Author Topic: Can the lab power supply be changed to a AGM battery charger?  (Read 5479 times)

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Offline djsb

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Can the lab power supply be changed to a AGM battery charger?
« on: January 03, 2012, 01:25:00 pm »
I am having problems charging up my motorcycles Odyssey PC310 AGM (absorbed glass mat) lead acid battery.
I have bought a charger that was meant to be able to charge this battery when it is over discharged (below 10v OCV) but it has been damaged by the high current that it needs to supply (about 6 Amps). This battery has an internal resistance of 10's of milliOhms so is very nearly a short circuit.
Can Dave's lab power supply be modified so that it becomes a programmable lead acid battery charger?
Now that would be REALLY useful for me at the moment.
Any thoughts.

David.

A relevant page from the batteries technical manual is attached.
« Last Edit: January 03, 2012, 02:25:41 pm by djsb »
David
Hertfordshire,UK
 University Electronics Technician, London PIC,CCS C,Arduino,Kicad, Altium Designer,LPKF S103,S62 Operator, Electronics instructor.  http://debuggingrules.com/ Give a man a fish and you feed him for a day. Teach a man to fish and you feed him for a lifetime.
 

Offline Lightages

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Re: Can the lab power supply be changed to a AGM battery charger?
« Reply #1 on: January 03, 2012, 02:18:11 pm »
Get any dumb low quality battery charger that is available at any automotive shop and use it to get the battery up to the bulk charge voltage or close. Just watch the voltage with a meter and check it every 5 minutes. When the batteries get to absorb voltage, take it off the dumb charger. Then use a regulated power supply to hold the voltage at the recommended absorb voltage for a couple of hours. The regulated power supply might need to supply some high current for a while still until the current starts to drop.

Severely discharged lead acid batteries will not recover to full capacity and might not recover at all.

And yes, Dave's power supply with its CPU and sensing could be programmed to be a fully automated power supply charger.
« Last Edit: January 03, 2012, 02:29:41 pm by Lightages »
 

Offline djsb

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Re: Can the lab power supply be changed to a AGM battery charger?
« Reply #2 on: January 03, 2012, 02:22:09 pm »
Here is the full manual for anyone interested.
David
Hertfordshire,UK
 University Electronics Technician, London PIC,CCS C,Arduino,Kicad, Altium Designer,LPKF S103,S62 Operator, Electronics instructor.  http://debuggingrules.com/ Give a man a fish and you feed him for a day. Teach a man to fish and you feed him for a lifetime.
 

Online IanB

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Re: Can the lab power supply be changed to a AGM battery charger?
« Reply #3 on: January 03, 2012, 02:38:33 pm »
An over discharged lead acid battery is very likely ruined. Even if you resuscitate it, it is unlikely to achieve full performance again. For instance on two occasions where I have accidentally left the lights on in my car and needed a jump start, I have needed a new battery very soon after. Lead acid batteries really don't like being discharged.
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Online IanB

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Re: Can the lab power supply be changed to a AGM battery charger?
« Reply #4 on: January 03, 2012, 02:43:56 pm »
By the way, lead acid batteries need to be charged using a CC/CV protocol similar to lithium ion batteries. The low internal resistance will not matter to a proper quality charger as the constant current will restrict the charge current until the voltage reaches the required level for the constant voltage phase to take over. You should be able to find a proper lead acid charging program in one of the R/C hobby chargers from a company like iMAX or Turnigy.
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Offline G7PSK

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Re: Can the lab power supply be changed to a AGM battery charger?
« Reply #5 on: January 05, 2012, 09:40:45 am »
The problem with over discharged lead acid batteries is the build up of lead sulfide, By pushing a high current through the cells you can blast the sulfide off the plates but the sulfur that went into making the sulfide came from somewhere and that somewhere is from the acid. What I have done in the past with traction batteries is replace the acid then charge the cells individually until they "milk" the electrolyte goes white with bubbles, then remove the acid wash out the cell with deionized water to remove the sludge and the replace the acid with fresh. You cannot do this with gel,absorbed or sealed units, it is also not worth the cost or effort on small size batteries and the money spent on buying a battery charger to try and fix the problem is better spent on a new battery.
 

Offline kaz911

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Re: Can the lab power supply be changed to a AGM battery charger?
« Reply #6 on: January 05, 2012, 10:21:38 am »
The problem with over discharged lead acid batteries is the build up of lead sulfide, By pushing a high current through the cells you can blast the sulfide off the plates but the sulfur that went into making the sulfide came from somewhere and that somewhere is from the acid. What I have done in the past with traction batteries is replace the acid then charge the cells individually until they "milk" the electrolyte goes white with bubbles, then remove the acid wash out the cell with deionized water to remove the sludge and the replace the acid with fresh. You cannot do this with gel,absorbed or sealed units, it is also not worth the cost or effort on small size batteries and the money spent on buying a battery charger to try and fix the problem is better spent on a new battery.

You can blast AGM batteries as well. Most AGM chargers does that once pr. month or thereabouts. Normally you say AGM batteries can be charged at their AH rating divided by 8 (so 100 Ah battery = 12 amp charge) - Lifeline batteries are different - then can take Ah/4 - so 24 Amp for same battery max.

A "normal" 14.6 volt charge from a "standard" Led Acid "non smart"charger is actually quite equal to the "Blast charge"(Constant Voltage) you would get from smart charger once pr. month or on extreme low depleted batteries. So just use an old fashioned car charger to see if you can kick it back into life.  But if battery "measured" voltage after charge does not change or drops quick - one or more cells are dead.

Normal 3 stage charge is:
1. Charge with Cell Voltage of 2.35 (times number of cells)
2. When battery reach the charge voltage (2.35v x number of cells) switch to Constant Current at Charge Volt = 2.25-2.27 x number of cells) for 3-4 hours
3. Switch to 13.6 volt trickle charge

And then "smart chargers" have a "if battery was depleted a lot - or once pr. month"- continue "step one charge" for an extra 3-4 hours.

I would try to charge with a normal old car charger for 30 min - >  1 hour - and then check if battery voltage has increased (disconnect battery from charger and let it rest for 3-10 minutes before measuring) - if Voltage has increased - continue... if not - dead cells... and no way forward.
 

Offline djsb

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Re: Can the lab power supply be changed to a AGM battery charger?
« Reply #7 on: January 05, 2012, 11:17:18 am »
I think the battery is a dead parrot :(
I tried charging with my optimate and it reports that it's "weak". The OCV is around 10 volts and the battery will not hold any charge above that.
I think it's time for a new one.

David.
David
Hertfordshire,UK
 University Electronics Technician, London PIC,CCS C,Arduino,Kicad, Altium Designer,LPKF S103,S62 Operator, Electronics instructor.  http://debuggingrules.com/ Give a man a fish and you feed him for a day. Teach a man to fish and you feed him for a lifetime.
 


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