capping maximum input voltage

i have a 12v circuit board wired into my motorcycle which has an input tolerance of 11v-13v. it is powered directly from the battery which, by nature of the charging system can be upto 14.5v is there something i can put in line from the battery to the circuit board which will not allow more than 13v to the circuit board? i thought maybe a resistor in line maybe but i cant let the voltage drop below 11v. any help would be appreciated, thanks.

Find a proper switch mode / buck boost power supply that runs of 10-15 vdc or so ( to allow for the variation in the motorcycles voltage) and outputs a clean 12 vdc.

Phreak480 wrote: Find a proper switch mode / buck boost power supply that runs of 10-15 vdc or so ( to allow for the variation in the motorcycles voltage) and outputs a clean 12 vdc.

hi, thanks for the reply, so you mean a 12v power supply that is powered by a 12v battery, but the power supply can manage the variation in input voltage but outputs a solid 12v? can you give me a link to an example of what you are referring to, or shall i just google it? thankyou

I have no idea what kind of circuit board you are trying to power, but the Astron power supply on my repair bench has variable voltage. It STAYS at 15 volts. I have powered everything that you can put in a vehicle with this 15 volts. If you are concerned and want to use a regulator of some sort, I need to know the maximum current draw of said circuit board.

What is the load in Amps or Watts? A simple Zener clamp (regulator) may be all that is required.

the circuit board contains 4 relays which i am using to power a remote start/ignition for my bike. the spec says max draw with all relays energised is 140mA. i can post a link to the system i am using but i am not sure if i am allowed, does it not say in the forum rules that you cannot post links to stuff? or have i read that wrong?

You can post a link. Some websites such as Ebay, sonicelectronics, are blocked by the server. Post it and I can figure it out if it is a blocked one. If this is designed for automotive/MC use, it will handle the 14. whatever volts you send to it.

this is the unit i am using http://www.quasaruk.co.uk/acatalog/DS-LEWES4%20Remote%20System-2.pdf

The unit's relays are rated for 5A and they typically have ~30mA coils which aligned with their data. (All relay operating less quiescent = 140mA - 14mA => ~120mA for 4 relays = 30mA per relay.) The 11V - 13V receiver is obviously not designed for automotive use - ie, typically 8V - 16V operation or tolerance. And whilst I thought a Zener regulator was fine for capping 140mA to 13V, it doesn't solve the problem of a cranking dip below 11V. Hence I agree with Master IAAI - get a dc-dc converter that outputs 12V at least 2W (~160mA) with an 8V or lower to 16V or higher input. Else get a receiver designed for automotive use.

ok, thanks for that advice. can you point me in a direction to such a DC-DC power supply that i would need? i cant seem to find one, or i am looking at the wrong things. thanks