super capacitors- have 1/5 claimed capacity :(

M

Matt Gruber

1 MW
Joined
Feb 8, 2007
Messages
2,594
Location
New Smyrna Beach FL
UPDATE: see post # 10
skip:
my car battery is 4 1/2 years old and only has 9.6v cranking for 10-15 seconds
i plan to connect this in parallel:
https://www.ebay.com/itm/Farad-Capacitor-2-7V-500F-6-Pcs-1-Set-Super-Capacitance-With-Protection-Board-/382202090308?_trksid=p2349526.m4383.l4275.c10#viTabs_0
anyone know the typical stand by current drain? will the car be dead in a week?
how big will it spark when i hook it up? :shock: Can I spot weld steel? :)
how long will it crank(without battery)? (125 amps to crank)
EDIT, after doing more research, these caps look better,
https://www.amazon.com/Energy-Density-Farad-Amperics-Supercapacitors/dp/B01GD7Q6DS/ref=sr_1_1?ie=UTF8&qid=1533669374&sr=8-1&keywords=amperics
only 2ma drain, stay in balance, no balancer needed
 
That's probably not a good choice to crank the motor without a battery in parallel. Remember that caps don't have any support voltage level like a chemical battery-- they can discharge a lot of amps, but only at a steadily diminishing voltage. The caps can stiffen the battery's voltage sag for a moment, but they need the battery to keep the voltage from dropping to zero.
 
Chalo
that is a potential flaw. maybe the circuit board will pop like a fuse :shock:
Won't know until it gets here (i placed the order)
an experiment for my birthday! (may have to blow out the flames :mrgreen:
.
guys
keep posting flaws :twisted:
 
Six 500F in series would be 83.3F. (caps in series work like resistors in parallel)

And C = I * dV/dT, or dV/dT = C / I

Drawing 125A from 83F the voltage will drop about 0.7 volts per second (assuming their internal resistance is negligible compared to the battery, etc).

They will look like a dead short when you first connect to battery, a precharge resistor is recommended. Otherwise damage may occur to your connectors, etc.
 
Alan B said:
Six 500F in series would be 83.3F. (caps in series work like resistors in parallel)

And C = I * dV/dT, or dV/dT = C / I

Drawing 125A from 83F the voltage will drop about 0.7 volts per second (assuming their internal resistance is negligible compared to the battery, etc).

They will look like a dead short when you first connect to battery, a precharge resistor is recommended. Otherwise damage may occur to your connectors, etc.
Click to expand...
Alan,
Thank You! Great info. Should have at least 5 seconds on a 14v charge.
Have two 25w 2ohm power resistors for precharge.
I hope i can leave the caps on all the time, but if they have a high drain, or get out of balance, i'll go plan B.
B. use caps for emergency start only. Hook thru 10a diode/precharge resistor/switch so they charge when running only and i throw switch. To emergency start, master power switch(across the diode/resistor/switch) is closed. zoom zoom :mrgreen:
 
Matt Gruber said:
B. use caps for emergency start only. Hook thru 10a diode/precharge resistor/switch so they charge when running only and i throw switch.
Click to expand...
Suggestion - leave it connected permanently. If not, the one time you need it, you will have forgotten to precharge it.
 
billvon said:
Matt Gruber said:
B. use caps for emergency start only. Hook thru 10a diode/precharge resistor/switch so they charge when running only and i throw switch.
Click to expand...
Suggestion - leave it connected permanently. If not, the one time you need it, you will have forgotten to precharge it.
Click to expand...
Yes, this is a flaw. I could forget.
It should still charge, however, it won't go to 14v . Maybe 11v? Might start, might not.
Will also carry a 2a step up converter. This won't work with a broken cell connection, so
I also plan to carry a small ac adapter, so i can charge the caps from an outlet.
It is 2.4a at 15v. Anywhere i go, there should be an outlet nearby. Even the car show has an outlet on the street lamps. While i would not want to lug a 35# battery and wait a few hours, the caps weigh little and should charge in 10 min or less.
 
Matt Gruber said:
It should still charge . . . .
Click to expand...
Not if it's disconnected.

