I want to charge a 12V battery using an AC to DC adapter. Do I need to have some sort of charger controller?

get a delco voltage regulator and wire it in plugged in without a switching transistor the batteries will explode or pop.I have done that exact thing. once they are fully charged they will act as direct short/resistance and overheat. i recommend installing a diode in line on - side between battery and- lead with diode wired as such ->I-batt+. This will stop electrons from flowing when + happens at - end of group. I have not tried this so I dont know how it will work I do know the gate should open in the diode and follow the path through the device and not the cells.try and lmk. it is kind of fun to pop batteries anyway but the acid is acid so be careful. A cb radio type power supply 7-10amp will definately be youre best bet.

It depends what sort of battery it is.

Lead acid batteries (car batteries) are fairly indestructible, but even so incorrect charging can be dangerous because it can release hydrogen gas which is a fire of explosion risk in confined space. Over charging at a high rate can also overheat the battery and physically damage it. The best option is a proper battery charger. A cheap charger would cost no more than a mains adaptor anyway.

For other types of rechargeable battery you absolutely need a proper battery charger, otherwise you will wreck the battery in a small number of charges (in the worst case, the first time you try to charge it).

If the machine is always used where there is a mains poiwer supply, why not just use a DC adapter instead of the battery?

To answer your specific questions

1) Yes.

2) No.

Ignore the advice in another answer about "limiting the current with a diode". If you knew enough to design your own battery charger properly, you probably wouldn't be asking this question!

Hi There,

Amazing. You just asked the right question at the right time!

Anyone Can Help Me? Too? I am stuck very far out in the sticks. No way to buy a new battery here without having it shipped in.

I have a truck battery which seems to be about dead. The starter just turns over very slowly, but engine will not start. I know it is because the voltage is a bit too low. But no friends with jumpers in the vicinity.

Here is the same question as the original: Can I use a Compaq Notebook PC power adapter, output:3.18A 60 watt max, at 19 volts, to connect to the truck battery, and then have it charge to the point where I can start? Will this harm the truck/car battery?

Should the power adapter be destroyed in the process, do not care. Just want to get the truck started and get back to civilization.

Any knowledgeable help that can be provided will be GREATLY appreciated! Tks! Tks! Tks!

And the sooner the better. Thank you, again!

To (1); The battery does not draw more current then that the adapter can handle. In your case I would suggest a 1Amp adapter will do nicely.

To (2); The internal resistance of the battery changes to an extend that the charging stops.

Do not leave the adapter connected while using the battery.

As an option, why don't you get a 5 or 6 Amp power supply from one or other electronics shop. Then you don't have to worry about charging batteries.

Have fun

1. If the charging voltage used is much greater than the current battery voltage, the battery might draw current greater than the converter's rating. However, if the converter has a built-in current limiter, this will prevent the converter from frying.

2. The charging current of a battery usually decreases as it's terminal voltage increases. A fully charged battery will still pull a very small amount of current once it's terminal voltage nears the charging voltage. To ensure that the battery stops drawing current, place a diode between the charger and the battery. The diode will turn off if the difference between the charger and the battery is less than around 0.7 volts, thus ensuring zero current drawn.

First you must see the adapter output voltage. A 12 volt battery must required 13.75 approximately DC voltage to charge. You can charge battery with adapter but you must keep attention that even battery or adapter should not be much hot during charging. Second output current must be 1 to 2 ampere. In this way you can charge 12 volt battery but first for the one hour continues, if you found not fully charge then increase the charging timing. But keep this in your mind that continues charging with adapter can damage your battery.

12v Battery Adapter

You should not be using this type of battery indoors, as it can emit dangerous and explosive gases.

Get a plug in supply, it's a lot easier, smaller, and cheaper.

You need 14-15 volts to charge a 12 volt battery, so the adaptor may only partially charge the battery. It may also over charge it, depending on the exact voltage and current it delivers.

1. yes

2. no. see above re dangerous gas.

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