How to Charge a Sealed Lead Acid (SLA) Battery

Probably, if you regulate the charge voltage to something like 13.8V, heating shouldn't be a problem so long as the charge current doesn't go beyond the maximum allowable for the battery.

Drita420

33Ah 12Volt SLA:

Constant voltage 13.8Vdc current limited to 300mA for 20 hours at charging temperature range 32 to 104 F (0 to 40 C).

The 300mA constant current charge will continue until the battery reaches a level of charge that allows it to float charge at 13.8 Volts.

If you are in a hurry:

The battery has a maximum 9.9A charge rate as long as the temperature is maintained between 32 to 104 F. (0 and 40 degrees C.)

Hot climates limit the charging rate.

Jon

You mean constant current, max voltage limited to 13.5 Vdc.

If you supply a constant voltage , the current will be dependent on the load.

Yahlasit

Yahlasit,

Actually I meant 13.8 Volts open circuit and current limited to 300mAmps closed circuit.

Jon

Yes. Quite correct but not very informative, perhaps I can help:-

What many people don't realize is that lead acid batteries change dramatically their voltage depending upon their state of charge. Other batteries also do it but to a far lesser degree.

If the terminal voltage of the charger is set say to a max of 13.2 volts, but the transformer and the other parts cannot (for example) deliver more than 2 amps, then a current of 2 amps will flow at a voltage (assuming battery discharged say to 12 volts) slightly above the actual terminal voltage of the battery. The difference will depend upon the physical size of the battery....larger batteries a small difference, small batteries a larger difference...

Difficult to picture for some.......sorry.

As charge enters the battery, its terminal voltage will rise slowly (or fast if the battery is tiny!!), the current will eventually start to drop as the nearer the battery voltage gets to 13.2 volts.

Theoretically the battery will never get to 13.2 volts (the nominal voltage for a 6 cell LA Battery), because as the voltage rises, the current keeps getting smaller.....as the difference between the charger voltage and the battery voltage lessens....

In actual fact, many charges offer therefore a higher voltage to allow the battery to be fully charged, cars for example generally charge to around 14.4 volts......

I in fact on the chargers that I have built over the years for caravans and the like, still use 13.2 volts (2.2 volts per cell), even though the maximum charge achieved is only about 70% of the maximum battery capacity or so.

The reason that I do that is that I do not want the battery gassing, which also ages it quicker.....I bought a huge battery, so 70% full still can last us several days without recharging.......if need be.

Though I must also re-iterate that the original manufacturer is a good source for exact infos for the battery you have bought......and should be read fully before attaching/designing a charger......just in case you need the guarantee.....!!!

Goto the web and look for the manufacturer's charging instructions, follow these......

Never overcharge or let the the battery stay discharged for long without re-charging.

Put it on charge at 12.7 - 13.3 Volts if using voltage regulation and it will charge over a shorter period or using current control you can charge at Battery Capacity divided by 10 which in your case is 3.3 amps. This will come to full charge in 10 hours. This is the recommended constand current charge rate. Using Constant Voltage, a battery can start at high current and will as the cell voltage rises give a back voltage which will reduce the current anyway. You can also leave the battery on trickle charge which is rated at max 300 mAmps

irelandeng,

To compare notes:

The charge algorithm for lead-acid batteries is similar to lithium-ion but differs from nickel-based chemistries in that voltage rather than current limiting is used.

12.7 - 13.3 Volts seems to be the charging voltage for Nickle based batteries. It could hardly satisfy the needs of a lead acid battery.

13.8 to 14.7 is recommended for most lead acid batteries. The exceptions are small sealed lead acid batteries (SLA), which can be charged to 2.50V/cell (15Volts) without adverse side effect.

Lead-acid batteries should not be fully charged as quickly as nickel based systems so the divide by 10 rule and lower charging voltage and constant current for NiCad doesn't work well for the lead based chemistry.

Your comment that "Using Constant Voltage, a battery can start at high current and will as the cell voltage rises give a back voltage which will reduce the current anyway. Is in line with the manufacturers recommendation given "per cell."

However your comment that: "You can also leave the battery on trickle charge which is rated at max 300 mAmps" is not correct. 300mA is the normal charging rate for the 33Ah SLA Battery.

A trickle charge for lead acid batteries is produced by a constant voltage that allows them to take whatever current they need to sustain a float charge. The minimum would be 13.5 to 13.6 Volts.

