ok electrical question

[JWalker]

I'm trying to put together a charging system...

Our energy budget says we will use aprox 11 amps/day

I'm planning on using two 6 volt golf cart batteries with somewhere around 200 amp hours (215) (230)

I have a 12 amp alternator on the yamy outboard,

and I am planning on putting a 60 watt solar panel on the back.

Soooooooooo

hows this charge controller thingy work?

I know I'm supposed to put it between the solar panel and batts....
but they all seem to have different amp ratings (7) (10) (30)

I'd like to be able to add another 60 watt panel in the future in case
I can no longer handle my lust for an engel.

do I need to run the alternator through it also, or can I just plug that
into the batts and be ok?


can anyone offer me clarity?  ???

[s/v Faith]

You can put a charge controller on your alternator input, but you are not likely to need it.

 I have mine wired through the controller, but that has as much to do with the fact that I have a run of 12 ga wire from the lazarette and it makes sense to hook up both.  My old Yamaha 6 put out 6a max, but the voltage would go crazy high when motoring for long periods of time (system voltage of 19.6 vdc seen once)....  really too high.  You are going to need a controller, might as well use it.

 You might consider a simple charge controller like the 'Flexcharge NC-25a' would fill the bill for you (you can spend much more, but not really gain much).



 A 60w panel is really too big to go without a charge controller.

Take a look at page 6 of this earlier thread we had that included lots of good thoughts on energy budgets.  You might be cutting it close to go with an Engle with a 60-w panel.... probably want to take a good look at it.

[JWalker]

Thanks for the reply Faith.

Ok, on the charge controller....I can run both the alternator and the solar through a single controller?

I think I'd prefer to have the alt going through a controller....just makes me feel happy.



On the engel, I have read that a reasonably daily useage was somewhere in the 17 amp area....

I see that doing the math from the other thread that

60 / 18 = 3.3 x 4 hours/day = 13.2 amps.

the four hours is northern winters.....

I have been using another formula that I found that seems to be soemwhat agreed on for southern cruisers which is watts x .3 (I'm in the south and planning to head further south)

60 x .3 = 18 amps

Thinking that I will probly have some room from the first panel, and the alternator if needed, my thoughts were that this was a good fit.

Should I be looking at more? That would be 120 watts of solar

120 / 18 = 6.6 x 4 = 26.4 amps

120 x .3 = 36 amps

our current figured budget is 11 amps....plus added engel 17 amps = 28 amps.....

not much room on the top one. but then, the engel is a lust object at the moment!  ::)

any idea if the watts x .3 is worth anything for southern cruising?

[s/v Faith]

First,

  The outboard's output is best viewed as 'supplemental' in my view.

Yes, you are likely to motor, but you never want to HAVE to motor.  In several months of cruising (with solar + outboard) I found it best to consider the outboard as extra because you never know when you may be able to do without it.  Either anchored in the same place for a period of time (you do not want to run the outboard at high enough RPM to charge.. it is really hard on it... and you.  We went a month of cruising in the Bahamas, where we were moving from place to place and never started the outboard....

  It is a good capability to have, as extra amps are always a good thing.... but I would not rely on them too much.

Yes, to answer you question.. you can run all the charging inputs through your charge controller together. 

  As to the formula, the numbers work but are close.  It is funny how the things that are 'extras' are the killers.  For us, the lap top was a killer... major amp draw!  I have a 135w panel I plan to mount for the extra amps I need.

  We were fortunate to have purchased a Honda 1000, it filled in the gaps... .6 gallons of gas would run much longer then the outboard and gave us many more amps... of course the generator is not KISS and you are wise to budget for the amps you need via solar.

  Does the 60w panel have favor for size, cost, or do you have it already?

[TOMT]

     Hello JWALKER!

      I have the same flexcharge NC 25a as S/V faith was recommending with 4 golf cart batteries charged by a wind charger & solar, perkins 4-108.

       I drove myself crazy trying to figure electrical needs so I just plugged and played. Batteries are now 9 years old and the flexcharge is still working well, I have had all the power needed so far. I pay extra attention and keep the batteries up and so far no problems. BTW I bought the batteries at a SAMS Club. 

        When the batteries are fully charged the flexcharge will shunt the extra power to other necessity's. 


           TOM

[skylark]

Connect a fuse to the positive output of the charge controller. Connect your system positive to the other side of the fuse.  Your system ground can be connected directly to the charge controller.

The solar panel positive and negative get connected to the appropriate connectors on the charge controller.  You can parallel solar panels as long as you don't exceed the amp rating for the charge controller. 

To calculate the amp rating of a solar panel, divide the wattage by the rated voltage. For example 60W/17V = 3.5 amps.

To estimate how much power you will get out of a solar panel, a rule  of thumb is that you will receive about 4 hours a day of full output. Obviously the actual output will vary.  But for a 60W panel, the output is 3.5 amps X 4 hours  = 14 amp-hours.

Be aware that your battery will only take a part of that as a charge.  I am not sure of what that factor is, perhaps it is 75%.

[JWalker]

Thanks for the input everyone!


I can put a 90 watt panel on the back as easy as a 60.

90/17 = 5.2
x 4 = 20.8

That should give us a good extras margin


Ok, I know I'm asking for more than I want to know....why sometimes I hear 18 volts, other times 17 volts....  is the voltage just a guestamate of what the panels will put out?

[s/v Faith]

I think that is an excellent idea.   I think you will be more happy in the long rum.

  For a battery to be charged, a current must flow into it (to reverse the chemical process whereby electricity is released from the cells). 

  An 'open' charging voltage of various devices may vary by quite a bit.  Loaded, the panels will not likely ever see the 17 dc volts...  open many will go as high as 22vdc.

  An increase in voltage is seen when charging... say something like 13.8 or above.  The 17vc construction is engineered to provide some charge in less then ideal conditions, without damage to the batteries in full sun.