Simple battery charging question..

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Audioguru

Joined: 19 Jan 2008
Posts: 1148
Helped: 95
Location: Toronto area of Canada

02 Nov 2009 21:09 Simple battery charging question..

Battery manufacturers do not say that Lithium batteries need to be discharged and recharged.
Also my lithium batteries do not.

I think your radio manufacturer wrongly copied the manual from an earlier radio that used an old Ni-Cad battery.

plainman007

Joined: 30 Sep 2009
Posts: 26
Location: gandhar

03 Nov 2009 6:20 Simple battery charging question..

Hmm there cant be a mistake in the manual because they clearly state that its a LI-Poly (which is the actual type of battery in the radio) and that it should be maintained this way for best performance.

I think the best way to keep batteries active is by using them a lot hmmmm Smile

But irrespective of which type of battery, its alway better to wait till a battery is almost completely discharged and then recharge it again ? Or do you recommend half consumed batteries being charged as is to full ?

Thanks

Audioguru

Joined: 19 Jan 2008
Posts: 1148
Helped: 95
Location: Toronto area of Canada

03 Nov 2009 14:14 Simple battery charging question..

Your radio manufacturer does not manufacture Li-PO batteries. Look at the website of the battery manufacturer to see about their batteries.

A Lithium battery has only a certain number of charge-discharge cycles before it is dead so wasting some cycles will shorten its life.

Each battery type is different.
A lead-acid and a lithium battery are destroyed if they are discharged too far. A Ni-Cad or Ni-MH battery cell doesn't care if it is discharged to 0V, but then in a battery some cells might become reversed voltage which will destroy them.

plainman007

Joined: 30 Sep 2009
Posts: 26
Location: gandhar

04 Nov 2009 17:29 Simple battery charging question..

Just one more thing to clarify. So when a battery is fully charged it attains its voltage (which can be seen in a multimeter) as 12v if its 12v battery or it usually is supposed to show more. Then as it is used it keeps on supplying 12v dc and at anytime that its considered delivering power ? the mutimeter would show 12v or more only ? And then as a batt requires to be charged it drops and shows lower readings on the multimeter.

Ok let me ask it in a more simple way. I charge a 12v dc battery fully. I test it with the MM. Its shows 13v maybe. Then i start using it. After a few usage sessions it shows 12v on the MM. Then some more usage and it shows 11 or maybe 10v. Is it time to charge it ? At which stage would you say the battery has depleted and needs a charge ?

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Audioguru

Joined: 19 Jan 2008
Posts: 1148
Helped: 95
Location: Toronto area of Canada

04 Nov 2009 21:00 Simple battery charging question..

Each cell of a lithium battery is charged to 4.2V.
So 3 cells in series charge to 12.6V. The minimum allowed voltage for a lithium cell is 3V so when the battery voltage drops to 9V then the load should be disconnected and the battery should be charged properly.

plainman007

Joined: 30 Sep 2009
Posts: 26
Location: gandhar

05 Nov 2009 6:05 Simple battery charging question..

But how do i know how many cells are in my battery. It looks like one plastic square block. With everything sealed and is supposed to be maintenance free. It has just two small terminal plates emanating from within the battery.

Audioguru

Joined: 19 Jan 2008
Posts: 1148
Helped: 95
Location: Toronto area of Canada

05 Nov 2009 14:50 Re: Simple battery charging question..

plainman007 wrote:

Are you talking about the Li-Po battery in your radio? Or a sealed gel-cell lead-acid battery?

plainman007

Joined: 30 Sep 2009
Posts: 26
Location: gandhar

05 Nov 2009 19:13 Simple battery charging question..

Any battery ? Wether a gel battery or a gel sealed battery ? How does one tell how many cells it consists of ?