I think the KISS principle applies here. Use a fuse, a limiting resistor and a Schottky diode so that the supercap charges in 15 minutes or something, at a rate of under an amp. Then just have a simple (but high current) switch to connect the ultracap to the battery when you need it.
 
bill
i did find a guy that leaves his connected all the time. i agree that is the best way. should start really fast, as the voltage for the 1st second or 2 will be as high or maybe higher than a new battery alone. Say i stop for gas, it should be near 14v on start, vs. 12.6-13v. and it won't dip to below 11v for a while. so only if they leak too much current over 2-3 weeks will i disconnect the caps. They can be totally dead, and i can find a way to charge them, it could take some time, i may have to walk back in and ask to plug in the caps to charge. Could ask the guy behind my car, can you plug this in your cigarette lighter to charge my booster? Most people will help a guy with a 46-60 year old vette.
Here is what inspired me to do something similar:
https://www.youtube.com/watch?v=cq3ihYJ4rbE&t=10s
 
when it sits more than 10 days i have to add gas to the carb. so before, i can precharge the caps, then turn on master power switch for the start. I need to "forget" now and then to test the battery. if it fails in my garage, no big deal. most times that is where they die. Once the battery is just dead weight, i'll remove it. if my old SLA's from my ebike still work, i'll put 1 or 2 of those in. (i have 3).

UPDATE: lightweight set up replaces 35# La with 9# SLA plus 3# super caps.
Guy on utube https://www.youtube.com/watch?v=_A4KbeO2QnE has done this, he calls it a hybrid. Can use the sla to charge the caps many times, but it is too weak for dependable direct starting . I think he has a good long term plan. Why lug around a 35# LA when all it needs are caps and one good SLA? I don't want to totally eliminate the battery, because i need to make it home in case the alt. dies.

edit: here is a 12v 9ah 135max amp for 17.99 free ship https://www.ebay.com/itm/INTERSTATE-BATTERIES-HSL1079-12V-9Ah-Battery/183352510955?epid=4019913778&hash=item2ab0a949eb%3Ag%3AzXkAAOSw3pZbCh99%3Asc%3AUSPSPriority%2132169%21US%21-1&_sacat=0&_nkw=9ah+12v+battery&_from=R40&rt=nc&LH_TitleDesc=0 good for hybrid, NOT made in China :shock:
 
ordered 2 resistors 100 watt on ebay $1.36ea
0.5 and 0.35 ohm
gives 4 combos .2, .35,.5, and .85 ohm
since i want the brake lights and coil to work with a charging failure, this gives 4 power levels to try out. i don't want the future SLA to be hooked direct since i want it to last a long time and not be stressed. I've had lightly stressed SLA's last 5 yrs, even 10 yrs for 1 pair. I'd consider lithium except my cars are fiberglass/resin and any fire risk is too much. I'd use tool packs, but the voltage does not match up. And they cost way more. Going to 12lbs from 35 is really good on a 3400lb car. And the whole set up will cost similar to an ordinary car battery. and should only need the $18 SLA replaced from time to time.
.
EDIT
I think i'll put a 4 pole switch i have across the power resistor for charging failure. will be enough of a challenge to get the caps charging fast, like 2 min after 5 seconds of cranking with the pwr resistors.
Then, by closing the switch, there will be full puny power from the sla for an emergency ride home. I did have the alt. quit in 1999, so this is pretty rare.
 
Found some tests and 3 days self-discharge. I think i'd rather build a portable jump start box that will work on any car.
Will have to find a good step-up converter to charge to 15v with a weak battery, as low as 6v.
And i'll include an old wall wart so i can plug it in. The old 2.4a transformer type i have can take a power surge no problem, as i'll use a 20-30 amp bridge rectifier.
And a cigarette lighter plug in case a passer by wants to help out.
This all assumes the china caps are decent quality, which everyone knows is a crap shoot. If poor, then plan F.
:mrgreen:
as for the car w/weak LA, i'll just put 1 or 2 old SLA's in parallel. they are not doing anything anyway, so they could extend the LA life months or maybe years. or i could leave 1 with a diode so it is always fully charged for the cap jump starter.a 5+ years old sla is old for a direct jump start :|
 
