Supercapacitors anyone?

[Martaine2005]

The ‘add a circuit’ fuse adapter is connected to what circuit?
Some sensitive circuits clamp down to avoid surges or voltage spikes.
Try a different circuit like side lights for example. These should work with ignition off. But I’d still go directly to the battery. If you’re on a circuit via the computer, the voltage can drop as low as 2V while cranking. This obviously isn’t certain with your vehicle. Have you tried measuring voltage on the circuit while cranking?
Try and measure a couple of different circuits, you may find one that’s not affected at all while cranking.

Martin

 

[pootler]

The ‘add a circuit’ fuse adapter is connected to what circuit?
Some sensitive circuits clamp down to avoid surges or voltage spikes.
Try a different circuit like side lights for example. These should work with ignition off. But I’d still go directly to the battery. If you’re on a circuit via the computer, the voltage can drop as low as 2V while cranking. This obviously isn’t certain with your vehicle. Have you tried measuring voltage on the circuit while cranking?
Try and measure a couple of different circuits, you may find one that’s not affected at all while cranking.

Martin

Thanks martin

I will try some other circuits.
Currently connected to AUX fuse.
Its funny, but what I would thought would be a relatively simple thing as this request would already be catered for by manufacturers
If I stop the car, continue listening to music on the Acc position, then when I want to drive off, not have the whole thing lose its connections!, and have to reboot.

Cheers

Pootlers

 

[pootler]

Pootler,
Yes, at .5amps the super caps should work well. At 1 amp draw the caps should keep the voltage above 4 volts for maybe 7 seconds. Further, you can put your caps on the output of the convertor and only 1 resistor and one diode is needed. I recommend that you use a Schottky diode for their low voltage drop, maybe a 1N5820 that's capable of 3 amps. A 10 ohm 3 watt resistor should limit the charging current to reasonable 1/2 amp. See attached dwg.

I assume the hub is a USB hub that supplies power to the other devices. If it was an Ethernet hub I would think recovery would be automatic.

P.S. It's probably not required but another Schottky diode on the output of the convertor might be needed. Maybe others here can comment.
View attachment 51426

Hi Frankchie,

As mentioned I am a total noob at this circuit stuff

I do not completely understand your diagram, probably because it assumes pretty basic things that I cannot assume

So----- I did my own version in my own 3 dimensional drawing, trying to understand EXACTLY what connects to what.

Is this correct? - or have I placed the components in the wrong places

The capacitors in parallel with themselves and across the output is I believe correct.

Sorry for needing an ''idiots guide''

pootler

 

[Frankchie]

pootler,
No, your diagram is not correct. Sorry that my original diagram wasn't clear. I have revised it below. If you have any questions feel free to ask.
Frank

 

[pootler]

pootler,
No, your diagram is not correct. Sorry that my original diagram wasn't clear. I have revised it below. If you have any questions feel free to ask.
Frank

Thank you

- appreciate your patience

 

[pootler]

pootler,
No, your diagram is not correct. Sorry that my original diagram wasn't clear. I have revised it below. If you have any questions feel free to ask.
Frank

Just discovered a couple of N4007 shottky diodes in my junk drawer.
Instead of buying another spec,, is it worth trying one of these first to check if this circuit actually works in real life in the car?

thanks

pootler

 

[Martaine2005]

The 1N4007 diodes have a forward voltage of about 0.7V. Unlike the schottky of approx 0.3V.

Martin

 

[pootler]

The 1N4007 diodes have a forward voltage of about 0.7V. Unlike the schottky of approx 0.3V.

Martin

.475V for the 1N5820

 

[Frankchie]

Yes, it's worth a try.
Although a quick Google did not find an n4007 Schottky diode. There is a 1n4007, but i don't think that is a Schottky.
In any case, it's worth a try.

 

[Bluejets]

.475V for the 1N5820

@ 3A.....

 

[Bluejets]

Specification-78ah 680 C.C.A TYPE EXTRA HEAVY DUTY

Power obtained from add a circuit fuse adapter - separate 5A fuse.
Earthed using dedicated earthing point.

Cheers

Pootler

1 down....about a dozen or more circuit unknowns to come........

 

[ratstar]

Hey Pootler, does your name come from your car, or your computler? =)

 

[pootler]

Hey Pootler, does your name come from your car, or your computler? =)

Both

 

[pootler]

Yes, it's worth a try.
Although a quick Google did not find an n4007 Schottky diode. There is a 1n4007, but i don't think that is a Schottky.
In any case, it's worth a try.

HI,

Been unavailable for a bit.
Have ordered the diodes and resistors, so should have them next week.

