Lead Acid Battery Charger Help Request

[jagzviruz]

Hi people ..

I am trying to make a Lead Acid Battery charger for a
Sunca 6V 4.5Ah
Can anyone help me with a schematic ? I would like to make it a dual purpose for a 12 V as well..I was wondering if a Bridge out put to LM317 to Output terminals will suffice to make a charger ??And yeah how should we conect the terminals for the charger ? I mean

+ of charger to + of battery or
+ of charger to - of Battery ?

 

[Hero999]

And yeah how should we conect the terminals for the charger ? I mean

+ of charger to + of battery or
+ of charger to - of Battery ?

If you really need to ask this then perhaps you don't have enough experiance to build this project.

 

[bizzareodave]

If you really need to ask this then perhaps you don't have enough experiance to build this project.

LOL!

AAaaand, a single LM317 won't cut it...

note: I'm agreeing heavily with Hero999

 

[RODALCO]

Get some experience first, and do some reading re chargers.
Some of your suggestion re connecting the accu will be instant smoke or fire.

Be safe and buy yourself a charger from the local shop with does the job instead of burning your house down.

 

[mvs sarma]

Hi people ..

I am trying to make a Lead Acid Battery charger for a
Sunca 6V 4.5Ah
Can anyone help me with a schematic ? I would like to make it a dual purpose for a 12 V as well..I was wondering if a Bridge out put to LM317 to Output terminals will suffice to make a charger ....................QUOTE]

Hi,
there are application circuits with LM317 for Lead ACID bTY charging. One example i am attaching. here the output is adjustable. For managing the 12 V bay the value of R2+P2 should be aroud 1290 ohms as per the article. thus you might add an additional resistor in series and by pass the same for 6 volts. perhaps a 680 ohms. as R2a. The input for 6 v bty shall be around 11V DC and for 12 V bty around 17V DC.the current is as per circuit is little over 1 amp. if you need to reduce it try changing R1 to 1 Ohm 5Watts.

try it out.

 

[bizzareodave]

and for 12 V bty around 17V DC

I don't know where you got that from, but I would recommend around 14V charge voltage for a 12V SLA, and the circuit you posted up before would take a bloody long time to charge a 4.5Ah SLA.

As RODALCO suggested, just go buy one it will be cheaper and safer.


But if you insist on making one yourself, take a look at the L296 from ST Microelectronics

http://www.st.com/stonline/products/literature/ds/1333/l296.htm

It is a DC switching regulator up to 40V 4A output. Make sure you heat sink it well if you intend on using it...

 

[fever]

follow this
**broken link removed**

 

[jagzviruz]

Thanks everyone for your advices .. have been busy over the past few days ... and thanks for advicng me to buy the charger .. but i plan upon makng the kit .. coz nothing beats the risk to burn the house down ..

 

[sam2]

Heres one for 6 and 12v **broken link removed**

 

[bunghole]

mvs sarma,
i looks at the diagram and want to know which side the battery links to, if its a "cycle use" charger and if you can use it to charge a 12v 18.0Ah lead acid battery and what kind of supply you need for it
,Thanks

 

[mvs sarma]

mvs sarma,
i looks at the diagram and want to know which side the battery links to, if its a "cycle use" charger and if you can use it to charge a 12v 18.0Ah lead acid battery and what kind of supply you need for it
,Thanks

you have to supply DC to it as input at pins called '0' and '+'

the output will be taken for charging at pins called '-' and '+' and these are on the right side of the image where you also find pin details of LM317.

Initially you have to calculate the values for 13.8 volts and the current sense resistor value for the current you needed.

Obviously +ve of bty is connected to +ve of charger output-- (this prevents any accidental wrong connection with all knowledge one has-- ref to post originators-doubt)

 

[ericgibbs]

hi jagviruz,
Attached two versions of a sealed lead acid charger.
By choosing the components shown, you can charge 6v or 12v batteries.

The layout pcb is also shown, but the transformer tags shown may differ
from yours, take care.

Regards
EricG

 

[mvs sarma]

hi jagviruz,
Attached two versions of a sealed lead acid charger.
By choosing the components shown, you can charge 6v or 12v batteries.

The layout pcb is also shown, but the transformer tags shown may differ
from yours, take care.

Regards
EricG

Hi EricG,

Perhaps the fuse F2 shold be after D2 and before the Battery +ve.

It is not easy to adjust 13.8v output as with bty it will fall and without a demmy load (dMM) being the only load diode D2 drop cant not be measureable. thus it may be better to have a resistor of say 6.8K or 12K (depening on Bty,) so that the voltage can be set.

Finally the circuit may not have short cct protection with bypass transistor.

 

[ericgibbs]

hi sarma,
the fuse #2, is to protect you in the event if you ever short the output
terminals with the battery connected. Shorting a sealed lead acid battery
is not a good idea. They get very hot and vent electrolyte, blowing out
the seals.

I designed the charger to be a 'floating type' constant voltage charger, so
the equipment that the charger/battery powers, can be connected all the
time.[ set fthe output for 13.8v or 6.9v to suit your battery]

You could add an extra fuse if you wish.

Hope this helps

Regards
EricG
I dont understand the question about the diode/resistor, please explain.

 

[mvs sarma]

Hi EricG,

that if fine ,thanks

 

[ericgibbs]

hi sarma,
the reason why I do not have a dummy load across the output is so that the
battery is not slowly discharged, when the mains supply is not connected.
Thats why the diode is also included, no discharge path thru the adjustment
resistors.

If you want to add current limiting, connect a low value, high wattage
resistor in the emitter path of the power transistor. The 7812 will internally
limit to about 1 amp.

Regards
EricG

 

[mvs sarma]

...................

You could add an extra fuse if you wish.

Hope this helps

Regards
EricG
I dont understand the question about the diode/resistor, please explain.

Hi, i mean to say that (without floating issue), if there is no load the output will be measured by DMM without the diode drop of say 0.7Volts. thus if we adjust 13.8V, by the time actual load is given the output will be less by 0.7 ie., 13.1 volts approx.

whereas if you have a output bleeding resistor just after diode to neg comm, this issue will not arise.
A 1 mA load may not matter I believe.
Hope i am more clear now-- sorry for lack of vocabulary

 

[ericgibbs]

hi sarma,
you will find that with the battery connected that there will be sufficient residual current flowing into the battery via the diode that you will be able adjust the voltage ok.
I have about 100+ laser systems using the charger setup, no problems in the past 10 years.

Give it a try.
Regards
EricG