One solar panel, multiple charge controllers?

[Nan and Sandy Sanders]

HI Rob. It should work but..... Keep in mind you will only need one 
or two hundred Ma max to keep the batteries charged if you start out 
charged so a 250 watt panel is over kill. The other thing you will 
have to be careful about is rfi. Long connecting wires and switching 
regulators will be real easy to hear on your HF rig.
One other thing. It will not take long to approach the cost of a few 
hundred feet of 10-2 and an outdoor outlet box (digging a trench is 
good exercise).
      Sandy



At 09:24 AM 3/20/2014, Robert Seastrom wrote:

>Hi guys,
>
>I'm trying to think through an engineering problem and would like to 
>solicit some thoughts.
>
>Living in the country as I do, there's a tendency to accumulate 
>vehicles.  If you want them to start when bidden (particularly the 
>diesel trucks with two 12v lead acid batteries in parallel so they 
>can self-discharge through each other) it's a great idea to have 
>them on a battery tender of some sort.
>
>The current count of vehicles I'd like to support is three, and it's 
>cost-prohibitive to run electricity over to where they're parked (at 
>least until at some point in the distant future when I build a shop 
>over there, at which point the whole discussion is moot).
>
>Decent size solar panels, along the lines of a CS6P, are available 
>for reasonable prices.  I have a post hole digger and can easily set 
>a timber with a panel mount on top at an appropriate angle facing 
>south.  Now the question is what to do with the output of the panel.
>
>The panel in question is 37 volts open circuit and 30 volts optimal 
>operating voltage, 250 watts.  That oughta be enough
>
>I suspect that just having one single charge controller and 
>paralleling two trucks with lead acid batteries and a trailer with a 
>small gel cell that runs its lights isn't the swiftest 
>idea.  Besides, theres i2r losses to consider when running tens of 
>feet of 12v (maybe not that big a deal at battery-tender level 
>amperages, but still).
>
>Perhaps just fusing the panel output and running a drop to each 
>vehicle and regulating it down with a charge controller (series type 
>not shunt type obviously) on each vehicle would do the right 
>thing...  but then I worry about what might be inside the regulator 
>- here in the future with switching power supplies being the norm, 
>several buck regulators on the output of one current source might 
>end up fighting each other.  But maybe not a big deal if there was a 
>decent sized cap across the solar panel?
>
>Any thoughts on the right approach (optimally one that might involve 
>maximum application of off-the-shelf components rather than 
>from-scratch construction) would be greatly appreciated.
>
>Thanks,
>
>-r
>
>
>
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