Capacitor in parallel to a battery bank.

Helloo friends...


Plzzz give ur views....about connecting the capacitor in parallel to a battery bank to a battery bank to extend the life of a battery bank.waiting for ur...replies ...

Girishh said:

Helloo friends...


Plzzz give ur views....about connecting the capacitor in parallel to a battery bank to a battery bank to extend the life of a battery bank.waiting for ur...replies ...

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What is capacity of capacitors ?

What is size of batteries ?

What you consider under "life" (power supply time before battery become discharged or complete life time before battery die) ?


Best regards,
Peter

Connecting a capacitor across a battery bank will extend the life of a battery if there is substantial HF ripple. The current flowing into a battery need not be equally distributed evenly across the whole of any given plate, depending on th series impedance of the path. The effect is that if all the current is attracted to a tiny area of a plate, then this area will suffer premature ageing and die, the current will then flow to a different area of the plate and the process is repeated, eventually the total effect of all these dead areas will be noticed in a lack of capacity. Its called "micro charging" , so anything that reduces the AC content will also mitigate against the stray capacitance and inductance of the battery plates causing these "hot spots".
Frank

I'd say it might lessen the battery life, as the capacitors have to be charged every time the circuit is turned on - presuming the caps have been discharged. Neglecting the leakage current that is refreshed during operation.

kam1787 said:

I'd say it might lessen the battery life, as the capacitors have to be charged every time the circuit is turned on - presuming the caps have been discharged. Neglecting the leakage current that is refreshed during operation.

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......Agree.

It's interesting that car manufacturers are putting (planning to?) capacitors across the car battery in "stop start" technology i.e. when the engine is switched off as you stop at traffic lights and restarted when you press the accelerator (gas).

Stated advantages are much longer life 4X to 5X that expected by battery alone (life is based on number of start cycles).
Allows smaller battery capacity to be used with the capacitors.

So I'd say it has been evaluated, tested and proven for this application, so it can extend battery life, but as always it depends on the application.

I think that we need additional informations from thread owner:

What battery type, chemistry, capacity ?
What capacity of battery and capacitor ?
What design/application ?
.
.
.

pinout said:

It's interesting that car manufacturers are putting (planning to?) capacitors across the car battery in "stop start" technology i.e. when the engine is switched off as you stop at traffic lights and restarted when you press the accelerator (gas).

Stated advantages are much longer life 4X to 5X that expected by battery alone (life is based on number of start cycles).
Allows smaller battery capacity to be used with the capacitors.

So I'd say it has been evaluated, tested and proven for this application, so it can extend battery life, but as always it depends on the application.

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In car start/stop situation battery dont starts to crank engine from 12,72-12,73V if good battery have higher voltage then 13V, maybe 13,3-13,5V if there is no additional loads in car (radio, lights,...). Starting in that situation will not affect on battery life. Battery life in linked with many parameters, such as level and number of deep discharge, temperature, age, vibrations, ... There is point to use capacitor in this situation if capacitor is charged by some other source then alternator, lets say brakes, solar panels,... This can be good way for cold cranking at cold winter morning, to use super capacitor charged before at home to boost car battery.


For now based on given thread information, just adding super cap to standby battery in parallel will discharge battery and for sure this will decrease battery life.


Best regards,
Peter

Hi Peter,

In car start/stop situation battery dont starts to crank engine from 12,72-12,73V if good battery have higher voltage then 13V, maybe 13,3-13,5V if there is no additional loads in car (radio, lights,...). Starting in that situation will not affect on battery life. Battery life in linked with many parameters, such as level and number of deep discharge, temperature, age, vibrations, ...

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I stand to be corrected but the article I read on modern stop-start technology, literally stops the engine and cranks the engine when re-starting the journey.
It states the battery life is related to the intensity of the cranking current each time the engine cranks.
The 'usual' work around has been to put a much higher capacity battery in the vehicle, but this increase the weight.
The modern approach will be add parallel capacitors which as well as extending the battery life (measured by the number of cranks) allows a smaller than conventional battery to be used.

So in this situation battery life is increased.

Need more info from the OP to be able to discuss any merit for their situation.

pinout said:

Hi Peter,
I stand to be corrected but the article I read on modern stop-start technology, literally stops the engine and cranks the engine when re-starting the journey.
It states the battery life is related to the intensity of the cranking current each time the engine cranks.

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No, this is wrong. Worm engine needs less power for re-starting, plus battery have reised voltage over 13V if battery is in normal condition.

pinout said:

The 'usual' work around has been to put a much higher capacity battery in the vehicle, but this increase the weight.

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Often this is bad solution for many cars. Because on city driving battery never recharge completely and sulphatisation process starts. Manufacturer choose exact battery capacity which is needed to start healthy and good engine, also alternator capabilities is determined according to battery and electrical loads in car. As result of this on positive pole of battery you will find white/blue deposits. Better is to have full battery than semi charged battery for starting. Semi charged battery will give less current for cranking and weak sparks (gasoline engine). In many EU countries car must have turned main lights on, day/night without exception. This prevents battery to be recharged full in many cars specially in older cars, plus if we put bigger battery this make situation worse.

pinout said:

The modern approach will be add parallel capacitors which as well as extending the battery life (measured by the number of cranks) allows a smaller than conventional battery to be used.

So in this situation battery life is increased.

Need more info from the OP to be able to discuss any merit for their situation.

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I have to admit I didnt try this. For now I dont see point of this, except what I mention before.

Additional, super cap can filter voltage ripples from alternator to make steady voltage for fine newer car electronics. I will say this is main reason for this how I see, but I dont want to doubt in manufacturers solutions, specially if car is made in Germany.



Best regards,
Peter

About 40 years ago I bought a calculator that used an LED display. It was powered from a little 9V alkaline battery that did not last long.
The display became dim when the calculator was used for a few minutes.


The display was multiplexed so that one digit was lit at a time with fairly high peak currents. I fixed the problem by adding a 47uF capacitor to the supply after the power switch to supply the high peak currents.

Hi Peter (tpetar),

I'm have just a glancing interest in the automibile industry, but a "News and New Product" item "150F at 14V" caught my attention in Elektor May 2012.

Snippets from the item.

Australia based CAP-XX super capacitor module supplies cranking current stop-start; idle-stop; micro-hybrid vehicles.
Supplies up to 300A for each engine start.
Tested under the New Europeand Drive Cycle (NEDC) standard.
Completed 110,000 stop start cycles compared to 44,000 cycles of conventional battery
Added benefit that it will start an engine at low temperature where the battery only will fail
It does include control electronics in the module to balance voltages, limit current and manage stop-start functions.
Their website is www.cap-xx.com but I couldn't find much for this discussion!

Thanks peter ,,,


i have 19000uF/400 volt capacitor is connected across 25 numbers of 12 volt batteries,,from life i mean complete life tym...

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Thanks to all of you friends for your valuable comments... i think adding the capacitor across the battery will reduce its peak current and therefore increase the life span of the battery...i would like to know what calcultaion should i do ..like reating of capacitor ...battery rating energy densuty etc../////

i have 19000uF/400 volt capacitor is connected across 25 numbers of 12 volt batteries,,from life i mean complete life tym...

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The capacitor can buffer ripple current up to ms time range, e.g. the 100 Hz ripple of a single phase inverter. The carrier frequency of a pwm inverter ("HF ripple") would be usually already absorbed by the bus capacitors, depending on the design.

Check that the ripple current doesn't exceed the capacitor rating.

Those super caps have a pretty high impedance for a normal 150 amp starter load. Even a 150 F size cap could not provide enough power to even get that starter motor turning.