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ice
04-29-2005, 08:31 AM
Most of u know the chargers that come with emergency lights..
which use "Sealed Lead Acid"[SLA] batteries

I have a query...

suppose the charger is built for a 6V ,1000mA SLA,
can i use it for charging a 12V,1000mA SLA?
or would it charge up to 6V at the most?

-ice

vikas
04-29-2005, 03:29 PM
Well i dont think so . Most chargers use the batery voltage level to determine the amount of charge and vary current accordingly . So a 6v charger will see that the battery is already charged and it does not need any further to recharge the system .. So no charging will occur ( Correct me if im wrong ) .

jack
04-30-2005, 12:08 PM
Well depends upon extent to which battery was discharged. If battery voltage falls below 6volts, your charger will charge it upto to 6volts and soon when the battery gains enough potential, charging current is almost negligible. So no more charging beyond this.

ice
04-30-2005, 07:20 PM
Thanks guys..

subot_robot
04-30-2005, 11:11 PM
Hi,
I am looking for 6v 4.5A sealed lead acid battery charger circuit. Have any one of u built one? Please give the circuit of the charger . I am using 2 6v 4.5A sealed lead acid battery for my robot and i need a charger to charge it.
Is there any commercially available charger for 6v 4.5A SLA battery. If yes, how much it may cost?
Thanks

Subot_robot

jack
05-01-2005, 01:17 PM
You can make your own charger by using LM317 voltage regulator. Mount it on proper heat sink, and it will give suffice current to charge your battery. Voltage should be around 7.2 - 7.5Volts, read the datasheet to calculate the value to resistance to get this voltage.

vikas
05-01-2005, 03:34 PM
yep lm317 will be the simplest and best one to start with .

subot_robot
05-01-2005, 10:46 PM
Thank u jack and vikas,
i'll soon study lm317 datasheet and try to build a charger for 6v, 4.5A battery.
Will i be able to run four 12v 1A motor from two 6v 4.5A battery connected in series? And how long the battery may last with this load?

subot_robot

happy_99
05-02-2005, 12:32 AM
Will i be able to run four 12v 1A motor from two 6v 4.5A battery connected in series? And how long the battery may last with this load?

From net

Amp-Hour. A battery capacity rating that equals the achievable product of the current drain and the time duration of that drain. The greater the AH rating, the longer the operating battery life. For a known current drain requirement, dividing the amp-hour rating by that drain yields the operating time duration of the battery supply.

The 4 motors 'll be drawing a total of 4A. And theoretically the battery should last for 1.125 hours or 67 minutes and 30 seconds (Time duration=Ah rating/Current drain ie, 4.5/4=1.125) But practically it 'll be something less then the theoretical value. This's because

1. The printed value may not be the actual Ah rating
2. Losses
3. Motor 'll be drawing more current than the rated current

Regds

happy_99

subot_robot
05-02-2005, 11:50 PM
From the link provided by happy 99

a 1Ah battery cannot supply 1 amp for an hour. It will probably explode if you tried. It will probably supply a third of an amp for 3 hours however and not suffer significant damage.

Does that imply that i should not try to run the motors with total loading of 12v 4A from 12v 4.5A sealed lead acid battery configuration? What configuration is safe to use? Should i use four 6v 4.5A SLA batteries connected in series and parallel configuration resulting in 12v 9A or should i go for single 12v 7.5A SLA battery. weight of the battery is one of the main issue for my robot. Which choice will be lighter.
It is sufficient even if i get 12v 4A for half an hour from 12v 4.5A configuration. Please guide me in this regard. Have any of u used SLA batteries for the robots?

Thanks

Subot_robot

happy_99
05-03-2005, 04:49 PM
Hi subot_robot

Sealed-Lead-Acid batteries can deliver a wide range of current up to many times their capacity.

The AH rating given on the battery is usually 20hr rating. A 60Ah battery means it's able to deliver 3A (60/20) continuous for 20hrs. But if u draw a higher current, say 6A, then the battery life will be lower than the theoretical expected value of 10 hours. The life is further decreased if u draw even more current, say 12A.

In your case, you may use a single 12V 4.5Ah SLA battery. Since the motors draw 4A, the battery life will be around 30-35 minutes. Another alternative is to use a 12V 7Ah (wt. 2.6kg) battery which lasts for abt 60 minutes, which I think will be the best suited in your case.

I've used Exide Chloride Dragon (6V 4Ah) in my project. It provides 4-6A for abt 20min. I'm using it for the last 4 months without any problem, so I think you woun't find any problem with your idea.

Check the Exide website for the details of Chloride and EP Series batteries (Chk 20hr and 1hr ratings)

http://www.exideindustries.com/eil/ind_bat/Chloride%20Safe.htm
http://www.exideindustries.com/eil/ind_bat/ep%20series.htm

Regds

happy_99

jack
05-03-2005, 05:37 PM
I believe it should work. Consider a 500VA UPS, which usually have 12V/7AH battery, and gets flat after a backup of about 20min. It means current should be around 7/.33 = 21Amps.

My today’s experience…….
Luckily today I was replacing my old UPS battery with a new one. So I thought, why not measure the current with my 10Amps DMM. When I switched by PC on backup, current was exceeding 9.1 – 9.8 Amps to come out of the range of my DMM, wires were also hot enough. And within a second UPS tripped automatically, as if it was able to sense that the wires were not thick to carry that much current, or whatsoever the reason maybe.

Final clue….
Safety fuses for battery are rated at 35Amps in my UPS, so it clearly indicates that any current less than this should come in safe limit.

happy_99
05-03-2005, 11:32 PM
That was a nice example jack :-)

BTW which battery are u using jack? what is it's price?

