Can a Capacitor smooth out the current drawn from a battery when portable?

Hello all

Looking in the back of a car fitted with some big audio amps, I got chatting (no surprise there), and the conversation moved on to the capacitors used to smooth out the power supply into the amp when the bases kicks in.

So now for a couple of questions

1) Could something like this could be used to flatten out the current draw when talking on SSB while portable? 

2) I'm I being naive thinking it's as simple as putting any capacitor between the + & - leads?

73

Ray 2290, thinking of putting a wet finger into the plug socket

wet finger  ?  that could be frying tonight 

skyrider wrote:

wet finger  ?  that could be frying tonight 

I see what you did there, Carry on Screaming I do believe. 

Hello Ray,

Now you're in the realm of 'audiophiles' where gold plated connectors, oxygen free copper cables and fairy dust rainbow unicorns frequent.

(Well that's the cat amongst the pigeons out of the way.)

In a word, not really.....unless your battery is knackered.

Your average car battery is an instantaneous high current draw type which is usually a must for getting that starter motor turned over. If the solenoid struggles firing and the engine lumps over when it does the battery is kaput....usually found out on a cold winters morning.

More modern lithium/poly-what-his-face and other exotic material batteries can supply instant high current as well as longer current draw use. That one's a must for modern cars frequented with multimedia centres, multiple charge outlets, air conditioning, independent heating and the usual tosh you just can't live without.

I really couldn't tell you a darned thing about massive battery systems in electric cars...or their apparent 'environmental' qualifications. (Yeah, right. )


You're right in that your peak current draw will be on your SSB peaks, AM peaks (as well as carrier wave demands), or all the damned time with FM and digital modes. (Just about.)

What are you planning to run? (1kW linears?!?)

Mind you even 100 Watt linears are going to be drawing a fair amount of current and can flatten your battery on a hill-top DX in no time at all. (Ask anyone stuck on a hill after such an event.)

As for so called "400 Watt" linears most of them aren't, the electronics inside will give that away.

The 'field' operators of the world usually start carrying 'spare' batteries and even the odd generator or two in their quest for power utilisation. Fingers often bitten with RF noisy 'cheap' generators or batteries that don't muster their manufactured claims are sometimes the order of the day. Many however run successful DX-peditions so that's probably your go-to for information.....you probably won't find a "super-cap" anywhere in their arsenal.


As for you simply connecting + and - leads.....I've heard tell that sometimes you get that wrong.


Nice idea Ray, probably get some conflicting cr*p about it all especially from the boys who's audio system is more expensive than the car it's fitted to, the MOT isn't worth the paper it's written on and the 'tyre slick' isn't hiding the baldness from the last doughnut.

The above in jest as well as hopefully useful information.....so keep ya knickers on.  


All the best,
Victor

Victor wrote:

Hello Ray,

Now you're in the realm of 'audiophiles' where gold plated connectors, oxygen free copper cables and fairy dust rainbow unicorns frequent.

(Well that's the cat amongst the pigeons out of the way.)

In a word, not really.....unless your battery is knackered.

Your average car battery is an instantaneous high current draw type which is usually a must for getting that starter motor turned over. If the solenoid struggles firing and the engine lumps over when it does the battery is kaput....usually found out on a cold winters morning.

More modern lithium/poly-what-his-face and other exotic material batteries can supply instant high current as well as longer current draw use. That one's a must for modern cars frequented with multimedia centres, multiple charge outlets, air conditioning, independent heating and the usual tosh you just can't live without.

I really couldn't tell you a darned thing about massive battery systems in electric cars...or their apparent 'environmental' qualifications. (Yeah, right. )


You're right in that your peak current draw will be on your SSB peaks, AM peaks (as well as carrier wave demands), or all the damned time with FM and digital modes. (Just about.)

What are you planning to run? (1kW linears?!?)

Mind you even 100 Watt linears are going to be drawing a fair amount of current and can flatten your battery on a hill-top DX in no time at all. (Ask anyone stuck on a hill after such an event.)

As for so called "400 Watt" linears most of them aren't, the electronics inside will give that away.

The 'field' operators of the world usually start carrying 'spare' batteries and even the odd generator or two in their quest for power utilisation. Fingers often bitten with RF noisy 'cheap' generators or batteries that don't muster their manufactured claims are sometimes the order of the day. Many however run successful DX-peditions so that's probably your go-to for information.....you probably won't find a "super-cap" anywhere in their arsenal.


