# Suitable battery

Discussion in 'General Electronics Chat' started by Lightfire, Feb 24, 2011.

1. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
Hi,

I am planning to build something. But I don't know what battery is SUITABLE and EXACTLY fit for my project.

My devices were all rated as:

VOLT: 12 V
AMPERE: 0.21 A
WATTAGE: 5 W

Let's say my devices were 10 and they are connected each other in a PARALLEL connection.

Which do you think is the suitable and exact battery that will run this project???

2. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
What is the maximum length of time you expect to operate the circuit?

Do you want rechargeable batteries, or primary batteries?

Is their a weight restriction?

What is the load that you are powering?

3. ### debjit625 Well-Known Member

Apr 17, 2010
790
186
I think its DC...
So P = V * I .i.e.. 12 * 0.21 = 2.52 watt ,how its 5 watt

Now if the voltage is 12V and current is 0.21 Amp (210 mA) of each load which kind of battery you will need ? it depends on you i.e.. how long you wish to power your load.Now if they are connection in parallel that means the total voltage for the circuit will be 12V but the current for 10 loads will be (0.21 * 10 = 2.1 Amp) so if you need them to power for 1 hour you need a 12V 2.1Ah (Amp Hour) battery.Normally we use a bit more Ah then the required one and also their are some fixed value of Ah that you can get from the market not all.

Good Luck

4. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
Let's say 2 hours.
Recheargable batteries.
1 minigram joke, no there isn't
the device? um, let's say lights....

5. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
p.s. how can i know if how many ampere is my bulb is cuz there are only two description were there. am V-12 volt W=50 w so whats the AMP???

thanks and sorry for asking these questions...

6. ### debjit625 Well-Known Member

Apr 17, 2010
790
186
So its 12V 50Watt
Now P = V * I
I = P/V
I = 50/12
I = 4.1667 (approx)

7. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
In the beginning, you wrote that you wanted a 12v battery, load was 0.21A/210mA (which is 2.52W) and then 5W. Did you mean that you were going to operate two lamps in parallel?

Later, you write 50W, which is as mentioned above, 4.1666... Amperes.

You need to tell us what you're powering.

Incandescent lamps are very inefficient.

8. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
Ah so sorry for confusing.

why did i ask this one here. hehe no no, the halogen (or the second one i posted) is another question. im just asking how to get the ampere but no no, never mind this one...

no no, 5 w (im very wrong sorry) the above poster was correct it's 2.52 amp.

i would like to operate ten bulbs in a parallel circuit.

spec
volt 12 volt
ampere 0.21
watt 2.52

9. ### blueroomelectronics AAC Fanatic!

Jul 22, 2007
1,758
98
Again for how long? Minutes? Hours? Seconds?

Oct 5, 2010
690
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11. ### SgtWookie Expert

Jul 17, 2007
22,183
1,728
Ahh, that's 2.52 Watts; don't get confused.

OK, so you'll have 25.2 Watts total power, and 2.1 Amperes current, and you want to operate it for 2 hours maximum.

A sealed lead-acid battery would probably be your most economical solution, if you sized the battery AH large enough. You will get longer service life if you don't discharge it past ~75%; that means a higher initial cost for the larger capacity battery, but it will be less expensive in the long run. If you discharge it below 50%, you will have a very short battery life.

Your minimum AH rating will be about 2.1A x 2 / (1-50%) = 4.2/.5 = 8.4 AH; but actually a bit larger than that, because batteries lose more power internally if they are discharged at a high rate - so round it up to 9AH.

A better AH rating would be 2.1A x 2 / (1-75%) = 4.2/.25 = 16.8 AH or higher. The battery would last 3 to 5 times as many charge/discharge cycles.

12. ### timrobbins Active Member

Aug 29, 2009
318
16
Are you going to just power the lights from a battery, or from a mains charger, and only use the battery when there is no mains?

You want rechargeable batteries - is this the only application for the batteries? How are you going to recharge them? Are you wanting the batteries to have a long service life before they fade away from cycling age? Are you in antartica or the sahara desert? Do you only want 2hrs, or is 1h 59 ok, or would you sometimes want 2hrs 20 minutes?

13. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
Hello, what if I want to make everything more ideal. I mean, I want to make the battery exactly. no excess no lacking. i know it's impossible to buy in market. so im asking this question,

how to make my own battery?

14. ### debjit625 Well-Known Member

Apr 17, 2010
790
186
You cant make a perfect battery at home but for fun you can....

When I was in 7th grade I did it,we have a topic on cell (battery) in our physics book from which I started.I used diluted sulphuric acid (H2SO4) as the electrolyte solution,zinc as the negative electrode (cathode),copper as positive electrode (anode) ,it was just a simple Voltaic cell.

Their are many other ways to make a battery at home,one of them is lemon battery just give a search on google......

Good luck

Dec 26, 2010
2,147
300
You may have a bit of fun with home-made batteries, but don't expect to be able to produce much power in this way.

If you need a good light for use when mains power is unavailable, you should begin by trying to get the highest possible efficiency light source.

As SgtWookie has pointed out, incandescent lamps are not efficient. You might get better results with fluorescent tubes, or perhaps LEDs. This might allow you to have a smaller and cheaper battery, or more light.

Have you chosen halogen bulbs because they are all you can get hold of?

16. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
Honestly, yes. In Philippines, here, it is very hard to find fluorescent tube. Fluorescent tube is the one that produces the white (or daylight) light, right? If I can only find fluorescent tube, I will go and buy it as soon as possible.

Any ideas??? will you please say if it is for automotive or marine???

Dec 26, 2010
2,147
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Fluorescent tubes are made with different light qualities, not always "daylight". See this link: http://en.wikipedia.org/wiki/Fluorescent_lamp_formats

Do not buy anything unless you are sure that it is right for your use. Fluorescent tubes need special circuits to operate from low voltage DC - most fluorescent lamps are made for mains use.

Your last question puzzles me. Why do you ask if "it" is for automotive or marine? Do you want to know if a lamp designed to run from a vehicle battery would be suitable?

A vehicle lamp might be OK, but you would need to check the ratings: the power consumption might be too high. Some vehicles such as big trucks also use supply voltages of 24V or more, which may be higher than you would want.

18. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
That's why I am not buying anything except halogen lamps as I know it is OK for a 12 v battery that produces DC.

I asked it so I could find it easily. If that lamp is mostly used in automotive, I might go to an automobile shop to find it.

Yes. That's why I always buy a lamp that it is for vehicle.

I want a fluorescent lamp which can be lighted DIRECTLY to a 12 volt battery or can be lighted without any circuits or any other such.

Any help???

Dec 26, 2010
2,147
300
Are there any discussion forums more local to your area? This might help you to contact people with knowledge of what is available in your region. You might also be able to use your own language, instead of having to struggle with English.

20. ### Lightfire Thread Starter Well-Known Member

Oct 5, 2010
690
21
Thanks a lot Adjuster. thanks for advising me to find a local forum for me so i can communicate easily. thanks so i can use my own language without STRUGGLING WITH ENGLISH... BYE BYE AAC community! i got a lot of knowledge from you guys! especially to my friends!!!!!

bye bye!!!