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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
Posted to sci.electronics.repair,alt.engineering.electrical,sci.chem.electrochem
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Evaluating used gel-cell batteries?
Gell-cell batteries in UPS's: other than loading with a known load and timing
how long it takes to drain the battery, is there a simple way to measure the health of a gel-cell? Impedance? Thanks, S. |
#2
Posted to sci.electronics.repair,alt.engineering.electrical,sci.chem.electrochem
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Evaluating used gel-cell batteries?
I will be interested to read the direct answer to your question.
A slightly different observation is that peeking inside the cells after removing plastic cover plate and the individual caps [taking precautions for acid spills] has often revealed very healthy looking plates that have simply dried out. In that case, I have injected 10 cc's or so of deionized or distilled water and recharged with an automobile charger. The SLA cells have then delivered many months of good service in UPS useage. Little luck reviving the cells when inspection shows significant "bloom" spanning the plates. "SparkyGuy" wrote in message obal.net... Gell-cell batteries in UPS's: other than loading with a known load and timing how long it takes to drain the battery, is there a simple way to measure the health of a gel-cell? Impedance? Thanks, S. |
#3
Posted to sci.electronics.repair,alt.engineering.electrical,sci.chem.electrochem
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Evaluating used gel-cell batteries?
SparkyGuy wrote:
Gell-cell batteries in UPS's: other than loading with a known load and timing how long it takes to drain the battery, is there a simple way to measure the health of a gel-cell? Impedance? Thanks, S. No. Testing tells all. |
#4
Posted to sci.electronics.repair,alt.engineering.electrical,sci.chem.electrochem
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Evaluating used gel-cell batteries?
On Wed, 8 Jul 2009 17:13:32 -0700, SparkyGuy
wrote: Gell-cell batteries in UPS's: other than loading with a known load and timing how long it takes to drain the battery, is there a simple way to measure the health of a gel-cell? Impedance? 1. Charge the battery with the UPS or whatever. Attach a 12V tail lamp. Time how long it takes before the bulb goes dim. Compare with a known good battery. Not every analytical, but good enough. 2. http://www.westmountainradio.com/CBA_ham.htm I have one of these and use it to characterize cell phone LiPo batteries and some gel cells. The method is the same a before. Charge the battery as best you can. Use the CBA II to discharge the battery. However, this time, you get a nifty discharge graph. As before, compare with a known good battery. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
#5
Posted to sci.electronics.repair,alt.engineering.electrical,sci.chem.electrochem
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Evaluating used gel-cell batteries?
In article .net,
SparkyGuy wrote: Gell-cell batteries in UPS's: other than loading with a known load and timing how long it takes to drain the battery, is there a simple way to measure the health of a gel-cell? Impedance? A good auto battery seller should have an electronic tester. These give all the parameters of the battery including actual amp/hour capacity. -- *I'm not being rude. You're just insignificant Dave Plowman London SW To e-mail, change noise into sound. |
#6
Posted to sci.electronics.repair,alt.engineering.electrical,sci.chem.electrochem
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Evaluating used gel-cell batteries?
"SparkyGuy" wrote in message obal.net... Gell-cell batteries in UPS's: other than loading with a known load and timing how long it takes to drain the battery, is there a simple way to measure the health of a gel-cell? Impedance? Yes, you are already at the door of the solution. Charge it up and load it significantly and measure the output voltage (which really sags under heavy load as the battery ages, due to its increased internal impedance). In the automotive realm, it was once called "cranking voltage." The ignition system was disabled so the battery voltage output could be measured while the starter motor was running. Now, decent garages have test gear that does a high current load test without all the muss and fuss. |
#7
Posted to sci.electronics.repair,alt.engineering.electrical,sci.chem.electrochem
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Evaluating used gel-cell batteries?
1. *Charge the battery with the UPS or whatever. *Attach a 12V tail
lamp. *Time how long it takes before the bulb goes dim. *Compare with a known good battery. *Not every analytical, but good enough. Very careful not to reverse charge a cell. Do not discarge further than 10V. If you are watching the voltage when the first cell becomes completely discharged you can see a quick voltage drop by 2V, continuing the discharge would ruin the battery. |
#8
Posted to sci.electronics.repair,alt.engineering.electrical,sci.chem.electrochem
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Evaluating used gel-cell batteries?
"Jeroni Paul" wrote in message
... 1. Charge the battery with the UPS or whatever. Attach a 12V tail lamp. Time how long it takes before the bulb goes dim. Compare with a known good battery. Not every analytical, but good enough. If you load at 20% of the Amp Hour rating until the voltage falls to 11.9v you will have a quick test that is meaningful for go-no go test comparison with a known good battery. Another is to note the ability of the battery to taper off to 0 amps when charging to 14.4 volts. If the battery keeps pulling current it will likely self-discharge. This is valid for duali purpose automotive, RV and marine batteries, but a real deep cycle will act differently and start boiling with high voltages.and keep drawing current so beware. Very careful not to reverse charge a cell. Do not discarge further than 10V. If you are watching the voltage when the first cell becomes completely discharged you can see a quick voltage drop by 2V, continuing the discharge would ruin the battery. |
#9
Posted to sci.electronics.repair,alt.engineering.electrical,sci.chem.electrochem
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Evaluating used gel-cell batteries?
