Fluid, Battery Levels & Solar Charge Controller?

[peterh]

Planning ahead a bit, I'd like to install a fluid (fresh,grey, and black tank) and battery level gauges. Some RVs I've seen have these: you push a little button and the gauge lights up to tell you how full the selected tank is or what your battery condition is. Where do I find one of these, and does anyone have any recommendations?

Another thing I'd like to install is a solar panel setup, and need suggestions for charge controllers. The trailer will have a 50w Siemens/Shell panel fixed to the roof (I just bought the panel) and I'll add 15w portable/movable panels (probably something like Gina's briefcase/folding panels) if it turns out the rooftop unit doesn't keep us juiced when we park under a tree.

Harbor Freight has a 7A/105W Solar Charge Controller that doesn't seem to include a blocking diode. I could add that, but is this a good deal or does anyone have a better suggestion?

--Peter

[Morgan]

Peter,

That thing is not really a charge controller. A charge controller senses the state of charge of the battery and sends charging current as needed. I suspect that thing from Harbor Freight just sends a fixed voltage to the battery so you could boil the battery when you have lots of sun.

RV Solar Electric has a book "RVER'S GUIDE TO SOLAR BATTERY CHARGING" that would be a good investment. They also sell components.

[Per Walthinsen]

Peter:
We've had the Acu-Gage, from Snake River electronics installed for a few years, and it seems to work reliably. www.snake-river.org. Used to be in Idaho, but I see they moved to Alabama. Go figure.
Their website is under reconstruction at the moment, it appears, but they do have a description of their latest model, which seems to be an improvement.
This unit is mainly for "plastic" tanks. If yours are metal you may have to use their internal sensors in the tanks. What we have uses foil-mounted sensors on the outside of the tanks, so installation is pretty smooth and there is zero chance for leakage.
Calibration is pretty straightforward, but how accurate it becomes depends to some extent on how you level the trailer (meaning the tanks). If you have a way of routinely leveling the trailer there is no real problem with accuracy.
As I mentioned, ours is an older unit. The newer one shown on the website seems to include some added electronics. The advantage I see with our more crude model is that there is absolutely no phantom current drain, just a momentary slight electrical drain at the moment you push a test button. It is set up for measuring up to four tanks, so the fourth one could measure diesel fuel, waffle syrup, goats milk, or whatever liquid you can think of.

[Brian B-P]

Originally posted by Harbor Freight
Protects your car's 12 volt battery from over charging and discharging when using solar panel charging systems. Handles solar panels up to 105 watts.

* Maintenance-free protection
* For 12 volt solar panels and batteries only
* Battery charging/full LED indicator lights

Cut-in voltage: 13, Cut-out voltage: 14.2 volts...

This is a simple controller, which prevents overcharging the battery as could happen without any controller. Since it is simply either on (directly connects panel to battery when battery voltage drops under 13V) or off (disconnects when battery voltage reaches 14.2V), it does not control the rate of charge, which is safe as long as the panel is within the rated output. It will not optimally charge the battery, since it does not manipulate the charge rate.

This is the same thing (different brand, same charging control logic) as I have, but I do not have enough experience with it to offer a useful evaluation.

[Gina D.]

Brian is correct, this is typical of most of the lower cost controllers, which is just fine for our pretty small application in comparison to, say, powering a milking barn.

Per has a milking barn next to his house, along with an airport and an electric crickett chaser factory, so this would not apply to him.

I didn't see where it indicated there were no blocking diodes, but the panels, if you get the same one I have, DOES have them. Duplication is a fail safe, not mandatory in this application as well.

THAT said, it will probably do just fine, BUT for a few bucks more, you can get a better one that has a proven track record and is a little more durable. I have a small ASC Controller which has served me well in 2 trailers.

The smaller panel is a 3 amp panel (As I recall) so the 8 amp controller is overkill for just it, but it gives you room to grow.

[Per Walthinsen]

Peter:
Apparently my remote "blocking diode" did not work on Gina. Oh, well.
In rereading your post I noticed that you are also looking for a battery level gauge. Despite the danger of Gina's wrath coming down on me I will respond (with trepidation):
We traveled far and wide with the state of our electrical system being a partial mystery. I had a voltmeter, which told me something, but not nearly enough about what was happening. I needed a battery meter. After looking at the ones available, getting opinions from various people, peering into my wallet, etc. etc. I went for a Xantrex Link 10 unit. You can find the description if you Google West Marine or Xantrex.

This little gem does several crucial things: it toggles between a voltmeter, an instantaneous + or - ampmeter, amp-hour meter referenced to full charge, percentage of full charge, plus a number of other functions. For example, if you watch the ammeter as you turn on a light, it will instantly and accurately tell you what the amp drain of the light is. It can be calibrated with Peukert's coefficient to compensate for different discharge rates and other cool 'lectric functions.

The result of all this information is that the usage of electricity is highly visible and easy to evaluate. You always know everything from charging rate to how much you have left and so on. I find it an absolutely super tool for knowing what's going on. Not cheap, but the price has come down some. Don't really know how I survived without it. My cricket chaser factory now runs very efficiently.

[peterh]

Don't worry about Gina, Per. All you need is to wear this and you'll be safe.

--P

[Gina D.]

That won't help hide him. There will be a residual glow from all the leds and panel meter backlights that will penetrate that thing..and give him away.

[Donna D.]

This just popped up from a newsgroup I belong to..FWIW:

In the May, 2007 issue of Nuts and Volts magazine
http://www.nutsvolts.com there is an article describing a way to use a microcontroller interface to sense water in a dog's bowl. Michael Simpson describes a way to make sensors that do not contact the liquid but instead are mounted underneath and outside the bowl. In his application, when the
bowl runs low on water, it triggers a light alerting the owner. The trigger
could just as easily trigger a valve to refill the water.

His idea appears to be easily transported to other things that hold liquid,
such as RV water, waste and sewage tanks. The current technology sucks.

I wish I had the time to fool with this. It looks like it would be a lot of
fun. It looks like it would work better than current sensor technology.
Many sensors pierce the tank and are susceptible to corrosion and the
effects of the flotsam. Commercial replacement systems are expensive and
their operation is suspect. A reliable, build-it-yourself external sensor
replacement, one that the owner could understand and adjust via programming,
is the ultimate solution.

This uses electricity. If electricity scares you then apply the normal
caveats.

Steve

[Pete Dumbleton]

What I did for the under-bench ten-gallon tank on my Scamp 13 was cut a round hole in the bench's vertical surface and installed a marine deck screw-vent with a clear color. I then filled my tank one gallon at a time and marked each on a vertical line on the tank's side. I open the vent, shine in my flashlight if need be and see the level of the tank. No batteries needed except for the flashlight.