As for you simply connecting + and - leads.....I've heard tell that sometimes you get that wrong.


Nice idea Ray, probably get some conflicting cr*p about it all especially from the boys who's audio system is more expensive than the car it's fitted to, the MOT isn't worth the paper it's written on and the 'tyre slick' isn't hiding the baldness from the last doughnut.

The above in jest as well as hopefully useful information.....so keep ya knickers on.  


All the best,
Victor

Hi victor

You can keep the gold plated unicorns, water filled cables and rainbow coloured connectors and stick them in a black Ford Focus, then take it to every motor show for 12 months by which it's old news and out of date 

I'm not planning on running any amps while portable (been there and done that). 
Just looking at ways to get more out of my batteries as my net nights are getting longer.

So it's going to be 1 of the following.

A bloody long extension lead
Hacking the nearest street light
Some kind of generator (petrol or pedal power)
Another battery

I have almost solved the + & - lead problem. 
Batteries pre wired with a lead and T plug, radio wired with a T socket, no chance of getting knickers crossed 

Thank you for the help Victor

Best 73

Ray

What about a leisure battery.
They stand a bit of hammering flattening and recharging. 
I run my heater in the shack off one and works well.

Ha! Ha!   No worries there Ray mate.  

I would normally say keep your radio activities shorter but you do a fantastic job chairing those nets Ray that any help is worth it.

Alan's suggestion of a leisure battery is a good'un, just make sure you charge it up before venturing off.

(T connectors is a great idea. Was that from Mr Campervan Man?)


I wish you all the best with it,
Victor

A capacitor will not do anything like that.
Across the pos and neg it could reduce ripple if there was any.

As you most likely know it would just block DC in line so no good there either.

Victor wrote:

Ha! Ha!   No worries there Ray mate.  

I would normally say keep your radio activities shorter but you do a fantastic job chairing those nets Ray that any help is worth it.

Alan's suggestion of a leisure battery is a good'un, just make sure you charge it up before venturing off.

(T connectors is a great idea. Was that from Mr Campervan Man?)


I wish you all the best with it,
Victor

Ha Ha Ha    me keep my radio activities short.

Mmmm that has given me an idea for a speed net, call in, drop your call sign/handle off and go. Net lasts 30 minutes and batteries stay charged     

I have thought about a leisure battery and a split charging system in the mobile shack with a pre made cable with a T connector to remove the whole crossed wires thing that I'm famous for.

The T connector idea is thanks to the Chinese, who use them a lot on there QRT,/TYT radio's

Cheers Victor

73

Ivy Mike wrote:

A capacitor will not do anything like that.
Across the pos and neg it could reduce ripple if there was any.

As you most likely know it would just block DC in line so no good there either.

I don't think there is any ripple on the power line and I didn't know a capacitor would block DC current when in line.

Cheers Mike

Without getting toooo technical a capacitor will store energy.  To be precise 0.5*C*V*V measured in 
Joules. 
 
1 Joule per second = 1Watt.  For a 10W CB rig transmitting for 1 second requires 10 Joules. 
 
So the required capacitor size =  0.14 Farad or 140,000uF. 
 
But this is only half the story.  As soon as energy is drawn from the capacitor it voltage will drop. For a 0.5 second 10 Watt burst the capacitor voltage will drop to 8.45V. 
 
So using a capacitor at the CB rig terminals is not really going to do much UNLESS you have high  resistance power feed cables.  Most car wiring is capable of 10Amps with little voltage drop so again not much to be gained. 
 
Last point is that what energy you take out of the capacitor has to be put back in.  So this implies a duty cycle. 
 
Now given the about equation people can do the math for a Super Capacitor.  e.g 2.7F @ 16V

This would help reduce any voltage dip at the CB rig due to power cable resistance. 
 
One great thing about capacitors is that they do store energy and many have low series resistance and low induction so are able to deliver spikes of energy exceeding the charge rate. 
 
As an example in the 80s I designed high energy solid state capacitor changing systems for scientific research.  One system (can't say where) would charge a bank of capacitors for 20 minutes at 50kJ/s.  That is a huge amount of energy and makes a very on big "flash and bang" when discharged in milli-seconds