Stereo Memory Wire Draw - Some Data !

Maine Sail · #1 (**permalink**) 01-16-2008

Hi All,

I've seen this question come up numerous times over the years and it's going on at another forum right now.

I wanted to post some actual data so people are not so paranoid about conceting the memory wire from their 12V car type stereo to a "constant" source for fear of draining the batteries.

The first picture shows the actual memory draw with fairly standard "high power" deck made by Kenwood.

The deck draws .007 amps per hour while off! So there is no need to lose all your presets such as bass or treble settings, clock or AUX input setting by not wiring in the constant memory wire for fear of draining your batteries.

Radio turned off memory wire - amp draw:

Turned on & set to "Tuner" volume set to "Zero" - amp draw:

SailorMitch · #2 (**permalink**) 01-16-2008

Thanks -- good info since I have the same issue on my boat. I had already gathered the draw wasn't much but it's good to have something to back it up. I keep a watch on the charge on my 2 AGM Grp. 31's each winter and have never had a noticeable drop. This is the third winter for them.

Valiente · #3 (**permalink**) 01-16-2008

Huh. Live and learn. I thought that stereo presets were stored on a CMOS-style chip (it wouldn't have to be much of a chip) powered by a button battery, as in motherboard in PCs.

So if you take a "car stereo" style unit off its 12 VDC power supply, all presets are lost?

I have a full-sized home amp and tuner aboard, and the tuner seems to stay "memorable" unplugged for some time.

sailingdog · #4 (**permalink**) 01-16-2008

Valiente-

Most of the new stereos have clocks and other features that require power, not just the station memory.

labatt · #5 (**permalink**) 01-16-2008

Just reminded me of a small project for next season... wiring up a secondary 12v source for the radio memory 1) So I don't have to run a wire to the batteries that's always hot, ans 2) Just in case.

Thanks for the info though!!

Valiente · #6 (**permalink**) 01-16-2008

Quote:

Originally Posted by sailingdog

Valiente-

Most of the new stereos have clocks and other features that require power, not just the station memory.

Fair enough, but when they are removed from the power (assuming they are connected via the DC panel and not directly to the batteries with an inline fuse on the pos side), do they lose the time and the presets like a clock radio with a dead 9 volt in it?

A car is a different story in that there isn't usually a switch between the "always on" components (like power locks) and the "ignition switched" ones, like the starter. In a boat, you can (and should, IMO) completely shut down the DC side when off the boat. I customarily only leave the charger on a single AC side circuit, and it feeds DC to my batteries 12 hours a day because I didn't want to haul them off the boat.

But that's it.

CharlieCobra · #7 (**permalink**) 01-16-2008

I turn everything on the DC panel off except the pumps and leave the charger on.

artbyjody · #8 (**permalink**) 01-16-2008

Home Depot carries a solar powered security light that can last for up to 14 days without being recharged. The battery is slightly larger than one of those lantern batteries... and the solar panel is maybe 6 inches by 5 inches... That would be an ideal solution to 'memory' dependent functions... I use the thing on my art studio and it i gets sun maybe 3 hours a day if lucky.. it costs about $80. But easily adaptable to a marine environment...for those not wanting to go the whole solar route...but requires a low drain or interment burst for say a security light...I have used it for almost two year and once installed - just works... post is merely for those that have DIY alternative method seeking thinkology...

sailingdog · #9 (**permalink**) 01-18-2008

It depends. Some will lose the clock settings, some the memory settings, some both... it really depends on the manufacturer.

Quote:

Originally Posted by Valiente

Fair enough, but when they are removed from the power (assuming they are connected via the DC panel and not directly to the batteries with an inline fuse on the pos side), do they lose the time and the presets like a clock radio with a dead 9 volt in it?

A car is a different story in that there isn't usually a switch between the "always on" components (like power locks) and the "ignition switched" ones, like the starter. In a boat, you can (and should, IMO) completely shut down the DC side when off the boat. I customarily only leave the charger on a single AC side circuit, and it feeds DC to my batteries 12 hours a day because I didn't want to haul them off the boat.

But that's it.

wind_magic · #10 (**permalink**) 01-18-2008

Most boats should probably have some kind of solar panel/charger on them anyway, they sit so long the batteries self-discharge and get ruined. Anybody who has to worry about the current draw of a car stereo when it is off has to worry more about self-discharge of the batteries, because you're losing more power there than the radio draws.