__________________

Wrong!!!!!!!!!!!!!!!!!!!!

 

Use a 'hydrometer' and a DVM. The hydrometer should read about 1.280 to 1.30 for a fully charged battery.

The hydrometer measures the specific gravity of the battery acid.

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

but i don' t have one

i have an multimeter , is there any way to use it .

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Wrong!!!!!!!!!!!!!!!!!!!!

 

you can use a zener diode with an SCR to make a charging circuit ... look for this on the internet ...

 

hi,
Most garages used to have a hydrometer, perhaps they would check the SG of the battery.

Another way to check for a full charge is when the acid starts to produce gas bubbles near the end of charge time.

This will not tell the 'condition' of the battery, as you know as a battery is discharged and recharged it will start to lose 'capacity'.

A new battery which has say a 100AH rating, after a number years and many recharge cycles could be as low as 50AH and it would gradually lose capacity with time and use.

For a quick capacity test, use a 12v car bulb/lamp, to discharge the battery, use say a 12Watt lamp. Time the period in hours how long it takes to discharge to 10.8V [NO lower]. This will give a rough indication of the AHr capacity.

Recharge the battery, note the value of current with time and work out the AHr energy required to recharge to 14.8V [its should start to 'gas' about 14.8V. The recharge is not 100% efficient, only about 50/60% to allow for this in your sums.

Usually if a fully discharged battery [10.8v] recharges quickly when using a domestic battery charger indicates the battery has lost capacity.
Does this help.?

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Eric, great info. I worked in a shop for awhile and they just had a charger that would put it through a duty cycle after a charge.

But if it coughed it's guts up then the machine would do the analysis & spit out tape to give to the customer. Instant sale.

 

thanx alot

i will try it .

shams.......

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Wrong!!!!!!!!!!!!!!!!!!!!

 

one thing else ....

about the 10.8v ,

when the batter goes under this value , what could be happen ..

and once , i make an inverter cir and connect 12v \ 7 A battery

and discharge it until its value become 6 v ..

and when i connect it to the charger , its no long charge .

is the reason that goes under 10.8v ...

thanxxxxxx

shams......

__________________

Wrong!!!!!!!!!!!!!!!!!!!!

 

the plates get sulphated. Difficult to recover but if you pump a constant current at say 1/20 or 1/30 of the AH rate of long time of say 4 days or so , it might recover. Obviously you should not add acid to make up the Sp.Gr. but only top with distilled water upto the marked level. It needs lot of patience.
Try google for recovering sulphated lead acid batteries.

__________________
Regards,
Sarma.

 

With a hydrometer you can measure each of the 6 cells in your 12V battery. With a multimeter you can measure the average state of charge, which is just as good as long as the cells are about the same.

At 80º F (26.7ºC), a battery at 100% state of charge measures 12.65 volts (brand-new batteries frequently measure 13V or so); 75% = 12.45, 50% = 12.24, 25% = 12.06, and at 11.89 volts it is said to be completely discharged. If a 12V wet-cell battery drops below 10.6 volts, it's toast. These numbers vary for maintenance-free, gel-cell and AGM batteries.

Rule of thumb, charge the battery at a constant 14.5 volts, at a starting current that is no more than 10% of the reserve capacity of a deepcycle, or 25% of the amp hour rating of a cranking battery. It's finished when the amount of current it will accept stops declining.

Fully charge your battery, wait 3 or 5 hours for the surface charge to dissipate, then measure the voltage with your multimeter.

If your battery is not specifically designated as a "deep cycle" battery, repeated deep discharges (below 90% state of charge) will seriously shorten its useful life. A deepcycle battery is designed for deep discharges, down to 20% state of charge, although it will last longer with a lower average depth of discharge.

Sulfation happens any time the battery is at less than 100% state of charge. The other killer of batteries is inadequate electrolite. Check the level in each cell (more often in hot weather) and add enough distilled water to keep the plates covered.