SparkyGuy wrote:
Gell-cell batteries in UPS's: other than loading with a known load and timing how long it takes to drain the battery, is there a simple way to measure the health of a gel-cell? Impedance? Thanks, S. How about ESR? Bob Parker's Blue ESR meter will give you some static clues as to the condition of batteries if compared to known good ones... http://www.flippers.com/esrkthnt.html (near the bottom of the page) John :-#)# -- (Please post followups or tech inquiries to the newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out." |
#10
Posted to sci.electronics.repair,alt.engineering.electrical,sci.chem.electrochem
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Evaluating used gel-cell batteries?
"SparkyGuy" wrote in message obal.net... Gell-cell batteries in UPS's: other than loading with a known load and timing how long it takes to drain the battery, is there a simple way to measure the health of a gel-cell? Impedance? Thanks, S. One easy way to tell if the battery is any good is "how many years has it been in service ?" Most gell cell batteries have a maximum life of 5 years, this actually varies from as low as 3 years to 5 years life. If it's at three year battery and the UPS is not preforming as it should be, replace the batteries. Also try to get the same brand of battery that's in there for replacement. There is alot of third party batteries out there that claim to be just as good as the big name brands, but there not. I like Panasonic and CSB brands, they are a little bit more pricey, but worth it. For discharging, look for the AmpHour rating on the battery. If you put a load on the battery that draws about that much current, you at "1 C" which means that the battery should supply that current for 1 hour before it is discharged. For testing batteries, don't use more that that amount of current because the AH rating falls off above it, and use the 10 volt rule that a previous poster wrote is a good guide. Shaun |
#11
Posted to sci.electronics.repair,alt.engineering.electrical,sci.chem.electrochem
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Evaluating used gel-cell batteries?
On Jul 10, 1:46*pm, John Robertson wrote:
SparkyGuy wrote: Gell-cell batteries in UPS's: other than loading with a known load and timing how long it takes to drain the battery, is there a simple way to measure the health of a gel-cell? Impedance? Thanks, S. How about ESR? Bob Parker's Blue ESR meter will give you some static clues as to the condition of batteries if compared to known good ones... http://www.flippers.com/esrkthnt.html(near the bottom of the page) John :-#)# -- * * (Please post followups or tech inquiries to the newsgroup) * John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 * Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) * * * * * * * * * * *www.flippers.com * * * *"Old pinballers never die, they just flip out." If you put an ESR meter accross batteries you will blow the meter!!! ESR is to be measured with no active voltage! |
#12
Posted to sci.electronics.repair,alt.engineering.electrical,sci.chem.electrochem
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Evaluating used gel-cell batteries?
On Jul 8, 8:13*pm, SparkyGuy wrote:
Gell-cell batteries in UPS's: other than loading with a known load and timing how long it takes to drain the battery, is there a simple way to measure the health of a gel-cell? Impedance? Thanks, S. The best test is to fully charge the battery, and then put a known resistive load accross it. The ideal load should be 25% of the amp hour rating of the battery. Time how long it takes for the battery voltage to drop 10% below its nominal voltage rating. A battery rated at 12.5 Volt nominal would be considered discharged at 11.36 volts. Fully charged with no load it should be putting out at least 13.8 to 14.5 Volts. For example, if a battery is rated at 12.5 Volts / 7.5 Amp hours, the test load should be rated to pull 1.87 Amps at 12.5 Volts. The resistance of the load should be 6.7 ohms. The power dissapation would be about 24 Watts. Therefore the resistor for the load should be rated at 6.7 ohms at 50 Watts. Always use double the calculated watts for the resistor rating to prevent the resistor from over heating. There are commercialy made battery load testers that have high wattage ratings to fit the required battery test range, and they have adjustable load resistance. Most of these testers have a load test that can quickly measure the internal resistance of the battery under test. (The battery internal resistance test is sort of hard on the battery). With the 6.7 ohm / 50 Watt resistor accross the battery, it should take 4 hours for the battery to reach the 11.36 Volt level. The recomended maximum charge current for a 7.5 Amp hour battery would normaly be 1.87 Amps, unless the battery is to be quick charged. This value is 25% of the rated Amp hours of the battery. For quick charging the manufacture spec must be considered. Normally to exend the life span of the battery most manufactures use 50% of the 4C factor. This is why the battery would take 8 hours to fully charge. After the battery is charged, the charger will go to the float mode. The float charge would be 1/10 of the 4C factor which should be 187 ma in this case. The 4C factor is the 1/4 Amp hour rating of the battery. For testing purposes, you can use higher resistances. This can also give you an idea about the battery's condition, not as accurately. Batteries do not always behave exactly the same at different loads. Internal thermo factors, and the stability of its internal chemical reaction are factors to be considered. The older the battery the less stable its internal stability may be. At greater loads, a battery will more easily exibit any defects or deficiencies. As for the gell cells that are used in UPS's, from our experience we found that they are best to be changed during their third year. We found that after three years, they no longer give optimum performance. This is because when inside the UPS unit, there is some heat, and they battery is constantly charged. At times the UPS batteries are surge loaded at times. When these UPS's work in the battery mode, they generaly pull more than the long term recomended amount of power from the battery. UPS's are emergency devices, and the manufactures try to make them as economic as possible. Their weak point is usually the batteries. We have a battery change schedule for our clients which is every 2.5 years. This way we normally do not see any battery failures. Jerry G. |
#13
Posted to sci.electronics.repair,alt.engineering.electrical,sci.chem.electrochem
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Evaluating used gel-cell batteries?
