Testing gelcell SLA batteries

Smoke_Maker

Joined Sep 24, 2007
126
One is a UB1280ZH
NON-SPILLABLE BATTERY
SEALED LEAD-ACID BATTERY
1280 12V 8Ah.

Bill, don't count out batteries that have low voltage reading, I would charge them until the current stops drooping, that means the battery has accepted as much charge as it can hold for that cycle. Batteries that have been unused for a while tend to increase in capacity after several cycles.

You have a 8Ah battery, technically it should be able to support a 1A load for 8 hours before it reaches 10.5V under load (and 12V without load). This is a good way to see how much capacity the battery will hold, then you need to decide if the battery has enough capacity for the project you want to use it for.

Think of a battery as a one gallon can, over the years it gets dents and crushed, it still holds liquid but not as much as when it was new.

Also, there is nothing wrong with using a battery that has one cell shorted as long as it will deliver the required current for the project you use it in, it makes a great battery for projects that needs a 9V or 5V supply. Think of it as ultimate reassignment of parts before it go's to the re-cycler.
 

CraigHB

Joined Aug 12, 2011
127
I have a couple UPS units that take the 18Ah SLA batts, like the kind you find in emergency lights. I had one of the batteries completely fail in an ugly way recently. I started smelling a sulpher-like gas in my office. Took me a little while to figure out where it was coming from. One of the batts in the UPS was very hot and bulged.

The UPS takes 3 pairs of two so I pulled the bad pair and I'm running on the other 2. The battery was only like a year old. I didn't know they could fail catastrophically like that. I hate to think what would have happened if I had been out of the office for a time. The battery probably would have exploded and ruined my expensive UPS unit. Then the acid would have burned a hole in the floor.

At first, I thought the charging system in the UPS had faulted, but I checked the voltage and it was correct. The other two batt pairs have been running perfectly cool for over a month now so for sure that wasn't the problem.

I usually do a run-down test on the UPS units once a year. It's pretty obvious how the batteries fall off in capacity as they age. I always get the AGM ones and avoid the gel cells. The AGM ones are much better. It seems to vary, but they usually last at least 3 years before they start losing a lot of capacity. I've been using these particular UPS units over 10.

Car batts can be hard to test without an expensive load bank, but I have an inexpensive power inverter I can clamp on that makes it pretty easy to do a run-down test on them. I just plug a 100W utility light into the inverter. I use my DMM to get a current reading then multiply by the time it takes to shut down to calculate amp-hours.

Just taking a battery's voltage doesn't give you the whole picture. It could just be the charge is low. If it comes off the charger with low voltage, it's definitely shot. If it comes off the charger with good voltage, you have to load test it to see what kind of shape it's in.
 

nsaspook

Joined Aug 27, 2009
7,299
I fail to see what that has to do with a textbook-referenced claim that a load must be placed on the battery in order to properly test it.
If the battery was close to the rated voltage then a charge acceptance test with a load test would be warranted but the odds of a lead-acid battery recovering anything more that 50% of rated capacity after sitting at 10 volts longer than a few weeks is remote because of irreversible hard crystal growth.

I love working on cars. One of my best buddies (Chrysler master mechanic) and I restored classic barracudas in California in the early 1980s as a side line when I worked for Hughes Aircraft near Long Beach.
 

SgtWookie

Joined Jul 17, 2007
22,210
I love working on cars. One of my best buddies (Chrysler master mechanic) and I restored classic barracudas in California in the early 1980s as a side line when I worked for Hughes Aircraft near Long Beach.
Gee, I didn't know you were a HAC employee at one time. While you were down there, I was in RSG in El Segundo, Imperial Hwy @ Hughes Way. I can't recall offhand what group was in Long Beach, but the F/A-18 simulators were down there. They were really something for the time.

[eta]
I used to enjoy working on cars - not so much anymore. I think it was the Jag that finally turned me off to it. We had a 1988 XJ-S V12 Hess & Eisenhardt convertible conversion; midnight blue body & top, biscuit interior, Dayton wire wheels. It looked great and was a blast to drive, but it was a royal PITA to work on. The E-types were so much easier.
 

kcarring

Joined Jan 22, 2011
38
I suppose I could charge them then discharge them using a 12V car light bulb and measure duration.
After 4 years in the RV industry, and coming across thousands of batteries, unhappy people, tons of test equipment, including a $1000 battery analyzer...

you're correct thats the best test.

Charge it. Giving it a standing time. Load it down and check it against its C20 rating. Done. You KNOW if the thing is good, or not, period. If it isn't, attempt a desulphation if it's usage history warrants that... (if you even know the history). If it fails desulphation, recycle it.

There really is no other way in my opinion, I put away all the load testors and the theories and the specific gravity check... it all potentially lies to you.

just my 2c
 

kcarring

Joined Jan 22, 2011
38
irreversible hard crystal growth.
If you are referring to sulfation, it is often reversible. And nearly every battery is sulfated, if it has sat on the shelf too long before you bought it. There are dozens of good techniques for desulphation, from PWM, polarity switching, current based, voltage based. My personal favorite is a coil based circuit called a stingo. I totally agree though, some just don't come back to life. I do however have over 20 batteries better than 85% recovered acquired from the dump, that have been in daily use pushing over 1000 amp hours daily. Day in, day out. Few of those batteries showed over 10 volts when I acquired them.
 