Thanks

Audioguru

Joined: 19 Jan 2008
Posts: 1148
Helped: 95
Location: Toronto area of Canada

05 Nov 2009 19:19 Simple battery charging question..

You need to know the chemistry of a battery to charge it properly.

dadansoy

Joined: 06 Nov 2009
Posts: 2
Location: us

06 Nov 2009 3:59 Re: Simple battery charging question..

i know the Sealed bateries isstandardized in sizes. Capacity depends on size and since there are many competitors in the market, the same size means the same capacity

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AbtElectronics deals

plainman007

Joined: 30 Sep 2009
Posts: 26
Location: gandhar

07 Nov 2009 9:24 Simple battery charging question..

Dear Audioguru,

But how can a normal layman who doesnt have an electronics background understand all this. Its so technical. Im mainly interested in maintaining my batteries properly but dont have much tech knowledge. The radios which i have have no markings on the battery giving the company details etc. I think thats impractical and its very unlikely that all radios batteries carry the address and details of the battery manufacturer. This said, it mentions its a li-poly battery and it also says OUTPUT - 7.4v 1200mah. Based on this can you tell me how this battery should be charged. The chargers that come with the radios are desktop base chargers. The manual says the batts take about 5 hrs to charge and its better to leave it for 2 hrs after the green led (fully charged) lights up on the charger. This has proved right in actual experience. For a fully discharged radio in about 4.5 hrs the green led lights. And we leave it for 2 hrs more and then remove the batt. The dealer said the batt is capable of 450 cycles.

Also after the batt is charged and im not going to be using the radios for say a month. Is it ok to leave the battery with the radio or should i detach the batts. And if the radio is just going to be stored for longer say 3 to 4 months of disuse. Is it good to discharge and the recharge the batt fully once in a month. Is this good for the battery ?

Thanks a lot. I really appreciate your effort in explaining this to me.

Audioguru

Joined: 19 Jan 2008
Posts: 1148
Helped: 95
Location: Toronto area of Canada

07 Nov 2009 16:40 Simple battery charging question..

A rechargeable lithium cell has a nominal voltage of 3.7V so two in series are 7.4V. The radio should have a circuit to disconnect the battery when its voltage drops to 6V. The charger should have a circuit to limit the charging current to about 400mA and limit the voltage to 8.4V and disconnect the charging when the charging current drops to about 36mA.

I don't know if your radio has a clock or something that drains the battery when the radio is turned off. It it doesn't then a fully charged battery can sit in the radio for years.

It wastes the limited number of charge cycles to discharge the battery for no reason.

plainman007

Joined: 30 Sep 2009
Posts: 26
Location: gandhar

08 Nov 2009 9:00 Simple battery charging question..

Hi,

I have categorised my questions into basic categories of doubt. Would be great if you can just answer quoting the point no. This will ensure i get all my answers for each doubt that i have. Smile

1. It doesnt have a clock or any function on it. It a very simple type of professional radio. No display nothing. Just on/of & volume on one knob and channel selection on another. I think the radio senses a drop in voltage and then the transmitting LED blinks non stop to show a low battery. I think its safe to off the radio immediately and then recharge as soon as possible right ? Since i think its not good to leave a battery in discharged condition for long ?

2. I dont think it has any function that runs in the background while the knob is in off position. So i assume its ok to just leave the battery packs in the radio ? Cause its so inconvenient and risks ending up with a loose batt clip etc if i needlessly detach the battery every week and put them back in, and that would mean picking up a new radio if the batt clip breaks or something. So is it ok to leave the batt inside ?

3. We use these radios on an average of once in 2 weeks for events. Do you think that kind of usage is enough to keep the battery healthy ? So i can skip the monthly discharge > recharge cycles.

4. If im going to leave the radio unused for about 2 months or so Ill fully charge then discharge to 50% and store it ? I think 50% charge is suggested for storing batteries for long periods ?

5. What is the rough expected life of a battery like this considering our sparse usage pattern ? I mean if a person charges & uses this radio once in 3 days and gets x years of life span out of the battery. If a person charges & uses it 3 times in a month will he get a longer life of battery or is the life span duration fixed irrespective of charging pattern.

Thanks a lot for your contributions. I think this post will turn into a mini course on battery maintenance for all people who seek advice on this particular subject.

