Super Capacitors - Real or not

atferrari

Joined Jan 6, 2004
4,764
Besides the Gavin's actual goal, what he is trying to do, is what we implement when including bulk caps in a circuit to cater for sudden (local) demands.
Is my perception wrong?
 

Lestraveled

Joined May 19, 2014
1,946
The trojans he is using are deep cycle batteries. The lower the current draw, the more amp hours he will get out of them. The super caps main job is to supply the peak amps demanded by the hard starting loads (motors) and reduce the peak amps that the batteries see. The batteries will supply more over all amp hours this way. If you look at the discharge curves for lead acid batteries, you will see that the available amp hours drops as the current draw increases.

Per the Trojan T-105 data sheet, available amp hours per current draw.
C/1 (105 amps) = 105 AH or 1 hour
C/5 (21 amps) = 185 AH or 8.8 hours
C/10 (10.5 amps) = 207 AH or 19.7 hours
C/20 (5.25 amps) = 225 AH or 42.8 hours

C/1 verses C/10 yields twice the energy.
 
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MikeML

Joined Oct 2, 2009
5,444
If the high-current draw lasts as long as it takes to start a motor, and this is happening infrequently, why bother???
 

Lestraveled

Joined May 19, 2014
1,946
If it were happening infrequently I would also say, "why bother." But, per Gavin's description of his electrical environment, he has a lot of motors.
 

Lestraveled

Joined May 19, 2014
1,946
I miss-understood Gavin's statement about the life of his batteries. He wants to extend the life time of his batteries, not how long they last between charging.
 

MikeML

Joined Oct 2, 2009
5,444
So he thinks that reducing the peak current demand is going to extend their life? I would like to see some research on that...
 

Lestraveled

Joined May 19, 2014
1,946
I agree, I have not seen any data concerning that aspect. Intuitively, I would agree with less peak current equals longer life, but that is not doing good science.
 

Brownout

Joined Jan 10, 2012
2,390
Maybe he really means the drop in battery ouput voltage during short, high current draws. The low ESR caps would lower the effective output resistance of the battery/cap combo.
 

AnalogKid

Joined Aug 1, 2013
10,987
Somewhere in there might have been a good thought. While the high-need-for-control approach might be to put a very high current dc/dc on the cap array output and maybe diode-OR or power MOSFET-OR the utput with the batteries, what about...

Let the intrinsic difference in ESR between the batteries and the caps handle the load sharing. Hang the caps directly across the batteries, and they should share the transient load current proportionally to their conductances. Or something like that. Unless the battery ESR is lower. Just a thought...

ak
 
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GopherT

Joined Nov 23, 2012
8,009
The benefit if his end goal to battery life is even unproven to @Gavin Brunton and is an experiment. The OP's question was simply whether or not the unlabeled super caps he purchased were really 3000 F each (or 500F for a series stack).

Unfortunately, the OP never mentioned charge balancing. Series stacks of superCaps should be balanced for reasonable performance, lifetime and fault-finding. Similar to the way series stacks of lithium batteries should be balanced. Linear and other companies make balance chips.

http://www.linear.com/solutions/supercapacitor_charging?type=circuit
 
Hi, I live on a boat in London and im completely off grid. Ive recently bought 6 3000F 2.7v Maxwell super caps from ebay that are wired in series to give 16.2v capacity. This bank is wired in parallel with my 550ah battery bank. The thing is i bought the caps used and they are plain silver and unbranded. the seller has good reviews and said that the reason they were unbranded was because they were part of a much larger bank. I have not found any other unbranded maxwells on the internet. My question is how do i test them? I only have basic multi meters and a DC clamp meter. The caps are in the system and are accepting voltage. Infact there was a hell of a spark when I connected them to the batteries. Should of probably used a resistor to get them up to voltage.

Also will the supper capacitors cause the Alternator or Solar charger to not function properly owing to the reduced resistance of the capacitors vs a lead acid battery?
Gavin, did you ever determine if the Caps are Maxwell? How about your use of your capacitors to help you start the motor? I guess that is the primary end result of all your efforts here, Go to Maxwell's youtube videos to get some hookup information that they have with their Capacitor hybred units to help start diesel engines on big trucks. I found them to be helpful. Maxwell's Ultracapacitor-Based Engine Start Module - http://www.maxwell.com/esm/ .
 
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