Charging batteries with a variable power supply
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 10th April 2007, 06:34 AM #1 jacquesl   diyAudio Member     Join Date: Feb 2005 Location: Lego Land Charging batteries with a variable power supply How to charge a normal lead acid car battery and an Absorbent glass mat 7ah battery I have a diode built into my power supply How can I build a charger that will maintain the battery for then needed, it’s like a UPS type Will it work if I use my 1.5A variable power supply and set the output to exactly 13.80 volt DC, will that charge my battery to 13.80 and maintain it without overcharging for a couple of years and without making gas builds ups In my test it’s a discharged battery and the power supply is set to 13,80V DC and if I connect the wires the voltage drop down to 13.40v and it charge at a rate of 0.20A, but why not 1A or 1,5A ?
leto
diyAudio Member

Join Date: Apr 2007
Re: Charging batteries with a variable power supply

Quote:
 Originally posted by jacquesl it charge at a rate of 0.20A, but why not 1A or 1,5A ?
Mainly because of battery overheating risks... I think !

 13th April 2007, 06:23 PM #3 Anthony C Smith   diyAudio Member   Join Date: Jun 2005 Location: Sunderland the best way to charge a SLA or Vrsla type battery is using a controlled impedance charger. sounds bad but in practice its a 317 regulator from nat semi or sgs. sgs has an app in the l317 data sheet on this, circuit is simple placing a .22 R resistor in serise with the output, with feed back poost resistor, output impedance is them RS (0.22)*Rf/Ri so real resistor is .22 R, apparent is much higher. see http://www.st.com/stonline/products/...2154/lm317.pdf figure 12 works for all batteries of the sla type I have tried, prevents boiling the battery. __________________ Anthony C Smith MAES MinstSCE -I think rain is wet so who am I to Judge-
 13th April 2007, 06:36 PM #4 jacquesl   diyAudio Member     Join Date: Feb 2005 Location: Lego Land Thanks man, it looks nice, I’ll try it out, I have some LM317 regulators, and in my datasheet from “Fairchild semiconductors” they don’t give some sweet examples from the LM317.
krokkenoster
diyAudio Member

Join Date: Mar 2012
Location: ISANDO GAUTENG
Charger

Quote:
 Originally Posted by jacquesl Thanks man, it looks nice, I’ll try it out, I have some LM317 regulators, and in my datasheet from “Fairchild semiconductors” they don’t give some sweet examples from the LM317.
I know that this is a thread of long ago but did you solve the low current output of your P.S.U.? I built a lot of chargers of this kind for lift trucks and all they were was a stabilized PSU with a current limiter to protect the poor transformer if the customer start to use the charger to drive the truck when the batteries were depleted
Your PSU "see" the battery as just another load.Do you have a 723 type I.C. ? Scrap it that is the worst I.C. on the market!!!!!!!!!! I eventually replaced it with a discrete circuit but I used small power transistors where a small transistor was specified (3amp vs.100mA) The extra expense of those power transistors paid for itself in reliability .

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