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Simple battery charging question..

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Junior Member level 3
Sep 30, 2009
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I have what seems to be a sealed battery. Its a black block like thing. Dry sealed battery. Id like to know the proper way to store such batteries as ive heard they can lose their ability to perform if left idle for a few months etc. Id like to know how to charge and discharge this battery. How to know how much power is in it, maybe by using a digital multimeter ? And how to discharge it (maybe by attaching a particular voltage bulb and letting it burn till the battery goes dead). As this battery is needed to be used only once in 6 months or so. So id like to know how to keep the battery alive during storage.

Thanks a lot...

It is advisable to avoid using a component that could not be identified. There are hazards. Check for hazards.

Sealed bateries come in standardized sizes. Capacity depends on size and since there are many competitors in the market, the same size means the same capacity (almost always). So, give us the size or a photo.

Everything you need to know should be printed on the battery case (nominal voltage, capacity, often even charging conditions). There are also manufacturer datasheets available.

Your sealed battery might be lead-acid, Ni-Cad, Ni-MH or Lithium.
They are all different.
You don't say which type you have.

as for discharging methods, I tend to use a halogen car head lamp it will rapidly and safely discharge the battery. as previous post said most of these batteries have the same characteristic depending on their physical size. if you post the info and maybe include a pic that would help a lot in helping you with the capacity info.

Hi, Im so sorry. Im not exactly an elctronics expert. I will post a pic immediately. But i think being a new member may not allow me to post or attach pics here. Or i will first go get the battery and come and list whats printed on the label.

Plz give me a few hrs as im at home now.



Its a 12v, 0.8ah battery. The dealer says its a jelly type battery. Its sealed and is nothing but a plastic block with just 2 terminals thats all. The rest is like one plasticine block.

My reason for this post is that i would like to learn how to properly maintain this battery since its going to be used only once in 6 months to run a small motor in a gadget. The rest of the time its just going to remain idle and i dont want it to die out on me.

My friends have advised buying a mutimeter and checking how much voltage is in the battery maybe once in 15 days and then charge the batt accordingly before shelving.

Another friend suggested a simpler method to just charge the battery fully and shelve it. And maybe once a month take it out and charge it. And he said its better to drain it to almost a dry stage and then charge it fully before shelving again for another month. He said instead of the mutimeter the bulb would be more layman and would not only show how much power is in the battery by brightness and also help to drain the batt efficiently.

Kindly advise.

I guess that your battery is a sealed lead-acid gell type. It dies in 1 month or 2 months without being trickle-charged. You can trickle charge it with a small solar panel.

If you discharge it (your friend said to drain it) then it is ruined.

Here you can find some hints
The best way to store it is keeping it charged to its floating voltage, that means to source it a very small current (about 5 to 10 mA) and controll the voltage which should stay in the 13,6 to 14V range. Some types float at 14.5V and this is easy to see because they keep the voltage under very small charging currents. A too high voltage can damage it and also, discharging it to a low point (usually less than 12V) also will, surelly, damage it. If you can´t keep it in the floating region then fully charging it every two months will be enough. The same apllies to other battery types (NiCd for example) but the voltages are a little bit diferent. Before reaching the floating point the charging current should be limited, usually to 1/10 of the rated capacity of the battery.


Audioguru > My second friend did mention however not to drain to completely flat too. He told me that. He said that would also damage the battery. Thats why he said to start charging it when the bulb dims out itself.

Paul > I use this battery only once in 6 months. Can i just charge it fully, store it, then just pick from shelf after 2 months and charge fully again (without bothering to check it etc) and store. Or should i check. If yes. Then how should i check ? Multimeter or bulb method please ?? Bulb method would help check and drain battery too if its still at half capacity right, cause they say its bad to charge a battery which is not 90% discharged either, right ?


I suggest your checking the voltage and if it goes near or bellow 12V charge it again. I think 6 months is too much time for a low rated capacity as 0.8Ah. Experience shows it must be done every 1 or 2 months. Some new batteries retain charge for 3 to 4 months but this time declines after aging.

What does the 0.8ah mean in laymans terms ? Does the amps per hour mean how long it can hold power or how long it can supply power or how long it takes to charge ? 12v is the power right ? Whats the ah mean then please ?

Thanks Again

0.8Ah means you can sink 1A during 0.8h from it or wathever results in a voltage x current product that results 0.8. But be carefull, there is always an upper limit on the current you can sink without damaging it. 12V is just the nominal output voltage.

Hi Paul,

So based on my previous post. Which is the best method to adapt. Bulb draining or just on the shelf for 2 months to completely discharge the battery ?


If you want to measure the battery capacity, discharge it using a constant load (like a bulb or a resistor) and measure the time for the output voltage to drop to about 12V. Please note that a filament´s resistance shows some variation after heated. If you want to store it, just leave it on the shelf.

Added after 1 minutes:

You don´t need to completely discharge this type of battery to charge it again. This is a recomended procedure for NiCd batteries instead.

pauloynski said:
0.8Ah means you can sink 1A during 0.8h from it or wathever results in a voltage x current product that results 0.8. But be carefull, there is always an upper limit on the current you can sink without damaging it. 12V is just the nominal output voltage.
All lead-acid batteries have their capacity rated when the discharge current is at the 10 hours or 20 hours rate so the current is fairly low. This little 0.8Ah battery can supply 80mA for 10 hours or 40mA for 20 hours. It might supply 800mA for 15 or 20 minutes. It will be anout 10V when dead.

Please find attached the spec. of a similar battery. Please take a look at the specified capacity with respect to discharging time.

pauloynski said:
Please find attached the spec. of a similar battery. Please take a look at the specified capacity with respect to discharging time.
The Yuasa 12V/0.8Ah battery has a capacity of 0.8Ah at the 20 hour rate which is a current of only 40mA. Its capacity is 0.74Ah at the 10 hour rate which is a current of only 74mA. The end voltage is 1.75V per cell so the 12V battery will be only 10.5V.

I´ve just sent the pdf to show how is it specified and to give an example of what can be expected from such a battery. I agree with you Audioguru. No need to reply.

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