Lead acid batteries are used for storage and the systems they are designed for provide power except when the battery is called on to assist when the system is overloaded or unavailable. A motor vehicle after it is started gets power from the alternator and the recharging of the battery is controlled by the regulator.

I got this from manufacturer's data and experience in maintaining large battery systems and my automobiles over the years.

Jon

Drita420

I got that info from the BB battery website.

Jon

I this what you described?

Jon

Well done, if that is what he has.

I do not see any charge control, so no wonder his battery got too hot!!!

Thats what I got from his description.

He would do better with just one leg.

Half wave rectification would reduce the average voltage and the current.

Doesnt need the capacitor either.

Jon

Why the capacitor?

Lemmy70,

Because that is how he described it in the original post.

I wouldn't use one.

Jon

If thats a 12-0-12V transformer the DC output of that could get close to 16.5Volts. 12VACRMS x sqrt2(1.414) - 0.7V(Vdrop across diode)

Lemmy70,

Did you read number 10?

Calculate for half wave rectification and see what you get for average voltage and current.

Jon

Aah yus, me thinks I should pay more attention before rattling off. Apologies.

Lemmy70,

No worry.

Jon

Hello, I'm new to this charging SLA battery's, I have a 12volt 1000mah dc brick (wasn't intended for charging battery's but the ratings caught my eye) so i hooked it to my multimeter and the current is somewhere around 20v, when i connected it to my battery voltage drops to 13.7 volts and under the amp test it pulls about 0.32 - 0.35 amps (multimeter dial set to DCmA and the dial set to the 30 setting) so my question is do i need a capacitor/other components or will this work to charge them with just the dc brick to the battery the battery is 12volt 9ah, so if this will work without capacitors / regulators how do i know when the battery is fully charged will the amps from the charger drop to 0 or is it safe to just keep it connected (i noticed on my UPS it has a constant charge of 24 volts) please let me know. thank you

The output voltage is too high for safety, you will probably damage the PS eventually, or the battery......

If you read my previous post here, it may give you some tips on how to charge a LA battery properly.

If you need further help, just ask.

sorry i mistyped on the UPS, voltage for my ups is 27v (but that's for two battery's hooked together) so if i do the math right it should be 27 / 2 = 13.5 volts constant charge (per battery), and should equal about 2.25v a cell * 6, so i think my ups is right.. anyways was just confirming since the dc power brick put out a constant 13.5 13.7volts so i though i might be able to just use it.. on another note i just bought replacement battery's for my UPS but they make a sizzle noise and about few hours i hear a high pitch whistle noise (valves leaking?) Is this normal for new batteries? They are in a standby UPS so i dont get why they are sizzling and whistling I checked the specs for the battery and it meets my UPS requirements, 12v 9AH high rate Batts that came with my UPS http://www.bb-battery.com/productpages/HR/HR9-12.pdf and the ones i replaced them with (sizzle noise and whistle) http://www.csb-battery.com/upfiles/dow01257835948.pdf any ideas?

That sound is of a (Sealed) LA battery being violently overcharged and gassing so hard that the special "anti-gas" mat inside cannot handle the amount of gas being produced.....

The gas is a very explosive mixture of hydrogen and oxygen, a spark and you will be in Heaven (or Hell!!)......

VERY VERY DANGEROUS WHAT YOU ARE DOING!!!!

Looking for the reason with a cigarette in the mouth has cost many people their sight!!!

Use a good DVM and measure the voltage across the batteries when the fizz, if its over say 13.5 volts (I think it will be much higher!!) 14 volts or more for each 12 volt battery), then the charger is defective.

Probably the new batteries are also damaged, so do not expect to get your money back.......

I build LA Battery chargers occasionally as a hobby, for caravan 12 volt batteries. My batteries work for at least 10 years, I cannot say for how long as the last one is still in use.....

Maybe the charger is at fault and that is why the old batteries failed as well.

Believe me, the charger is not doing a good job or you bought new "defective" batteries.......but ask yourself:- "Where is the energy coming from to boil two batteries first?"

This is NOT your problem.

We need to know the voltage across each battery when "ON" charge.......not when the charger is not active! Actually when the battery starts to get warm (do not wait till it boils please.......also, not when its cold either.......

