SIr I Have a 12V 170AH lead acid battery which i used for my power inverter.
170AH is a huge capacity since I need a power full automatic charger to properly charge it. Can any one help me to solve my automatic battrey charging problem. please send me the circuit diagram and explaination.
THANTS..

 

Lead acid batteries are easy to charge due to their chemistry because they automatically reduce the charge current as the battery becomes charged without any sophisticated electronics, although if it is a modern sealed battery with gel rather than real acid, there may be a maximum allowable charge current.

It's just like charging a car battery. Apply 14V and the battery will take whatever it wants - high current at first but trailing off to a trickle as it becomes charged after a few hours. Timing is not an issue - you cannot over-charge if the voltage is right. However there will need to be some means of limiting the curret to protect the charger.

A car battery charger will do it but take quite a while because of the high amper-hour rating.

 

A car charger may not be sufficiently limited and burn out.

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hi dimper,

With your 12V 170AHr battery, what duty cycle is it used for?. eg: Used for say, 1 day/week and on standby for 6 days/week.

Depending on the duty cycle and the available time to recharge it, a different current rated charger will be required.

How 'fast' do you want to recharge it?

A standard car battery charger would recharge it, but it would take awhile.

Lets know.

Eric

 

Is there any method to protect my battery from over charging. how can i know that the battery is full.

 

hi,

The charger you design will have a maximum voltage which it can charge the battery to.
When the battery voltage reaches this charger voltage, the charge current will reduce to a trickle charge.

If lead acid batteries are left for any period of time they will slowly discharge,
this is why a final light trickle charge can keep the battery topped up.

You could get a Hydrometer to check the Specific Gravity of the battery acid to determine the condition of the battery,
or just check all the cells are gassing.

Eric

 

what should be the specific gravity of fully charged battery.

 

It will be marked on the side of the Hygrometer.

A simple google finds plenty about it, try http://www.nwes.com/using_batteries.htm

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hi dimper,
I should have said Hydrometer for SG, not Hygrometer for humidity!.
Edited: my earlier post.

An SG for a lead acid battery is around 1.280 from memory, I'll recheck.

Is it possible you can answer my prvious post questions?.
With your 12V 170AHr battery, what duty cycle is it used for?. eg: Used for say, 1 day/week and on standby for 6 days/week.

Depending on the duty cycle and the available time to recharge it, a different current rated charger will be required.

How 'fast' do you want to recharge it?

webquote:
Fully charged batteries have a SG of 1.255 to 1.280. Fully discharged batteries have an SG of 1.110 to 1.130. Reading the SG can tell you both what the state of charge of the battery is, and also whether all the battery cells are performing properly.
Eric
Look at:
http://www.globalresourceoptions.com.../BatMaint.html

 

Is there any method to protect my battery from over charging. how can i know that the battery is full.All commercial car or vehicle battery chargers have some sort of mechanism to limit the maximum current otherwise they would burn out while attempting to charge a discharged battery. Sometimes its as crude as relying on the impedance of the transformer secondary.

Most chargers have an ameter so you can see when the battery is charged (when the current has reduced to a trickle).

 

All of this depends on how often you use your battery.

A car battery charger should work but will take a long time. Don't worry about current limiting, most lead acid batteries don't need it and any decent battery charger should limit the current to a level it han handle.

If you want to charge it slowly then an LM338 voltage regulator circuit will charge it in about 45 days (assuming about 75% charge efficeincy). You can get circuits for this on the Internet and if you want to charge it faster build a charger with a higher output current.

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hi dch,
Q:
there any method to protect my battery from over charging. how can i know that the battery is full.
All commercial car or vehicle battery chargers have some sort of mechanism to limit the maximum current otherwise they would burn out while attempting to charge a discharged battery. Sometimes its as crude as relying on the impedance of the transformer secondary.

Most chargers have an ameter so you can see when the battery is charged (when the current has reduced to a trickle).

If you are talking standard lead acid batteries, you can, as already been posted check the SG of the battery acid.
When ALL the cells start to freely 'gas' is also a good indication of a full charge.

Most 'bog' standard battery chargers 'rely' on the poor voltage regulation of the transformer to reduce the charge current
during the initial recharge of a 'flat' battery.

Problems can arise. if when the battery is fully charged and the charger voltage rises say to over 15Vdc and
starts to 'overcharge' the battery.

If you have the skill and time, its best to make your own charger, to suit your application. ie; Cyclic or Standby.

Eric

 

Battery chargers can be simple or complex depending on the objectives, features and flexibility desired. There is tons of information available if you would just search for it. Data sheets on battery charger ICs give lots of background information as well as specific device information.

Your question on how to stop a charge on a lead acid battery is pretty simple, most chargers will work as a current limited charger but will monitor the battery terminal voltage as it accepts the charge. When the battery terminal voltage reaches a predetermined setpoint, say 13.5VDC, the circuit will switch to a constant voltage charge of say 13.6VDC which will allow only a small trickle charge to remain, keeping the battery 'topped off'.

Different battery types (chemistry), ni-cads, ni-mh, etc all require different charging strategies and there is no substitute for educating yourself if you are going to design you own.

Good luck

Lefty

 

Some even have a transformer with a high leakage inductance to do that.

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You build a 3 stage 12V battery charger.
Stage1:
Charge battery at/below the max current allowed until apx 14.2Vdc is reached on battery terminals.
Stage2:
Maintain 14.2Vdc across battery terminals until the current into battery reduces to a set point (say 1Amp)
Stage3:
Switch to a float charge (13.8Vdc) to keep battery charged but prevent over charging. Maintain this float charge indefinitely until AC power is lost. On restoration of AC power, go back to stage 1.

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