Battery 12Volt

[watzmann]

Hi All ,

i have a battery 12 VDC 7AH, i need to charge this battery but i don't have a 15 power supply ,

i'm going to buy a 15 volt transformer with a 1 or 2 A and use it , is it possible ...... or i'm wrong?

 

[HiTech]

1-2 amp charge current will do the job but it's much better if you can charge it at a lower charge current and slower rate than a fast one. The battery will provide longer run times on a slow charge versus a hefty 2 amp one. You'll also have to monitor the battery's temperature as that is what ruins them most often- overheating. There are many circuits on the net that you can build for a controlled charger for a 12v battery. You can also buy commercially made ones too.

 

[ericgibbs]

Hi All ,

i have a battery 12 VDC 7AH, i need to charge this battery but i don't have a 15 power supply ,

i'm going to buy a 15 volt transformer with a 1 or 2 A and use it , is it possible ...... or i'm wrong?

hi,
Is it a sealed lead acid battery SLA ?, if Yes, they are not charged with a 15Vdc supply.

 

[HarveyH42]

https://www.allelectronics.com/cgi-...2-STAGE_CHARGER_FOR_LEAD-ACID_BATTERIES_.html

I've been using this one with a 12V 7 AH SLA, been working fine. Unless you already have most of the parts, probably won't beat the price...

 

[watzmann]

my battery is SLA one , and it's manual says cahrged at 15VDC 2 A.

i have another solution , i have a power supply provide 40 volts so i think i can limit that using LM7815 to be just 15 VDC

 

[ericgibbs]

my battery is SLA one , and it's manual says cahrged at 15VDC 2 A.

i have another solution , i have a power supply provide 40 volts so i think i can limit that using LM7815 to be just 15 VDC

hi watzman,
Unless you have designed a 'smart' charger I would recommend that you dont use a constant 15V charge voltage?
The one that Harvey has posted is a 'smart' charger.

Use 14V for cyclic use and 13.8V for float use.

Have you calculated the heat generation in the 7815 with a +40Vinp and a 15Vout at 2Amps??? [its 50Watts]

Check the datasheet!

 

[watzmann]

i'll look for this charger at RadioShack Stores

 

[HiTech]

hi,
Is it a sealed lead acid battery SLA ?, if Yes, they are not charged with a 15Vdc supply.

Automotive charging systems operate between 13 & 15 volts, typically 13.8-14.2 but 15v isn't too uncommon. Being a SLA type battery, he would have to manually monitor the charging process unless he opts for the smart charger as mentioned. Manual monitoring is a crap shoot since sooner or later one will get distracted and leave it heat up. It's not the preferred method to prolonging battery life.

 

[watzmann]

i have found an old Ac power Adabter provide 15 Volt with 530mA.....i tried to charge my battery using the powersuppy but !!!!!

it successfullay charged my battery to 12.1 but in in 5 minutes !!!!!!

why that happened?

 

[audioguru]

The 15V power supply is being shorted down to 12.1V and its output current is a few Amps.

The power supply has a max allowed output current of 530mA. It doesn't limit the current and you are overloading it. It might overheat and catch on fire or an internal fuse will blow and make it worthless.

 

[watzmann]

o.k , i have anoteher old one provide 16 Volt and 900mA, can i use this one ?

 

[audioguru]

How are you going to limit the voltage to 15V?
How are you going to limit the current to the 900mA max allowed from the power supply?
How are you going to detect when the battery is fully charged then switch it off so it doesn't overcharge?

 

[chemelec]

Buy yourself a 10.5 VAC transformer, rated at 2 to 3 amps.
Put a 5 amp bridge rectifier on the output. Also a 1000 or 2000 uF filter cap.

Now connect it to your battery to charge it.

This will charge it to about 14.7 volts.
It will start out at about a 2 amp charging rate and will automaticaly taper off to a Trickle charge as the battery charges up.

Gary

How are you going to limit the voltage to 15V?
How are you going to limit the current to the 900mA max allowed from the power supply?
How are you going to detect when the battery is fully charged then switch it off so it doesn't overcharge?

 

[watzmann]

limiting the voltage to 15 V by using LM338

limiting the current to max 900mA ..... this power supply max output is 900mA

i'll detect that my battery is full charged by using AVO meter each 15 minutes .

Finally i decided to buy a Tonger avery small one is sufficent for my robot .

 

[chemelec]

I would recommend 14.5 Volts, NOT 15 Volts.

Typical charge time will be at least, overnight for a Full Charge.

A Lead acid battery starts out drawing Maximum Current, but as it charges up, the Current goes Down.
The Final Charge rate is only a few Milliamps.

And you Can't charge a lead acid battery with a Constant Current. A continuous 900 mA will Damage the Battery.
********************************************

limiting the voltage to 15 V by using LM338

limiting the current to max 900mA ..... this power supply max output is 900mA

i'll detect that my battery is full charged by using AVO meter each 15 minutes .

Finally i decided to buy a Tonger avery small one is sufficent for my robot .

 

[watzmann]

please chemelec could recomend me a suitable charger i can buy.....because i'm actually i'm in trouble now as i can't charge my battery using power supply and then damage it and in the same time i can't use it well.

so tell me if i can build a good ghrager bymyself , or where can i buy a suitable one .

 

[HarveyH42]

http://www.talkingelectronics.com/projects/BatteryCharger-12vSLA/BatteryCharger-12vSLA.html

This one looks simple to build, parts aren't exotic...

 

[chemelec]

please chemelec could recomend me a suitable charger i can buy.....because i'm actually i'm in trouble now as i can't charge my battery using power supply and then damage it and in the same time i can't use it well.

so tell me if i can build a good ghrager bymyself , or where can i buy a suitable one .

Sorry, I don't know of any chargers like this that you can buy.
And it would be Too Expensive for me to build you one and send it to you.
But I could give you a Simple Schematic of the one I previously described to you.

Take care....Gary

**broken link removed**

This one looks simple to build, parts aren't exotic... .

This will work, but its a pretty low charge current.
Also might be difficult to get these parts in Egypt, although there was a fairly good supplier in Cario, when I went there last year.
Sorry, don't remember the name of it.

 

[mamun2a]

u talk a lot but got know sol.
as far i know from AAA bat recommends, dats charge it with same v and 1/10 of the current. but u all are far away from there

though i also know nothing about it...

 

[HiTech]

Black & Decker sells a Smart charger for as little as $33 US.
**broken link removed**

It's actually manufactured by Vector Inc.. I have one of the upper models and it wirks like a charm on SLA and other LA batteries, including gel cell types.

The Battery Tender is another good charger and is avaialable in international configurations as well as US..
**broken link removed**