Radar power use question

[ddsailor25]

We have a 29' sailboat and I'm starting to look into radar setups. I have never used one before so this is completely new to me. One of my concerns with a radar set up is the power useage. Most of the ones I am reading about are 4kw radars. I'm assuming that the 4kw output is a burst power output and is not a constant draw. The only time that we will be using it will be in low visability days and would most likely be under power as well. Our alternator is a 40 amp alternator and our battery bank consists of 2 80 amp hour batterys that are new.
If people can also comment on their systems and what they like or dislike that would be very helpful as well. Thanks for any imput.

Dave

[Tim]

I have a Furuno 1622 (2002 vintage) that draws an observed 2.5 Ah in transmit mode, which is an easily-sustainable draw for just about any small boat's electrical system.

I can't speak authoritatively for the newer versions of radar units, but I suspect that actual battery draw for most small-boat radars would be comparable to my observations.

[Oscar]

What Tim said.

Also, most radars have a standby mode, where they use little or no power. Then you can activate it with one button when you are actually looking at it. Also there are modes where you can tell it to do a certain number of sweeps every so many minutes. This reduces consumption even more. You would set alarms and it would alert you if it noticed any solid objects.

Having said all that..... For navigation in reduced visibility on a small vessel radar comes at a considerable cost. For (heavy) traffic avoidance I would FIRST install an AIS receiver, which takes up almost no space and weighs very little.

I have experience using the above and was most impressed. I can expound if you are interested.

[DaleH]

Amp Draw:

I know Garmin and Raymarine 4kw radars draw 34 watts during transmit and 10 or less on stand-by. To get amps, one divides wattage by voltage, assuming 12.6 VDC as nominal. So the amp draw would be 3-amps in transmit and < 1-amp in stand-by.

Note your power lead may be configured with a larger rated fuse, say 5 to even 10-amps. This is for peak start-up/power draws and to allow for fluctuations in voltage.