Battery charger question

It's 100 A-hr, not A/hr. Tell us what kind of battery.

TVP45:

Like I told ya before, you need to get some sun and fresh air==A-HR or A/HR--give us a break.

Donzi

Donzi - You are off base here. Units are critically important. Two multimillion dollar satellite launches failed because of unit mismatches. A ten AmpHr battery can deliver a very wide range of currents, I, such as 5 or 10 or 20 amperes, for various time periods, T. The product of that time T multiplied by the current I is 10 AmpHours. (Only over a certain limited range - you can not typically get, say, 10,000 amps out of a 10 AmpHr battery, even for a second.)

The specification 10 A/HR means exactly ten amperes are delivered, at the rate of 10 amperes per hour, which is a redundant specification identical to 10 Amps, since Amperes have the units of electrical charge delivered, per second, or Coulombs/sec.

As another example of unit confusion, an ounce of gold weighs more than an ounce of lead, yet a pound of gold weighs less than a pound of lead, and a gram of gold weighs exactly the same as a gram of lead. And there over 20 different sized Barrels - Beer, oil, wine, etc. Helen of Troy knew all about this.

Here is a rule of thumb for lead acid / gel cell / agm (adsorbed glass matt) / valve regulated lead acid batteries. For maximum longevity, the charging current should not exceed 1/10 of the AmpHr rating. Thus, a 100 AmpHr battery should be charged by a current not exceeding 100 x 1/10 = 10 amps. There are actually rather complex time dependent charging regimes, where the charging current is varied as a function of time and battery temperature. But most home made chargers are either approximately constant voltage or sometimes constant current "float chargers".

Here is one of many references: http://www.mpoweruk.com/chargers.htm

That amperage output will charge the battery. I would increase the output. The 4 amp output will take over 24 hrs to charge the battery. The rate at which you can charge the battery would depend on the type of battery also. An industrial lead acid battery most chargers are sized to charge the battery in 6 hrs. Amp Hr Rating of the battery ÷ amp output of the charger will give you charge time.

hey again, ive registered now, so il upload a pic of the battery label

Eltek Pacific
Unit 1
22 Narabang Wy
Belrose NSW 2085
Tel: 02 9479 4200
Fax: 02 9450 1661
Supplier's Website

Have you been on to the battery manufacturer to see what they say, Mate?

and the other one couldnt get it any clearer sorry

"12 V 100Ah/10 hr to 1.80V/cell at 20 degrees celcius

12 V 100Ah/8 hr to 1.75V/cell at 77 degrees Farenheit

Float voltage : 13.62 v @ 20 degrees celcius

and the connection tourque"

also could a car alternator do the job of charging a battery of this magnitude?

A proprietary 12VDC charger would do for the second one.

also could a car alternator do the job of charging a battery of this magnitude?

Yes a car alternator has more than enough capacity -- the hazard would be that its current and voltage regulation would be inadequate for the particular battery.

To echo what others have said, you really need to have the manufacturer's literature on the battery: gell cells, flooded lead acid, and absorbed glass mat (AGM) all should be charged differently. Some AGM batteries have no limit on charging current (within temperature limits), but strict limits on voltage.

If you go to www.alcad.com you will find more about that battery than I will bet you ever wanted to know.

Jack Jersawit

I believe you've got one of those absorbent glass mat batteries for a UPS? Probably a valve-regulated one? I'm over my head, so I'm not gonna guess, only give a couple of "look-outs".

Those things have a sensitive charging curve and need a temperature sensor to keep them from overcharging.

I would not use an alternator, or even an unattended regular battery charger.

I would make sure I had the battery in a ventilated area.

You should get information off the manufacturer. You might also look at Power-One who makes chargers that might work for this particular guy.

Good luck.

thanks for the input

I'l keep researching

You can charge under existing condition but will take longer time that is around 12 hr. but if you can increase amp then charge time will be less this is just how much amp you put in and what type of bateery you have will dictate the time of charging

Aside from good generic information, there are also links to manufacture sites with more specific information... here:

http://www.solarnavigator.net/battery_charging.htm

The charging regimen for each individual battery type can be very different even though the batter voltage is the same. They can have different chemistries and designs. Charging a battery with the wrong charging regimen can lead to overcharging and destroy the battery and maybe even cause it to explode.

