help regarging solar charging control !! Urgent !!

[mashal8050]

Hi all !
I have a solar pannel in which
no. of cells =40
Volts per cell = 0.5V
Total V = 40 x 0.5 = 20V
As watts of per cell is 1.85W so
Total W = 40 x 1.85 = 75W Approx
I = 75/20 = 3A approximately.
I need to charge a battery of 12V and 5A, what Ah it will have !
therefore I need help regarding the battery charging control or a battery charger circuit !
i got the following circuit diagram but i am not able to understand it quite well ..
Any help would be highly appreciated
Regards

 

[rahdirs]

@mashal8050: Do u need an explanation of the circuit or do u just need to know Ah of battery ??

12V is battery voltage rating and given that there is a fuse before battery of 5A,the maximum charging current of your battery must be 5 A.

So your battery rating might be 40 -70 Ah
12V,1A - 5Ah battery.
12V,10.5A - 150Ah battery

 

[BradtheRad]

I = 75/20 = 3A approximately

If it puts out 3A, then in 12 hours it will fully charge a 36 AH battery.

However consider that during winter, you get shorter charging sessions.

a battery of 12V and 5A

Do you mean that the maximum available current from the battery is 5A?

Then that is about the capacity of a C cell. Maybe 2 to 3 ampere-hours.
By assembling maybe 10 of them in a string, you get 12V, making 24 to 36 W-hrs.

Your PV panel would charge it in about 2 hrs.

 

[mashal8050]

@ rahdirs

no i found this circuit on net and yes I cannot understand it ...
I want to design a battery charger in accordance with these solar panel specs any alternative circuit that can help me ?? thanks

- - - Updated - - -

If it puts out 3A, then in 12 hours it will fully charge a 36 AH battery.

However consider that during winter, you get shorter charging sessions.



Do you mean that the maximum available current from the battery is 5A?

Then that is about the capacity of a C cell. Maybe 2 to 3 ampere-hours.
By assembling maybe 10 of them in a string, you get 12V, making 24 to 36 W-hrs.

Your PV panel would charge it in about 2 hrs.

okay that is really helpful ! so what circuit should be suitable for battery charging.

 

[rahdirs]

@BradtheRad: What is the maximum charging current that you give on a battery ???

I found on the net & found different people saying C/7,C/10 etc....as in this link.
http://www.navitron.org.uk/forum/index.php?topic=12122.0

So can it mean that for a battery of capacity C for a maximum of 5 A charging current,
C/7 = 5 A => C = 35 Ah.
So does it mean for any battery with capacity < 35Ah will heat up/explode on giving 5A current.

 

[BradtheRad]

@BradtheRad: What is the maximum charging current that you give on a battery ???

I found on the net & found different people saying C/7,C/10 etc....as in this link.
http://www.navitron.org.uk/forum/index.php?topic=12122.0

So can it mean that for a battery of capacity C for a maximum of 5 A charging current,
C/7 = 5 A => C = 35 Ah.
So does it mean for any battery with capacity < 35Ah will heat up/explode on giving 5A current.

The faster you charge a battery, the more closely it should be monitored, because when it is full, it starts to generate heat. The higher the temperature, the more harm done to the battery.

A healthy battery might absorb a C/1 charge rate, but as soon as it is full its temperature will go up. If it has much internal resistance then the injury is greater.

I have a 'fast' charger for AA batteries. I'm not sure it works right, because after a few charges it has ruined a few of my rechargeables. They get alarmingly hot by the time it shuts off.

C/10 is often quoted as a 'safe' rate. It's easy to remember. Nicads can tolerate this level continually, yet last a few years. Lead-acid can tolerate occasional mild overcharging, although the electrolyte bubbles away.

NIMH and L-ion should be taken off charge when they are full.

 

[mashal8050]

hey so can u help me regarding battery charging circuit ..

 

[rahdirs]

The faster you charge a battery, the more closely it should be monitored, because when it is full, it starts to generate heat.
A healthy battery might absorb a C/1 charge rate, but as soon as it is full its temperature will go up.
C/10 is often quoted as a 'safe' rate.

@mashal8050: As your maximum current is 5A & C/10 charging current is safe, your battery could be of 5*10 = 50 Ah capacity.
Now to prevent over-charging & to limit charge rate of battery you need a charge controller/battery charger.

You could use charge controller circuit easily available or connect in series a current-sensing resistor so as to limit the charging current & detect when the battery is almost fully charged.

 

[rahdirs]

@BradtheRad: As the discussion in this thread was mostly on batteries,let me ask it here instead on a thread.
what would happen if i apply 10 V across at 12 V battery at C/10 charging current.A 12 V battery,so 13.6 V should be float voltage & 14.4 V the cyclic voltage.
What would happen if i apply 10 V across such a battery,i understand that the current flows from the battery to source??If i can stop such current,what will happen then??Battery doesn't charge or will it charge slowly ??

By,the way charge-controllers available in the market,how do they stop current in reverse direction,from battery to source ???

(1)Current Limiting - The circuit for the current limiter uses a sense resistor placed in series with the emitter of the output pass transistor. Two diodes placed between the output of the circuit and the base of the pass transistor provide the current limiting action. Is this a good way of current limiting???