# Battery charging circuit problem.......anyone know how to solve?

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#### hcchuar

##### New Member
i have use below circuit to built a car battery charging circuit (12V), the problem i face is the current still supplied to battery eventhough i switch on/off 'S2',

Before i switch on the power supply, but the battery is connected, RED LED will be ON
when i switch on the power supply, GREEN LED will be on, when i switch on/off the 'S2' , GREN LED will also be on, but the current is still charging.

when charging, RED LED will be on when i adjusted the charging voltage is lower than battery voltage, and 'S2' is off

NOTE: i have take out the 1N457 and connected directly because i cannot find in the market overhere, and i try replace by 1N4148, the result i get also failed
anyone can help me solve this problem?

i am taken this circuit at following link

latest edit
forget what i say at previous section,the final experiment as i done is also same with following diagram(without 1N457), after i connected to car battery and before switch on the power supply, 'charge' LED will on(S2 off), after i switch on the power supply,' float' LED will be on(S2 off),as a example, if i set the charging voltage is 14V, the voltage will be increase by slower and slower(13.1V,13.2V......), and the current also decrease by slower and slower(1A,0.5A0.3A,0.25A,0.24A,0.23A........ )

after i switch on the S2, 'charge' LED will be on and the charging voltage always 14V (if i set the charging voltage is 14V), and the current always 1A (always 1A if my input current is 1A)

so should i switch on the S2 when charging?

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#### MrAl

##### Well-Known Member
Hi,

Wow, that circuit sure is complicated for what it does. There are other
versions of this type of charger which are much much simpler and do the
same thing. Look on the National Semi. site or ask here.

#### hcchuar

##### New Member
Hi,

Wow, that circuit sure is complicated for what it does. There are other
versions of this type of charger which are much much simpler and do the
same thing. Look on the National Semi. site or ask here.

Hi,

i failed to find the circuit, can u attached the address here?

#### user_88

##### Member
Have you tried to operate your original circuit without any modifications?

Are you sure that the LM301 amplifier can operate in single supply mode .... with only +15 volts?
Maybe try LM358 op-amp .... which is verified to be good for single supply operation.

#### hcchuar

##### New Member
Have you tried to operate your original circuit without any modifications?

Are you sure that the LM301 amplifier can operate in single supply mode .... with only +15 volts?
Maybe try LM358 op-amp .... which is verified to be good for single supply operation.

i didn't try the original circuit because i cannot get the 1N457 overhere, but i have tried replace it by 1N4148, i still fail to get the result,
LM358 have 2 opamp, may i know how to connect it?

now my output is
battery connected, power supply off =charge LED on
power supply on =float LED on

battery connected, power supply on, S2off =float LED on (charging by increase voltage slower and slower,13.1,13.2,13.3.....,current decrease 1A,0.5A0.4A0.35A.......), by opinion, current is decrease and decrease when the battery is near fully charge

battery connected, power supply on, S2 on =charge LED on (V maintain at input charging voltage, 14V as example, current always 1A as example) ,by opinion, current would not stop when the battery is fully charge

through the link, i'm not clear about the explanation, so i'm not sure i'm correct or not, anyone can help me?

#### user_88

##### Member
If you have LM358 .... try it out .... straightforward hookup for DIP.
See p.9 of data sheet.:

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