K7GUH

Joined Jan 28, 2011
190
My Q&D test: put a 12 volt 50 watt bulb on the battery. If the battery shows less than 10.5 volts under this load, recycle it. If in doubt, try charging it first, using less than 4 amp charger. Then do the bulb test.

FWIW, we have an almost infinite supply of used but usable batteries from a hospital that routinely changes batteries after one year service. Most of them are 7.5 Ah batteries; we don't get many duds, and the good ones will run a 5 watt T/R for ten or more hours. No high tech testing involved.
 

nsaspook

Joined Aug 27, 2009
7,299
If you are referring to sulfation, it is often reversible. And nearly every battery is sulfated, if it has sat on the shelf too long before you bought it. There are dozens of good techniques for desulphation, from PWM, polarity switching, current based, voltage based. My personal favorite is a coil based circuit called a stingo. I totally agree though, some just don't come back to life. I do however have over 20 batteries better than 85% recovered acquired from the dump, that have been in daily use pushing over 1000 amp hours daily. Day in, day out. Few of those batteries showed over 10 volts when I acquired them.
If it's a big old golf-cart or traction battery with 1/4 inch plates for a new reaction surface and caps to flush out the gunk and add new electrolyte sure they can be recovered but a AGM or GELL battery is toast when the surface of the lead plates are hard crystallized. I'm not a 'desulphation by electronics' fan.

I've recovered lots of junk batteries for profile testing (charge/discharge cycle life and charge efficiency) with my Multi-Battery solar charging system prototype.
http://www.flickr.com//photos/nsaspook/sets/72157622934371746/show/
http://code.google.com/p/solar-monitor/
 
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Smoke_Maker

Joined Sep 24, 2007
126
My Q&D test: put a 12 volt 50 watt bulb on the battery. If the battery shows less than 10.5 volts under this load, recycle it. If in doubt, try charging it first, using less than 4 amp charger. Then do the bulb test.

FWIW, we have an almost infinite supply of used but usable batteries from a hospital that routinely changes batteries after one year service. Most of them are 7.5 Ah batteries; we don't get many duds, and the good ones will run a 5 watt T/R for ten or more hours. No high tech testing involved.
If in doubt, try charging it first

But when is the battery fully charged????

I contend that the battery is not fully charged until the current stops dropping at whatever voltage.

Once again batteries are like dogs, don't over feed them (over charge) don't starve them (under charge) and don't expect a dog to run a marathon if he doesn't get exercises from time to time. (the phone company has big banks of batteries they exercises on a regular schedule).

So to really bring the battery back to health put the battery back in training, exercises it. In a used neglected battery the capacity will increase with each cycle of charge and discharge, when you see the percentage of capacity level out it's as good as it's going to get.
 

Smoke_Maker

Joined Sep 24, 2007
126
If it's a big old golf-cart or traction battery with 1/4 inch plates for a new reaction surface and caps to flush out the gunk and add new electrolyte sure they can be recovered but a AGM or GELL battery is toast when the surface of the lead plates are hard crystallized. I'm not a 'desulphation by electronics' fan.
Sulfation is a part of the discharge process and your right when the sulfation becomes "very hard" it is irreversible.

"Discharge
During discharge, the lead dioxide (positive plate) and lead (negative plate) react with the electrolyte of sulfuric acid to create lead sulfate, water and energy.

Charge
During charging, the cycle is reversed: the lead sulfate and water are electro-chemically converted to lead, lead oxide and sulfuric acid by an external electrical charging source.

Sulphation may occur if a battery is stored for prolonged periods in a completely discharged state or very low state of charge, or if it is never fully charged, or if electrolyte has become abnormally low due to excessive water loss from overcharging and/or evaporation. Sulphation is the increase in internal resistance of the battery due to the formation of large lead sulphate crystals which are not readily reconverted back to lead, lead dioxide and sulphuric acid during re-charging. In extreme cases the large crystals may cause distortion and shorting of the plates. Sometimes sulphation can be corrected by charging very slowly (at low current) at a higher than normal voltage.

http://www.mpoweruk.com/leadacid.htm

The high voltage will overcome the high internal resistance of the battery and the low current will keep the gassing from being excessive so the bubbles of hydrogen and oxygen will recombined, this reverse flow of electrons is whats converts the lead sulphate back into lead, lead oxide and sulfuric acid.

I know you know this I just want other readers to understand what go's on inside the battery.
 

thatoneguy

Joined Feb 19, 2009
6,359
If in doubt, try charging it first

But when is the battery fully charged????

I contend that the battery is not fully charged until the current stops dropping at whatever voltage.
Battery is fully charged, or has taken as much charge as it can, when its temperature increases at the rate power is pushed into it (ΔT/Δt has a sudden ramp). There are a ton of ΔT/Δt chargers around, though most cutoff once the rate of voltage increase stops increasing ΔV/Δt or Current intake drops faster ΔI/Δt (Method you use, which is acceptable for some chemistries).

In other words, there isn't really a single point measurement to signal a battery is full, only a change in the reaction of the battery to being charged that signals it cannot take anymore charge.
 
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