Ex train super caps maxwell

IF YOU ARE NOT A FINANCIAL MEMBER OR YOU HAVE LESS THAN 30 POSTS AND YOU POST ANYTHING FOR SALE, IT WILL BE DELETED.
Forum rules
All may view this forum, only AEVA Members may post here.
Post Reply
antiscab
Senior Member
Posts: 2700
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

Ex train super caps maxwell

Post by antiscab »

Not mine, but saw on facebook in Melbourne

https://www.facebook.com/groups/2979133 ... 2/?sfnsn=m
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells
T1 Terry
Senior Member
Posts: 1155
Joined: Thu, 30 Sep 2010, 20:11
Real Name: Terry Covill
Location: Mannum SA

Re: Ex train super caps maxwell

Post by T1 Terry »

Hi Matt, how do you calculate the equivalent Ah capacity or Wh from each of these 48v capacitors?

T1 Terry
Green but want to learn
User avatar
coulomb
Site Admin
Posts: 4316
Joined: Thu, 22 Jan 2009, 20:32
Real Name: Mike Van Emmerik
Location: Brisbane
Contact:

Re: Ex train super caps maxwell

Post by coulomb »

T1 Terry wrote: Mon, 13 Apr 2020, 12:27 how do you calculate the equivalent Ah capacity or Wh from each of these 48v capacitors?
I'd say energy E = ½CV² (Joules) = (1/7200)CV² (Wh) (C is capacitance in farads, V is voltage in volts).

Then take off a generous 20% for the capacitors, because you usually can't efficiently get the last bit of energy out of them, since it's at a fraction of a volt. But by this point, the energy storage is usually soberingly low.

Edit: Ah doesn't really make sense for capacitors, since their voltage is so variable.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.
antiscab
Senior Member
Posts: 2700
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

Re: Ex train super caps maxwell

Post by antiscab »

I'd say these caps are only any good in a hybrid application
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells
T1 Terry
Senior Member
Posts: 1155
Joined: Thu, 30 Sep 2010, 20:11
Real Name: Terry Covill
Location: Mannum SA

Re: Ex train super caps maxwell

Post by T1 Terry »

Sorry for the dumb questions, but the 48v mentioned as the base block voltage, is that peak or nominal? Do capacitors even have a nominal voltage?
I thought capacitors were not intended to be run near their rated voltage so if the rated voltage is 48v per pack, what would a sensible running voltage be?
I was looking at the possibility of using these supercaps with a smaller capacity battery pack for the big bus project. As a capacitor can handle a rapid recharge and discharge, they would be better suited for the long regen on the down hill runs and that full power burst required ever so often where batteries along would suffer a serious voltage sag and a faster loss of cycle life.

T1 Terry
Green but want to learn
antiscab
Senior Member
Posts: 2700
Joined: Mon, 26 Nov 2007, 05:39
Real Name: Matthew Lacey
Location: Perth, WA

Re: Ex train super caps maxwell

Post by antiscab »

absolute max voltage is 51v. 48v is as high as I would go, to keep some margin
Matt
2017 Renault zoe - 25'000km
2007 vectrix - 156'000km
1998 prius - needs Batt
1999 Prius - needs batt
2000 prius - has 200 x headway 38120 cells
T1 Terry
Senior Member
Posts: 1155
Joined: Thu, 30 Sep 2010, 20:11
Real Name: Terry Covill
Location: Mannum SA

Re: Ex train super caps maxwell

Post by T1 Terry »

Thankyou Matt, that gives me a figure to work from with 48v being the upper cut off point. Now to work out the battery pack size working backwards using an upper limit for the cells well in the safety zone for both capacitors and cells.

T1 Terry
Green but want to learn
evcruiser
Noobie
Posts: 10
Joined: Mon, 22 Oct 2018, 14:53
Real Name: Peter
Location: Sydney

Re: Ex train super caps maxwell

Post by evcruiser »

You don't just connect caps across your battery. Their size/weight efficiency is like 10% that of batteries in that mode. Using standard electronics your voltage can only drop say 15% before your vehicle wont run so your capacitor capacity de-rating factor would be more like 85% in that case. This is on top of the low power density of the caps.
Caps are great for quantity of discharges and extreme current but they need special electronics that utilises the capacitor power when they are right down in voltage, to make them a useful package.
The guys at Maxwell are enthusiastic to discuss it to generate sales but they cant steer you to anyone that can build those inverters.
I'd like to find where the custom cap inverters are made for buses and see what it would take to get the power electronics together to make caps practical for a car. With it you could supply any voltage or current for 30sec to get you off the lights pronto.
francisco.shi
Senior Member
Posts: 430
Joined: Mon, 17 Sep 2018, 16:30
Real Name: Francisco
Location: Brisbane, Strathpine

Re: Ex train super caps maxwell

Post by francisco.shi »

You need a back boost converter. Essentially the cap +'ve to an inductor. The other side of the inductor to the output of a half bridge and the half bridge supply connected to the battery/ bus terminals. The -ve all together. That will be the basic topology. Then you need a control circuit that controls the current in and out by changing the duty cycle. The good thing about this design is you can not overvoltage the caps I'd you mess up.
So in the end you need an inverter just for the caps.
Post Reply