The "nest" and its loads

[scrubjaysnest]

This will give you an idea of what power we need to make up with our solar.
These are worst case figures; some like the reefer fan, 12 hours or the inverter are rare occurrences. The water pump is 0 because from Dec 1 until the first week of March this year it was used only once. Notice this is enough usage to draw down the batteries to just below 50% soc for 1 day. Our more typical usage takes 3 to 5 days to get to 50% soc. This why an audit of what you use should be done first before going out and getting your solar system.
200 watts of solar * 3 hours = 600 WH so 5 hours of full sun will just make it.

Basic formulas:
All watts are E*I=W; in all cases E = 12 Vdc
WattH or WH are watts * number of hours device is used
All currents measured with DC clamp on meter.


http://i.imgur.com/aSUGASKl.jpg "border=0" (http://i.imgur.com/aSUGASK.jpg "target=new")
http://bit.ly/1CIRlV8 (http://i.imgur.com/aSUGASK.jpg "target=new")

Ok now it is more or less easy to follow.

Added updated table.

[LoveToCamp]

Scrubjay, I am not criticizing a bit, so please don't take it that way. While some of you on the forum have electronics down pat, there are some of us (at least me, anyway), that didn't pay enough attention in science to be fluent in electronic values.

So, a helpful column to add to your assessment is how many hours a day you factored for each item. This way, I could do some math with your numbers, and possibly figure out how to do a similar calculation for my use. Having the hours-used would allow me to verify that my way of thinking was correct (or incorrect).

Where do you get the values for each of your items, especially thinks like LED lights, refer fan, and things without obvious values? Dig for a label? I tried putting a multimeter inline with some items, and it didn't display a result that made sense to me, when I tried to determine the load to something last year. I have not figured out that process, yet.

Thanks for posting your results. Gives me something to try to mimic, to see how much extra capacity I have with my 100w panel. Batteries are topped-off every day when I am camping.

[scrubjaysnest]

Got to thinking about that after I posted I'll edit the original post. All currents were measured with a DC clamp on meter. Watts = Amps measured * 12 volts
for starters.

[Padgett]

That is how you create an energy budget though using a spreadsheet helps (If you don't have Excel, Open Office (free) has a good one).

Just ordered one of these (http://www.amazon.com/MASTECH-MS2108A-Current-Clamp-Meter/dp/B009CNYJG2/) because it has both AC & DC clamp on amp measuring and can measure capacitance to 4mf. Looks like an inexpensive all in one.

More when it arrives.
ps: the one with blue clamps is 50c cheaper but sounds like the same gutz.

[scrubjaysnest]

I ordered the one from Sears on line and picked up at the store to save on shipping. Some Radio Shacks also carry one. They get expensive if you buy from an electric supply house. Another choice is to put in a Trimetric or Clipper battery monitor. For the last two you install a shut in the negative battery load lead. The Trimetric gives you amps used, amps charged ,soc, watts and watt hours used or replaced and other stuff. From reading on the solar-electric forums you need to use care when setting up the Trimetric.

Have not really heard any thing about the Clipper.

[scrubjaysnest]

Kind of have the table more usable.

[tentcamper]

scrubjaysnest, Very nice chart. Good idea to have an understanding where you use your battery power.

What is the fridge fan? Is it the fan in the back for traveling or is it a fan inside the fridge?

We almost always have the water pump on because most CS we stay at don't have water hook-ups. But I don't think it runs for more than 5 minutes total during a day. I think it pulls from 4 to 7 amps when running depending on the pressure while it is running. But when it's not running, it's not pulling any current.

Have you figured our the load from the propane detector, radio antenna, and propane water heater??

[Bill]

Scrub Jays Nest -

That table is a really nice piece of work. Lots of information, and enough definition that we can all see where the numbers come from, and how to make changes if we would like different starting numbers.

I'm especially impressed that you found a way to format the table. VBulletin software is not very good at all for that purpose.

Bill

[scrubjaysnest]

scrubjaysnest, Very nice chart. Good idea to have an understanding where you use your battery power.

For the amount of dry camping we do you need a good handle on power use.
Did some testing with the inverter and laptops and it took two days to get the batteries to 70% soc. That's with a 12 hour rest period. Solar with the cloud cover yesterday was in bulk between 3 to 12 amps. When I turned it back on at 8 AM this morning the CC was in absorb at 10 AM with 11.4 amps; for my settings that's 14.9 volts at the batteries or 170 watts from the 3 panels total. The roof mounted one had a bit of shade.

What is the fridge fan? Is it the fan in the back for traveling or is it a fan inside the fridge?
The fan to pull hot air from the top of the reefer. It's really a don't care for us as the first nights stop is a 4 hour drive so the TV puts that little bit back.

Some on the forum user do use it when camping in hot weather is why I put it in.

We almost always have the water pump on because most CS we stay at don't have water hook-ups. But I don't think it runs for more than 5 minutes total during a day. I think it pulls from 4 to 7 amps when running depending on the pressure while it is running. But when it's not running, it's not pulling any current.
This is why the math for the toilet WH; you have to convert seconds or minutes of run time to hours. For us we don't use the water p-p a couple of 2 1/2 gal water containers by the sink.