 

Hey there!
Maybe someone has some ideas....
i just bought a 25Ah car battery (was alot cheaper than a maintenance free SLA), and i needed a high capacity to run a 150w inverter for a couple a hours every second day or so, (if you a south african, you'll know why---LOADSHEDDING!)
This will be to run my filter system in my aquarium while the government tries to figure out a solution to this big mess!
Anyway, the specs i got from the bat supplier are as follows:
*Terminal voltage at full charge: 13.8V
*Check water (not maintenance free)
*it is a deep discharge battery (hybrid- whatever that means)
*should be charged at 15Amps! (with intelligent charger that costs more than 10 times the price of the battery!), which blasts the plates with 15A, and then somewhere along the process, drops down to finish off the charge.

Now i'm worried about the 15A part, and have no intention of getting a transformer the size of the battery!
I can get a swithcmode laptop charger as a power supply instead, and then build a regulator to maintain the 13.8V or so.
Can this battery be charged the same way as a SLA, with constant voltage, continuously (so its always charged, and ready to go).
can i set charge current at 0.1C (2.5Amps) and get a full charge?
Help me soon someone,

My poor fishies

 

"hybrid" probably refers to dual-use (cranking and deepcycle).

If you charge at 13.8v, the battery will probably not achieve 13.8v. (you might measure 13.8v or more immediately after charging, but lead-acid batteries have what is called "surface charge", which drops off quickly and isn't really available to your load.) I don't know if 2.5 amps is enough to reach a full charge, but 10 would suffice, or 8 or even 6....it just takes longer.

Once fully charged, a 13.8v float charge at a current equal to about 1% of the AH rating should be enough to keep it charged and ready to go. This is the best way to maintain your battery to get the longest life from it.

One thing to keep in mind during charging, it can be damaged if the electrolyte temp exceeds 125º F (51.5º C) for any length of time. If you hear it boiling, turn it off. Some gassing is normal.

note above I said a charging current of 10% of the AH rating....should have been 10% of the RC (reserve capacity) of a deepcycle battery, or up to 25% the AH rating of a cranking battery. sorry bout that.

 

hi ziyad,

Excom in SA loading shedding should only put you without power one day each fortnight, from 8am thru 5/6pm.
Unless you are in Cape Town or Jo'burg.?

The battery could be charged at a float charge of 13.8v, say 2 to 3Amps max, dont force a 15A fast charge, the battery life will be shortened.

Excom say, that the shedding should only last a couple of years, as you may already know SA has a 15% short fall in its power generation.

__________________
Eric
"Good enough is Perfect"

PIC tutorials:
Gramo's: www.digital-diy.net/
Bill's: www.blueroomelectronics.com/

 

Thanks dude, but now i'm even more confused!
i need a charger thats "smart" enough to do all the work for me. i just want to connect it permanently, and it must do the rest:
Full charge, float charge, everything!
A schematic, or something.
The switching from mains to inverter, and all that is easy, its the charger / battery maintenance stuff that worries me.

 

i am in Jo'burg, and we have power cuts every Monday, Wednesday, and Friday for 4 hours at a time.
They say a couple a years, but i think what they really mean is at least 7!
Please bring your candles and gas stoves along if you comming for the 2010 world cup.
15% shortfall in its power generation, and 115% shortfall in the brains department. and just by the way, looks like the big boys in eskom are going to get over 10 million bucks or so as bonuses for "good peformance"

Anyway, about my fishies now...
the filter system cannot be switched off for even an hour, coz the bacteria in the filter medium dies if there is a lack of flow / oxygen.
If this happens, the filter will contaminate the water with all kinds of goo that will poison the whole system.
Sometimes its not as serious, but i dont take chances, as i have already lost some fish in the initial load shedding stages.
i currently have UPS systems doing the job, but they driving me crazy, too bulky, too short time ( +- 3hrs.), too much beeping, and i want to use larger batteries...its a long story!