How to effectively make use of a 12V 1.2Ah battery?

Kermit2

Joined Feb 5, 2010
4,162
The battery can easily perform a 10 to 15 minute demonstration of your boost converter circuit.

It should then be immediately recharged. Discharged LA batteries will quickly sulfate and become un-usable if not recharged promptly.

Just put a cheap multimeter on the battery to monitor voltage.
12.0 to 11.9 volts is about to 50% discharged. This is measured while loaded and delivering power to the circuit. The voltage will rebound when power drain stops and show a much higher voltage.

Don't be fooled, the battery is drained at this point and further discharge will physically damage the delicate lead lattice holding the active chemical compounds. Overcharging will physically damage them as well, but not as suddenly.
 

Thread Starter

Devika B S

Joined Mar 8, 2017
144
The battery can easily perform a 10 to 15 minute demonstration of your boost converter circuit.

It should then be immediately recharged. Discharged LA batteries will quickly sulfate and become un-usable if not recharged promptly.

Just put a cheap multimeter on the battery to monitor voltage.
12.0 to 11.9 volts is about to 50% discharged. This is measured while loaded and delivering power to the circuit. The voltage will rebound when power drain stops and show a much higher voltage.

Don't be fooled, the battery is drained at this point and further discharge will physically damage the delicate lead lattice holding the active chemical compounds. Overcharging will physically damage them as well, but not as suddenly.
 

Alec_t

Joined Sep 17, 2013
14,280
You can buy a dedicated lead-acid battery charger. A good quality one will automatically regulate the charging current according to the state-of-charge of the battery.
Is this a school/college project?
 

Thread Starter

Devika B S

Joined Mar 8, 2017
144
You can buy a dedicated lead-acid battery charger. A good quality one will automatically regulate the charging current according to the state-of-charge of the battery.
Is this a school/college project?
Yes it is a college project. Unfortunately, the chargers available online for lead acid batteries are 12V, 7.5 Ah or 12V, 5Ah. No charger is available for 12V, 1.2 Ah :(
 
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Kermit2

Joined Feb 5, 2010
4,162
Poorly regulated charging is not good for the battery

That being said...

It will reduce the usable lifetime of the battery. Do you expect to use this battery more than 50 to 100 times?
IF long life usefulness is not an issue then almost any SMALL battery charger will be sufficient for the short term life span of this small battery

LA batteries are rugged little performance machines. Treat them badly and they don't last as long as they could, b u t they will perform very well if recharged fully if improperly. You can trust it will give you at least 50 to 100 recharges and show no sign of trouble. Manufacturers occasionally make a bad one so this is NOT a guarantee but a general rule.
 
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MrChips

Joined Oct 2, 2009
30,701
Yes it is a college project. Unfortunately, the chargers available online for lead acid batteries are 12V, 7.5 Ah or 12V, 5Ah. No charger is available for 12V, 1.2 Ah :(
I use a 12VDC 1A cheap wallwart to charge my 12V 7Ah SLAB.
You can use it directly or you can build this 12V battery charger that outputs about 14.5V




The trick is to unplug the charger once the battery is fully charged. Avoid overcharging the battery. If the battery starts getting hot, it is time to stop charging.

This is a what a SLAB looks like when damaged from being overcharged.




Charging instructions as printed on the side of the battery:

Step 1: Constant current charge at 1.5-2A
Step 2: Constant voltage charge at 14.7-14.9V
Step 3: Float charge at 13.7-13.9V
 

ErnieM

Joined Apr 24, 2011
8,377
By high gain converter 12 to 48 do you mean this is a boost converter?

If so, your load on the 48 volts is around 80 ohms to get 0.6 A out for 48 x 0.6 = 28.8 watts, which has the 2.4 amp draw on the input. The actual load will be slightly larger in resistance as the converter has losses itself. Ignore the posts here that say you should put something else besides your unit on the battery, they do not understand your project.

Lead acid batteries are not the fussiest things in the world to charge. Using your car as a charger will work, as will a lab bench supply: current limit this to around 60 mA and set the voltage to 13.6 (someone please check me there) and connect directly to the battery.
 

Alec_t

Joined Sep 17, 2013
14,280
Unfortunately, the chargers available online for lead acid batteries are 12V, 7.5 Ah or 12V, 5Ah. No charger is available for 12V, 1.2 Ah
You still seem to be having a problem distinguishing Amps from Ampere-hours. Battery chargers are not rated in Ampere-hours (Ah), they are rated in Amps (A). That rating indicates the maximum current that they can provide safely. Either charger could in theory charge your 12V 1.2Ah battery (which itself will probably have a label indicating its maximum safe charging current). Your battery may not be able to be charged at more than 0.25A, for example; the label will tell you.
 
