but leaves the current capability the same, as we all know. So placing two capacitors in series leaves the current capability the same (and hence the charge) but ups the voltage.

So if a Farad is one Coulomb at one Volt, then placing them in series gives you one Coulomb at two volts, and hence half the capacitance. One sort of get the feeling that you get only "half the energy", but in reality it's the same energy, but half the capacitance. Sometimes this stuff is just seriously confusing...

1 minute ago, Mark said:

Was that each or all inclusive...

http://www.ebay.com/itm/401148059166?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

£3.49 each R368. I am probably going to have to pay duty. Should not normally but our local post-office seems to work on the basis that if it is big you pay duty and if it is small you don't. I paid duty on a single replacement CD but not on the original set of three or four.

So quick sums. If you use 6 of them, you have a total capacitance of: (6*(1/500))^-1 = 83.3 Farad (at up to 16.2 Volt).

If you have it sitting at 14.5V and want to drop it no lower than 9V, you have a delta of 5.5V.

Lets work in Amp-seconds, as this is more conducive to engine starting. Then As = F * V = 83 * 5.5 = 456 amp-seconds.

So you can deliver 225A for about two seconds, or 112A for 4 seconds, or 55A for 8 seconds, etc...

That ought to start a tractor... if it's not a cold morning.

Side story: So we had two tractors on the farm. A Massey Ferguson 265 and a David Brown 990 (which was older than me). The Massey had a glow plug, but it was one of those things that just screws into the intake and cannot really heat things much. The David Brown had nothing at all.

So on a cold winters morning, the Massey would not start. You could not start that thing before 11AM! It didn't even help to jump a stronger battery onto it. The only thing that worked was a tow-start. Of course the Massey was the bigger tractor and so, for most tasks, that was the one you needed. So if you had to get that one going before 11AM, what you did was this: You started the David Brown (which always started immediately), and then you used that to tow the Massey.

The fun started if you parked the Massey with some implement attached the previous night, and now you could not lift the implement (no hydraulics until the engine runs) to tow it. So then you'd need like several people to remove and move the implement BY HAND... so my dad had this thing where he would detach the implement the night before and re-hook it the next morning for this reason only...

Kid you not.

I will post a FAQ from GW Store as soon as i receive it from them. They are currently in the process of completing this.

The two main disadvantages with supercapacitors versus batteries is:

1. A linear voltage discharge rate. So a 48 V system that had discharged to 36V still has three quarters of the stored energy. 
2. High self discharge rate. Supercapacitors discharge rate is measured in days where as LA batteries discharge rates are measured in  months.

4 minutes ago, Chris Hobson said:

A linear voltage discharge rate

Boost converter anyone? :-) Really, I think the best solution would be an inverter designed to boost from lower down, which might also explain why these guys want you to buy their inverter.

39 minutes ago, Chris Hobson said:

The two main disadvantages with supercapacitors versus batteries is:

1. A linear voltage discharge rate. So a 48 V system that had discharged to 36V still has three quarters of the stored energy. 
2. High self discharge rate. Supercapacitors discharge rate is measured in days where as LA batteries discharge rates are measured in  months.

Have an idea here, but need to make sure as half the stuff you guys talk about goes so fast past me, I just hear wooOOSH. But I will get the 'picture' shortly.
1. So on 12v system I should get more bang for my buck?
2. Would that be an issue If one runs it down every night, recharge the next day?

Just now, The Terrible Triplett said:

Have an idea here, but need to make sure as half the stuff you guys talk about goes so fast past me, I just hear wooOOSH. But I will get the 'picture' shortly.
1. So on 12v system I should get more bang for my buck?
2. Would that be an issue If one runs it down every night, recharge the next day?

I would imagine it might play some havoc with low DC disconnects on inverters, probably why you will need their inverter that can adjust for the lower voltage.

2 minutes ago, Sethm said:

I would imagine it might play some havoc with low DC disconnects on inverters, probably why you will need their inverter that can adjust for the lower voltage.

Good point!

Maybe a stupid question but what would the min volts need to be to still spit out 220v other side?

Want to power 100w at night till panels can re-charge the next day.

3 minutes ago, The Terrible Triplett said:

1. So on 12v system I should get more bang for my buck?

Nope. It would stay the same.

For example, lets use the "battery" from the tractor example above, so you have 83 Farad. On a 12V system you really have between 10.5V and 15.5V, so a delta of 5V, or 415 amp-seconds.

(For the tractor, I went with 9V as most starters don't mind a bit of low voltage once they get going).

