hardcore misery

Is it possible to make a battery charger that turns off automatically when the battery installed(for example, a cellphone battery) is already full-charged by the battery charger? or install a timer(which can be setup by the user, whether to set the timer at 3hrs or anytime you desired based on the estimated time the battery will be in full-charged)and shuts-off the battery charger?

it would be impractical to interface the batter charger on a Visual Basic program, so is there any way to do this?

Leftyretro

Most 'automatic' battery chargers utilize a end of charge voltage set-point to stop the main charge and/or switch to a trickle or maintaining charge.

Certainly a timer, mechanical or electronic, is a simple addition to make but without the voltage derived end of charge function it would still be possible to overcharge and damage batteries due to underestimating the state of charge of the battery when charging starts.

I'm sure there exists somewhere battery chargers with serial or other communications ports for computer communications, however standalone chargers are the most common.

Lefty

ericgibbs

You can interface the battery charger to the PC's Visual Basic program, using the PC's parallel port.

The port can drive a serial ADC, say 10 or 12 bit, the VB prog can read the battery state and then switch a relay
via the port to disconnect the charger from the battery at a predetermined voltage.

hardcore misery

yes, but it would be impractical to use a PC just for timing a battery charger... i hope that there are other ways to do that...

mcs51mc

Some do...

Please keep in mind that every type (chemistry) of battery needs other "end of charge" detection and other charging way!

Attached Files

power_management___a_multi_chemistry_battery_charger___an2107_12.pdf (694.4 KB, 227 views)

ericgibbs

Hi,
I read you OP as though you were asking if there was a way with VB?

[i]it would be impractical to interface the batter charger on a Visual Basic program, so is there any way to do this?[/I]

You could use a simple PIC, that has a 10bit ADC and say an internal osc.
Write a program to monitor the Vbty state and switch OFF a relay.

You could also use a OPA comparator to monitor the Vbty and switch OFF the
charge to the battery.

A timer is not the best way to go, as you dont know how long you will have set the timer for, the battery may not be fully discharged??

hardcore misery

your idea is very interesting however, i even don't have any knowledge in basic programming with PIC's

i have two ideas for this b.charger.

1. Put a timer circuit for switching off the battery charger (condition: this is good for those who knows the estimated time for charging up a battery)

2. Put an auto-shut off circuit that detects the battery whether it is fully charged.

if i we were only thought with basic programming for PIC's

Gayan Soyza

You still did not mention what battery you are going to charge.

Timer method is good if you know the EXACT TIME that it reaches to its fully charged condition from a dead battery. Otherwise it will be overcharged.

This can be done with a simple comparator IC to detect whether it is exceeding its calculated value.But personally I don't like this method.

once you trickle charge your batteries no more problem occured.

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Gayan
Forum Supporter

hardcore misery

oops! i forgot to mention that... it is for a cellphone battery...

just thinking of this..

cellphone charger -> "auto-shut off circuit" -> cellphone

so is there any chance for this?

thinking also for added features:

the charger shuts off then triggers an alarming sound or flashlights

hardcore misery

help me please..

mneary

You scared us away when you said 'cellphone'. The present state of cellphone batteries is lithium, which requires more than casual knowledge of the battery to prevent over/undercharging and fire. Some batteries have built in microprocessors that you need to communicate with.

I don't think this is a beginner project.

hardcore misery

so there are no ways to do this project with stand-alone circuits? so the only way is the PC-interfacing thing?

mneary

There may be a way, but it'll require more documentation than you've provided. A lot more. You've only finally mentioned 'cellphone' after three days.

Gayan Soyza

Here is one similar to simple NIMH charger.It designed for Li-ION.

See the attachments.But I cannot give a full guarantee with the charger,but it is quiet good done with familiar components.

If you have NIMH charger you can alter it to a LI-ION charger.

Here is the main link
http://www.shdesigns.org/lionchg.html

Attached Files

	lionchg.pdf (19.9 KB, 56 views)
	lionchg2.pdf (24.9 KB, 45 views)
	lionchg3.pdf (45.6 KB, 34 views)

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Gayan
Forum Supporter

hardcore misery

Thanks for all the response! i think i forgot to say something... all i need is a circuit with a switching feature(on/off) but the charger will be any cellphone charger which is already built.

my friend recommended me to use a comparator that switches off the charger if it detects the cellphone battery if its already full-charged.( but i don't have any circuit yet) this project is tentative. we need to think of other projects which is
also great... but i will pursue this project, if my group decided on this...