so i bench tested 1 of 3, Yuasa 10ah sla dated 4-13 ( from my wal-mart ebike)
i am impressed 8) at 11 amps, after 6 minutes steady 11.89v. :D
ended test since it will not be deep cycled, and at this level there is enough power for 30-60 seconds of cranking by itself, in theory, but it will always be used in parallel, or to charge caps.
There is 0.16 amps discharge into the LA if left connected, so i'll disconnect 1 wire anytime the car sits. The LA being a marine LA, has extra terminals, so this is easy. i even used copper washers 8) No spring clamps, they suck :roll:
The battery is behind the seat, and i leave the seat back forward, so it is impossible to forget. Every few months i'll check the LA by itself. I only drive this car 2 or 3 times a month, just to keep it running, so i don't mind the extra work.
Interesting that a $399 walmart ebike has such good SLA's 8) I still use the ebike, but with 2 dewalt and 2 makita tool packs, saved like 25 pounds.
Fun with ultracaps:
https://www.youtube.com/watch?v=EoWMF3VkI6U
.
i think i know how to charge the caps fast at home;
i have a 1978 10a charger. weighs 10#, i'll put a 50a bridge in it. i'll hook up the caps, and then plug it in :shock: ZAP :twisted:
 
Caps won't be here for a while, but I'm told they draw like a dead short, without a charge resistor.
So, for a test, i hooked my 2.4a wall wart to my DVM direct on AMPS. :twisted:
BANG! forgot i had a 5a fuse on it, and it popped. Good news as it proves there are more amps to come.
So jumped the fuse and crossed my fingers, hoping the 6a bridge would hold, i tried again.
17 amps :shock: from a 2.4a transformer. It takes some time for a heavy transformer to heat up, i'm sure it could charge the caps fast, 1 time for a jump, before being allowed to cool off. Will swap out the bridge for a 35a that i have.
So, if this works similar on my 10a charger, it could put out ~70 amps :twisted: I expect the caps would charge long before it even gets warm 8)
50a bridge should hold, but may order a larger one.
any comments?
 
Alan B said:
That kind of current is very hard on the diodes.
Click to expand...
I'm surprised the 6a didn't pop :|
I want enough time to check the balance, so i think the big charger would be too fast.
Have 4 or 5 of the wall warts, so if i smoke one, no big deal. got them for $2.25 surplus 10 yrs ago.
With a 35a or 50a bridge on a heat sink, they should barely get warm in 1 minute. The wire in the transformer is going to increase resistance as it warms up, and cut amps fast, i think. If it can do 5a toward the middle of the charge, i'll be real pleased. Can hook 2 in parallel if it disappoints.
I'm going to take a close look at the Publix EV charge station to see if they have an ordinary outlet. Just curious.
Did you look at the video? lots of sparks :lol:
 
swapped in the 35a bridge to the 2.4a ps. The bridge connects with solder only, so if the solder melts, the wire pops off, like a fuse, in case something goes crazy wrong, like hooked backwards.
hooked to 10' of 18awg, so the dead short is now only 15.4 amps. and hooked up a LED DVM that wakes up at 3v. And an old analog ammeter that only reads to 5a.
Years ago i attached the transformer and bridge to a 5x7" piece of aluminum, as a heat sink (from the deck of an old razor scooter.) And i added some lintels to my oatmeal, as a test. Oops! that is a different topic :D
 
this guy is smarter :twisted:
https://www.youtube.com/watch?v=1pnXaENvCKc
 
caps came in,
the good: all very near .10v so maybe can stay in balance.
the bad: based on my 22 second discharge test at 11 amps, down to 9v, i could expect only 2 seconds of cranking at 125a :cry:
It killed my $2 LED DVM, it started to smell and died.
seems to self discharge very quickly. drop to 8.12v from 8.28v in 15 minutes.
So what do you guys think i should do?
 
Punx0r said:
Throw them away and fit a proper starting battery :wink:
Click to expand...

That is what i'm thinking.
An ordinary 10ah SLA is far superior, as a booster.
 
You must log in or register to reply here.
Back
Top