We are trying to decide for you if the charger is defective or not.......up to now we have only heard from you things that would imply a defective charger.....

The voltage across the batteries without charger implies that the batteries are still probably OK......in spite of being boiled!!!!

Boiling can bend the battery plates and short out one or more cells......

You could also measure the voltage agross the outside battery terminals from the charger, BUT WITH THE MIDDLE LINK REMOVED BETWEEN THE BATTERIES, this will tell us the Open circuit voltage of the charger....

NOTE.

Some UPSs will not charge with the link missing, then measure the voltage when the battery just starts to warm up.....

Check here:-

Guest,

"Line Interactive UPS, without battery's the system wont operate or take on load so with a weak battery it will fail to provide power to the outlets."

Mine too.

And: Batteries are typically manufactured and kept dry until ready to ship to users. Then They are filled and partially charged (60%) tested and shipped.

A replacement car battery is usually on the shelf without electrolyte until purchased and/or installed.

Kuduk

Ok ill try to do an amp test on the ups, how many amps should it put out?

also not quite sure how i can test the amps (since the UPS outputs 27 volts), however on the 12v batterys i used a high intensity 12v lightbulb and both battery's pull about 1.04 amps

one of my dead batterys pulled 0.40 amps (didnt light up the bulb)

I know these new batterys work but its the sizzle and hissing that scares me

Also on a side note

on my old batterys only one failed, whats weird is a week before it failed i did a UPS test and it passed fine, then one night the power kinda droped from windy conditions so UPS went to switch over to battery and thats when the system just shut off, and i noticed the battery didnt hold amps anymore (voltage drops to 1. something volts on load and had 14 offload) (the other battery still reads good volts and has very good amps, but its a differnt brand and its older (from 06) (B.B HR9-12), the other battery i had UB1290 were cheap batterys (not even sure if they were high rate) i paid $35 for two of them.

ok heres what i did, I connected my multimeter to the positive (red cable) of my ups then i hooked the battery's link cable, negative cable (black) hooked to the UPS to the first battery black terminal then the other cable from my multimeter to the positive connection on the second battery

with the new battery's on the multimeter its showing 0.08A-0.09A, so i guess the UPS is charging the two battery's at 0.08 amps @ 27 volts, does this sound right?

also tried on my old battery's same thing 0.08A

Multimeter is on the 30 Setting and set to measure DC mA

sorry for all the posts but another wierd thing, with the UPS off it just did 0.08A with the ups ON (but nothing connected to the outlets) it starts at 0.36mA then steadly drops now its back at 0.08mA within a minute and after 3-4 minutes it droped to 0.05mA

seems odd the battery's would boil and vent @ 0.05mA

also these new batterys have a big sticker over the top of the battery (these batterys have round circles at the top and this sticker is covering two of the holes is this bad?)

picture of CSB battery http://www.portablepower.com/images/csb/39L104S3.jpg

I didn't put the sticker there but the company i bought from (actully i bought from site above, and it says warrenty void if removed) so im not going to touch it. but it seems bad in my opinion since they are where the vents are and could explain the loud whistle noise....

ok took the time to register so i don't have to keep posting as Guest, after about 30 minutes of it setup like this the mA droped to 0.03 mA , I shouldn't of used boil in the above post since the batterys are cold to the touch but i can hear them making boiling water noise (on another fourm someone said this is normal since the acid is rolling off the plates or something) but when i heard the whistle noise i know battery's aren't supposed to vent unless something is wrong.

multimeter

3 setting = .003 mA

30 setting = 0.03 mA

also its slowly changing again 0.03 to 0.02 mA after about an hour

so my guess is when the batterys are dead the ups can switch to a high mA to charge them and when they are charged it just does a trickle charge?, I'm not an expert on how sla chargers work but it seems like thats what its doing.

Are you certain that your meter has not been damaged?

yea I'm pretty sure my meter works fine, i tested with a little DC fan that has its output ratings on the label and the meter output everything exact

Fan said 12volt .06A and meter read it at 0.06A under usage. so it seems accurate, fuses are also good.

I always start the meter on the 10A it says 30 but has a 10A Max next to it.

so what do you think? my UPS outputs 0.02 mA (that seems pretty low for two battery's), thats like 0.01 mA per batt or trickle charge, and the voltage stays around 26-28 so thats pretty consistant, the actual battery's don't get hot or anything when hooked up. I can't tell what battery is venting or whistling since it happens randomly over hours (and both have to be hooked up to the ups to charge properly)., but i did notice one had alittle condensation over the cap so maybe that is the bad one.

