All the systems I ever designed and built were for 24hr operating systems with a 4 day reserve
I'm now looking at powering my RV at site and later the cabin with solar
But there will be probably 3 months between usage...
Ie do I just set a small 40watt panel or similar to keep the batteries topped up when I'm not there
Then hookup some larger panels when I get there to cover the usage
Do the standard controllers just break the connection with the relavent panels when no power is required ?
I never looked into this side of the side of the system and was just wondering
Our cabin system looks after itself. Three 208 watt panels feeding an Outback FM60 and a 24 volt battery bank. The sun waked it up and it goes into a short bulk charge every morning, then goes into absorb for the set time and floats the balance of the day. When it goes dark the FM60 goes into sleep mode, drawing only a very small amount of power until the next morning when the rising voltage wakes the controller up again. We snowshoe up every second weekend more or less and the batteries are always ready to work for us. I make sure the fluid levels are up in fall, like about now. I won't have to add any water until late spring, early summer.
We leave the inverter off, disconnected by pulling the breaker so there is no cabin load at all.
Before we had that system I did use a small panel set (30 watts) hooked to the RV batteries all winter That worked too.
You can get by with a small 15W solar panel, attached to your battery charger. Just make sure that your charger has a float mode. Some of the cheaper ones, like the Morningstar Sun Saver6 will overcharge your battery.
-f-
yes thats the idea I was working on- as I'm a tad worried about theft for the short term
something sufficient to counter the losses due to cold temps and 3 months of doing nothing
and I can leave a 50usd panel out rather than a 500usd
The only thing with panels is their cheaper the bigger you go ! oh just a bit more and I can have X
200usd gets you 50watts and 500 gets you 240w
I have the same Outback FM60 charge controller Mtn. Don has and like he says, it takes care of itself. My concern is if something ever breaks in the dead of winter and the GC2 batteries discharge to the point of freezing. I'm not sure if they would break open and leak acid or not.
"I'm not sure if they would break open and leak acid or not."
Each of my batteries sits in one of those "weather proof" plastic boxes. The lids are not on, but if a battery were to freeze or break and leak I believe the fluid would remain confined.
Keeping your battery charged will lower the freeze point. There is a chart that can be found on this page:
http://jgdarden.com/batteryfaq/carfaq4.htm#freeze_points
if you keep your battery 100% charged, you have to get to approx -77deg F to hit the freezing point.
I've seen a couple of posts on other forums that deal with this. A good controller, in theory, will handle the charging. One guy had a simple timer set up to cycle a 60 watt light bulb for a few times a day. The heat from the bulb helps keep system components warm also. Cycling the batteries keeps the battery temps warmer, as well as preserve their life and reduce sulfation. The trick is to find the balance so that the water level does not get too low in between visits.
Another guy used a commercial program to do the same thing, but it sends SMS text messages of the system status. Depending on the location, system size, and your budget, there are lots of options for remote sensing.
If you are an embedded electronic geek, you can program a controller with BASIC Stamp to do just about anything.
Thats some neat battery info- hopefully it won't get that cold !
but something to definetly concider
Quote from: NM_Shooter on September 30, 2011, 12:38:16 PMJust make sure that your charger has a float mode. Some of the cheaper ones, like the Morningstar Sun Saver6 will overcharge your battery.
That's a very useful bit of information.