R21-EC electrical

P

pvincent@live.com

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Apr 16, 2011
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Fluid Motion Model
C-24 C (Sterndrive)
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Still...
looking to power a laptop & small fan while off shore, what suggestions might you have for powering these type of items? Do you use an inverter plugged into the dc power (cigarette lighter) or purchase an additional power unit and wire it in?

thanks
 
A small inverter, in your case would be ideal. Just total up the amperage on what you want to run and get the appropriate size. For a small fan and a laptop, you could probably run it off the cigarette lighter outlet.

Charlie
 
thanks! would you happen to know where i could find the output rating of the cig. lighter?
 
Why not get a 12volt fan with a cigarette lighter plug and a 12volt input to variable voltage output transformer which you can set to suit your laptop voltage. Laptops are usually 15 to 19 volt. You can then use the laptop in your vehicles as well. Electronic (Tandy) stores sell the transformers.

Geoff
 
If you install an inverter to charge the notebook computer you may find you need one that has greater output than a cigarette-lighter plug-in will support. The R21 cigarette lighter outlet is fused at 15 amps. I tried my Dell on an inverter which requires less than 15 amps in my F-150 and it will not run the Dell's charger. One using 15 amps or less of input Keeps kicking out and will shut down (or self-destruct) with that computer. If I use one with enough output it will blow fuses on the lighter socket.

Using quick-and-dirty calculations the Dell requires 1.6 amps input at 120VAC (192 watts) and produces 3.34 amps at 19 VDC (63 watts) so inefficiencies in the conversion are pretty significant. A gross calculation is that the ratio of DC to AC is 10:1 (perfect world and ignoring the characteristics of AC current) so the required input at 12 VDC is going to be a minimum of 16 amps. The upshot is to be sure to size the inverter to match the load,

I finally installed a Cobra CPI 480 in the truck. The output is about double what I need for the Dell. That requires heavier wires (sized depending on length if far from the 12 VDC source) and proper fusing to allow it to produce its full output current. It will keep the notebook alive and in full use indefinitely.

The 12 VDC "transformers" sound interesting. I am not familiar with those but I suspect they are pretty inefficient. My "Juice 101" class seems to say the current has to be converted to AC, then adjusted to the proper voltage, then converted back to DC. (Maybe the solid-state geniuses have found another way, since that was in 1960.) You may find one that will work for your specific computer. I plan to research them just to see how they are rated.
 
Appreciate the replies!
as you reminded me - you can convert DC to DC with electrical efficiency - I like that route, as these devices have been around a while. The 15amp spec was helpful, so i know how much i can "hang" off of the single DC output the R21-EC has. I planned to get a DC fan, so I'll get a clunky multiple cig lighter
Last question - do any of you have an inline power meter, that either a. displays the voltage, b. alarms you when the voltage drops to low (to avoid battery damage) or c. does both a reading and an alarm?
thanks much,
ptv
 
You may already have the alarm function in some of your instruments. My Garmin GPS and Fishfinder can both alarm on user-set voltage levels. I believe that on the GPS, at least, it can be one of the values you can display on the screens.

I did some checking on DC/DC transformers and none that I found looked like simple plug-in devices. Most were componenets which could be wired to use various input and provide specific output values. I spent a fair amount of time looking but never did come up with an efficency number so I can't verify my suspicion that they have internal inefficiencies. Transformers and current switching can be pretty bad on efficiency. That's one reason the things get hot. If anyone can provide links to a plug-in device and/or efficiency information (real, not speculated like mine) I think a lot of us would appreciate it.
 
I have an R-21 EC and installed a 1000-watt Inverter XM in her. Glad I did. I use it for everything from running a laptop to running a blender to charging a cellphone. The inverter was $240, with another $150 worth of cable, wire, batery switch, etc. Eight hours of installation at $85/hour was another $680.
 
Here is a link to an electronics store in Australia with the 12v to various DCv for laptop computors, on Jaycar's page there is also a compatibility list ;-

http://www.jaycar.com.au/productView.as ... TID=1044#6

or Radio Shack (Tandy)

http://www.radioshack.com/graphics/uc/r ... _PM_EN.pdf

I think the advantage is they are simple plug in , no wiring and you can easily use them in another environment. Maybe they are not really electrically efficient, but if you use them to top up your laptop and not leave the laptop plugged in for extended periods when not running it doesn't really matter.

Geoff
 
Thanks. When you first mentioned Tandy I went directly to Radio Shack's web site here and found zip. I searched for many terms and came up dry. I just went in with the name of the device you show for Radio Shack and only literature shows up, still no product. I have always found their web site to be one of the worst for finding products. If I want something I walk into the store and find it myself. Surprising for such a large and old-line company. Or is that how they build store traffic?

I still don't find many here that are plug-in devices, but searching for "car laptop adapter" helps. I was searching for things like "DC/DC adapters", DC/DC voltage changers" etc. One just has to know exactly what to search for at times. :?

As to the link to the Australian site, that was interesting. I did find this one at Amazon using the more refined search. If it works, it would be an inexpensive way to go to keep a notebook alive. At 4 amps @ 19 VDC it should handle my Dell Inspiron 1545 but the reviews are not promising.

http://www.amazon.com/CablesToBuy-Unive ... B0022WRQWO

There was another link from Amazon to such devices:

http://www.laptoppartsnow.com/power-car ... 2godPky_ZA

It looks like one specific to my Dell is about $56 at my door. I might just install another Cobra. Not as portable, but surely more available power.

I installed the 400 watt unit I mentioned earlier (Cobra CPI 480) for about $50 by doing it myself. That included the inverter at $26.55 at Amazon, a NAPA BK 730-4750 fuse holder at $7.07 and a pair of AGU 40 fuses for that at $3.69. I used roughly $10 worth of #8 AWG stranded wire. If one can get by on 400 watts (to run a notebook you can "share" the unit by charging part time and using the full 400 watts for another item while running the notebook on the batteries) that is not a bad investment/performance ratio.
 
check west marine for 12v fan that draws only 1 amp ,i have one, sorry, cant recall name (2 am here) don l. :arrow:
 
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