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[SOLVED] Power supply behaviour

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shahbaz.ele

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dear all
my question is that if we short two batteries of different AH.
what would be their behaviour.
say BAT1 is 12V, 200AH and BAT2 is 12V,18AH
load is attached and we use it on and of (not regularly say in UPS)
what would the result,
when we use the load for some time and then cutt off
no charging is connected,
should the current flow from 200AH to 18AH.
 

Current will flow from higher voltage potential to lower. If BAT1 have voltage 12,72V and BAT2 have 12,50V in that case BAT1 will charge BAT2. When voltages become equal current stops.


Best regards,
Peter
 

If the batteries are connected in parallel total capacity will be bat1+bat2 (200+18),
and the current will flow towards lower volt .
In your case the voltage of both bat is equal so no current will flow from 200AH to 18AH .

Thanks
 
Last edited:

Its good to mention that this like battery exhibitions should stay only in theoretical or Proteus environments. :)

Battery with smaller capacity have insured death in this design (discharging and charging). At charging battery with smaller capacity only is safe in float charging voltage range. Current control and voltage control during charging are mandatory.

For short time, such as situations at winter when car battery is weak, this smaller battery can help to start car, but on longer. :???:

If BAT1 is in bad shape and have started sulphatization process or for any reason have lower voltage this will also degrade health of BAT2 by keeping BAT2 on lower voltage and not allowing BAT2 to become fully charged.



This combinations are NOT recommended for usage!.


Best regards,
Peter


;-)
 

I agree ,because if the load is according to bigger one then the battery with lower capacity will not tolerate the current
and surely the lower capacity batteries plates will burn.
 

During discharge process lower capacity battery (BAT2) will be highly discharged, under 10,5V and this situation will kill battery or seriously wound battery. :) In that case we can say we dont have battery or we have half from battery.

Also its very important to have the same battery type and chemistry (Starter - Deep Cycle).


In propper (the same capacity, health, actual status and shape, age, life history, internal resistance,...) parallel connection should looks like this:

2x12VoltinParallel.gif




If possible always avoid paralleling batteries.



Best regards,
Peter
 
Last edited:

It's very important that both batteries must be similar in terms of volt and AH,
either in series or parallel.
I have practically seen that the performance is well also in parellel (with similar batteries).
 

DIGITRONIC said:
I have practically seen that the performance is well also in parellel (with similar batteries).
Click to expand...

When you point gun in small AA direction, battery will confess that have 5Ah inside. :)

Usually in solar systems battery banks are in parallel and serial connections on wrong or tolerable way.



DIGITRONIC said:
It's very important that both batteries must be similar in terms of volt and AH,
either in series or parallel.
Click to expand...

If batteries must be combined better is serial link.



Best regards,
Peter
 

I am personally using 120AH+120AH in parellal with my inverter
for three and half years,without having any trouble.
So I have used the word "either" and "practically seen".

Thanks
 

Before connecting Battery's parallel an switch must be placed in between (e.g:MCB) because battery act as infinite source of current.The Voltage levels for battery must be same.
1)When battery connecting in series the current will get restricted to the 1st battery current.
2)For parallel connection as stated above .
Normally when batterys get charged in an string i.e all batterys voltage becomes same the current requirment by battery gets reduced & battery slowly stops taking current means its stop charging after trikkel charging.
Also while discharging battery with higher voltage will drop down to lower voltage battery i.e higher battery will dominate.
 
SACHIN C said:
Before connecting Battery's parallel an switch must be placed in between (e.g:MCB) because battery act as infinite source of current.The Voltage levels for battery must be same.
1)When battery connecting in series the current will get restricted to the 1st battery current.
2)For parallel connection as stated above .
Normally when batterys get charged in an string i.e all batterys voltage becomes same the current requirment by battery gets reduced & battery slowly stops taking current means its stop charging after trikkel charging.
Also while discharging battery with higher voltage will drop down to lower voltage battery i.e higher battery will dominate.
Click to expand...

This is very interesting.



Each battery have internal resistance which limit maximum current from battery, additional to this maximum current from battery depends from chemical materials state in that moment.

Usually each lead acid battery have declared maximum current what can produce.

Current in serial link will be the same in both batteries.

If we can get that battery with infinite source of current I want to buy ten of these.

For now I invest one "helped me" click in You. :)




Best regards,
Peter

:wink:
 
Actually infinite current flows through the battery when it is Shorted.
Here infinite not reflects the actual current will be infinite,it was used for battery maximum current like 150Ah or 200AH.......


Thanks.....:-D:shock:
 
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