2 gensets on same bus

[mobile_bob]

DaveW:

your comments now make sense to me, in that if i were to go the vrla battery route i would go with a different charging regime, i would also get some form of more accurate measurement of internal temp of one of the batteries, not just case temps.

if you were to use my suggested charging regime on that sort of battery i would expect to boil them dry in short order and have the vents blown off before that.

for me, the vrla battery doent make sense, but that is me and my system. i realize your milage may differ.

i went with the flooded cell because of its ability to take higher inputs, temp compensated of course, and its rugged nature.

i will also be using some solar, ~500watts, and some windpower <1000 watts, but i wanted to make sure the gen package was as efficient as i could make it, and size it to easily cover all that i have in mind, then reduce run time because of wind/solar inputs.

i am impressed with your system however it would not be the system to fit my needs.

bob g

[bitsnpieces1]

  3.0 watt consumption - 90 lumen...

Common misconception: that LEDs are more efficient than fluorescents.  Generally not true, at least not in the year 2006.  CFL bulbs are typically in the range of 40-60 lumens/watt.  And linear fluorescent (4 footers) run around 70-90 lumens/watt.  The LED bulb you describe was 30.

LEDs are getting more efficient, though.  But today, fluorescents are generally more efficient.

But, Holy Cow,  another thread taken way OT...

Bruce mentioned that he had a problem with flourescents, the LEDs seem to be a good, albeit capital expensive, alternative to incandescents in that case.  I also am looking at the LEDs in certain situations due to the fact that in those situations flourescents make my eyes hurt. 

[BruceM]

Thanks for the LED suggestion, BitsNPieces.  I bought some and was unimpressed with the output and light quality, except as you suggest- some special applications like spot lighting where the directional nature of the LEDs works well.

 I found the white LED's have a wierd flourescent blue/violet cast that bugs me, but mixed with some amber LED's they are fine.

Dave W., It sure was interesting to read of your AGM based battery system.  I also very much appreciate the references on charging info.  Thanks for sharing your knowledge. Have you run into any information on higher voltage (120V) DC systems?  I heard a rumor about stringing solar panels in series up to that high of a voltage  could be problematic but haven't been able to come up with anything more.

Best Wishes,
Bruce M
Metro 6/1
Snowflake, AZ

[DaveW]

Bruce M -
    Stringing any system in series or series/parallel can lead to problems.  It can be done, after all most batteries are made up of a string of 2 volt cells, but the higher the count the more attention to detail is needed.  Most of my systems are 48 volt, with one 72 volt and two 24 volt systems.  I have found that higher voltage systems seem to give less problems when 24 volt panels are used.  This is probably just fewer connections to worry about. I have had good luck with Sharp 175 panels, 35.4 volt, 4.95 amp.   They string together nicely at least up to 72 volts.
     However you go about it, fused combiner boxes that are truely weather tight are a must.  The higher the voltage, the more attention needs to be paid to balancing current flow and wire size.  A 1% loss is about all that should be allowed.  This may mean that you really need #2 wire when you were hoping to get by with 6 ga. Run lengths should be matched, which can be a bear depending on the number of combiner boxes in a system.
     A couple of good reads:

    A Guide to Photovolaic System Design and Installation - Cal Energy Commission  - abcsolar.com
    Planning a Code-Compliant, off grid PV System - Sandia and NMSU - nmsu.edu

As always, NEC and NEC Handbook should be at hand for light reading, especially note the changes to section 690.35 about grounding in PV systems above 12 volts.  So - short answer, yes it can be done.  Long answer, carefully....
     Finally, a question. Why a 120 vdc system?  I like 48 volts because so much telecomm equipment comes on the used market, and the higher voltages can be expensive to work with.  I only use the 72 volt system because I have an old Sola true sine wave inverter that refuses to die, it is over 25 years old now and still works like a top.
     Any questions, just ask.  Oh, and by the way, I have (reluctantly) inspected systems up to 480 vdc, 40,000 ah. Can literally make your hair stand on end.
DaveW

[BruceM]

Thanks, Dave W.  I'll quit hijacking this thread and send you a message.