That is Plan A
But--- in the meantime

I am playing with a programmable timed relay.
My plan 'B' idea goes like this:
The relay is set up as Normally Closed, so for most of the time, the hub power comes from the accessory fuse.
When the power is lost - or dips significantly?- during cranking, the relay switches to another 12V permanent feed.
I have found a permanent feed from the fusebox.
I have tried this in the house using an 12V ac/dc adapter, and the unit seems to work well.
When I transferred it to the car, it didn't!.
Having confirmed that power to the hub does not disappear during cranking, but drops a lot, I am pretty sure what is happening is that the voltage drop on the accessory feed during cranking is actually NOT ENOUGH to ''trigger'' the relay.
When I switch the engine off completely, the relay triggers.
In the house I was using a simple on/off switch to simulate starting, which obviously, sent the voltage to zero to trigger the relay.
So---is there a simple way I could actually INCREASE the accessory voltage drop ( or even drop it to zero ) during cranking , to make it trigger the relay,? - maybe a component that stops power passing below a certain voltage?

If anyone can enlighten me, great.

BTW, here is the unit I am using

https://www.ebay.co.uk/itm/DC-12V-2...Trigger-Cycle-Delay-Switch-Timer/164358160122


Thanks

pootler

 

[pootler]

HI,

pootler

Also - is this also not going to apply to the capacitors - I thought the capacitors would only start discharging when voltage onthe circuit drops to zero?
If cranking voltage is above zero, what tells the capacitor to discharge? - noob

 

[ratstar]

sounds like a job for a pull down resistor? But u wouldnt want to waste current from the battery, cause then the peripherals would never get power.

 

[Frankchie]

pootler,
Are you sure that the "stable" accessory feed actually solves your problem? Did you connect the router to that feed and test by starting several times and confirming the router is not interrupted? If that really solves your problem then the solution is just connect your router permanently to that feed. If the fuse for that feed is small, say less than 10 amps, then find another larger fuse to connect to. Chances are the small amount of current that your router draws will not overload a 10+ amp fuse. Usually there is some headroom on fused circuits.

Better yet, if the stable connection works then the original "aux" connection probably is malfunctioning. Look for corrosion somewhere, maybe on the fuse pins.

I wouldn't bother with the relay, it's not a good solution for a number of reasons.

Frank

P.S. the capacitor will start to discharge as soon as the feed voltage falls below the voltage of the capacitor. The feed voltage does not have to go to zero. And yes the capacitor voltage will then immediately start to decay at a rate that depends on the current draw. The theory is that the voltage will not decay significantly during the few second cranking period.

 

[pootler]

pootler,
Are you sure that the "stable" accessory feed actually solves your problem? Did you connect the router to that feed and test by starting several times and confirming the router is not interrupted? If that really solves your problem then the solution is just connect your router permanently to that feed. If the fuse for that feed is small, say less than 10 amps, then find another larger fuse to connect to. Chances are the small amount of current that your router draws will not overload a 10+ amp fuse. Usually there is some headroom on fused circuits.

Better yet, if the stable connection works then the original "aux" connection probably is malfunctioning. Look for corrosion somewhere, maybe on the fuse pins.

I wouldn't bother with the relay, it's not a good solution for a number of reasons.

Frank

P.S. the capacitor will start to discharge as soon as the feed voltage falls below the voltage of the capacitor. The feed voltage does not have to go to zero. And yes the capacitor voltage will then immediately start to decay at a rate that depends on the current draw. The theory is that the voltage will not decay significantly during the few second cranking period.

HI Frank

Sorry to bother you again.
Got the components, and built a trial circuit.

Sadly, it doesn't seem to have any effect in the car :-( - I still lose connection with the hub.
I took everything in to the house to check.
I used an AC to 12V DC adapter.
I left the caps to charge fully for 15 mins. ( a meter found that using the suggested resistor requires 12 mins to get to ( almost) full charge)
I used some usb devices in the hub to simulate a current draw of about .33A - a little bit less than is required.
I set up two multimeters - one looking at the voltage going into the hub, and the other looking at the current going to the hub.
When I disconnected power, the voltage and current drop significantly in less than a second?
I don't believe the hub devices would keep working with this lack of power.

I uploaded a small video of what happens - the moment the readouts change is the exact moment power is removed.

https://www.dropbox.com/s/wg0rlwtjpxkilg3/video test?dl=0

Any ideas?

Cheers

pootler

 

[Harald Kapp]

When I disconnected power, the voltage and current drop significantly in less than a second?

Exactly what I described in my post #4 and the reason why buffering on the 12 V side was recommended before.

 

[Frankchie]

pootler,
1. Are you using a Schottky diode?
2. The ammeter can add significant resistance. Try repeating the test without the ammeter, just monitor the voltage.
3. Make sure you have good solid connections.

a) Your video shows an immediate voltage drop from 5v to 4.15v. That suggests a standard silicon diode (not Schottky) and/or relatively high ammeter resistance. Even 1 ohm resistance is too high for this low-headroom circuit.
b) I am further troubled by the additional drop to 3.24v in roughly 3 seconds. That sounds like the caps are not really a total of 8 farads, more like under 3 farads.

Let us know what happens.
Frank