# will a 12v battery fry a 433mhz radio transmitter rated for 3v-12v

will a 12v battery fry a 433mhz radio transmitter rated for 3v-12v? a 12v battery when charged is at about 13volts so im afraid it might fry the radio? Should i just put 2 diodes in series with the battery to bring the voltage down abit?

They are sometimes uses with a very small 12V battery. Those batteries can also be a little higher than 12V.

What kind of batter is it ? 3 Li-ion cells can be 12.6 V -> okay. lead-acid battery can 14.5V -> not okay. A NiCd or NiMH battery pack can be 13.5V -> maybe not okay.

I assume that 10% higher voltage is no problem, as long as the transmission is short to prevent heat.

Its a sealed lead acid battery. transmission time is very short, about 2 seconds every 2minutes

I think 2 diodes won't hurt. When the battery is charged, it can go up to 14.7 V.

When you are not transmitting, the transmitter uses such little current, that the diodes do almost not lower the voltage. Therefor I'm not 100% sure that everything will be okay with 2 diodes.

If the transmitter works on 3-12V why not use the 12V sealed lead acid battery and use a 5V regulator to generate 5V from battery and feed that 5V into the transmitter.

wes000000: If the transmitter works on 3-12V why not use the 12V sealed lead acid battery and use a 5V regulator to generate 5V from battery and feed that 5V into the transmitter.

5v is to little and distance is a problem. i will just use a 12v regulator to ensure the voltage never goes above 12v. thanx

Maybe you could meet halfway with like a 9V LDO regualtor, because with a 12V regulator (even a LDO one) you are going to be throwing away some of the battery's capacity, as SLA battery capacity ratings are usually from full charge (14V say) down to 1V less than rated voltage (in this case 11V) so you are throwing away more than 1/3 of your capacity by using a 12V regulator.

And does the voltage affect the transfer distance, I didn't know it did but I suppose it's possible.

wes000000:
Maybe you could meet halfway with like a 9V LDO regualtor, because with a 12V regulator (even a LDO one) you are going to be throwing away some of the battery’s capacity, as SLA battery capacity ratings are usually from full charge (14V say) down to 1V less than rated voltage (in this case 11V) so you are throwing away more than 1/3 of your capacity by using a 12V regulator.

And does the voltage affect the transfer distance, I didn’t know it did but I suppose it’s possible.

Well if I use a 9v LDO regulator I’m burning up 12-9=3v. If I use a 12v LDO I’m only burning up the dropout voltage which would be 1v or somewhere around there. I think I will just buy a 12v switching regulator. They are expensive that’s the only problem

Perhaps you should cite the actual specs (website) for the transmitter, as indeed should always be the case when asking a question here.

To specify something as "operating from 12V" but not allow it to be tolerant of 14V from a SLA battery, is outright peculiar.

The small transmitter modules is very simple. You listing the voltage range to be from 3-12V, i can guess it is something like this: http://miniimg.rightinthebox.com/images/384x384/201209/hhgihj1348814186444.jpg

The circuit being a few transistors, some inductors and the SAW-oscillator is pretty robust, and the voltage applied is not critical.

I would guess that the transistors used are rated for maximum 30V, so powering it from a SLA battery won't be an issue.

// Per.