Now on a 24V system, my capacitance is going to come down. With 12 of these in series I only have 41 Farad capacitance, so about half. But my inverter can operate all the way from 21V to 31V, so I have a delta of 10V, or about double. I think you can already see that it is going to cancel out exactly in terms of amp hours.

However, in terms of work that can be done, the 12V system can do 415*12.5 = 5kw.s (5 kilowatt-second) whereas the 24V system can do 415*25= 10kw.s.

In other words, exactly what you would expect.

In theory, the higher voltage inverters should have a higher allowed delta, so a 48V system MIGHT give a delta of more than 20V, though with the top end around 62V, I doubt they'd allow you to drop below 40V unless specifically designed for that... so no, for the most part, using off the shelf components, it will all balance out.

9 minutes ago, The Terrible Triplett said:

Have an idea here, but need to make sure as half the stuff you guys talk about goes so fast past me, I just hear wooOOSH. But I will get the 'picture' shortly.
1. So on 12v system I should get more bang for my buck?
2. Would that be an issue If one runs it down every night, recharge the next day?

Unfortunately it is linear so you would under the same setup you would be at 9V. So under a 48V system you could cheat a bit an add a few more 2.7V cells and that ubiquitous Chinese inverter would allow you to go all the way to 42V.

 

Fwiw, when some of my Trojans started to give notice, I had my bank right down to 18V and the little Victron was still going (going crazy with the RED led... also this reminds me, really need to look at that low voltage cut-out now that I have AGMs in there). So you will probably have a bit more luck with the expensive inverter :-)

8 minutes ago, Chris Hobson said:

Unfortunately it is linear so you would under the same setup you would be at 9V. So under a 48V system you could cheat a bit an add a few more 2.7V cells and that ubiquitous Chinese inverter would allow you to go all the way to 42V.

 

40-48V for ours Chris

 

Want to use the little Victron for this, the current experiment is working like a charm.

So yes, want to have the low cutoff volt setting changed on it ... NO, If it can be done, I am NOT doing it myself. Maybe get it user adjustable.

2 minutes ago, viper_za said:

40-48V for ours Chris

 

That right I had forgotten 42V is the default 40V is the minimum. So one could get a delta of 18 V - maybe just maybe.

This all sounds really promising. What I would like is a 2kwh setup at 48V that I can put in parallel with my current array, and with a controller to make sure the capacitors do all the racehorse work, while the Trojans do the donkey work. If it lasts 20 yrs and is plug and play, sign me up....

 

 

16 minutes ago, DeepBass9 said:

This all sounds really promising.

My only problem is TTT is not going to know himself without cables of even length, busbars, specific gravity, etc. He might in his free time start fiddling........

26 minutes ago, Chris Hobson said:

My only problem is TTT is not going to know himself without cables of even length, busbars, specific gravity, etc. He might in his free time start fiddling........

Prentjie in my kop is nog nie ingekleur nie ... ek is dom met die goed.

Black and white pictures do not show the read WARNING signs clearly.

I just found this old video of that tractor, here starting at zero, no assist. Exactly how I remember it.

Sent from my GT-I9195 using Tapatalk

you have been warned: GW Store - stay the F00k away from them!

Capacitors do store electricity but you won't be able to draw and use the same kind of (Volts / Ampere) over a long period of time, like with batteries. Been there, done that, tested it, was fun. Popped some caps afterwards. Trying to use them for 20 hours simply doesn't work. 

you have been warned: GW Store - stay the F00k away from them!

Yeah I wondered why the alarm bells were going off when I saw that... I believe some branches left the franchise too. Wasn't solarsolved one such party? Please, nobody sue me for defamation or anything, just want to be informed :-)

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26 minutes ago, SilverNodashi said:

you have been warned: GW Store - stay the F00k away from them!

Depends. Been dealing with them for years, the main one in Fishhoek, never had a problem. He actually made deliveries in person.

And yes, there are/where franchise stores trading under the name that got a bad rep. Where sorted I believe.

On top of that, a while ago, the main GW store website was hacked, they lost a lot of business and rep, was sorted and subsequently has been sold. I had a look at the numbers.

29 minutes ago, SilverNodashi said:

Capacitors do store electricity but you won't be able to draw and use the same kind of (Volts / Ampere) over a long period of time, like with batteries. Been there, done that, tested it, was fun. Popped some caps afterwards. Trying to use them for 20 hours simply doesn't work. 

@Chris Hobson, see here comes the colour, red, warning.