Audioguru

Joined: 19 Jan 2008
Posts: 1148
Helped: 95
Location: Toronto area of Canada

08 Nov 2009 15:04 Simple battery charging question..

1) An electronic device that is powered by a rechargeable lithium battery is supposed to detect a low battery voltage (about 3V per cell) and switch off the load.
2) Yes leave the unused battery in the radio.
3) Yes do not discharge/recharge that wastes cycles.
4) A 40% charge is recommended for storage for years but you cannot determine 40%. For only a couple of months then leave the battery fully charged.
5) The battery can be charged/recharged about 450 times if it is not overcharged and if it is not discharged below 3V per cell.
Read about lithium batteries at The Battery University on the web. There are many other Battery Maintenance sites on the web.

plainman007

Joined: 30 Sep 2009
Posts: 26
Location: gandhar

09 Nov 2009 21:26 Simple battery charging question..

Hi Guru,

Thanks a lot for your help. I only didnt understand answer 1. My question was when the radio beeps a low battery alert. It must be switched off and charged asap ? Or a drained battery can be left for a few days before recharging without damage to the battery ?

Thanks

Audioguru

Joined: 19 Jan 2008
Posts: 1148
Helped: 95
Location: Toronto area of Canada

09 Nov 2009 23:22 Simple battery charging question..

I don't know if your radio is smart enough to switch itself off when its battery is low.

I think you should charge a drained battery immediatyely because if you don't then it might be left discharged for too long.

plainman007

Joined: 30 Sep 2009
Posts: 26
Location: gandhar

10 Nov 2009 21:19 Simple battery charging question..

Hi Audioguru,

So I think im safe with just using these radios and not bothering about battery conditioning etc since im going to use them approximately once a week or at least 3 times a month. If im not going to, maybe during the vacation months, then i will fully charge them and shelve them till next use which anyway wont last more than 2 months at a stretch.

What kind of batteries do UPS units and Emergency lights mostly use ? Lead acid ? Or are they also mostly sealed gelled batteries ? Do emergency lights which get used only once in a bluemoon need to be conditoned once in a while ?

Thanks...

Audioguru

Joined: 19 Jan 2008
Posts: 1148
Helped: 95
Location: Toronto area of Canada

10 Nov 2009 23:27 Simple battery charging question..

Correct.
You do not need to condition a lithium battery.

Correct.
UPS units and emergency lights use lead-acid batteries. Their charger trickle-charges them all the time to make up for self-discharge and maybe they are quickly tested once in a bluemoon.

plainman007

Joined: 30 Sep 2009
Posts: 26
Location: gandhar

16 Nov 2009 5:23 Simple battery charging question..

But what if an emergency light isnt always plugged into the wall socket. I mean its fully charged but then stowed away for emergency use. Then used ocassionally (twice a month) for maybe 30 mins.

Is this kind of usage ok ? Or does this usage pattern of Lead Acid Batteries qualify for battery conditioning (full discharge and recharge) maybe once in a month or on a quarterly basis.

Thanks.

Audioguru

Joined: 19 Jan 2008
Posts: 1148
Helped: 95
Location: Toronto area of Canada

16 Nov 2009 5:33 Simple battery charging question..

A lead-acid battery should always be fully charged. After sitting for a few months it gets sulphated and is ruined.
If it is used then it should be charged immediately.
It should be trickle-charged to make up for self-discharge.

There is no reason to wastefully discharge a lead-acid battery.

plainman007

Joined: 30 Sep 2009
Posts: 26
Location: gandhar

17 Nov 2009 17:03 Simple battery charging question..

Hi,

1. What if its not sitting for months at end. Maybe Just a month or 2 and then fully charged.

2. From what i understand about what you said. I think its better not to discharge the battery but better to just top it up once in a month ? If so how do i know how long to leave it in...just leave it overnight ? cause if its a trickle charge unit it wont overcharge right ?

3. Of course if this is connected to power always then i guess its being trickle charged internally in the light unit.

Thanks..

Audioguru

Joined: 19 Jan 2008
Posts: 1148
Helped: 95
Location: Toronto area of Canada

17 Nov 2009 17:13 Simple battery charging question..

You should use a proper battery charger circuit. It will not over-charge your battery but a cheap charger will.

A proper battery charger circuit will trickle charge your lead-acid battery all the time after charging it.