You need to measure the whole battery voltage when charging and gassing.....that will tell us a lot!

Usually this label will not cause problems PROVIDED CHARGING IS DONE CORRECTLY!

A correctly set up and used battery/charger system does not use much water in the battery for the first year or so of life, so refilling is not required till after the guarantee runs out.....or even MUCH later....

Be carefull, measuring amps can quickly kill your meter if you get it wrong.....like not using the (normally) 10 amp range......

Milliamp range is at best likely to blow the internal fuse......thats why I do my testing, or at least most of it, with the volts range, far more difficult to damage that!!!

kudukdweller9, Ok i hooked up my meter to the center circut like that picture and it says 0.08 (like before) but your diagram said something about a test so i tried it I added 100 watt light to the outlet and did a self test on the UPS , the rating read 2.68 A on the meter, then after ac power was restored its showing 0.60mA for about 1 minute, now reads 0.16 mA , then it jumped up to 0.60 A for about 2 seconds and quickly droped to 0.04 mA and then it slowly declines to 0.02 A where it stays for about 10 minutes then it went to 0.15 A (maybe finishing charging or leveling the battery's), then eventually droped back to 0.02, then after about 10 minutes it goes to 0.15A again) and i guess it repeats this proccess

0.02a -> 0.15A (about 1-2 minutes) -> 0.60a (about 2-10 seconds then fast drops to 0.02a) -> 0.02a (for about 10+ minutes)..etc

(also note this is a high power ups it can run a 200 watt PC & monitor for over 40-50+ minutes)

and that diagram is exactly how my ups is hooked up, i think it confuses people when they hear the ups voltage is 27 volts but the battery is only 12volts (when really its two battery's making a giant battery that outputs 26volts :)

When can you measure the battery voltage with "gassing" apparent?

they dont seem to be venting as bad as when i first got them, i have to keep them hooked up for hours i guess to get the pressure back up but the whistle is so fast i don't know if i could catch the volts in time.

also on one of the batterys on close inspection there is grease or wet spot on the cap cover, im not sure if this was there or not before, anyways it don't seem to get any new readings with amps so ill switch to voltage and try to catch it venting.

Stick the DVM on and start the charging, monitor the voltage.....if it goes above say 27 volts then I believe the charger is defective. But keep watching as see how high it goes, but when gassing starts, stop......

If the batteries gas violently at less than 27 volts (I have never seen that, but then I would expect that a cell is shorted or similar!), then the batteries are suspect.

Best of luck.

actually, i have to do fyp project called battery monitoring system, that it can be keep on track the 1.voltage & 2.current, at now, i confuse what to do with my project, could u give some guideline...tq

Rain,

Sounds right to me.

Your problem sounds mighty strange. Perhaps the bug in the electronics dryed up and is no long messing things up.

Kuduk

maybe or its just a defective battery (faulty rubber valve cap or something that fails under the normal pressure loads) or it got damaged in shipment, maybe overfilled..etc

I searched under google and it seems some other people have problems with this brand battery.

look at this guys battery

http://www.tmk.com/blog/?p=12

If i can exchange these what other brand should i look for

PowerSonic , tempest or enersys (wish i could find B.B batterys)

Andy the battery whistled but the voltage didn't change at all it keeps a constant 28.17 volts (except when the internal fan goes on then it drops to 26.97 volts) then when it shuts off it goes back to 28.17.

when i heard the whistle sound nothing changed meter still said 28.17.

That is a bit too high, your charger is charging to a higher voltage than it should do......

I personally never charge above 13.2 volts per battery (Very conservative), but even 13.5 per cell should be OK. More and I am VERY suspect about the charger.....to me its charging far too "hard"......

If there is a a form of adjustment on the charger, then try setting it to say a max of 27 volts (or less - 26.4 volts is my conservative favourite - if you accept a slight loss of capacity, but with a very long battery life!)

