Greening Your Home - Inverter questions

Okay here's the deal...I have a couple of batteries off my boat that just sit in the basement all winter long, not doing anything but get topped off every month. I am really starting to get excited about solar/wind/alt energy. So I thought I could start small and do something with this deep cycle battery I pull off my boat every year. I have a solar panel (5w/12v) that I keep on the batteries during the summer while the boat is in the driveway to keep them topped off and ready to go for the weekends. So I thought I could just keep them topped off with it during the winter and use my 400w(800w peak) inverter and do things like charge my cell phones, charge my rechargeable batts (aaa/aa/etc).

I know that it isn't much, but its a way to start, even if it is really small. Here are my questions...

1. Will the inverter always be running at 400w, or will it just depend on what I have connected to it at the time???

2. When trying to calculate how long the deep cycle battery will last (it is a 210 RC, calculated to 87.5 Ah battery), what figures from the power supply do I use...example - I have a charge for my blackberry that states
input - 100-240v 0.15A
output - 4.2v .75A
so what do I use for the wattage used??? input of 18watts or output of 3.15watts???

using these two values I get these calculations...(Ah/2 for 50% safe discharge of battery)
18w/12v=1.5A, (87.5Ah/2)/1.5A=29.16 hours of use
3.15w/12v=.2625A, (87.5Ah/2)/.2625A=166.66 hours of use

Which is correct?? I know it really doesn't matter since they are way more than needed to charge the blackberry battery, but I would just like to know how many things I can end up doing with this setup. I don't want to discharge too much since I have a very small solar panel and it's not really made to "charge" it, only really maintain it.

Any info will be helpful. Thanks.

Wondering how you did on your project.

The inverter is rated to deliver this power when on and connected to a load that requires it.

Use the charger output you figured, 3.15 W.

Were you to connect your battery directly to your Blackberry device (not its charger), it theoretically would not discharge to 50% charge for 167 hours, if supplying it with 0.2625 A continuously. But I wouldn't do it.

It'd be helpful to know the model of your inverter, charger, batteries, and solar cell. Even a "cheap" Optima deep cycle battery at Kragen's Auto can cost more than $200 so I'd also be mindful of what you charge your battery with, especially if connecting a PV device directly to its terminals.

Solar PV systems with batteries use charge controllers that regulate voltage, current, and discharge depth, while protecting for over- and under-charging. The NEC Article 480 also specs environmental criteria in conjunction with storage batteries; and allowing for gas venting and diffusion; cell part scatter mitigation; flame arresters; pressure release vent for "sealed" batteries. Commonly practiced is the use of temperature sensors near the batteries.

Hi wingrider78,

I got lost a bit.
here is my take on it...

i'm guessing you have two spare batteries that you want to use for your solar project.
you already have a small solar panel.
and you know what you are going to charge with your solar panels.

so far so good?

Any battery has input and output values. The input value is always higher than the output and the input value is the amount of power you need to charge the battery with.
While the output is simply the power the battery gives off.

Yeah, don't count on that 5w panel lasting forever.
They don't, ALL solar panels deteriorate over time, most fail completely at some point.

How I know, mine doesn't work anymore after 4-5 years.

And it's nice folks are thinking green, but it's as cheap if not
cheaper to plug in a normal trickle battery charger.