How To Build +12V Battery Reverse Protection Circuit?

[kengloong]

battery reverse protection

Anyone can help to give me some idea to buid a +12V battery terminal reverse protection circuit to prevent my circuit board blow/ damage...

Thanks & best regards,
keng Loong

 

[koky]

reverse current/battery protection circuits

if your load is low put a diode 1N4007 in series to positive supply with cathode connectd to load side. If your board need a lot of current, put a fuse in series to positive supply an 1N5408 diode with cathode connected after fuse in the load side and anode connected to negative supply

 

[leomecma]

battery reverse

If you are using a linear supply suggestion of Koky that put an serie diode is the best (more easy and simple), but if you are using switched supply the best is put a thermistor in series and a diode after then in paralel, look it in attachment.... sometimes is good put a varistor too, but it's depends of characterist of input signal and all values depends of real circuit ...

If your supply is linear and need much current you can put two diodes in paralel, and in serie with then or use a diode with more current capability.


leomecma

 

[sunsina]

building a 12v ups

if your circuit consumes low power use this configuration below to make your device polarity
independant.

Note:there is about 1.4 volt Voltage Drop

 

[platonas]

12v protection circuit

Another one idea is to supply a 12v relay through a diode. When the relay is activated it will connect your load (PCB) on its input, which should be correct polarity since the diode can allow the relay to energised only in correct polarity supply.

With this method, you waste some more power but there is no voltage drop due to the diode.

 

[kengloong]

reverse protection for 12v circuit

Is the circuit that provided by you all can be used in UPS (Uninterruptible Power Supply)? I planned to change the battery using Car Battery. Is it will work or I need to modify the UPS circuit? How to let the battery to be charge faster than the ordinary UPS? Please advice.

Thank you.

 

[wlhsaso]

12v reversal curcuit

if your circuit consumes low power use this configuration below to make your device polarity
independant.

Note:there is about 1.4 volt Voltage Drop

this circuit is afull wave rectifier bridge and it is simple four diodes in one package tat provides polarized DC whatever the polarity of the input terminals.

 

[kengloong]

12v battery protection diode

I already tried the circuit whose provided by KOKY, which using Diode 1N4007. For your info, I changed the diode from 1N4007 to 1N4001. This circuit is worked only without any load. But when I switched on my computer, the UPS indicated Baterry Low and my computer straight away shuting down.

So, is it because of the diode that I'm using? I changed the diode from 1N4007 to 1N4001 is because accordinh to thesalesman, the 1N4007 is just capable to 400V 1A, but 1N4001 its can reache 600V 1A.

Hope to hear from you all soon.

 

[Borber]

how to build a 12v battery

Placing diode in series with + terminal will lower supply voltage for 0.7V. This can be the reason that UPS is indicating low battery. The first idea that came to my mind is to use two relays.
Relay A changes polarity if needed and relay B delays switch on until polarity is changed.

 

[jodokus]

how to build a 12v computer

With a diode you loose 0.7V and with a relay your protection is expensive and perhaps too slow. Best reverse battery protection is using a "reversed" mosfet in series with the supply line. In the minus line an Nchannel fet will do the job, connect drain to battery-minus and source to the minus-in of the circuit to be protected. connect gate to the plus. the idea is that a fet works well when drain and source are reversed but there is an intrinsic diode that spoils the effect in most circuits but not in this case. The same trick can be done with a p-channel fet in the plus line. With a protection like this you only loose a few millivolt when selecting the right fet.

 

[Borber]

protection against battery reversal

Agree with jodokus. And schematics is:

 

[echo47]

12v ups circuit

kengloong, your salesman is wrong. 1N4001 is 50V, 1N4007 is 1000V. Here's a data sheet:
**broken link removed**

 

[Borber]

diode battery 12v

Yes diodes are different. But battery voltage is only 12V. Another question is what is the battery current, is it greater than 0.7A?

 

[kengloong]

build 12v ups

The current of the battery is 45 Ampere per Hour.

 

[Borber]

which diode 12v circuit

No it is not battery current. It is the capacity of your battery. You must measure battery current when UPS is switched at full load. And then you can decide what kind of diode of MOSFET you can use for protection.