The best bet is to contact the battery manufacturer and ask them for the charging requirements.

Proceed very carefully.

Good luck

Call technical support at EnerSys. They make Odyssey..would be able to give you all chemitry algorithm's for the various batteries

If you understood what your battery label is telling you fully, you would realize that the battery manufacturer has set an upper limit of voltage at 2.40 volts per cell, for a 12 volt battery (6 cells) that is 6 x 2.40 = 14,4 volts.....the charger you are looking at goes higher.....14.5 volts, not good.....

Remember that the allowed charging level is affected by the temperature, higher temp = lower limit....if you do not charge at high rates, you can forget this point....

If you want the battery to last, do not charge beyond a max of 14 volts (my batteries cut off at 13.6 volts!)....then make sure that either your charger cuts off (and restarts at 12.6 or a little higher) or goes into "trickle" charge mode....

You did not give the type of Lead Acid battery, so it is difficult to be precise (contacting the manufacturer or his web page was good advice!), but assuming you want it to last, do the following:-

1) charge at a maximum current of 1/20 of capacity. Its enough for most uses....never more than 1/10C.....

2) Stop charging at a max of 14 volts (or slightly less), this means that the battery is not completely full, but will not gas/lose water if of an open type.

3) Restart charge on or before 12.6 volts, this is the point at which non leisure batteries start to sulfate. Some like to trickle charge when battery is full, I personally do not....if you select to trickle charge, make sure that battery voltage is either completely stable over long periods or goes slightly down, but never UP beyond the charge stop point!!!

4) if the battery stays idle for long periods, get a small unit (they are quite cheap, run off the batter power,) sometimes called an activator, they prevent sulfation and according to the manufacturers, will convert sulfation back into a proper battery chemicals again...I have no personal experience of such, but evidence seems overwhelmingly good....

5) Buy a good voltmeter or 2 before starting to buy or build. Never believe what the manufacturer tells you!! Its mostly lies.....check it all yourself. Why 2 meters? One for volts, one for amps at the same time......

6) Remember, if battery is an open type, that they can gas and this gas is highly explosive, no smoking or naked lights and make sure that the gas does not enter your house, garage or car, it must be vented outside and do not use normal ventilators that could cause a spark!!! The ventilator needs to be of a special type that is sealed. They are sold at 12 volts for use in yacht bilges, but are expensive.....

This list is not complete, but gives you a good starting point.

Construction of your own charger can be fun and also save money, provided you are knowledgeable with regard to power and Electrical/electronic construction, if you are not, go and buy a proper unit!!!

Dear,

For 100Ah Battery you need to charge at the rate of 10 amps i.e. for any battery the charging rate is 0.1C, C= Ah, here 100 Ah battery and charging rate is 0.1 C = 10amps.

Secondly charger type is constant current, o/p voltage is 2.25 V per cell if your battery is SMF. Charger output should not exceed 13.5V to 13.8V max. ( 12 V battery contains 6 cells. no of cells X 2.25V

In case of lead acid battery charger voltage is 2.35V /cell 2.35X 6 = 14.10V and charging current is 10 amps on charge mode. After completion of charge it is to be kept on float mode @ 2.15V / cell. i.e. 2.15X 6 = 12.90V. This is the correct method of charging a lead acid battery. This will give you good life when compared to SMF battery. SMF battery has got its own advantage like no maitainance required etc.

A couple cautions:

SMF (sealed maintenance free) is too broad a term for determining characteristics of a battery, because it lumps together gel cells with AGM batteries (and even some flooded types).

Obviously, the float voltage recommended in this post (2.15V per cell) is incorrect for your battery. Use the label data, and get additional info from the manufacturer.

There is no single "correct method of charging a lead acid battery" and an expensive AGM battery, which has the potential for lasting 10 years with correct charging, can have its service life reduced to months, if charged incorrectly.

The only valid data comes straight from the manufacturer.

Ken, as usual, we cannot do without you. I gave you a GA for a GREAT answer....