Jerry G. wrote:
On Jul 10, 1:46 pm, John Robertson wrote: SparkyGuy wrote: Gell-cell batteries in UPS's: other than loading with a known load and timing how long it takes to drain the battery, is there a simple way to measure the health of a gel-cell? Impedance? Thanks, S. How about ESR? Bob Parker's Blue ESR meter will give you some static clues as to the condition of batteries if compared to known good ones... http://www.flippers.com/esrkthnt.html(near the bottom of the page) John :-#)# -- (Please post followups or tech inquiries to the newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out." If you put an ESR meter accross batteries you will blow the meter!!! ESR is to be measured with no active voltage! Not in this case - the Bob Parker ESR design can handle up to around 45VDC (input cap is rated at 50V) safely, but I have an 18V MOV on mine to help protect against higher charges. If you had looked at the link you would see the chart shows a few batteries with typical ESR values. I posted that years ago (a fellow in AU created it) hoping to get some interest in folks seeing if ESR would help show if batteries are failing and be able to monitor them as a result. A simple circuit that would start beeping when the batteries reach a certain ESR = time to test! John :-#)# -- (Please post followups or tech inquiries to the newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out." |
#14
Posted to sci.electronics.repair,alt.engineering.electrical,sci.chem.electrochem
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Evaluating used gel-cell batteries?
On Wed, 8 Jul 2009 18:50:11 -0700, John Keiser wrote
(in article ): I have injected 10 cc's or so of deionized or distilled water ... How? I presume you drilled? |
#15
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Evaluating used gel-cell batteries?
notme wrote:
On Wed, 8 Jul 2009 18:50:11 -0700, John Keiser wrote (in article ): I have injected 10 cc's or so of deionized or distilled water ... How? I presume you drilled? I've seen a number of gel-cell batteries with rubber vent caps under a plastic plate. It's fairly simple to pry them up and squirt a little water in, but I haven't had any luck with that fixing them. |
#16
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Evaluating used gel-cell batteries?
Charlie+ wrote:
On Sat, 25 Jul 2009 22:25:56 -0700, none ""karls\"@(none)" wrote: I've seen a number of gel-cell batteries with rubber vent caps under a plastic plate. It's fairly simple to pry them up and squirt a little water in, but I haven't had any luck with that fixing them. I do it when they are brand new - then every two years - then the gellcells last for a long time. I add 5ml when brand new to each cell, then approx 2ml at subsequent 2yr intervals. This is fine for batteries that dont move - you would have to be choosy doing it with batteries in very portable equipment that gets thrown around! No magic in the figures - that is what it took in my Yuasa batts to JUST cover the plates/pads with minimal layer of liquid. Quite how they dry out I dont understand - but they do - I set my float charges at 13.25v rather than the cram full voltage, the idea was to keep any float gassing off to the minimum. Charlie+ Thanks for the tip. I'll have to try that. Taking the charge voltage down from 13.8v to 13.25v sounds worthwhile too. Good thinking. Since the batteries are made with vents, It was obvious that they were venting something... You took the reasoning a step farther than I had. |
#17
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Evaluating used gel-cell batteries?
In article , none ""karls\"@(none)" wrote:
Charlie+ wrote: On Sat, 25 Jul 2009 22:25:56 -0700, none ""karls\"@(none)" wrote: I've seen a number of gel-cell batteries with rubber vent caps under a plastic plate. It's fairly simple to pry them up and squirt a little water in, but I haven't had any luck with that fixing them. I do it when they are brand new - then every two years - then the gellcells last for a long time. I add 5ml when brand new to each cell, then approx 2ml at subsequent 2yr intervals. This is fine for batteries that dont move - you would have to be choosy doing it with batteries in very portable equipment that gets thrown around! No magic in the figures - that is what it took in my Yuasa batts to JUST cover the plates/pads with minimal layer of liquid. Quite how they dry out I dont understand - but they do - I set my float charges at 13.25v rather than the cram full voltage, the idea was to keep any float gassing off to the minimum. Charlie+ Thanks for the tip. I'll have to try that. Taking the charge voltage down from 13.8v to 13.25v sounds worthwhile too. Good thinking. Since the batteries are made with vents, It was obvious that they were venting something... You took the reasoning a step farther than I had. We used to set the trickle charge on some really large eletrolyte batteries by the amount of bubbling. Constant current is good in this way, but peiriodic overcharging is also necessary above 14 volts, along with the normal float of 13.8. greg |
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