hello everyone recently I found a 12v 9ah battery in my stuff and decided to make a power box with it and I faced the following problems I hope you will help:

1- I need a 12 to 5 converter to charge my mobile and etc but the problem is that I need two output currents a 2amp output and a 1amp one so my question is can that be done with just one converter or should I use any additional circuit?

2- The kind of battery I am using is SLA and probably when the battery drains the voltage would decrease so I wonder if the output of the 12 to 5 converter will decrease too.

3- I probably need to recharge the battery in my car and since the standard charging voltage is 14.4 volts and the car battery voltage is 12v so I wonder if can charge my battery using that voltage, if yes how should I limit the current so that it becomes suitable for my battery?
thanks, everyone.

 

Hello,

You could use a buck converter.
This one has a large input voltage range:
https://www.amazon.com/RioRand-3-01-0076-Converter-Module-1-23V-30V/dp/B008BHAOQO

bertus

 

3-I probably need to recharge the battery in my car and since the standard charging voltage is 14.4 volts and the car battery voltage is 12v so I wonder if can charge my battery using that voltage, if yes how should I limit the current so that it becomes suitable for my battery?
thanks ,everyone.

-- buying a suitable charger avoids a lot of problems (perhaps→) Link1 ≈ Link2

 

-- buying a suitable charger avoids a lot of problems (perhaps→) Link1 ≈ Link2

Thanks for your answer so you mean if I use a charger which has a large input range and converts them all to 5v my problem will be solved right?

 

1-I need a 12 to 5 converter to charge my mobile and etc

How about using one of the automotive 12V to 5V USB converters that are available?

2- the kind of battery I am using is SLA and probably when the battery drains the voltage would decrease so I wonder if the output of the 12 to 5 converter will decrease too.

No, the output of a 5V converter is regulated to be basically independent of the input voltage.

3-I probably need to recharge the battery in my car and since the standard charging voltage is 14.4 volts and the car battery voltage is 12v so I wonder if can charge my battery using that voltage, if yes how should I limit the current so that it becomes suitable for my battery?

Yes that should work.
A small resistor in series will limit the charging current.
You probably want no more than about 1A charging current.
Try a 1 ohm, 5W resistor.

 

Yes that should work. A small resistor in series will limit the charging current.
You probably want no more than about 1A charging current. . . .

-- in case of left on its own nothing avoids overcharging the battery = you must sign an agreement with yourself that if you leave the site you disconnect all cables (no need to fine yourself coz your car may burn down like that) -- as it's seen from this DIY battery conditioning attempt it's not so likely -- but in principle it is likely

(very wild guess of ↑this↑) http://tinyurl.com/y2j5cobs e.g. many 12V 7A·h -s don't want to see too high initial charging currents = so for initial 10 to 20 minutes you need to limit your current below 2.4 ... 2.0 A -- , later when the battery has risen it's terminal voltage the 1Ω limiting resistor may do it's job . . . (you have to read the d/s of your particular battery model for proper/safe charging characteristics)

 

How about using one of the automotive 12V to 5V USB converters that are available?
No, the output of a 5V converter is regulated to be basically independent of the input voltage.
Yes that should work.
A small resistor in series will limit the charging current.
You probably want no more than about 1A charging current.
Try a 1 ohm, 5W resistor.

Thanks. Will your solution also work for the output of the 5v module because i need two outputs if yes how shoukd i calculate that? Is it the ohm's law?

 

P.S:my battery model is SB1290

 

Will your solution also work for the output of the 5v module because i need two outputs

Use one of the automotive converters that has more than one USB output.