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Thread Starter

Devika B S

Joined Mar 8, 2017
144
I have redesigned the entire converter (by changing load and by including a basic input filter) in such a manner that the converter draws only 1.05A power from the battery. Now I can safely use my battery I suppose.
 

Thread Starter

Devika B S

Joined Mar 8, 2017
144
By high gain converter 12 to 48 do you mean this is a boost converter?

If so, your load on the 48 volts is around 80 ohms to get 0.6 A out for 48 x 0.6 = 28.8 watts, which has the 2.4 amp draw on the input. The actual load will be slightly larger in resistance as the converter has losses itself. Ignore the posts here that say you should put something else besides your unit on the battery, they do not understand your project.

Lead acid batteries are not the fussiest things in the world to charge. Using your car as a charger will work, as will a lab bench supply: current limit this to around 60 mA and set the voltage to 13.6 (someone please check me there) and connect directly to the battery.
Yes boost converter and I am expected to charge the lead acid battery from a solar panel.
 

ErnieM

Joined Apr 24, 2011
8,377
Charging a lead acid battery from a solar is actually quite simple when the system is balanced. Just get a solar panel with a low output, say 100 mA max, and connect it thru a diode to the battery. The diode may already be in the panel too.

We do this on a lighthouse I volunteer at charging two deep cycle marine batteries directly off about 100 watts from the panels. No monitor, no limited, nothin. They chug along for several years like this
 

Thread Starter

Devika B S

Joined Mar 8, 2017
144
Charging a lead acid battery from a solar is actually quite simple when the system is balanced. Just get a solar panel with a low output, say 100 mA max, and connect it thru a diode to the battery. The diode may already be in the panel too.

We do this on a lighthouse I volunteer at charging two deep cycle marine batteries directly off about 100 watts from the panels. No monitor, no limited, nothin. They chug along for several years like this
Well, I am planning to use a 12V, 20 W panel to charge it. So it means 1.6A at best (like at MPPT). I am not using an MPPT solar charger. So the output current would be even lower. But wouldn't a 100mA output take hours to charge a 1.2 Ah lead acid battery? I mean isn't the time also important?
 

Thread Starter

Devika B S

Joined Mar 8, 2017
144
Poorly regulated charging is not good for the battery

That being said...

It will reduce the usable lifetime of the battery. Do you expect to use this battery more than 50 to 100 times?
IF long life usefulness is not an issue then almost any SMALL battery charger will be sufficient for the short term life span of this small battery

LA batteries are rugged little performance machines. Treat them badly and they don't last as long as they could, b u t they will perform very well if recharged fully if improperly. You can trust it will give you at least 50 to 100 recharges and show no sign of trouble. Manufacturers occasionally make a bad one so this is NOT a guarantee but a general rule.
 

Thread Starter

Devika B S

Joined Mar 8, 2017
144
Poorly regulated charging is not good for the battery

That being said...

It will reduce the usable lifetime of the battery. Do you expect to use this battery more than 50 to 100 times?
IF long life usefulness is not an issue then almost any SMALL battery charger will be sufficient for the short term life span of this small battery

LA batteries are rugged little performance machines. Treat them badly and they don't last as long as they could, b u t they will perform very well if recharged fully if improperly. You can trust it will give you at least 50 to 100 recharges and show no sign of trouble. Manufacturers occasionally make a bad one so this is NOT a guarantee but a general rule.
Well I would probably use the battery half an hour a day for about 15 to 20 days. Plus now I need just 1.02 (or 1.05) Amperes after redesigning the converter.
 

Thread Starter

Devika B S

Joined Mar 8, 2017
144
I use a 12VDC 1A cheap wallwart to charge my 12V 7Ah SLAB.
You can use it directly or you can build this 12V battery charger that outputs about 14.5V




The trick is to unplug the charger once the battery is fully charged. Avoid overcharging the battery. If the battery starts getting hot, it is time to stop charging.
I will definitely try building this charger.
 

ErnieM

Joined Apr 24, 2011
8,377
If you want a quick charge you need a charge controller. Trickle charging takes much less attention.
In the lighthouse system I mentioned we're only pumping a max of 7 or 8 amps into batteries rated for 200 AH. That keeps us topped off for the few days we actually load the system outside of a few spotlight every night.
The USCG has a separate very sophisticated system to keep their batteries charged to run the light itself. We just use ours for some housekeeping when we are there a few days a year.
 
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