Thanks for testing so well......

well the other day i tested it was doing 27 volts for some reason today it did 28 (maybe because nothing is hooked to the outlets) the other day i had my pc hooked up to the battery outlets., still even at 28, 29 volts would that make the battery's vent?

the pdf for this battery says

http://www.csb-battery.com/upfiles/dow01257835948.pdf

Float Charging Voltage 13.5 to 13.8 VDC/unit Average at 25 (77 )

Equalization and Cycle Service 14.4 to 15.0 VDC/unit Average at 25 (77 )

but thats a good idea with this UPS i get over 50 minutes runtime so if i can loose alittle of that for longer total battery life it would be worth it, ill look for an adjustment screw later on.

That is true, BUT the charger must stop or drop charging, not just continuously charging at those voltages.......yours appears to forget to stop at the right time!!!

And, as I thought I had mentioned already, doing it the way you mention WILL STILL shorten the batteries life........even if they did not even get to vigorous gassing continuously!

Vigorous gassing (Baked Beans?) is the killer over the (not so) longterm, weeks rather than months.

With a possible dangerous gas explosion as well......

Hm I'm not sure I always thought SLA Batterys can be kept on a constant charge, I know my UPS cuts the amps or lowers the amps when needed but it always keeps the voltage (no amps it cant charge right?)..

anyways i guess the only way to find out is to try another set of battery's if they sizzle or vent too then i know the ups is at fault

SLAs are sealed, but have a vent if they get too much pressure from overcharging.....its stops them exploding.......'nuff said?

NICADS and other batteries types also have a vent for when they get too hot and then they also lose water and therefore capacity!!

Its not a good idea to over charge anything.....

what about my old battery's is there anyway to bring them back to life with the proper saftey precuations, like gloves and glasses.

some places say carefully remove the cover and rubber valve caps then use a syringe to inject water into the dry cells, replace rubber caps, cover (superglue or tape) , charge while monitoring and you should end up with a good battery again..

has anyone tried this?

http://www.instructables.com/id/Refilling-SLAs-Sealed-Lead-Acid-battery/

ok i couldn't resist so i tried what i posted above but i didnt fill the cells all the way up like he did in that guide i put just alittle water in to test and it really does works amps and everything jumped on the battery .. now it can output 1amp+ @ 13.45 volts

so with that i decided to hook it to my ups with the other battery that never failed, and I don't hear any sizzle noises or venting on these battery's..

I think it narrows it down to the new batterys i got, Also i was looking around at other fourms about ups output voltages and its not abnormal for UPS to output 28volts thats about 14v per battery, although it is alittle high its not enough to boil the battery if anything it will kill its life by a year

I think your thoughts are flawed. The charger is defective and it will stay defective and you really don't think that an older battery, treated in that manner, will be reliable and work like a new one do you?

As I just posted a few minutes ago, you have now VERIFIED that the charger is overcharging.......otherwise how could an SLA be empty???

Do what you want, but remember my comments. You have neither found nor fixed the problem......your prerogative.

I am now un-subscribing from this blog, so send me a CR4 email if you need to talk.....

I won't be reading pr replying to this blog anymore as you don't appear to understand anything I have told you, so I am wasting "OUR" time......Bye.

Never tried it, but I see no reason for it not to work, but capacity will be down even if it does work.....the question is "is it worth it?" It may be interesting for you to try out....

If the old cells are dry, then you now KNOW, the charger is defective (and WAS defective)..........even SLAs only handle a bit of gassing not a lot!!!! Eventually all the water is gone.

AND while the water was being used up, the battery's capacity was going down and down and the temperature was going up and up.......over months or even years......not necessarily a fast process.....it depends on how much overcharging was done....

well its arguable why its dry , the old battery has a date code from 08, were an 10 now that's 3 years about how long a sla lasts (i bought it new from buy.com but it had a year old date code when i got it, also probably had permanent damage from sitting on the shelf for that long without a charge)

also the other battery i have is from 06 (the bb hr9-12) and its still works, outlasted every battery i put in this unit.

I really think it depends on the quality of the battery. As for the UPS i think its working fine, researching more it charges at 27 volts then it does a top charge at 28 volts.. I will contact the UPS manufacture and double check before i buy new battery's. also the battery i filled with water actually works really well, i was really surprised, I don't plan to use it as a permanent solution but to rather check for sizzle/bubble and venting. and right now i don't hear anything it been connected for 8 hours and its not even hot, under load it supplied good amps supported a 600 watt light for 30 minutes (could of went longer but UPS gets hot) so i stopped the test.

Interesting to say the least.