 

http://www.sunnybatt.com/pdf/SLA/SB/12/SB1290.pdf -- the Maximum charging current 3.6A almost accepts the 1Ω limit charging if the battery is not ?? too empty ??
__________

This one has a large input voltage range

http://www.ti.com/lit/ds/symlink/lm2596.pdf ← is better to design yourself there are optimal for output power inductors selection table
Figure 15. Undervoltage Lockout for Buck Regulator -- is good to have feature not implemented on (otherwise cheap amazon's ver.)
. . .
fast estimate for (1+2)A·5V÷78%(19.2W for the remaining terminal voltage 9.9V -- which is near too empty ) is 30 minutes run time at full power ← (Discharge Constant Power (Watts at 77°F / 25°C)) . . . for a new Battery

 

Thanks. Will your solution also work for the output of the 5v module because i need two outputs if yes how shoukd i calculate that? Is it the ohm's law?

In your initial post, you said you need two outputs. 2A and 1A. You do know that the loads will only draw what they need? So if your power source is rated at 3A or above, you can wire both loads in parallel.

I assumed that you thought you needed two power sources because the loads required different currents. But that’s not the way current ratings work on a power source. That is the maximum current supplied and as long as it’s greater than the required by the source, it will work. And current adds in a parallel circuit, hence 3A. 4A or more might be better.

 

In your initial post, you said you need two outputs. 2A and 1A. You do know that the loads will only draw what they need? So if your power source is rated at 3A or above, you can wire both loads in parallel.

I assumed that you thought you needed two power sources because the loads required different currents. But that’s not the way current ratings work on a power source. That is the maximum current supplied and as long as it’s greater than the required by the source, it will work. And current adds in a parallel circuit, hence 3A. 4A or more might be better.

Well Im not that sure about what you say. But you can correct me if i am wrong I think batteries draw current as much as there is not what they need. As I said I am not sure. But thanks anyway

 

Actually it is more complicated than either of you think.

If you are thinking about connecting this directly to a battery, that is a big no-no. You need a charger circuit in between that regulates the current in a complex way depending on the battery chemistry.

If you are talking about phones or other devices that charge via a USB connector, the charging circuitry is built in, and they determine how much current to draw base on some form of communication with the charging port. This might be two voltages on the data lines or might require negotiation using USB protocol. If they cannot recognize the capability of the charger, they default to 500 mA.

Bob

 

I think batteries draw current as much as there is not what they need.

If you are referring to load current, no.
A load draws only the current it needs from the battery or other source.

 

more might be better.

true in a sense of DC/DC efficiency but not the longevity of the converter's switch and inductor that degrade / age more rapidly at higher temperatures

two voltages on the data lines

https://www.androidauthority.com/usb-type-c-and-3-1-explained-656552/
but the information provided is better to be confirmed from multiple sources . . . as always

random find → https://www.makeuseof.com/tag/usb-car-charger-mistakes/ (as for the option -- "don't build it yourself")

 

Actually it is more complicated than either of you think.

If you are thinking about connecting this directly to a battery, that is a big no-no. You need a charger circuit in between that regulates the current in a complex way depending on the battery chemistry.

If you are talking about phones or other devices that charge via a USB connector, the charging circuitry is built in, and they determine how much current to draw base on some form of communication with the charging port. This might be two voltages on the data lines or might require negotiation using USB protocol. If they cannot recognize the capability of the charger, they default to 500 mA.

Bob

There are two charging parts in my device the important one is this 12 to 5 part which will be connected to my phone or tablet using a usb cable and the problem I was talking about is that my tablet needs 2amp and phone needs 1amp. So if I guess what you are saying is this: it is not important how much is the current i give my phone it draws as much as it needs, right? I am saying that because in most car chargers have two outputs a 2.1 amp and 1 amp

 

Read my post again. Your ports have to tell the phone how much current it can draw, or it will draw only 500 mA.

How you do that depends on what type of phone.

Bob

 

Read my post again. Your ports have to tell the phone how much current it can draw, or it will draw only 500 mA.

How you do that depends on what type of phone.

Bob

WOW! I didnt realy knew that. Would you please give me some kind of refrence because I want to use it in my future projects and also to mention it inmy refrences part in the research I am doing on this stuff. Thanks for your complete answer.

 

Use google, it is what I would have to do.

Bob

 

Hello,

Have a look at this page:
https://obddiag.net/usb-power.html

Bertus