Have you figured our the load from the propane detector, radio antenna, and propane water heater??

The detector I haven't measured. The antenna is off as it's powered only when the radio might be on. We don't use the radio and it's un plugged as the amplifiers were always on.
Our normal usage is ~15% per day as a FWIW.


See post 14 for redo pictures

[scrubjaysnest]

I have up dated the table in the first post, did forget to add in times.
For the most part divide wattH/day by watts and it will give you an hour figure.
The toilet is based on 10 second flushes times an average number of flushes. That number will be lower then most as we don't put any solids in the toilet.

The furnace for us is usually two 15 minute cycles with the thermostat set at 60 degrees.

The inverter is a really hard one, worst case is two laptops charging for 3 hours at about 12 amps but it is rare for both to be charged even on the same day.

I added a portable O2 cool fan which runs from 10 pm to 5 am every night temps only get to about 70 degrees.

[Craigrrr]

Great info Scrubjaysnest, Looking at that my 160 watt panel wont make a dent.

But then we only use full off grid very seldom. I might have to re-think my large panel size and try to get a couple 200 watt panels that might have a smaller footprint.

[scrubjaysnest]

Great info Scrubjaysnest, Looking at that my 160 watt panel wont make a dent.

But then we only use full off grid very seldom. I might have to re-think my large panel size and try to get a couple 200 watt panels that might have a smaller footprint.
We have actually gotten on pretty well with 160 watts of solar. It does come up short during the winter months if you end up running the heat a lot. Our worst case was last winter we ran it one night from midnight until about 7 AM. Took about two days of good winter sun to recover. Sun angles are lower so even in full sun the panels don't receive the energy they do during summer. They are also marginal if you take a 200aH battery bank or larger down to 50% on a regular basis. It will work but battery life is reduced and it takes awhile to recover. With the 360 watts we now have, our estimated charge rate is 9.1% vs less then 5% with just the 160 watts.

The rule of thumb is don't go below 5% but shoot for a 10 to 13% rate of charge.

[scrubjaysnest]

A quick and dirty system test today. Ran the refrig on DC until the Trimetric showed 70% SOC. Let settle for 2 hours and battery voltage with both the Trimetric and a Fluke was 12.5 volts or about 60% SOC per Exide. With the four panels connected Trimetric shows 20.5 amps and the clamp on sears shows 22.3 or some where between 270 to 307 watts into the batteries. That's a pretty solid 10% rate of charge for each battery so not bad for a 50 degree day.
I'll do further testing and post the results in a chart format similar to the one here: The 12 Volt Side of Life (http://www.marxrv.com/12volt/12volt.htm)

[scrubjaysnest]

Or how not to get it right the first time.:D

http://i.imgur.com/IPQZlv5l.jpg
This shows the new 4 way tilt system. For a little added security
the panels a bolted in place with allens in the travel position.
There is a left over bracket under each panel that I could make into
a locking system.

http://i.imgur.com/YFxQrDnl.jpg
So many options, for getting panels into the sun.
I enlarged the stands for the 2 100 watt portable panels.
Glued some fittings, but not the ones that allow tilting the
panels for different latitudes. Frames are ty-raped to the panels.


http://i.imgur.com/ie2o566l.jpg

The new breaker panel, box for the Trimetric shunt and
other stuff.

[Craigrrr]

Looks good!

[scrubjaysnest]

This is some test data results put into a SOC chart from the 12 Volt Side of Life.



http://i.imgur.com/xvpfngVl.jpg "border=0" (http://i.imgur.com/xvpfngV.jpg "target=new")
http://bit.ly/1CIRlV8 (http://i.imgur.com/xvpfngV.jpg "target=new")

Values on the chart were not corrected for temperature.
Trimetric SOC is based on battery bank size, how much current you put in or take out and over how long. The discharge rate was between 11.1 amps and 11.6 amps. The load used was the refrig at highest setting plus a small amount used by the CC and Trimetric.

Kind of points out what I've been reading of late that SOC is not very accurate including S.G.
To me this a a 2 year old set of batteries starting point or base line.

Since this chart shows a measured voltage of 12.4 volts to be between 50 to 60% SOC it may help some with the comments rickst29 and myself have made in the Solar panel basics thread I started.

The unloaded Fluke readings were about after a 12 hour rest time.

[scrubjaysnest]

I've updated/corrected the load table in the first post of this thread.

Below is a table of test data after discharging the batteries to about 60%. I used the refrig on DC as the load as it's pretty close to a 5% discharge rate.
The Tristar was set at 15 minute sample intervals and from time to time I checked the Trimetric, a clamp on Sears AC/DC meter and a Fluke for voltages.

http://i.imgur.com/Sr3biGll.jpg "border=0" (http://i.imgur.com/Sr3biGl.jpg "target=new")
http://bit.ly/1CIRlV8 (http://i.imgur.com/Sr3biGl.jpg "target=new")

For a period of time the results with full sun show about a 11% ROC when the system hit 20 amps.