6V Charge Controller Recommendation for Sensor

David and Laura

On the other end of the scale, we have a remote sensor that we want to power via solar that requires a 6V supply. The supplier recommends using a 6V AGM or Gell cell along with a 6V charge controller (they suggest the Rogue Rhino-5).

The sensor takes approximately 100ma, and We'd like for it to be able to run for at least one gloomy week before the battery gets to 50% SOC. If our calculations are correct, that works out to approximately 17 AH worth of battery (34 AH in total), and 100 Watt-hours to recharge from a 50% SOC. Given this, we figure we should be able to get away with a small-ish 40 watt panel.

Here's a preliminary bill of materials, and some initial price estimates:

Solar Panel - 40W, Approximately $60
Charge Controller, Approximately $50
Gel Battery, 32 AH, Approximately $70

Does this configuration sound reasonable? Any alternate recommendations on a 6V charge controller?

NorthGuy

Re: 6V Charge Controller Recommendation for Sensor

I'm doing the same thing, except that my sensors only need 3mA @3.3V. I'm getting two 2.5AH 2V batteries (the smallest I could find) and 2W panel with Vmp = 6.

It is to be installed outside, and it was really hard to find a battery that would stand -40C, which can happen here. Finally, I found these, probably the world's smallest lead-acid batteries.

I couldn't find any reasonable 4V controller and I decided that I'll make my own (simplified) controller.

David and Laura

Re: 6V Charge Controller Recommendation for Sensor

Cool (literally!). What type of sensor are you running?

NorthGuy

Re: 6V Charge Controller Recommendation for Sensor

David & Laura wrote: »

Cool (literally!).

It was less than -47C one time, but cannot tell exact number - that's where the thermometer ends.

David & Laura wrote: »

What type of sensor are you running?

I want to control climate for my batteries. They're in the garage. The controller will open and close the door to keep them cool during summer and warm during spring/fall. To do that, I need to know the temperature outside. So, I'm putting out a temperature/humidity sensor. Sort of weather station. It'll sit outside and send the information wirelessly to the controller. Some day in the future, I'm going to use this information to control the barn fan. I didn't want to change batteries there all the time, so I decided to go solar. The solar panel will produce enough power 99% of the days, and in case it doesn't, the batteries will last for two weeks. A little overkill, but that's about the smallest setup I could get.

zoneblue

Re: 6V Charge Controller Recommendation for Sensor

You might not need a bettery that size. I use a 5Ah sealed agm cell, (the type used in UPS) to power a electric fence unit that draws nominally 50mA.
I use a 3 dollar switchmode regulator to float the cell at 13.8v from a 10W amorphous panel. Itll go for weeks of no sun i reckon.

Regulator is this one:
http://dx.com/p/mini-dc-dc-voltage-stabilizer-regulator-module-red-126106

If its really cold then lithium might be a better bet. A laptop battery or something like that?

PNjunction

Re: 6V Charge Controller Recommendation for Sensor

NorthGuy wrote: »

Finally, I found these, probably the world's smallest lead-acid batteries.

I can't think of any better small AGM's than the Enersys-Hawker Cyclon (individual or monobloc) for small projects. I love them because they are vastly superior to the typical ups-style lead-calcium agm. They are pure-lead spiral wound, and as such can take HUGE amounts of input current. 2C is not unheard of, and I typically charge mine from 0.4C to 1C (at 10 hour rate capacity) at 2.45 - 2.50v per cell, and let them float afterwards as long as I can.

Note however that they also require that you feed them a *minimum* 0.4C inrush current for longest life AT the 2.45-2.50v/cell CV charge. Like their bigger pure-lead brothers the Odyssey / Genesis agm's etc, they don't like to be tickled to death with low current. This might make it easier to use off the shelf stuff for panels, controllers, etc.

The Cyclon Application Manual is amazing for such small cells, even though my last reference found to them was from 1998, but online can be found easily enough.

Just make sure that you are getting FRESH cells, and not new-old stock older than about 2 years, or having an soc of under 12v upon receipt. My personal limitation is for 12.4 volts minimum on receipt, but obviously the fresher the better.

I'd like to see the specs on the Rogue-Rhino controller mentioned by the Op to see if it meets the 2.45v / cell minimum absorb voltage...