Regds

happy_99

subot_robot
05-04-2005, 08:53 AM
Thank u roboticists happy_99 and jack, I am really grateful for ur detailed guidance when i needed them the most. i have to power my robot with the batteries in another 2 days. Right now i am running it off the 12v 5A power supply. I think i will go for 6v 4.5A battery. Does the company of the battery matter? How much does Exide chloride dragon cost? Do u get 6v across the battery or load when u r driving 4A or higher load?

Now another task ahead of me is to build charger circuit for 6v 4.5A batteries. happy_99, how do u charge ur batteries? Did u build ur own charger or bought one? Which choice do u recommend?

Thank u all

Subot_robot

jack
05-04-2005, 01:49 PM
That was a nice example jack :-)

BTW which battery are u using jack? what is it's price?

Regds

happy_99

Hi happy_99,

It is Exide Chloride Safepower, I got it for Rs.500.

happy_99
05-04-2005, 11:50 PM
Does the company of the battery matter? How much does Exide chloride dragon cost? Do u get 6v across the battery or load when u r driving 4A or higher load?

How do u charge ur batteries? Did u build ur own charger or bought one? Which choice do u recommend?Subot_robot

Yes offcourse the company matters. There are a lot of fake ones too, which claims 4Ah and you'll get only 2/3rd of it. I'm a customer of EXIDE :-) and there are a lot of other good ones too. The voltage, I've not checked it actually (and unfortunately my multimeter is dead now :-() About the price I'll get it tomorrow (I don't remember exactly as one of my friend brought it for me)

The charger is simple and crude. Charging it using my 6v 500mA adapter for abt 12hrs. Anyway I don't recommend that, build one yourself. You may find a lot of designes from google. You can build one around LM317.

Regds

happy_99

ice
05-05-2005, 11:13 AM
happy_99
..are the exide batts "sealed" lead acid batts?
or r they the ones which vehiles use,the small ones?

also how many charge cycles before your battery went dead,a rough idea?

-ice

jack
05-05-2005, 03:28 PM
happy_99
..are the exide batts "sealed" lead acid batts?
or r they the ones which vehiles use,the small ones?

-ice

Hi ice,

Yes, they are sealed lead acid battery. Not the one which are used in vehicle, in which you have to pour distilled water!

jack
05-05-2005, 03:44 PM
happy_99

also how many charge cycles before your battery went dead,a rough idea?

-ice

Are you asking me?? Anyway my old UPS battery was Panasonic and was about 5years old. Can't say much about number charge cycle, but should be many hundreds! BTW, this battery is still working fine for small loads.

ice
05-05-2005, 05:31 PM
Thanks

ok..supposing i got an SLA...it all boils down to the charger..

..

subot_robot
05-05-2005, 06:21 PM
Can I charge exide chloride dragon 6v 4.5A battery from the emergency light which has a 6v 4.5A battery? By the way what is the difference between exide chloride dragon and ordinary SLA battery?

thanks

Subot_robot

jack
05-05-2005, 11:50 PM
Thanks

ok..supposing i got an SLA...it all boils down to the charger..

..

I'm using this http://www.uoguelph.ca/~antoon/circ/vps.htm as a charger, its working fine for me. But remember you will need a real big heat sink to get 1.5amps current. If you still need higher current try using LM350, which is similar to LM317, except the maximum current rating is 3amps. I don't know about any readymade charger.

jack
05-05-2005, 11:55 PM
Can I charge exide chloride dragon 6v 4.5A battery from the emergency light which has a 6v 4.5A battery?

thanks

Subot_robot

Yes, you can, until unless specifications are not violated.

happy_99
05-06-2005, 01:46 AM
happy_99
..are the exide batts "sealed" lead acid batts?
or r they the ones which vehiles use,the small ones?
also how many charge cycles before your battery went dead,a rough idea?
-ice

Jack has already answered it, and a few more lines from me. The chloride series batteries from EXIDE comes maninly for use in inverters and emergency lightings. I'm using one (CHLORIDE Dragon - 6V 4Ah) for last 4-5 months without any prob (ice, it's still alive :-)) . It cost you abt Rs.250/-(not very sure)

Regds

happy_99

pkshima
05-06-2005, 10:47 AM
hi all,

I would rather suggest building a SLA charger using the L200 regulater which has current limiting as well which is important for most batteries.
You will read something like "Intial charging current less than : 0.39 A"
or something.

You will find a good and simple way to build that at

http://www.myra-simon.com/bike/charger.html

I built in and it works great for me.
The L200 is available at approx Rs 60 at shop 462, lajpat rai market.
Its also available at shop rs 463 but he will charge rs 80 simply because he loves fleecing people.

ice
05-06-2005, 10:56 AM
Thanks for ur replies...

im looking out for 2 12Volt batts..current/voltage rating depends on price and total weight..because all this would be going onm a mobile robot..

05-06-2005, 08:21 PM
hi all,

I would rather suggest building a SLA charger using the L200 regulater which has current limiting as well which is important for most batteries.
You will read something like "Intial charging current less than : 0.39 A"
or something.

You will find a good and simple way to build that at

http://www.myra-simon.com/bike/charger.html

loves fleecing people.

Nice suggestion. Maximum charging is quite an important issue, but most of the time is gets limited by the transformer current rating and thus falls into safe area.

jack
05-06-2005, 08:31 PM

happy_99
08-05-2005, 12:47 AM
Here's a very good circit using LM317/LM350/LM200. It's well documented. The charger is current limited voltage regulated and is best suited for lead-acid batteries.

http://www.vt52.com/diy/myprojects/other/charger/charger.htm

A document on Using ans Charging SLA Batteries