Sealed leadacid UPS battery testing/conditioning

[Chancy99]

Hi All -

I have several UPS's here that use the typical 12V 18AH sealed lead-acid batteries. A couple of these have died, in that they light up the "replace battery" LED or similar means.

I've pulled the batteries out, but I'm sure that they're not ALL bad - there's about 10 of them. I hope not - they run around $35.00 each How can I test them, and is it possible to recondition them ?

I know one is definitely bad - it only shows 1.8V total. It doesn't seem to take a charge from my bench power supply - 14.5V and it only pulls 2mA.

Two that came out of a single UPS both show 13.1V, yet the UPS claims they're bad. They appear to have taken a charge, since they'll only accept about 300mA or less from my bench power supply set to 14.5V. But *something* must be wrong with one or both of them.

Help ?

Dean.

 

[jbartos]

Suggestion: Try to locate the battery and UPS manufacturer over:

http://www.thomasregister.com

and type Batteries: Lead Acid under Product or Service that will return 108 companies to potentially contact for tech support.
Do this likewise for UPS

 

[Aranrhod]

If you have pulled so many bad batteries out of a UPS I would question the UPS charging circuit. Lead acid batteries are very forgiving, even sealed ones, and shouldn't die in quantities like you seem to find. Compare trying to charge a Li-ion battery and see how fussy they are.
There aren't many things that can go wrong with a sealed battery if it's properly managed. But a modern charging circuit actually puts transient (sub millisecond) shorts on the battery, and looks at the response, then makes a complex decision as to the likely life left in it. If it fails this test the circuit marks it bad. So a battery marked 'bad' might still 'work' but it IS definitely on the way out. So change it as soon as funds permit.

 

[Chancy99]

These UPS's are all on the order of 5 years old, and I think that's the specified lifetime on the batteries. Given that not all batteries are the same, I'm sure that some have been "worked" harder than others, and those are the failing ones.

The others should be more or less OK though, and I just want to identify them.

Thanks for the replies people -

Dean.

 

[peebee]

What temperature are the batteries at? Be aware that battery life drops off quickly at any temperature above 70F. Battery life increases below 70F, but capacity goes down.

How old are the batteries? Expect a 5-year max. life out of most sealed-cells.

 

[engineermc]

TO RECOVER DEAD BATTERY, I HAVE USE TWO TECH.

1. CHARGE BY BENCH DC POWER SUPPLY AT 15 V CURRENT 10-15 % OF AH CAPACITY UNDER CVCC MODE.KEEP FOR SIX HOURS, WHEN IT STOPS TAKING CURRENT.

NOW DISCHARGE IT USING 12 OHM / 20 WATT WIRE WOUND RESISTANCE, UP TO THE VOLTAGE LEVEL GOES 7.5V

REPEAT THE PROCESS AGAIN. IF YOU BATTERY CHAGING CURRENT IMPROVES MEANS IT TAKES 10-12 % OF AH CAPACITY IN CVCC MODE OF POWER SUPPLY, CHANCES ARE YOUR BATTERY 50 - 60 % CHANCES ARE YOUR BATTERY IS RECOVERED. IF SITUATION IS SAME. GO FOR ANOTHER TECHNIQUE.

2. THE REASON FOR GOING THE BATTERY IN HIGH IMPEDENCE, THAT
BATTERY HAS DEVELOPED HIGH IMPEDENCE, WHEN WE APPLY POWER SUPPLY IT TERMINAL DEVELOP VOLTAGE OF 20-30 V , A FICTIOUS VOLTAGE, THAT BATTERY NEED TO BE CHARGED USING PULSE CHARGER BASED CIRCUIT,OR GIVING TRICLE CHARGING, LIKE IN AUTOMOBILE

OR USING 555 TIMER DEVELOP THE CIRCUIT.
THIS CIRCUIT CAN BE DEVELOPED BY YOUR OWN BY USING FOLLOWING PRINCIPLE

PULSE VOLTAGE[ RMS][KEEPING PULSE FREQUENCY UPTO 1-2 KHZ
FIXED]= CURRENT[FIXED=2-5 % OF AH CAPACITY ]*BATTERY RESISTANCE.

MEANS WHEN BATTERY IMPEDENCE IS MORE VOLTAGE WILL BE MORE ACROSS IT [ AFTER FEW SECONDS BATTERY START REDUCING IS HIGH IMPEDENCE AND CIRCUIT SHOULD STOP REDUING PULSE VOLTAGE.]

THIS IS THE ONLY AND LAST METHOD YOU CAN APPLY, TO RECOVER DEAD BATTERIES.
THE BATTERY NOT RECOVERED BY SUCH TECHNIQUES IS DEAD FOR EVER.


RECOMMANDED GUIDE LINE TO KEEP YOU BATTERY HEALTHY.

1. YOU BATTERY NEED TO BE DISCHARGE, ONE IN A WEEK FOR LET
SAY ONE HOUR UPS BACKUP, GET MIN 15 MIN DISCHARGE ONCE IN WEEK.

NOTE CHARGING CURRENT IT SHOULD BE 10 -15 % OF AH CAPACITY. CHARGER SHOULD BE CVCC TYPE.
IN CASE THE CURRENT IS LESS AFTER DISCHARGE, ASK YOUR UPS VENDOR TO FIND SINGLE FAULTY BATTERY IN TOTAL BANK OR PROBLEM WITH HIS CHARGER.
ALL CHARGER SHOULD BE CVCC TYPE. WITH GOOD FILTER CAPACITOR.
ANY QUESTION

FROM
EX- AIRCRAFT ENGINEER
MUKESH CHAUHAN

 

[MarkAthay]

A UPS is not a battery friendly environment. 5 years is a good life in most UPS applications. You can pick and choose which battery to replace, but my experience is that you'll be back in there replacing a battery soon. The failed batteries put an additional strain on the remaning batteries through overcharging. Not only are you straining the aged batteries, but the new ones you just put in. If you only have to coax another year's worth of life, replace just what you have to, if you want another 5 years worth of life replace the entire bank. That's what I'd do anyway.

Mark in Utah

 

[jbartos]

Suggestion: The battery quality is also important. Some batteries are manufactured so-so to begin with.

 

[Chancy99]

Guys - thanks for all the advice. I'll do what I can to check the batteries, and any that are marginal at all will be replaced.

Dean.

 

[Chancy99]

Hi -

From another thread referencing this one :

dumbo (Nuclear) Jan 19, 2003
Discharge down to 30 mA and repeat until the sulfur deposit disolves this could take a while you got a good start. I have read that some have had success in reversing the deadness. Each time should show some improvement. Be patient, could take weeks, use only trickle current.

What exactly is meant by discharge down to 30mA ?

Dean.