Hi Guys ,
what about the minmum charge current you all siad that it is between 1/10 to 1/20HR to charge a battery is there a minimum current or if the current goes down these values the charge will only take more time ,
by the way a couple of two days ago my car battery went dead it is 50AH and I recharged it with a two amperes regulated power at 14 V i put it for approximately 1 hour and twinty minuets I installed the battery in the car and guess what? everything was OK , I used a typical LM 338 IC cercuit not a charger circuit just a regulated 14 V 2A current! by the way my battery was of the sealed kind with a little green ligh power indicator so what do you think?

 

Fine Sir,
it doesn't mean that you have charged the battery fully? a partially charged battery also can start the car and the battery will then on get charging current from the car's charging system.

Also, we don't generally speak personal ideas while discussing and suggesting methods. Afterall for the other person seeking advise, it cost damages of equipment due to hasty or fastening advises.

these are accepted procedures. If some one made a charger that would charge a battery with in 2 hours completely, use it gladly ,but be ready for early replacement of battery.

You can't generalize that industry supplied items are all confirming to the LA or SLA or GEL battery charging standards.

__________________
Regards,
Sarma.

 

Attached a datasheet for further analysis.

__________________
Regards,
Sarma.

 

A Normal Maximum Charge rate is1/10 Capacity.
There is No Miminum charge rate.

As to your 2 amps on that car battery, All it did was create, what they call a "Surface Charge".
Enough current to start the car (if it Starts Quickly) But Not propery Charged.

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hello everyone, im new here, and desperately want to get it right!
i'm making a charger for a 2.3A SLA battery, and so far, i found a decent schem. for a constant voltage charger. it charges at 650mAh, and thats a bit over the 1/10C rating!
i would idealy need 230mAh. i cannot use a transformer smaller than 2A, as this is part of a circuit that operates a credit card machine, and the battery will be used as a backup only during a power failure. could i add a constant current circuit to this, or just add a series resistor?
if so, what value?
Thanks in advance

 

Why not just use my circuit?

Its also a constant Voltage charge with a Current limit that you can easily set to 230 mA.

http://www3.telus.net/chemelec/Proje...er/Charger.htm

Even though this shows a Center Tapped transformer, a regular transformer and a full wave bridge is quite acceptable.

Your 2 amp transformer is Probably OK, But you didn't say at what voltage it is?

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uhhh, SLA needs a constant voltage for a float charge. 1/10C will boil it away in a few weeks.

 

You obviously didn't look at my charger.

It is Both Voltage and current Regulated.
And it Definately won't boil it away if set up properly.

Set it to 13.6 volts for a continuous Float charge,
Or 14.6 volts for a normal re-charge operation.

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I responded to ziyad's post.

Sorry for the confusion.

 

Thanks for the quick response, as for my transformer, its rated 12V at 2 amps, but if with no load, or slight load, reads over 15V. ir it doesnt work, i will change it, but that part is not so serious.
From what i have read on this forum, i think, a SLA (12V) can be charged continuously at 13.6V without causing damage, coz the current drops to near zero at full charge.
If i go with your charger, can it be connected permanently to the battery, and also, can the battery be connected to the charger without any power on the input of the circuit, (like a power failure)?
one more thing, (i hope ), can i stack voltage regs in parallel to increase current handling?

 

I checked out your website, Mr. chemelec.
Really cool stuff you got there!
About your circuit diagram, ..........
1) RX is rated at 4K7, and according to the formula, RX= 06V / 0.120A, which should be 5 OHMs, right? Or am i a bit mixed up? The circuit i came accross first, turns out to be just about identicle to yours, only it has an led between the collector of the transistor, and the adjustable pin of the v-reg (goes off when fully charged / minimum current is reached)
. they use a 1 ohm resistor (in the same place as your diagram) for a 650mAh charge, which complies with you formula.
2) i want to use your circuit to charge higher current batteries, of between 25 and 45AH. im assuming i could get away with an LM338, on a large cool rib, but i doubt the transistor will survive. Can i use a TIP41C instead (15A Rated, as opposed to the 0.6A of the 2N4123) ? Other substitutes? ideas?

 

Finally i found that link to the circuit i referred to above.
here it is...
http://www.shdesigns.org/gcellchg.html

 

Sorry about that TYPO. It should have read 4R7, Not 4K7.
(4R7 = 4.7 Ohms.)
This is Now Corrected.

Yes you can use an LM338 for higher current.
But the 2N4123 is still OK.
Its the Resistor that Needs to be Greatly Increased in Wattage.
The Transistor is only a Low Currents Switch.

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Thanks for that. i figured there was a TYPO Boo Boo.
I,ve used a 2N2222A transistor in place of the one you use, as i just could'nt get hold of the 2N4123.
it seems to work fine.
.....Now, back to the questions.......
Can i stack v-regs in parrallel to double or triple current handling?
If so, i suppose i would have to accomodate for about 2Volts more on the input side for this for each reg?

 

Any Small NPN Transistor is OK.

Paralleling Regulators is not really recommended.

But Adding a "Pass Transistor" will work.
Check out the Data Sheet of the LM317 for info on doing this.

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